Patent Publication Number: US-2003231076-A1

Title: Structure of non-reciprocal circuit element

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a non-reciprocal circuit element which gives a direction to transmission of signals using a magnetic substance and a communication circuit module provided with the same as a circuit element.  
       BACKGROUND OF THE INVENTION  
       [0002] As for a non-reciprocal circuit element such as a circulator or an isolator, which is used as a front-end part connected to an antenna of a mobile communication device, miniaturization, reduction in thickness and improvement of electric properties have been demanded increasingly. Especially, there is a strict demand for improvement of an insertion loss characteristic, which affects a battery life in a terminal. Thus, various kinds of steps have been taken to satisfy the above demands.  
       [0003]FIG. 27 is an exploded perspective view showing a conventional circulator  1 . The conventional circulator  1  comprises a discoid ferrite member  2 , a magnet  3 , a parallel flat-plate capacitor  6   a ,  6   b  and  6   c , an input-output terminal part  7 , and yoke materials  4  and  8 . The magnet  3  is disposed so as to be opposed to the ferrite member  2 . The parallel flat-plate capacitor  6   a ,  6   b  and  6   c  constitutes a capacitor for matching. The input-output terminal part  7  has an input-output terminals  7   a ,  7   b  and  7   c  connected to outer circuits (not shown) The yoke materials  4  and  8  house the ferrite member  2 , the magnet  3  and the like to constitute a magnetic circuit.  
       [0004] Although the yoke materials  4  and  8  are engaged with each other to be integrated, FIG. 27 is the exploded view of the yoke materials  4  and  8 . Three center electrodes  5   a ,  5   b  and  5   c  are arranged around the ferrite member  2 . The center electrodes  5   a  to  5   c  are formed of an electro conductive thin plate material. The center electrodes  5   a  to  5   c  are electrically insulated with each other and superposed so as to intersect with each other at an angle of 120 degrees.  
       [0005]FIG. 28 illustrates structures of the center electrodes  5   a  to  5   c  and the ferrite member  2 . An insulating layer  9   a  is disposed between the center electrode  5   a  and the center electrode  5   b  and an insulating layer  9   b  is disposed between the center electrode  5   b  and the center electrode  5   c . Respective one end of the center electrodes  5   a  to  5   c  are connected to a circular earth plate  5   b  disposed on the lower side of the ferrite member  2 . The insulating layers  9   a  and  9   b  disposed between the center electrodes  5   a  to  5   c  are not shown in FIG. 27. The circular earth plate  5   p  is not shown in FIG. 30 because it is provided on the lower surface of the ferrite member  2 .  
       [0006] The whole structure will be described again. Referring to FIG. 27, the lower electrodes of the three parallel flat-plate capacitors  6   a ,  6   b  and  6   c  are disposed at predetermined positions in the yoke material and connected to the yoke material  8 . The center electrodes  5   a  to  5   c  are, on other end, connected to the upper electrodes of the parallel flat-plate capacitors  6   a  to  6   c . The circular earth plate  5   p  in the ferrite member  2  on the side of the yoke material  8  is connected to a predetermined position on the yoke material  8 . The yoke materials  8  comprises earth terminals  8   d ,  8   e  and  8   f . The earth terminals  8   d ,  8   e  and  8   f  are connected to outer circuits (not shown) so as to input or output signals. A hole H for housing the ferrite member  2  is formed in the input-output terminal part  7 . The input-output terminals  7   a  to  7   c  are formed in a resin structure body by insert molding. Three electrodes extended from the input-output terminals  7   a  to  7   c  on the lower surface of the input-output terminal part  7  are connected to respective ends of the center electrodes  5   a  to  5   c  connected on the parallel flat-plate capacitors  6   a  to  6   c . Although the input-output terminal  7   c  is not shown in FIG. 27 because it is positioned at a hidden position, the input-output terminal  7   c  is disposed between the earth electrodes  8   e  and  8   f.    
       [0007] Parts correspond to each other according to alphabets attached to reference numerals allotted to the parts in the figure.  
       [0008] In FIG. 27, the structure of the circulator was described. However, an isolator is configured by ending one of the input-output terminals with a resistor in the structure of the circulator.  
       [0009] The above is the basic structure of the conventional non-reciprocal circuit element. In order to improve miniaturization and mass production property of one layer of the non-reciprocal circuit element, a structure in which the center electrode part or a capacitor part or both are combined in one substrate has been proposed in recent technique trend. More specifically, there have been proposed various kinds of structures in which the center electrode part or the capacitor part or both are combined in one substrate by disposing electrodes three-dimensionally using a multilayer technique.  
       [0010]FIG. 29 illustrates a structure in which the center electrode part is integrated by a multilayer substrate. An essential structure of the multilayer substrate is shown in FIG. 30. The basic structure in FIG. 29 is the same as that of the circulator described in FIG. 27. Referring to a multilayer substrate  265  shown in FIG. 30, center electrodes  275   a ,  275   b  and  275   c  are layered through insulating layers. The center electrodes  275   a  to  275   c  are disposed so as to intersect with each other at an angle of 120 degrees. Terminal electrodes  271   a ,  271   b ,  271   c ,  271   d ,  271   e  and  271   f  for internal connections are disposed on the lower surface of the multilayer substrate  265 . These terminal electrodes  271   a  to  271   f  are connected to the ends of the center electrodes  275   a  to  275   c  through via hole conductors. In FIG. 30, a connection state of each electrode through the via hole conductor is conceptually represented by broken lines. In addition, referring to FIG. 29, the terminal electrodes  271   a  to  271   f  for internal connections formed on the lower surface of the multilayer substrate  265  are connected to electrodes  266   a ,  266   b ,  266   c ,  266   d ,  266   e  and  266   f  formed on the upper surface of the input-output terminal part  267 , respectively. The electrodes  266   a  to  266   c  are extended to the lower surface of the input-output terminal part  267  and connected to upper electrodes of the parallel flat-plate capacitors  6   a  to  6   c . The electrodes  266   a  to  266   c  are further extended to be connected to the input-output terminals  267   a  to  267   c . The input-output terminal  267   c  is not shown in FIG. 29. The electrodes  266   d  to  266   f  are extended to the lower surface of the input-output terminal part  267  to be connected to the yoke material  8 . Parts correspond to each other according to alphabets attached to reference numerals allotted to the parts in the figure.  
       [0011]FIG. 31 illustrates a structure in which center electrodes and a capacitor part are integrated using the multilayer substrate. The essential part of the multilayer substrate is shown in FIG. 32. The basic structure in FIG. 31 is the same as that of the circulator described in FIG. 27. Referring to a multilayer substrate  285  shown in FIG. 32, center electrodes  295   a ,  295   b  and  295   c  are layered through insulating layers. The center electrodes  295   a ,  295   b  and  295   c  are disposed such that their longitudinal parts intersect with each other at an angle of 120 degrees in a plan view. Electrodes  296   a ,  296   b  and  296   c  are formed so as to be opposed to an earth electrode  292 . Terminal electrodes  291   a ,  291   b ,  291   c ,  291   d ,  291   e  and  291   f  for internal connections are disposed on the lower surface of the multilayer substrate  285 . The center electrodes  295   a  to  295   c  are, at one end, connected to the electrodes  296   a  to  296   c  and the terminal electrodes  291   a  to  291   c  through via hole conductors. The center electrodes  295   a  to  295   c  are, at other ends, connected to the earth electrode  292  and the terminal electrodes  291   d  to  291   f  through the via hole conductors. Referring to FIG. 31, the terminal electrodes  291   a  to  291   f  formed on the lower surface of the multilayer substrate  285   a  reconnected to electrodes  286   a ,  286   b ,  286   c ,  286   d ,  286   e  and  286   f  formed on the upper surface of an input-output terminal part  287 . The electrodes  286   a  to  286   c  are provided in the input-output terminal part  287 . The electrodes  286   a  to  286   c  are connected to the input-output terminals  287   a  to  287   c . The input-output terminal  287   c  is not shown. The electrodes  286   d  to  286   f  are extended to the lower surface of the input-output terminal part  287  to be connected to the yoke material  8 . Parts correspond to each other according to alphabets attached to reference numerals allotted to the parts in the figure.  
       [0012] As described above, a communication circuit module element has been formed by integrating some circuit elements in a wireless circuit constituting a front-end part or the like while a single part represented by a non-reciprocal circuit element has been miniaturized. This results in reduction in the number of parts and saving space. More specifically, in a case where the communication circuit module comprising a non-reciprocal circuit element constituted as a single part is formed, the non-reciprocal circuit element is mounted on a substrate constituting the communication circuit module and then packaged.  
       [0013] According to the improved conventional circulator (using the multilayer substrate) shown in FIGS. 29 and 31, the number of parts is reduced and troublesome assembly is eliminated as compared with the circulator shown in FIG. 27. As a result, a mass production property is improved and miniaturization is implemented. However, as compared with a structure in which earth ends of the center electrodes formed of metal foil are extended to the lower surface of the ferrite member to be connected to a common circular earth plate, a potential equalization property of each center electrode at the earth end is not enough in the improved conventional circulator. Therefore, according to the improved conventional circulator, deterioration of the electric properties or a rise in earth impedance could occur.  
       [0014] Furthermore, when the communication circuit module provided with the non-reciprocal circuit element is formed, so long as the non-reciprocal circuit element is constituted as a single part, there is a limit of reduction in the occupied space on the substrate of the non-reciprocal circuit element, which prevents miniaturization of the communication circuit module. This is because it is necessary to mount the non-reciprocal circuit element on the communication circuit module at a distance from the parts disposed around it at the time of mounting.  
       [0015] Furthermore, in a case where a part generating heat such as a power amplifier is contained in the communication circuit module, since it is necessary to consider a heat release measure, there is a limit in material and structure of the multilayer substrate used as the main component. As a result, the degree of freedom of the circuit composition is lowered and its integration becomes difficult.  
       SUMMARY OF THE INVENTION  
       [0016] According to an embodiment of the present invention, there is provided a non-reciprocal circuit element comprising at least three center electrodes superposed and arranged so as to intersect with each other; a capacitor connected to one end of the center electrodes in parallel; earth electrodes connected to the other end of the center electrodes and disposed between center electrodes at least one by one; electrical isolation layers arranged between the center electrodes and the earth electrodes; a ferrite member arranged adjacent to the center electrodes; a magnet for applying a direct current magnetic field to the ferrite member; and a yoke material combined with the ferrite member and the magnet to constitute a magnetic circuit.  
       [0017] According to the above structure, since one or more earth electrodes are formed between respective layers of the three center electrodes formed separately, there can be provided a non-reciprocal circuit element in which a potential equalization property of each center electrode on the earth side can be improved and electric properties are not deteriorated even if the center electrodes are formed using a multilayer substrate. In addition, there can be provided a non-reciprocal circuit element having small earth impedance.  
       [0018] Furthermore, according to another embodiment of the present invention, there is provided a non-reciprocal circuit element comprising at least three center electrodes superposed and arranged so as to intersect with each other; the electrical isolation layers disposed between the center electrodes; a capacitor connected to one end of the center electrodes in parallel; a ferrite member arranged adjacent to the center electrodes; a magnet for applying a direct current magnetic field to the ferrite member; a yoke material combined with the ferrite member and the magnet to constitute a magnetic circuit; a multilayer substrate comprising the center electrodes and the electrical isolation layer; and via hole conductors provided in the multilayer substrate and connecting layers at connection points in the multilayer substrate comprising connection points of both ends of the center electrodes. In addition, the via hole conductor connected to the other ends of the center electrodes has electric resistance lower than that of the another via hole conductors.  
       [0019] According to the above structure, since the electrode pattern of each layer in the multilayer substrate is connected by the via hole conductor, the non-reciprocal circuit element can be manufactured while the substrate is formed and its mass production property is considerably improved as compared with a case where a side electrode is separately formed. Furthermore, at this time, since the via hole conductor connected to the other ends of the center electrodes has electric resistance lower than that of other via hole conductors, there can be provided a non-reciprocal circuit element in which earth impedance is reduced and electric properties are excellent as compared with a case where uniform connections are made by via hole conductors having the same conductivity.  
       [0020] Furthermore, it is preferable that the via hole conductors connected to on one end of the center electrodes have a total sectional area larger than that of the via hole conductors connected to the other end of the center electrodes or the via hole conductors connected to other electrode patterns in the multilayer substrate.  
       [0021] According to the thus non-reciprocal circuit element, since the via hole conductor having electric resistance lower than that of the other via hole conductors can be formed with relative ease, its mass production property is considerably improved.  
       [0022] According to still another embodiment of the present invention, there is provided a non-reciprocal circuit element comprising at least three center electrodes superposed and arranged so as to intersect with each other; a capacitor connected to one end of the center electrodes in parallel; the electrical isolation layers arranged between the center electrodes, respectively; a ferrite member arranged adjacent to the center electrodes; a magnet for applying a direct current magnetic field to the ferrite member; a yoke material combined with the ferrite member and the magnet to constitute a magnetic circuit; a multilayer substrate comprising the center electrodes and the electrical isolation layers; and an earth electrode provided on the end surface of the multilayer substrate. Furthermore, the other ends of the center electrodes are extended to the end surface of the multilayer substrate to be connected to the earth electrode.  
       [0023] According to the above structure, since the other ends of the three center electrodes separately formed are connected to the earth electrode on the end surface of the multilayer substrate, there can be provided the non-reciprocal circuit element in which a potential equalization property of each center electrode on the earth side can be improved and electric properties are not deteriorated even if the center electrodes are formed using a multilayer substrate. In addition, there can be provided the non-reciprocal circuit element having small earth impedance.  
       [0024] In addition, it is preferable that the capacitor is formed in the multilayer substrate. Thus, the non-reciprocal circuit element can be further miniaturized.  
       [0025] According to still another embodiment of the present invention, there can be provided a non-reciprocal circuit element comprising at least three center electrodes superposed and arranged so as to intersect with each other; the electrical isolation layers arranged between the center electrodes; a capacitor connected to one end of the center electrodes in parallel; a ferrite member arranged adjacent to the center electrodes; a magnet for applying a direct current magnetic field to the ferrite member; a yoke material combined with the ferrite member and the magnet to constitute a magnetic circuit; and a multilayer substrate comprising the center electrodes and the electrical isolation layers. Still further, the capacitor comprises a pair of counter electrodes arranged on the opposite sides and a dielectric layer sandwiched between the counter electrodes and the capacitor is integrated with the multilayer substrate. One of the counter electrodes is connected to one end of the center electrode and the other counter electrode is exposed on a surface of the multilayer substrate.  
       [0026] According to the above structure, since the electrode of the capacitor on the earth side can be connected to the outer electrode at the earth potential by the shortest distance, earth impedance is reduced. In this case, since the capacitor is composed of a pair of counter electrodes and a dielectric layer, there can be provided a pure capacitive element which does not contain an unnecessary inductance component as compared with a case where the capacitor is formed by a multilayer structure using a plurality of counter electrodes. Thus, there can be provided the non-reciprocal circuit element having the excellent electric properties.  
       [0027] Furthermore, when the capacitor is layered in the multilayer substrate, it is preferable that the dielectric layer is made of a material having dielectric constant higher than that of the electrical isolation layer. Thus, even when the capacitor is formed by a single-layer structure, sufficient capacitive value can be obtained.  
       [0028] In addition, it is preferable that an earth electrode is provided between the layers of the multilayer substrate other than the dielectric layer and this earth electrode is connected to the other ends of the center electrodes. Thus, since there is provided the earth electrode connected to the other ends of the respective center electrodes, a potential equalization property of each center electrode on the earth side can be improved and there can be provided the non-reciprocal circuit element having the further excellent electric properties.  
       [0029] Furthermore, it is preferable to further comprise a surface electrode exposed on a surface of the multilayer substrate and connected to the other ends of the center electrodes and it is preferable that the yoke material is formed of an electroconductive material and the yoke material abuts on the surface electrode to be connected. Thus, by electrically connecting the earth electrode to the yoke material directly, earth impedance of the multilayer substrate can be lowered using low impedance of the yoke material. Consequently, there can be provided the non-reciprocal circuit element having favorable electric properties.  
       [0030] In addition, according to the communication module of the present invention, it is preferable that the multilayer substrate is the main component of the communication circuit module. Thus, since the non-reciprocal circuit element is comprised in the multilayer substrate serving as the main component of the communication circuit module, it becomes less necessary to consider the positional relation with the parts arranged around it. As a result, the non-reciprocal circuit element having excellent electric properties according to the present invention can be taken in the communication circuit module while the effective occupied space is reduced.  
       [0031] In addition, it is preferable that electrode patterns comprising the center electrodes are provided in the multilayer substrate and an electrode thickness of the center electrode is larger than an average value of an electrode thickness of the other electrode patterns provided in the multilayer substrate.  
       [0032] Thus, conductor resistance of the center electrodes at the non-reciprocal circuit element part can be lowered by an additional minimum step. As a result, transmission loss can be reduced and there can be easily provided the communication circuit module comprising the non-reciprocal circuit element having the excellent electric properties.  
       [0033] In addition, when the communication module is formed and parts are mounted on the multilayer substrate, it is preferable that at least one of the parts abuts on the yoke material. Thus, it becomes possible to effectively release the heat of a mounted part to the outside through the yoke material. As a result, highly effective heat releasing structure can be provided without using specific multilayer substrate material or multilayer structure. Consequently, there can be provided the communication circuit module in which the degree of freedom of the circuit structure is high and the degree of integration is also high.  
       [0034] Furthermore, in a case where the part generating heat is a power amplifier, since its heat releasing is very important, the effect according to the present invention is especially prominent.  
       [0035] Still further, in a case where the communication circuit is formed, it is preferable that a plurality of non-reciprocal circuit elements is provided. If so, even if the communication circuit module uses a plurality of frequency bands such as dual band, triple band or the like, it becomes less necessary to consider its positional relation with parts arranged around it. As a result, it becomes possible to take a plurality of non-reciprocal circuit elements in the communication circuit module while effective occupied space is reduced. Consequently, an integrated small multi-band communication circuit module can be provided.  
       [0036] Furthermore, it is preferable that the yoke materials are not separately prepared in the plurality of non-reciprocal circuit elements but a set of yoke materials is shared. Furthermore, it is preferable that a set of magnets is shared.  
       [0037] Thus, since the number of parts can be reduced, there can be provided the multi-band communication circuit module in which the plural circulators, which are excellent in view of mass production property and costs, are comprised.  
       [0038] In addition, it is preferable to provide a cavity for housing one part or all of the ferrite member and the yoke material in the multilayer substrate in such a manner that the surface of the members does not protrude from the multilayer substrate. Alternatively, it is preferable to provide a cavity for housing one part or all of the magnet and the yoke material in the multilayer substrate in such a manner that the surface of the members does not protrude from the multilayer substrate. Thus, since there is no projection which becomes a problem in mounting one surface of the communication circuit module, it can be easily mounted to a circuit substrate such as a mobile phone or the like.  
       [0039] According to the present invention described above, there can be provided the non-reciprocal circuit element which implements miniaturization and mass production without deteriorating the electric characteristic. In addition, there can be provided the communication circuit module provided with the non-reciprocal circuit element in which effective occupied space is reduced without deteriorating the electric characteristic. Furthermore, there can be provided the communication circuit in which heat generated by the mounted parts can be released by a simple method without being subjected to various restraints in the material or configuration of the multilayer substrate.  
       [0040] Furthermore, the electrical isolation layer, according to the present invention, can be composed of a layer such as an electrically insulating layer, a dielectric layer or the like. In addition, according to the present invention, a distance between the ferrite member and the center electrodes is such that both are adjacent. This distance is set such that magnetic influence generated by the magnetic circuit comprising the ferrite member can be fully accepted by the center electrodes. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0041] The objects other than the those of the present invention will become more apparent from the following detailed description of the present invention and clear from the appended claims. Implementation of the present invention will remind those skilled in the art of many benefits which were not referred to in this specification.  
     [0042]FIG. 1 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a first preferred embodiment of the present invention;  
     [0043]FIG. 2 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a variation of the first preferred embodiment of the present invention;  
     [0044]FIG. 3 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a first structure of a second preferred embodiment of the present invention;  
     [0045]FIG. 4 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a second structure of the second preferred embodiment of the present invention;  
     [0046]FIG. 5 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a first variation of the second preferred embodiment of the present invention;  
     [0047]FIG. 6 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a second variation of the second preferred embodiment of the present invention;  
     [0048]FIG. 7 is an exploded perspective view showing a circulator according to a third preferred embodiment of the present invention;  
     [0049]FIG. 8 is a longitudinal sectional view showing the circulator according to the third preferred embodiment of the present invention;  
     [0050]FIG. 9 is an exploded perspective view showing a multilayer substrate constituting the circulator according to the third preferred embodiment of the present invention;  
     [0051]FIGS. 10A to  10 C are plan views showing structures and positions of via hole conductors in a multilayer substrate according to variations of the first to third embodiment of the present invention;  
     [0052]FIG. 11 is an exploded perspective view showing a multilayer substrate constituting a circulator according to a fourth preferred embodiment of the present invention;  
     [0053]FIG. 12 is an exploded perspective view showing a circulator according to a fifth preferred embodiment of the present invention;  
     [0054]FIG. 13 is a longitudinal sectional view showing a circulator according to the fifth preferred embodiment of the present invention;  
     [0055]FIG. 14 is an exploded perspective view showing a multilayer substrate constituting a circulator according to the fifth preferred embodiment of the present invention;  
     [0056]FIG. 15 is an exploded perspective view showing a communication circuit module according to a sixth preferred embodiment of the present invention;  
     [0057]FIG. 16A is a sectional view showing a non-reciprocal circuit element part of a communication circuit module according to a first structure of the sixth preferred embodiment of the present invention;  
     [0058]FIG. 16B is a plan view showing the non-reciprocal circuit element part of the communication circuit module according to the first structure of the sixth preferred embodiment of the present invention;  
     [0059]FIG. 17 is a partially cutaway view in perspective showing a non-reciprocal circuit element part in a multilayer substrate of a communication circuit module according to a first structure of the sixth preferred embodiment of the present invention;  
     [0060]FIG. 18 is an exploded perspective view showing a communication circuit module according to second structure of a sixth preferred embodiment of the present invention;  
     [0061]FIG. 19A is a sectional view showing a non-reciprocal circuit element part of the communication circuit module according to the second structure of the sixth preferred embodiment of the present invention;  
     [0062]FIG. 19B is a plan view showing the non-reciprocal circuit element part of the communication circuit module according to the second structure of the sixth preferred embodiment of the present invention;  
     [0063]FIG. 20 is a partially cutaway view in perspective showing the non-reciprocal circuit element part in a multilayer substrate of the communication circuit module according to the second structure of the sixth preferred embodiment of the present invention;  
     [0064]FIG. 21 is a sectional view showing a multilayer substrate according to a first structure of a seventh preferred embodiment of the present invention;  
     [0065]FIG. 22 is a sectional view showing a multilayer substrate according to a second structure of the seventh preferred embodiment of the present invention;  
     [0066]FIG. 23 is an exploded perspective view showing a communication circuit module according to an eighth preferred embodiment of the present invention;  
     [0067]FIG. 24 is a sectional view showing the communication circuit module according to the eighth preferred embodiment of the present invention;  
     [0068]FIG. 25 is an exploded perspective view showing a communication circuit module according to a ninth preferred embodiment of the present invention;  
     [0069]FIG. 26 is a sectional view showing a non-reciprocal circuit element part of the communication circuit module according to the ninth preferred embodiment of the present invention;  
     [0070]FIG. 27 is an exploded perspective view showing a circulator according to a first conventional example;  
     [0071]FIG. 28 is an exploded perspective view showing a center electrode part of the circulator according to the first conventional example;  
     [0072]FIG. 29 is an exploded perspective view showing the circulator according to the first conventional example;  
     [0073]FIG. 30 is an exploded perspective view showing a multilayer substrate of the circulator according to the first conventional example;  
     [0074]FIG. 31 is an exploded perspective view showing the circulator according to the first conventional example; and  
     [0075]FIG. 32 is an exploded perspective view showing a multilayer substrate of a circulator according to a second conventional example. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0076] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.  
     [0077] (First Embodiment)  
     [0078] According to a first embodiment of the present invention, an example in which only a center electrode part is composed of a multilayer substrate will be described. FIG. 1 illustrates a structure of a multilayer substrate  10  of a circulator according to the first embodiment of the present invention. The structure of the whole circulator is such that a multilayer substrate  265  of a circulator shown in FIG. 29 is replaced with the multilayer substrate  10  shown in FIG. 1. Therefore, detailed description of the structure of the circulator according to this embodiment will be omitted.  
     [0079] Center electrodes  12   a ,  12   b  and  12   c  are elongated rectangular frame-shape in plan view. The center electrodes  12   a  to  12   c  are layered and arranged such that elongated parts in plan view intersect with each other at an angle of 120 degrees . Earth electrodes  13   a  and  13   b  are disposed between the center electrodes  12   a  to  12   c , respectively. Insulating layers α serving as electrical isolation layers are provided between the earth electrodes  13   a  and  13   b  and the center electrodes  12   a  to  12   c . Thus, the center electrodes  12   a  to  12   c , the insulating layers α and earth electrodes  13   a  and  13   b  are laminated. The insulating layers α are disposed at both outer ends of the center electrodes  12   a  and  12   c . As described above, the multilayer substrate  10  is provided.  
     [0080] Terminal electrodes  11   a ,  11   b ,  11   c ,  11   d ,  11   e  and  11   f  for internal connections are disposed on the lower surface of the multilayer substrate  10 . One end of the center electrode  12   a  is connected to the terminal electrode  11   a  through a via hole conductor γ. One end of the central electrode  12   b  is connected to the terminal electrode  11   b  through a via hole conductor γ. One end of the center electrode  12   c  is connected to the terminal electrode  11   c  through the via hole conductor  7 .  
     [0081] The other ends of the center electrodes  12   a  to  12   c  are connected to the earth electrodes  13   a  and  13   b  through the via hole conductors y. The other ends of the center electrodes  12   a  to  12   c  are also connected to the terminal electrodes  11   d  to  11   f , respectively. In the figure, connection points through the via hole conductors γ are conceptually shown by thin broken lines.  
     [0082] According to the structure of the circulator of this embodiment of the present invention,  
     [0083] the earth electrodes  13   a  and  13   b  are disposed between the center electrodes  12   a  to  12   c , and  
     [0084] one end of the center electrodes  12   a  to  12   c  is connected to the earth electrodes  13   a  and  13   b . Thus, a potential equalization property of each of the center electrodes  12   a  to  12   c  on the earth side is improved and an insertion loss characteristic is also improved.  
     [0085] Measured results of the insertion loss characteristics of the circulator according to this embodiment and the conventional circulator comprising the multilayer substrate  265  shown in FIG. 30 are shown in table 1. The measurement was performed under the condition that the center frequency is 1.96 GHz and a device size of the circulator is 3 mm square.  
                       TABLE 1                                   Insertion loss (dB)                                                    Conventional example   0.82           First embodiment   0.54                      
 
     [0086] According to the circulator of this embodiment of the present invention, the potential equalization property of each of the center electrodes  12   a  to  12   c  on the earth side and the insertion loss characteristic is improved as compared to the conventional one.  
     [0087] In addition, although earth electrodes  13   a  and  13   b  are disposed between center electrodes  12   a  and  12   b , and  12   b  and  12   c , respectively, plurality of earth electrodes may be disposed between center electrodes  12   a  to  12   c.    
     [0088] In addition, an electrode pattern and a position of each electrode shown in this embodiment is not limited to the above and any change is possible so long as it is within the scope of the present invention, where by the same effect can be obtained. For example, as shown in FIG. 2, instead of the via hole conductors γ, the electrode patterns of the layers may be connected to each other through an electrode pattern ε formed on the outer surface of the multilayer substrate  20 .  
     [0089] Referring to FIG. 2, terminal electrodes  21   a ,  21   b ,  21   c ,  21   d ,  21   e  and  21   f  for internal connections are provided on the lower surface of the multilayer substrate  20 . One end of the electrodes  21   a  to  21   f  is extended to an edge of the multilayer substrate  20 . One end of the center electrodes  22   a  to  22   c  is connected to the electrodes  21   a  to  21   c  through the electrode patterns ε formed on the outer surface of the multilayer substrate  20 . The other ends of the center electrodes  22   a  to  22   c  are connected to the earth electrodes  23   a  and  23   b  through the electrode patterns ε formed on the outer surface of the multilayer substrate  20 . At the same time, the other ends of the center electrodes  22   a  to  22   c  are connected to the terminal electrodes  21   d  to  21   f , respectively through the electrode pattern ε. In the figure, the connecting points by the electrode patterns ε are conceptually shown by broken lines.  
     [0090] (Second Embodiment)  
     [0091] According to the second embodiment of the present invention, center electrodes and a capacitor part comprises a multilayer substrate. FIG. 3 illustrates a multilayer substrate  30  of a circulator, according to the first structure of the second embodiment of the present invention. FIG. 4 illustrates a structure of a multilayer substrate  40  of a circulator according to the second structure of the second embodiment of the present invention. The structure of the circulator is such that the multilayer substrate  285  of the circulator shown in FIG. 31 described in the conventional example is displaced with the multilayer substrate  30  shown in FIG. 3 or the multilayer substrate  40  of shown in FIG. 4. Therefore, detailed description of the whole circulator will be omitted.  
     [0092] The multilayer substrate  30 , according to the first structure of this embodiment of the present invention, comprises center electrodes  32   a ,  32   b  and  32   c , earth electrodes  33   a  and  33   b , and terminal electrodes  31   a ,  31   b ,  31   c ,  31   d ,  31   e  and  31   f  for internal connections. The structures of the electrodes  32   a  to  32   c ,  33   a ,  33   b , and  31   a  to  31   f  are basically the same as those of the center electrodes  12   a  to  12   c , earth electrodes  13   a  and  13   b , and terminal electrodes  11   a  to  11   f  in the first embodiment of the present invention. According to the multilayer substrate  30 , an earth electrode  33   c  is provided outside of the center electrode  32   a  with the insulating layer α disposed therebetween. Counter electrodes  36   a ,  36   b  and  36   c  for forming a capacitor are provided between the earth electrode  33   c  and the terminal electrodes  31   a  to  31   f . The counter electrodes  36   a  to  36   c  are opposed to the earth electrode  33   c  through a dielectric layer β. In this case, a capacitor is composed of the earth electrode  33   c , the counter electrodes  36   a  to  36   c  and the dielectric layer β disposed between them.  
     [0093] One end of the center electrode  32   a  is connected to the electrode  36   a  and  31   a  through a via hole conductor γ. One end of the center electrode  32   b  is connected to the electrodes  36   b  and  31   b  through the via hole conductor γ. One end of the center electrode  32   c  is connected to the electrodes  36   c  and  31   c  through the via hole conductor γ.  
     [0094] Other ends of the center electrodes  32   a  to  32   c  are connected to the earth electrodes  33   a  to  33   c  through the via hole conductors γ. In addition, the center electrode  32   a  is, on one end, connected to electrode  31   e  through the via hole conductor γ. The center electrode  32   b  is, on the other end, connected to the electrode  31   f  through the via hole conductor γ. In the figure, the connecting points by the via hole conductors γ are conceptually shown by thin broken lines.  
     [0095] As shown in FIG. 4, the multilayer substrate  40 , according to the second structure of this embodiment of the present invention, has basically the same structure as that of the multilayer substrate  30 , according to the first structure. Then, in FIG. 4, the parts corresponding to the parts allotted by reference numerals in the  30   s  in the multilayer substrate  30  are allotted by reference numerals in the  40   s  and thus, reference numerals in single figure and alphabets allotted at the end of the numerals which are allotted to parts of the multilayer substrate  40  (FIG. 4) are common to those of the multilayer substrate  30  (FIG. 3).  
     [0096] The multilayer substrate  40  further comprises another earth electrode  43   d . The earth electrode  43   d  is provided as an upper layer of the center electrode  43   b  which is the uppermost layer with the insulating layer α disposed therebetween. The earth electrode  43   d  is connected to other earth electrodes  43   a  to  43   c  through the via hole conductors γ. The earth electrode  43   d  is connected to the other ends of the center electrodes  42   a  to  42   c  through the via hole conductors γ. In the figure, connections through the via hole conductors y are conceptually shown by thin broken lines.  
     [0097] According to the circulator of this embodiment of the present invention,  
     [0098] the earth electrodes  33   a ,  33   b ,  43   a  and  43   b  are disposed between the center electrodes  32   a  to  32   c , and  42   a  to  42   c , respectively, and  
     [0099] one end of the center electrodes  32   a  to  32   c  and  42   a  to  42   c  is connected to the earth electrodes  33   a  to  33   c , and  43   a  to  43   d , respectively. Thus, potential equalization property of each of the via hole conductors electrodes  32   a  to  32   c  and  42   a  to  42   c  on the earth side is improved and the insertion loss characteristic is improved.  
     [0100] Measured results of the insertion loss characteristics of the circulator, according to this embodiment and the conventional circulator shown in FIG. 31, are shown in a table 2. The measurement was performed under the condition that the center frequency is 1.96 GHz and a device size of the circulator is 3 mm square.  
                       TABLE 2                                   Insertion loss (dB)                                                    Conventional example   0.91           First structure of   0.65           second embodiment           Second structure of   0.59           second embodiment                      
 
     [0101] According to the circulator of this embodiment of the present invention, the potential equalization property of each of the center electrodes  32   a  to  32   c  and  42   a  to  42   c  on the earth side and the insertion loss characteristic are improved. In addition, as shown in the multilayer substrate  40 , in a case where the earth electrode  43   d  which is not a counter electrode for forming the capacitor is further provided between layers other than the layers in which the center electrodes  42   a  to  42   c  are formed, a further preferable effect can be obtained.  
     [0102] Furthermore, although each of the earth electrodes  33   a  to  33   c  and  43   a  to  43   c  is disposed between center electrodes  32   a  to  32   c , and  42   a  to  42   c , respectively, a plurality of earth electrodes may be disposed between center electrodes  32   a  to  32   c  and  42   a  to  42   c.    
     [0103] In addition, a plurality of earth electrodes may be disposed between layers other than layers in which the center electrodes are formed and a plurality of earth electrodes may be disposed at a place other than the dielectric layer β in which a capacitor is formed.  
     [0104] An electrode pattern and a position of each electrode shown in this embodiment is not limited to the above and any change is possible so long as it is within the scope of the present invention, whereby the same effect can be obtained.  
     [0105] For example, as shown by the multilayer substrate  50  in FIG. 5, the counter electrodes  56   a ,  56   b  and  56   c  for forming the capacitor may be disposed above the center electrode  52   c  of the uppermost layer. In addition, as shown by the multilayer substrate  60  in FIG. 6, a plurality of sets of counter electrodes for forming the capacitor (two sets of counter electrodes  66   a  to  66   c  and  67   a  to  67   c  in FIG. 6) is provided and those counter electrodes are opposed to the earth electrodes  63   c  and  63   d  across the dielectric layer β in the thickness direction of the multilayer substrate  60 . Thus, the capacitors may be formed.  
     [0106] More specifically, according to the multilayer substrate  60  shown in FIG. 6, the counter electrodes  66   a  to  66   c  and the earth electrode  63   c  form a first capacitor, the counter electrodes  66   a  to  66   c  and the earth electrode  63   d  form a second capacitor and the counter electrodes  67   a  to  67   c  and the earth electrode  63   d  form a third capacitor.  
     [0107] In addition, according to the multilayer substrate  60  shown in FIG. 6, although a large capacity can be formed, since the capacitors are layered, unnecessary inductance component could be generated at the capacitors. Therefore, if priority is given to suppression of the unnecessary inductance, it is preferable that the capacitor is of a single-layer structure as shown in FIGS.  3  to  5 . However, in that structure, the capacitor capacity sometimes comes short depending on the center frequency and an element size of a non-reciprocal circuit element to be formed. In this case, the dielectric layer β disposed between layers in which the capacitor is formed is to be formed of a material having dielectric constant higher than electrical isolation layers (insulating layers) between other layers. Thus, sufficient capacity can be obtained.  
     [0108] (Third Embodiment)  
     [0109] According to a third embodiment of the present invention, earth impedance in a multilayer substrate is reduced by using low impedance of a yoke material. A circulator, according to the third embodiment of the present invention, is shown in FIGS.  7  to  9 .  
     [0110] A structure of the circulator shown in FIG. 7 is basically the same as that of the circulator described in FIG. 27. FIG. 8 is a longitudinal sectional view of the circulator shown in FIG. 7.  
     [0111] An input-output terminal part  77  is housed in a yoke material  78 . A circular hole H is formed in the center of the input-output terminal part  77 . A circular ferrite member  2  is housed in the hole H. A multilayer substrate  75  is set on the input-output terminal part  77 . A magnet  3  is set on the multilayer substrate  75 . In this state, a yoke material  4  is mounted on the yoke material  78 . The input-output terminal part  77 , the ferrite member  2 , the multilayer substrate  75  and the magnet  3  are housed inside the integrated yoke materials  78  and  4 .  
     [0112] The structure of the multilayer substrate  75  will be described with reference to FIG. 9. The multilayer substrate  75  has the same structure as that of the multilayer substrate  30 , according to the second embodiment, which was described with reference to FIG. 3. Then, in FIG. 9, the parts corresponding to the parts allotted to reference numerals in the  30   s  in the multilayer substrate  30  are allotted by reference numerals in the  90   s  and thus, reference numerals in single figure and alphabets allotted at the end of the numerals which are allotted to parts of the multilayer substrate  75  (FIG. 9) are common to those of the multilayer substrate  30  (FIG. 3).  
     [0113] The multilayer substrate  75  is different from the multilayer substrate  30 , according to the second embodiment of the present invention, in that an electrode  94  for connecting the yoke material is disposed on the upper surface of the multilayer substrate  75 . The electrode  94  is connected to other ends of the center electrodes  92   a ,  92   b  and  92   c  through via hole conductors γ.  
     [0114] The multilayer substrate  75  thus structured is connected to the input-output terminal part  77  as shown in FIG. 7. The input-output terminal part  77  is configured so that input-output terminals  77   a ,  77   b  and  77   c  are housed in a resin structure body. The input-output terminal part  77  has input-output terminals  77   a  to  77   c  connected to outer circuits (not shown). The input-output terminals  77   a  to  77   c  are housed in the resin structure body by insert molding. The input-output terminal  77   c  is not shown in FIG. 7 because it is positioned at a hidden part. Input-output electrodes  76   a ,  76   b ,  76   c ,  76   d ,  76   e  and  76   f  are provided on the upper surface of the input-output terminal part  77  in the figure. The input-output electrodes  76   a  to  76   c  are extended in the input-output terminal part  77  to be connected to the input-output terminals  77   a  to  77   c , respectively. The input-output electrodes  76   d  to  76   f  are extended to the lower surface of the input-output terminal part  77  to be connected to the yoke material  78 .  
     [0115] Terminal electrodes  91   a  to  91   f  for internal connections disposed on the lower surface of the multilayer substrate  75  in the figure are connected to the input-output electrodes  76   a  to  76   f . The yoke material  78  comprises a body part  78   a  and bent parts  78   b . The body part  78   a  has a flat-plate structure. The bent parts  78   b  are bent from both ends of the body part  78   a  at an almost 90 degrees angle. Projections  78   h  and  78   i  are provided at ends of the bent parts  78   b . As shown in FIGS. 7 and 8, the projections  78   h  and  78   i  are bent on the upper surface of the multilayer substrate  75  after the input-output terminal part  77 , the ferrite member  2  and the multilayer substrate  75  were housed in the yoke material  78 . The bent projections  78   h  and  78   i  are connected to the electrode  94  for connecting the yoke material formed on the multilayer substrate  75 .  
     [0116] According to the circulator of this embodiment of the present invention,  
     [0117] the earth electrodes  93   a  and  93   b  are disposed between the center electrodes  92   a  to  92   c,    
     [0118] On one end, the center electrodes  92   a  to  92   c  are connected to the earth electrodes  93   a  and  93   b , and  
     [0119] The electrode  94  (connected to the earth electrodes  93   a  to  93   c ) for connecting the yoke material provided on the surface of the multilayer substrate  75  is directly connected to the yoke material  78 .  
     [0120] Thus, a potential equalization property of each of the center electrodes  92   a  to  92   c  on the earth side is improved and the insertion loss characteristic is improved. Furthermore, earth impedance in the multilayer substrate  75  is reduced by using low impedance of the yoke materials  4  and  78 , so that the insertion loss characteristic can be improved.  
     [0121] Measured results of the insertion loss characteristics of the circulator, according to this embodiment, and the circulator, according to the second embodiment, are shown in a table 3. The measurement was performed under the condition that the center frequency is 1.96 GHz and a device size of the circulator is 3 mm square.  
                       TABLE 3                                   Insertion loss (dB)                                                    First structure of   0.65           second embodiment           Third embodiment   0.58                      
 
     [0122] According to the circulator of this embodiment of the present invention, since the electrode  94  (connected to the earth electrodes  93   a  to  93   c ) for connecting the yoke material provided on the surface of the multilayer substrate  75  is directly connected to the yoke material  78 , the earth impedance in the multilayer substrate  75  is further reduced as compared to the case, according to the second embodiment, so that the insertion loss characteristic is further improved.  
     [0123] In addition, the connection structure between the yoke materials  4  and  78 , and the earth electrodes of the multilayer substrate  75  is not limited to that in this embodiment and the same effect can be provided so long as the earth electrodes  93   a  to  93   c  of the multilayer substrate  75  are directly connected to either upper or lower yoke material  4  or  78 .  
     [0124] The aforementioned embodiments  1  to  3  are further preferably configured as follows. According to the embodiments 1 to 3, there are the following via hole conductors γ.  
     [0125] via hole conductor γ connected to an earth electrode connection end (one end) of the center electrode (hereinafter, it is referred to as a first via hole conductor γ)  
     [0126] via hole conductor γ connected to another electrode pattern in the multilayer substrate other than the earth electrode connection end (one end) of the center electrode (hereinafter, it is referred to as a second via hole conductor γ)  
     [0127] via hole conductor connected to a capacitor connection end (one end) of the center electrode other than the earth electrode connection end (the other end) of the center electrode (hereinafter, it is referred to as a third via hole conductor γ)  
     [0128] According to the above via hole conductors γ, the electric resistance of the first via hole conductor γ is preferably made lower than that of the second and third via hole conductors γ. For example, the electric resistance of the first via hole conductor γ can be lowered by increasing the total sectional area of that via hole conductor γ. In addition, the electric resistance can be lowered by adjusting conductor material of the first via hole conductor γ. Thus, the earth impedance in the multilayer substrate can be reduced.  
     [0129]FIG. 10A illustrates structures and positions of the via hole conductors γ, according to the first to third embodiments of the present invention. FIG. 10B illustrates structures and positions of the via hole conductors γ, according to the first improved example. FIG. 10C illustrates configurations and positions of the via hole conductors γ according to the second improved example. These figures are sectional views taken along the plane direction of the multilayer substrate. All of the electrode patterns shown in FIG. 3 are employed for the electrode patterns in the multilayer substrate connected to the via hole conductors γ. As the structure of the whole circulator, the structure of the circulator shown in FIG. 31 which was described in the prior art is employed. Referring to FIGS. 10A to  10 C, reference numerals ( 101   a ,  101   b  and  101   c ), ( 102   a ,  102   b  and  102   c ) and ( 103   a ,  103   b  and  103   c ) designate the second and third via hole conductors γ which are connected to the terminal electrodes  31   a ,  31   b  and  31   c  for internal connections in FIG. 3, but not connected to the earth electrodes. Reference numerals ( 101   d ,  101   e  and  101   f ) , ( 102   d ,  102   e  and  101   f ) and ( 103   d ,  103   e  and  103   f ) designate the first via hole conductors γ which are connected to the earth electrodes.  
     [0130] According to FIG. 10A, all of the via hole conductors γ  101   a  to  101   f  have the same diameter and individually are formed.  
     [0131] According to the first improved example shown in FIG. 10B,  
     [0132] the second and third via hole conductors  102   a  to  102   c  have the same diameter as that of the second and third via hole conductors  101   a  to  101   c  shown in FIG. 10A.  
     [0133] the first via hole conductors  102   d  to  102   f  have a diameter larger (twice the size in this example) than that of the first via hole conductors  101   d  to  101   f  shown in FIG. 10A and are individually formed.  
     [0134] According to the second improved example shown in FIG. 10C,  
     [0135] all of the via hole conductors  103   a  to  103   f  have the same diameter,  
     [0136] the second and third via hole conductors  103   a  to  103   c  are individually formed, and  
     [0137] first via hole conductors  103   d  to  103   f  are each composed of three via hole conductors.  
     [0138] In addition, the electrode patterns shown in FIG. 3 correspond to configurations and positions of the via hole conductors  101   a  to  101   f  shown in FIG. 10A. In the structure shown in FIG. 3, if the structure of the via hole conductors in the first and second improved examples shown in FIGS. 10B and 10C is employed, it is necessary to change the configurations of the electrode patterns of the multilayer substrate connected to the via hole conductors according to the change of the configurations of the via hole conductors.  
     [0139] According to the circulator using the first and second improved example of the via hole conductors, the total sectional area of the via hole conductors connected to the earth electrodes and its electric resistance are low, earth impedance in the multilayer substrate is reduced and the insertion loss characteristic is improved as compared to the circulator which does not employ these improved examples.  
     [0140] Measured results of the insertion loss characteristics of the circulator in which the first and second improved examples of the via hole conductors are employed in the first structure of the second embodiment are shown in table 4. The measurement was performed under the condition that the center frequency is 1.96 GHz and a device size of the circulator is 3 mm square.  
                       TABLE 4                                   Insertion loss (dB)                                                    First structure of   0.65           second embodiment           First improved example   0.54           of first to third           embodiments           Second improved example   0.57           of first to third           embodiments                      
 
     [0141] According to the circulator which employed the first and second improved examples of the via hole conductors, earth impedance in the multilayer substrate is reduced and its insertion loss characteristic is improved as compared to the circulator which did not employ these improved examples.  
     [0142] In addition, according to the structure in the first improved example, although it is thought that the same improved characteristic effect can be obtained even when the diameters of all of the via hole conductors  101   a  to  101   f  are increased under a condition that the diameters are the same, the following inconvenience will arise.  
     [0143] The total sectional area of via hole conductors y occupying the element sectional area is increased and a crack is likely to be generated in the substrate as a matter of processing concerned.  
     [0144] The total sectional area of via hole conductors y on the side connected to the input-output terminals is increased and unnecessary capacity is likely to superimpose on a transmission line as a matter of circuit concerned.  
     [0145] In view of the above problems, it is preferable to employ the first improved example (the total sectional area of the via hole conductors γ on the side where the earth electrodes are connected is increased).  
     [0146] Furthermore, the first and second improved examples of the via hole conductors γ are implemented not only in the circulators described in the above first to third embodiments of the present invention, but also in the conventional structure in which there is no earth electrode between layers of the center electrodes, and the same effect can be provided.  
     [0147] The structures, according to the above first and second improved examples, are not limited to the above and the same effect can be obtained so long as it is within the scope of the present invention. In addition, the first via hole conductor γ may be formed of a conductor material having electric conductivity higher than that of the conductor material of the second and third via hole conductors γ under the condition that the total sectional area of via hole conductors γ is the same.  
     [0148] (Fourth Embodiment)  
     [0149] A fourth embodiment of the present invention refers to a non-reciprocal circuit element in which the ends on the earth side (the other ends) of the center electrode are extended to the end surface of the multilayer substrate and connected to earth electrodes formed on the end surface of the multilayer substrate. FIG. 11 illustrates the structure of a multilayer substrate  110  of a circulator according to the fourth embodiment of the present invention.  
     [0150] Since the whole structure of the circulator is the same as that of the circulator shown in FIG. 29, its detailed description will be omitted.  
     [0151] The multilayer substrate  110  comprises center electrodes  112   a ,  112   b  and  112   c  each having elongated rectangular frame shape in plan view. The center electrodes  112   a  to  112   c  are arranged and layered so that longitudinal parts intersect with each other at an angle of 120 degrees in plan view. The center electrodes  112   a  to  112   c  are layered through insulating layers α, respectively.  
     [0152] Terminal electrodes  111   a ,  111   b ,  111   c ,  111   d ,  111   e  and  111   f  for internal connections are disposed on a lower surface of the multilayer substrate  110 . Among the above electrodes, one end of the electrodes  111   d  to  111   f  is extended to the end surface of the multilayer substrate  110 .  
     [0153] One end of the center electrodes  112   a  to  112   c  is connected to the terminal electrodes  111   a  to  111   c  through via hole conductors γ. The other ends of the center electrodes  112   a  to  112   c  are extended to the end surface of the multilayer substrate  110 . Earth electrodes  113   a ,  113   b ,  113   c  and  113   d  are formed on the whole of the four end surfaces except for the upper and lower surfaces of the multilayer substrate  110 . The other ends of the center electrodes  112   a  to  112   c  are connected to the earth electrodes  113   a  to  113   d . The center electrodes  112   a  to  112   c  are connected to the terminal electrodes  111   d  to  111   f  for internal connections through the earth electrodes  113   a  to  113   d . In the figure, the connections through the via hole conductors γ are conceptually shown by thin broken lines.  
     [0154] According to the circulator of this embodiment of the present invention,  
     [0155] the other ends of the three center electrodes  112   a  to  112   c  formed on separate layers are connected to the earth electrodes  113   a  to  113   d  formed on the end surfaces of the multilayer substrate  110 .  
     [0156] Thus, potential equalization property of the center electrodes  112   a  to  112   c  on the earth side is improved and its insertion loss characteristic can be improved.  
     [0157] Measured results of the insertion loss characteristics in the circulator, according to this embodiment and the conventional circulator shown in FIG. 29, are shown in a table  5 . The measurement was performed under the condition that the center frequency is 1.96 GHz and a device size of the circulator is 3 mm square.  
                       TABLE 5                                   Insertion loss (dB)                                                    Conventional example   0.82           Fourth embodiment   0.70                      
 
     [0158] According to the circulator of this embodiment of the present invention, the potential equalization property of each of the center electrodes on the earth side and the insertion loss characteristic are improved.  
     [0159] In addition, the electrode pattern and position of each electrode shown in the above embodiments are not limited to the above, and it is changeable so long as it is within the scope of the present invention, so that the same effect can be obtained. For example, these embodiments can be applied to a structure in which the capacitor described with reference to FIG. 31 in the prior art is integrated in the multilayer substrate.  
     [0160] (Fifth Embodiment)  
     [0161] A fifth embodiment of the present invention refers to a non-reciprocal circuit element in which  
     [0162] center electrodes and a capacitor part are composed of a multilayer substrate,  
     [0163] a capacitor is composed of a pair of counter electrodes opposed to each other across the dielectric layer β, and  
     [0164] the counter electrode on the earth side of the counter electrodes is exposed on the surface of the multilayer substrate.  
     [0165] Structure of a circulator will be described with reference to FIGS.  12  to  14 .  
     [0166] In a multilayer substrate  125 , the center electrodes and the capacitor part are formed. The multilayer substrate  125  comprises a terminal part for outer connections and an input-output terminal part. As shown by a sectional view in FIG. 13, cavities  129  and  130  are formed on the lower surface of the multilayer substrate  125  in the figure. The cavity  129  houses a ferrite member  122 . The cavity  130  houses a yoke material  128 . Since the ferrite member  122  and the yoke material  128  are housed in the cavities  129  and  130 , respectively, the outer connection terminals provided on the lower surface of the multilayer substrate  125  in the figure abut on a mounted surface of the element.  
     [0167] The structure of the multilayer substrate  125  is shown in FIG. 14. The multilayer substrate  125  comprises center electrodes  142   a ,  142   b  and  142   c . The center electrodes  142   a  to  142   c  are layered so that their longitudinal parts intersect with each other at an angle of 120 degrees with an insulating layer α disposed therebetween. Electrodes  146   a ,  146   b  and  146   c  for forming a capacitor are disposed so as to be opposite the center electrode  142   a  across the insulating layer α in between. The earth electrode  143  is disposed so as to be opposed to counter electrodes  146   a  to  146   c  with a dielectric layer β disposed therebetween. Terminal electrodes  141   a ,  141   b ,  141   c ,  141   d ,  141   e  and  141   f  for outer connections are disposed so as to be opposite both ends of the earth electrode  143  in the plane direction with the insulating layer α disposed therebetween. The center of the earth electrode  143  in the plane direction is exposed on the lower surface of the multilayer substrate  125  in the figure. Since the insulating layer α and the electrodes  141   a  to  141   f  are provided only both ends of the earth electrode  143 , a cavity  130  is formed at the center (the exposed part of the earth electrode  143 ) of the lower surface of the multilayer substrate  125  in the figure. A yoke material  128  is housed in the cavity  130 . The housed yoke material  128  abuts on the earth electrode  143  so as to be connected.  
     [0168] One end of the center electrodes  142   a  to  142   c  is connected to counter electrodes  146   a ,  146   b  and  146   c  for forming the capacitor, and the terminal electrodes  141   a ,  141   b  and  141   c  through electrode patterns ε formed on the side surface of the multilayer substrate  125 . The electrodes  146   a  to  146   c  and the electrodes  141   a  to  141   c  are connected in such a manner that ones on the same position in the lateral direction are connected to each other through the electrode patterns ε on the side surface of the multilayer substrate  125 . Referring to FIG. 14, the same alphabets are allotted to the end of the reference numerals for the electrodes  146   a  to  146   c  and the electrodes  141   a  to  141   c  to be connected to each other.  
     [0169] The other ends of the center electrodes  142   a  to  142   c  are connected to the earth electrode  143  through the electrode patterns ε formed on the side surface of the multilayer substrate  125 . At the same time, the other ends of the center electrodes  142   a  to  142   c  are connected to the terminal electrodes  141   d  to  141   f  for outer connections through the electrode patterns ε.  
     [0170] An opening  148  for forming a cavity  129  is provided in each layer under the center electrode  142   a . In FIG. 14, the electrode patterns ε for connections are conceptually shown by broken lines.  
     [0171] According to the circulator of this embodiment of the present invention,  
     [0172] electrodes of the capacitor on the earth side, which are exposed on the multilayer substrate surface are grounded by using low impedance of the yoke material.  
     [0173] Thus, earth impedance in the multilayer substrate  125  is reduced and its insertion loss characteristic can be improved.  
     [0174] Measured results of insertion loss characteristics in the circulator according to this embodiment and the conventional circulator shown in FIG. 31 are shown in table 6. The measurement was performed under the condition that the center frequency is 1.96 GHz and a device size of the circulator is 3 mm square.  
                       TABLE 6                                   Insertion loss (dB)                                                    Conventional example   0.91           Fifth embodiment   0.73                      
 
     [0175] According to the circulator of this embodiment of the present invention, the earth impedance in the multilayer substrate is reduced and its insertion loss characteristic is improved.  
     [0176] In addition, the electrode pattern and position of each electrode shown in the above embodiments is not limited to the above, and it is changeable so long as it is within the scope of the present invention, so that the same effect can be obtained.  
     [0177] In the above first to fifth embodiments of the present invention, the present invention was described using the circulator in which a center frequency is 1.96 GHz and a device size is 3 mm square as a typical non-reciprocal circuit element. However, the present invention can be effective to another circulator having a different center frequency and device size. In addition, the present invention has the same effect in an isolator in which one of input-output terminals is ended by a resistor. Furthermore, the present invention can be implemented for components of the non-reciprocal circuit element other than the multilayer substrate without any particular limitation.  
     [0178] (Sixth Embodiment)  
     [0179] A sixth embodiment of the present invention refers to a communication circuit module provided with a non-reciprocal circuit element. In general, the communication circuit module is composed by integrating at least two or more devices and a circuit element in a multilayer substrate, which constitutes a wireless part of a mobile communication device.  
     [0180] As examples of such a device, there are a duplexer, an LPF (Low Pass Filter), a BPF (Band Pass Filter), a switch, a PA (Power Amplifier) and the like. As a circuit element, there are a capacitor, an inductor, a resistor and the like.  
     [0181] In recent years, since circuit parts have been increasingly made IC-compatible, some communication circuit modules have the following structures. According to this kind of communication circuit module, land pattern for mounting IC or the like is provided on a mounting substrate surface. The IC is mounted on the land pattern and an IC mounted surface is resin-molded and packaged.  
     [0182] In the following description, a structure of the communication circuit module other than a part comprising a non-reciprocal circuit element is not referred to because it does not have an effect on the present invention.  
     [0183] A first structure of this embodiment will be described with reference to FIGS.  15  to  17 . Referring to FIG. 15, center electrodes and a capacitor part of a circulator are formed in a multilayer substrate  155 . The multilayer substrate  155  also functions as the main component of the whole communication circuit module. Parts such as various kinds of chips are mounted on the surface of the multilayer substrate  155  and circuit elements are built in it. A sectional view of an essential part of the communication circuit module in which the circulator is composed is shown in FIG. 16A and its back side view is shown in FIG. 16B.  
     [0184] A cavity  156  for housing a discoid ferrite member  152 , and a cavity  157  for receiving a yoke material  158  are provided in the multilayer substrate  155 . The cavity  156  has a size for housing the ferrite member  152  and it is formed on one side of the multilayer substrate  155 .  
     [0185] The yoke material  158  comprises a flat-plate body part  158   a  and bent parts  158   b . The bent parts  158   b  are bent from both ends of the body part  158   a  at an almost 90 degrees angle and have a length dimension such that the multilayer substrate  155  can be fit in the thickness direction.  
     [0186] The cavity  157  is provided on one side of the multilayer substrate  155  and comprises a groove part  157   a  cutting across the cavity  156  and through holes  157   b  are provided on both ends of the groove part  157   a  and piercing the multilayer substrate  155 . The groove part  157   a  has the same depth as the thickness of the yoke material  158  and horizontal and vertical dimensions such that the body  158   a  of the yoke material  158  can be housed.  
     [0187] The through hole  157   b  has a size such that the bent part  158   b  of the yoke member  158  can pass through it. The distance between the both through holes  157   b  and  157   b  is set so as to be the same as the distance between the bent parts  158   b.    
     [0188] In a state in which the ferrite member  152  is housed in the cavity  156 , the yoke material  158  is housed in the cavity  157 . In this state, the yoke material  158  is mounted in the cavity  157 . More specifically, the bent parts  158   b  are inserted into the through holes  157   b  and the body  158   a  is housed in the groove part  157   a . A depth dimension provided by adding up the depth dimension of the cavity  156  and the depth dimension of the groove part  157   a  are set so as to be the same as or a little bigger than a thickness dimension provided by adding up the thickness dimension of the ferrite member  152  and the thickness dimension of the yoke material  158 . As a result, in a state where the ferrite member  152  and the yoke material  158  are housed in the multilayer substrate  155 , the yoke material  158  will not protrude from the surface of the multilayer substrate  155 .  
     [0189] Meanwhile, a magnet  153  is disposed on a surface of the multilayer substrate  155  opposite to the surface in which cavities are formed. The magnet  153  is disposed so as to be opposite to the ferrite member  152  across the multilayer substrate  155 . A yoke material  154  is disposed so as to cover the magnet  153  on the multilayer substrate  155 . The edge of the bent part  158   b  of the yoke material  158  which passed through the through hole  157   b  is engaged with the yoke material  154 .  
     [0190] According to the thus-formed communication circuit module, the surface (corresponding to the surface in which cavities are formed) on which the module is mounted on another member becomes the same surface. This is because the ferrite member  152  and the yoke material  158  are housed in the cavity  156  and the cavity  157  so that the yoke material  158  does not protrude from the module mounting surface.  
     [0191] A structure of the multilayer substrate  155  is shown in FIG. 17. Center electrodes  172   a ,  172   b  and  172   c  are layered and disposed so that their longitudinal parts intersect with each other at an angle of 120 degrees in a plan view. Earth electrodes  173   a  and  173   b  are disposed between the center electrodes  172   a  to  172   c , one by one. The insulating layers α serving as an electrical isolation layer are disposed between the center electrodes  172   a  to  172   c  and the earth electrodes  173   a  and  173   b.    
     [0192] Counter electrodes  176   a ,  176   b  and  176   c  for forming a capacitor, which are disposed outside of the center electrode  172   a , are disposed at the end. The electrodes  176   a  to  176   c  are arranged on the same plane. The counter electrodes  176   a  to  176   c  located opposite the center electrode  172   a  through the insulating layer α. An earth electrode  173   c  is disposed more outside of the counter electrodes  176   a  to  176   c . The earth electrode  173   c  is disposed so as to be opposite the counter electrodes  176   a  to  176   c  through a dielectric layer β.  
     [0193] An opening  178  for forming the cavity  156  is provided in the dielectric layer β disposed between the counter electrodes  176   a  to  176   c  and the earth electrode  173   c . The insulating layer α is provided outside the multilayer substrate of the earth electrode  173   c . An opening  171  for forming the groove part  157   a  of the cavity  157  is provided in this insulating layer α. The earth electrode  173   c  is exposed on the surface of the multilayer substrate  155  because of the groove part  157   a  formed by the opening  171 . Openings  177  for forming the through holes  157   b  of the cavity  157  is provided in each insulating layer α constituting the multilayer substrate  155 .  
     [0194] One end of the center electrodes  172   a  to  172   c  are connected to the earth electrodes  173   a  to  173   c  through via hole conductors γ. The other ends of the center electrodes  172   a ,  172   b  and  172   c  are connected to the counter electrodes  176   a  to  176   c , respectively through via hole conductors γ. The same alphabets are allotted to the ends of the reference numerals for the center electrodes  172   a  to  172   c  and the counter electrode  176   a  to  176   c  to be connected to each other. In addition, leader lines are connected to the other ends of the center electrodes  172   a  to  172   c  to be connected to predetermined circuits in the communication circuit module.  
     [0195] A second structure according to this embodiment of the present invention is described with reference to FIGS.  18  to  20 . The second structure is basically the same as the aforementioned first structure. In FIGS.  18  to  20  showing the second structure, reference numerals in the  180   s  and  200   s  are allotted. Parts to which reference numerals in the  180   s  are allotted correspond to the parts to which reference numerals in the  150   s  are allotted in the first structure and parts to which reference numerals in the  200   s  are allotted correspond to the parts to which reference numerals in the  170   s  are allotted in the first structure. Here, among corresponding reference numerals, the reference numerals allotted to a single figure and alphabets allotted to the end of the reference numerals are common between the first and second structures.  
     [0196] Referring to FIG. 18, center electrodes of a circulator are formed in a multilayer substrate  185 . The multilayer substrate  185  also functions as the main component of the whole communication circuit module. Parts such as various kinds of chips are mounted on the surface of the multilayer substrate  185  and circuit elements are built in it. A sectional view of an essential part of the communication circuit module in which the circulator is composed is shown in FIG. 19A and its back side view is shown in FIG. 19B.  
     [0197] A cavity  187  for hosing a magnet  183  and a yoke material  184  is provided on one side of the multilayer substrate  185 . The cavity  187  has a size for housing the magnet  183  and the yoke material  184 . The depth dimension of the cavity  187  is the same as or a little bigger than a dimension provided by adding up the thickness dimension of the magnet  183  and the thickness dimension of the yoke material  184 .  
     [0198] The yoke material  184  comprises a flat-plate body part  184   a  and bent parts  184   b . The bent parts  184   b  are bent from both ends of the body part  184   a  at an almost 90 degrees angle and have a length dimension in the thickness direction such that the multilayer substrate  185  can fit in.  
     [0199] The cavity  187  has a body  187   a  and through holes  187   b  provided on both ends of the body  187   a  and piercing the multilayer substrate  185 .  
     [0200] The through hole  187   b  has a size such that the bent part  184   b  of the yoke material  184  can pass through. The distance between the both through holes  187   b  and  187   b  is set so as to be the same as the distance between the bent parts  184   b  and  184   b.    
     [0201] The yoke material  184  is housed in the cavity  187  in a state where the magnet  183  is housed in the body  187   a  of the cavity  187 . More specifically, the bent parts  184   b  are inserted into the through holes  187   b  and the body  184   a  is housed in the body  187   a . The depth dimension of the cavity  187  is set so as to be the same as or a little bigger than a thickness dimension provided by adding up the thickness dimension of the magnet  183  and the thickness dimension of the yoke material  184 . Therefore, in the state where the magnet  183  and the yoke material  184  are housed in the multilayer substrate  185 , the yoke material  184  will not protrude from the surface of the multilayer substrate  185 .  
     [0202] Meanwhile, a ferrite member  182  is disposed on a side surface of the multilayer substrate  185  opposite to the surface in which the cavities are formed. The ferrite member  182  located opposite the magnet  183  across the multilayer substrate  185 . A yoke material  188  is provided so as to cover the ferrite member  182  on the multilayer substrate  185 . The edges of the bent parts  184   b  of the yoke material  184  which pierced the through holes  187   b  are engaged with the yoke material  188 .  
     [0203] According to the thus-formed communication circuit module, the surface (corresponding to the surface in which cavities are formed) on which the module is to be mounted on another member becomes the same surface. This is because the magnet  183  and the yoke material  184  are housed in the cavity  187  and the yoke material  184  does not protrude from the module mounting surface.  
     [0204] A structure of the multilayer substrate  185  is shown in FIG. 20. Center electrodes  202   a ,  202   b  and  202   c  are layered and disposed so that their longitudinal parts intersect with each other at an angle of 120 degrees in a plan view. Electrodes  203   a  and  203   b  are disposed between the center electrodes  202   a  to  202   c , one by one. The insulating layers are disposed between the center electrodes  202   a  to  202   c  and the earth electrodes  203   a  and  203   b , respectively.  
     [0205] An electrode  204  for connecting the yoke material that is disposed outside of the center electrode  202   c  is disposed at the end. The electrode  204  is disposed so as to be opposite the center electrode  202   c  through the insulating layer a.  
     [0206] The insulating layer α is also provided outside the center electrode  202   a  in the thickness direction of the multilayer substrate. An opening  201  for forming the body  187   a  of the cavity  187  is provided in this insulating layer α. The center electrode  202   a  is exposed on the surface of the multilayer substrate  185  because of the body  187   a  of the cavity  187  formed by the opening  201 . In addition, the insulating layer α may be further provided between the body  187   a  of the cavity  187  and the center electrode  202   a . Openings  207  for forming the through holes  187   b  of the cavity  187  are provided in each insulating layer a constituting the multilayer substrate  185 .  
     [0207] The center electrodes  202   a  to  202   c  are, on one end, connected to the earth electrodes  203   a  and  203   b  and the electrode  204  for connecting the yoke material through via hole conductors γ. The center electrodes  202   a  and  202   b  are, on one end, connected by leader lines in parallel to a capacitor (not shown) which is formed in the multilayer substrate  185 . On the other end, the center electrodes  202   a  and  202   b  are connected to leader lines to connect predetermined circuits in the communication circuit module.  
     [0208] The electrode  204  for connecting the yoke material, which is exposed on the surface of the multilayer substrate  185 , is connected to projections  188   h  and  188   i  provided in the yoke material  188 .  
     [0209] According to the first and second structures of this embodiment of the present invention, positions of the ferrite member and the magnet are reversed. Accordingly, the structure of the multilayer substrate and the structures of the cavities provided in the multilayer substrate are a little different.  
     [0210] According to the communication circuit module of this embodiment of the present invention, there is no projection which becomes a problem in view of mounting on a surface of the communication circuit module. More specifically, the yoke material housed in the multilayer substrate and the multilayer substrate are on the same surface. This kind of communication circuit module can be easily mounted onto a circuit substrate such as a mobile phone or the like.  
     [0211] According to the communication circuit module of this embodiment of the present invention, as compared with a case where a circulator is mounted on a substrate as a single part as in the prior art, it is less necessary to consider a positional relation with parts arranged around it. Therefore, the circulator can be taken in the communication circuit module while an effective occupied space is reduced.  
     [0212] According to the communication circuit module of this embodiment of the present invention, since the earth electrode connected to one end of the center electrodes is provided between layers in which the center electrodes of the circulator are formed in the multilayer substrate, non-reciprocal circuit element provided with excellent electric properties can be built in.  
     [0213] (Seventh Embodiment)  
     [0214] A seventh embodiment of the present invention has a feature in a structure of a multilayer substrate. FIG. 21 illustrates a first structure and FIG. 22 illustrates a second structure of this embodiment.  
     [0215] As shown in FIG. 21, according to the first structure of this embodiment of the present invention, the electrode thickness of each electrode pattern  230  on a layer on which the center electrode is formed in a multilayer substrate  232  is set so as to be larger than the electrode thickness of each electrode pattern  231  of another layer. As a result, conductor loss at the center electrode part is reduced and loss at the circulator part can be reduced.  
     [0216] As a method of implementing the above structure,  
     [0217] the electrode patterns  230  on the same plane including the center electrodes are selectively formed by printing several times, or  
     [0218] when the electrode patterns  230  on the same plane including the center electrodes are formed, a mesh of a printing screen or printing conditions are adjusted so that the electrode patterns  230  may be formed thick.  
     [0219] The effect provided by employing the structure in FIG. 21 is favorable regardless of its forming method. According to the second structure of this embodiment, as shown in FIG. 22, only the electrode thickness of the electrode pattern  240  which is the center electrode in the multilayer substrate  242  is set so as to be larger than the electrode thickness of another electrode pattern  241 . In this case, another electrode pattern  241  comprises an electrode pattern formed on the same layer (the same plane position) as the electrode pattern  240 .  
     [0220] As a result, conductor loss at the center electrode part is reduced and loss at the circulator part can be reduced.  
     [0221] As a concrete method of implementing the above structure, there is a method in which only the center electrode part is formed by printing several times. The effect provided by employing the structure in FIG. 22 is good regardless of its forming method.  
     [0222] (Eighth Embodiment)  
     [0223] An eighth embodiment of the present invention refers to a communication circuit module provided with a non-reciprocal circuit element. The communication circuit module of this embodiment will be described with reference to FIGS. 23 and 24.  
     [0224] According to a multilayer substrate  215 , center electrodes and a capacitor part are formed inside it. The multilayer substrate  215  constitutes the main component of the whole communication circuit module. A power amplifier  219  is mounted on the surface of the multilayer substrate  215  in addition to parts such as various chips. Since electrode structures and sectional configuration of the circulator are the same as those in other embodiments, their description will be omitted.  
     [0225] A cavity  216  for housing a discoid ferrite member  212 , and a cavity  217  for receiving a yoke material  218  are provided in the multilayer substrate  215 . The cavity.  216  has a size for housing the ferrite member  212  and it is formed on one side of the multilayer substrate  215 .  
     [0226] The yoke material  218  comprises a flat-plate body part  218   a  and bent parts  218   b . The bent parts  218   b  are bent from both ends of the body part  218   a  at an almost 90 degrees angle and have a length dimension such that the multilayer substrate  215  can be fit in the thickness direction.  
     [0227] The cavity  217  is provided on one side of the multilayer substrate  215  and comprises a groove part  217   a  cutting across the cavity  216  and through holes  217   b  provided on both ends of the groove part  217   a  and piercing the multilayer substrate  215 . The groove part  217   a  has the same depth dimension as the thickness of the yoke material  218  and horizontal and vertical dimensions such that the body  218   a  of the yoke material  218  can be housed.  
     [0228] The through hole  217   b  has a size such that the bent part  218   b  of the yoke member  218  can pass through. The distance between the through holes  217   b  and  217   b  is set so as to be the same as the distance between the bent parts  218   b.    
     [0229] In a state in which the ferrite member  212  is housed in the cavity  216 , the yoke material  218  is housed in the cavity  217 . In this state, the yoke material  218  is mounted in the cavity  217 . More specifically, the bent parts  218   b  are inserted into the through holes  217   b  and the body  218   a  is housed in the groove part  217   a . A depth dimension provided by adding up the depth dimension of the cavity  216  and the depth dimension of the groove part  217   a  is set so as to be the same as or a little bigger than a thickness dimension provided by adding up the thickness dimension of the ferrite member  212  and the thickness dimension of the yoke material  218 . As a result, in a state where the ferrite member  212  and the yoke material  218  are housed in the multilayer substrate  215 , the yoke material  218  will not protrude from the surface of the multilayer substrate  215 .  
     [0230] Meanwhile, a magnet  213  is disposed on a surface of the multilayer substrate  215  opposite to the surface in which cavities are formed. The magnet  213  is disposed so as to be opposite the ferrite member  212  across the multilayer substrate  215 . A yoke material  214  is disposed so as to cover the magnet  213  on the multilayer substrate  215 . The edge of the bent part  218   b  of the yoke material  218  which passed through the through hole  217   b  is engaged with the yoke material  214 .  
     [0231] In the communication circuit module provided with the above basic structure, according to this embodiment of the present invention, a cavity  215 H is provided in the surface of the multilayer substrate  215  on an opposite side of the surface in which the cavities are formed. The cavity  215 H is formed so as to be connected to an open end of one through hole  217   b . The cavity  215 H is disposed on the side opposite to the other through hole  217   b . The cavity  215 H has a size such that an end portion  218   h  of the bent part  218   b  protruding from the one through hole  217   b  can be housed. The depth dimension of the cavity  215 H is set so as to be the same as the thickness dimension of the bent part  218   b.    
     [0232] After the bent part  218   b  was inserted into the through hole  217   b , the yoke material  218  is mounted on the multilayer substrate  215 . In this state, the end portion  218   h  of the one bent part  218   b  is bent toward the side of the cavity  215 H and housed in the cavity  215 H. At this time, the end portion  218   h  and the multilayer substrate  215  are on the same surface. In this state, the power amplifier  219  is mounted on the cavity  215 H. The mounted power amplifier  219  abuts on the end portion  218   h  of the yoke material  218 .  
     [0233] According to the communication circuit module of this embodiment of the present invention, even when there is a part which generates heat such as a power amplifier  219 , the heat of the power amplifier  219  can be effectively released toward the mounted substrate side through the end portion  218   h  of the yoke material  218 . Therefore, favorable heat releasing structure can be implemented without employing a multilayer substrate material having high heat conductivity or using a thermal via. As a result, the degree of freedom of the circuit structure is increased, so that highly integrated communication circuit module can be implemented.  
     [0234] In addition, the contact structure between the yoke material  218  and the mounted heat generating part (power amplifier  219 ) is not limited to the above structure and it can be changed so long as it is within the scope of the present invention and the same effect can be obtained.  
     [0235] (Ninth Embodiment)  
     [0236] A ninth embodiment of the present invention refers to a communication circuit module provided with a non-reciprocal circuit element. This embodiment is described with reference to FIGS. 25 and 26.  
     [0237] The structure of this embodiment is basically the same as that of the sixth and eighth embodiments in the present invention. In FIGS. 25 and 26 showing this embodiment, reference numerals in the  220   s  are allotted. Parts to which reference numerals in the  220   s  are allotted correspond to the parts to which reference numerals in the  150   s  and  180   s  are allotted in the sixth embodiment and parts to which reference numerals in the  210   s  are allotted in the eighth embodiment. Here, among corresponding reference numerals, the reference numerals allotted to a single figure and alphabets allotted to the end of the reference numerals are common between the sixth, eighth and ninth embodiments of the present invention.  
     [0238] The sixth and eighth embodiments refer to a communication circuit module in which a single circulator is built in the multilayer substrates. In this embodiment, however, a plurality of circulators are provided in a multilayer substrate  225 . More specifically, center electrodes and a capacitor part of two circulators having different frequency bands to be used are provided in the multilayer substrate  225 . A pair of cavities  226 A and  226 B for housing the ferrite member  222 A and  222 B, respectively and a cavity  227  for receiving the yoke material  228  are provided in the multilayer substrate  225 . The yoke materials  224  and  228  constituting a magnetic circuit and a magnet  223  which magnetizes the ferrite members  222 A and  222 B are shared by the ferrite members  222 A and  222 B.  
     [0239] The multilayer substrate  225 , which comprises electrode structure including two circulators, is comprised. The electrode structure is the same as that of the multilayer substrate  155  described with reference to FIG. 17 in the sixth embodiment of the present invention. However, in this embodiment, a plurality of electrode structures are comprised in the multilayer substrate  225  in accordance with the number (2) of the circulators.  
     [0240] According to the communication circuit module in this embodiment, the plural circulators which operate in the different frequency band are integrated in one module. Therefore, as compared to a case where a plurality of circulators are mounted respectively as a single part, it is less necessary to consider a positional relation with parts provided around it. As a result, the plural circulators can be taken into the communication circuit module while the effective occupied space is reduced. Consequently, integrated small dual band communication circuit module can be implemented. Since each circulator shares a set of yoke materials  224  and  228  and one magnet  223 , the number of parts can be reduced as compared to the case when these are prepared separately. Consequently, there can be provided a dual band communication circuit module in which the plural circulators are comprised and which is excellent in view of mass production property and costs.  
     [0241] According to the present invention described above, there can be provided a non-reciprocal circuit element which implements miniaturization and mass production without deteriorating the electric characteristic. In addition, there can be provided a communication circuit module provided with the non-reciprocal circuit element in which effective occupied space is reduced without deteriorating the electric characteristic. Furthermore, there can be provided a communication circuit module in which heat generated by the mounted parts can be released by a simple method without being subjected to various restraints in the material or structure of the multilayer substrate.  
     [0242] Although the preferred embodiments of the present invention has been described in detail, it is clearly understood that combinations and arrangements of the parts in the preferred embodiments can be changed within the spirit and scope of the present invention to be claimed hereinafter.