Abstract:
An electronic module, comprising: a dielectric base plate having first and second opposing surfaces on which respective electrodes are disposed such that respective areas at the first and second surfaces are free of electrode material and aligned relative to one another to form a dielectric resonator; a first electronic component coupled to the base plate; and a first circuit sheet having first and second opposing surfaces, at least one aperture between the surfaces, and a conductor pattern disposed on the first surface, the first circuit sheet being disposed on the base plate such that: (i) the first electronic component is at least partially received within the aperture; and (ii) at least part of the conductor pattern is coupled to the dielectric resonator.

Description:
This is a division of application Ser. No. 09/060,190, filed Apr. 14, 1998 now U.S. Pat. No. 6,087,912. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a high frequency electronic part and, in particular, to a high frequency module, such as a voltage control oscillator, a filter, an antenna duplexer, and an antenna module, which is used in the microwave band, the millimeter wave band, etc. 
     2. Description of the Related Art 
     As a result of the recent increase in the demand for mobile communications systems and the increase in the amount of information transmitted, the communication band for mobile communication is being expanded from the microwave band to the millimeter wave band. In constructing a dielectric filter, a voltage control oscillator (hereinafter referred to as “VCO”) or the like is sometimes employed which includes a dielectric resonator (operating in a TE01δ mode) . The resonance frequency of an ordinary TE01 δ mode dielectric resonator is determined by an outer diameter of a cylindrical dielectric member. The coupling of the resonator with a micro strip line or the like is determined by the distance therebetween,. Accordingly, a high level of accuracy in size and positioning is required. 
     In view of this, the present applicant has proposed, in Japanese Patent Application No. JP-A-7-62625, a dielectric resonator and a dielectric filter in which the above problem has been eliminated and which excel in machining accuracy. 
     In the dielectric resonator and the dielectric filter of the above-mentioned patent application, electrodes are formed on both main surfaces of a dielectric plate, whereby part of the dielectric plate is used as a dielectric resonator. In such a dielectric resonator, the electrodes formed on the dielectric plate can be used as a high frequency ground plane, so that, by forming a micro strip line on another dielectric sheet or the like and stacking it together with the dielectric plate, it is possible to form a high frequency module, such as a VCO, including a dielectric resonator and an electronic part. 
     FIG. 9 is a sectional view of an example of the construction of such a high frequency module. In the drawing, numeral  1  indicates a dielectric plate on both main surfaces of which electrodes are formed. Numeral  2  indicates a dielectric sheet, on the upper surface of which wiring patterns  4  and  5  are formed and which has a through-hole th having a land P at a predetermined position. An electronic part in the form of a chip  28 , is mounted on the land P. Wiring patterns  23  and  24  are connected to each other by a bonding wire w. 
     As shown in FIG. 9, by adopting a two-layered structure, composed of the dielectric plate  1  and the dielectric sheet  2 , it is possible to use the electrode  15  on the dielectric plate  1  as a high frequency ground plane, forming the wiring patterns  4  and  5  on the dielectric sheet  2  as a micro strip line. 
     However, when mounting an electronic part, such as an FET, the ground connection of the electronic part is effected through through-hole th shown in FIG. 9, so that the grounding path becomes rather long, which may have an adverse effect on the high frequency characteristics. Further, since an electronic part in the form of a chip is mounted on the land having a through-hole, the structure is rather poor in heat radiation property, so that it cannot be applied to an electronic part in which a great quantity of heat is generated. 
     The above problem exists not only in the case in which a dielectric resonator is formed in a part of the dielectric plate  1 , but is common to cases in which a dielectric sheet or the like is stacked on a base material having a high frequency ground surface to form a high frequency module. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a high frequency module in which the above problems have been eliminated. 
     There is provided, in accordance with the present invention, a high frequency module of the type which is formed by stacking on a base material having a high frequency ground surface a sheet material or a plate material on the surface of which a high frequency circuit is formed and which consists of a dielectric or an insulating material, wherein an electronic part constituting a part of the high frequency circuit, is mounted or formed on the base material, and wherein a hole through which the electronic part is exposed is provided in the sheet material or the plate material, an electrode of the electronic part being electrically connected to a conductor pattern on the sheet material or the plate material by means of a bonding wire through the hole. 
     FIG. 1 is a sectional view showing an example of the above construction. As shown in the drawing, an electronic part  28  is directly mounted on a high frequency ground surface  15  of a dielectric plate  1 , and a dielectric sheet  2  having a hole  11  through which this electronic part  28  is exposed is stacked on the dielectric plate  1 . The electrode of the electronic part  28  and conductor patterns  4  and  5  on the dielectric sheet  2  are connected to each other through bonding wires w. 
     Due to this construction, the electronic part is directly mounted or formed on the base material having a high frequency ground surface, so that the ground connection of the electronic part is reliably effected, and there is no adverse influence on the high frequency characteristics due to the increase in the length of the grounding path. Further, since the heat generated by the electronic part is directly conducted to the base material, a high heat radiation property is obtained, so that it has no adverse influence on the electronic part and the peripheral members. Further, since the electronic part is provided on the base material, it is possible to reduce the height (thickness) of the whole, making it possible to reduce the height of the entire high frequency module. Further, since the electronic part does not protrude from the surface of the dielectric sheet or, if it does, it does so only to a small degree, the electronic part is mechanically protected. 
     Further, in this invention, an electronic part constituting a part of the high frequency circuit is mounted on the base material, and a conductor pattern for connecting the electrode of the electronic part is formed thereon. A conductor pattern electrically connected to the above-mentioned conductor pattern and a through-hole through which the electronic part is inserted is provided in the sheet material or the plate material. 
     Further, in this invention, an electronic part constituting a part of the high frequency circuit is formed on the base material, and a conductor pattern electrically connected to the electrode of the electronic part is provided on the sheet material or the plate material. 
     Further, in this invention, those portions of the base material opposite to each other with the dielectric plate placed therebetween are formed as non-electrode-formation sections, and electrodes are formed on both main surfaces of the dielectric plate to thereby form a dielectric resonator and a ground surface, the high frequency circuit including a conductor pattern connected to the dielectric resonator. 
     In the high frequency module, the electronic part can be directly formed on the base material, so that it is possible to use a sheet material or a plate material on which such an electronic part cannot be directly formed. Further, in the high frequency module, it is possible to easily form a high frequency module including a dielectric resonator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view showing an example of the construction of the high frequency module of this the present invention; 
     FIG. 2 is an exploded perspective view of a part of a VCO according to a first embodiment of this invention; 
     FIG. 3 is a perspective view showing a VCO module; 
     FIG. 4 is a perspective view showing the relationship between a ceramic package and a VCO module; 
     FIG. 5A and 5B are diagrams showing the construction of a dielectric resonator formed on a dielectric plate; 
     FIG. 6 is an exploded perspective view of a VCO module according to a second embodiment of the present invention; 
     FIG. 7 is an exploded perspective view of a part of a high frequency module according to a third embodiment of the present invention; 
     FIG. 8 is an exploded perspective view of a part of a high frequency module according to a fourth embodiment of the present invention; and 
     FIG. 9 is a sectional view showing the construction of a conventional high frequency module. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The construction of a VCO according to a first embodiment of this invention will be described with reference to FIGS. 2 through 5B. 
     FIG. 2 is an exploded perspective view of a part of the VCO. In the drawing, numeral  1  indicates a dielectric plate. On the upper surface of the dielectric plate  1 , there is formed an RF ground  15 , a part of which is formed as a non-electrode-formation section  17 . On the lower side of this dielectric plate  1 , there is formed an RF ground. That portion of this RF ground which is opposite to the non-electrode-formation section  17  is formed as a non-electrode-formation section of the same configuration. An FET  28  and a varactor diode  29  are mounted at predetermined positions of the upper RF ground  15 . Further, a thin-film inductor  30  and a thin-film resistor  31  are formed at predetermined positions of the RF ground  15 . The RF ground  15  is not formed in the regions where the thin-film inductor  30  and the thin-film resistor  31  are formed. 
     In the drawing, numeral  2  indicates a dielectric sheet formed of polytetrafluoroethylene or the like and equipped with four holes  11 ,  12 ,  13  and  14 . Further, there are formed a plurality of through-holes indicated by symbol th, and various conductor patterns are formed on the upper surface of the dielectric sheet  2 . 
     FIG. 3 is a perspective view showing the dielectric plate  1  and the dielectric sheet  2  of FIG. 2 stacked together. As shown in the drawing, the FET  28 , the varactor diode  29 , the thin-film inductor  30  and the thin-film resistor  31  are accommodated in the holes  11 ,  12 ,  13 , and  14  provided in the dielectric sheet  2 . As shown in the partial enlarged view of the drawing, the FET  28  is connected to micro strip lines  24  and  36  and a drain connection electrode  23  through bonding wires W. A similar connection through bonding wires is effected on the varactor diode  29 . The ends of the thin-film inductor  30  and the thin-film resistor  31  are connected to predetermined conductor patterns on the dielectric sheet  2  through electrodes formed in the inner surfaces of the holes  13  and  14  shown in FIG.  2 . 
     The thermal conductivity of the dielectric plate, which is formed of Ba(SnMgTa)O 3 , Ba(MgTa)O 3  or the like, is 2.0 to 5.0 W/(m·K), whereas the thermal conductivity of polytetrafluoroethylene is 0.1 to 0.3 W/(m·K), that is, the former is ten times or more higher than the latter, so that, as compared with the case in which the FET  28  is mounted on the dielectric sheet, the heat radiation property of the FET  28  is substantially improved. 
     FIG. 4 is a perspective view of the VCO module  21  shown in FIG. 3 and a ceramic package  50  for accommodating it before they are assembled. As shown in the drawing, on the upper surface of the dielectric sheet  2 , there are formed a micro strip line  24  constituting the main line and a micro strip line  25  constituting the sub-line such that they overlap the non-electrode-formation section  17  of the RF ground. One end of the micro strip line  24  is connected to a grounding electrode  27  through a resistor layer  26 , and the other end thereof is connected to the gate of the FET through a bonding wire (See FIG.  3 ). One end of the micro strip line  25  is connected to the grounding electrode  27  through the varactor diode  29 , and the other end thereof is a free end. Further, the thin-film inductor  30  is connected to the connection end of the micro strip line  25  corresponding to the varactor diode  29 , and a bias electrode  32  for applying bias voltage is connected to the thin-film inductor  30  through the thin-film resistor  31 . Further, the resistor layer  33  is formed between the bias electrode  32  and the grounding electrode  27 . 
     The drain of the FET  28  is connected to an input electrode  35  through a micro strip line  34 , and the source thereof is connected to one end of a micro strip line  36 . Further, a chip capacitor  40  is connected between the input electrode  35  and the grounding electrode  27 . The micro strip line  34  is equipped with a matching stub  37  which is near the connection point at which it is connected to the drain of the FET  28 . The drain connection electrode  23  is also used as a matching stub. 
     The other end of the micro strip line  36  is connected to the grounding electrode  27  through the resistor layer  38 . Further, another micro strip line  39 , which is at a fixed distance from the micro strip line  36 , is provided, and the end portion thereof is formed as an output electrode  41 . 
     The ceramic package  50  is composed of a first ceramic substrate  51  and a second ceramic substrate  52 . The first ceramic substrate  51  is equipped with a recess  53 , and an external terminal  54  is formed so as to surround the recess  53 . At the bottom of the recess  53 , there is formed a conductor. The VCO module  21  is accommodated in the ceramic package  50 , with the dielectric sheet  2  side facing downward, and the input electrode  35 , the output electrode  41 , the bias electrode  32  and the other grounding electrodes  27  are connected to the external terminal  54 . Then, the whole is sealed by a metal plate (not shown), whereby a surface mounting type VCO is completed. 
     FIG. 5A and 5B include a partial plan view and a partial sectional view showing the construction and resonance mode of a dielectric resonator formed on the dielectric plate. In the drawing, the solid line arrow indicates an electric field distribution, and the dashed lines indicate a magnetic field distribution. In this way, by arranging non-electrode-formation sections  17  and  18  opposite to each other with the dielectric plate  1  being placed therebetween, a TE 010  mode dielectric resonator is formed in that section. The micro strip lines  24  and  25  are magnetic-field-connected to this dielectric resonator. 
     As described above, the main line and the sub-line are connected to the dielectric resonator, and the varactor diode is connected to the end portion of the sub-line, whereby a band reflection type resonator is formed in which one end of the main line constitutes a resistor end, the other end thereof being connected to the FET. 
     Next, the construction of a part of a high frequency module according to a second embodiment of the present invention will be described with reference to FIG.  6 . 
     FIG. 6 is an exploded perspective view of a part of the high frequency module. In the drawing, numeral  1  indicates a dielectric plate, on the upper surface of which there is formed an RF ground  15 , a part of which is formed as a non-electrode-formation section  17 . On the lower side of this dielectric plate  1 , there is formed an RF ground having a non-electrode-formation section opposite to the non-electrode-formation section  17  and of the same configuration therewith. An FET  28  is mounted at a predetermined position of the upper RF ground  15 , and a varactor diode is mounted on the lower RF ground. Further, a thin-film inductor and a thin-film resistor are formed at predetermined positions of the lower RF ground. 
     In the drawing, numerals  2  and  3  indicate dielectric sheets formed of polytetrafluoroethylene or the like and equipped with holes  11 ,  12 ,  13  and  14 . Further, a plurality of through-holes are formed, and various conductor patterns are formed on the upper side of the dielectric sheet  2  and the lower side of the dielectric sheet  3 . 
     As is apparent from the comparison of FIG. 6 with FIG. 2, in this second embodiment, dielectric sheets are attached to the upper and lower sides of the dielectric plate to form circuits on the upper and lower sides of the dielectric plate. In this construction, both sides of the dielectric plate can be effectively utilized, and a reduction in the size of the entire structure can be achieved. Further, since the dielectric resonator and the micro strip lines placed on either side thereof are arranged symmetrically, it is possible to restrain the generation of an unnecessary mode in the dielectric plate. 
     Next, the construction of a part of a high frequency module in accordance with a third embodiment of the invention will be described with reference to FIG.  7 . 
     FIG. 7 is an exploded perspective view showing the construction of the dielectric plate side and the dielectric sheet side in the electronic part mounting portion. In the first embodiment, shown in FIGS. 2 through 5, the electrode of the electronic part and the conductor pattern on the dielectric sheet are connected to each other through a bonding wire. In this third embodiment, in contrast, the connection is effected through through-holes provided in the dielectric sheet. In FIG. 7, conductor patterns  61 ,  62  and  63  are formed on the upper side of the dielectric plate  1 , and an RF ground  15  is formed so as to cover the upper side except for the region where the conductor patterns are formed. The FET  28  is placed with its pad surface facing downwards and connected (bonded) to the end portions of the conductor patterns  61 ,  62  and  63 . The dielectric sheet  2  is provided with a hole  11  corresponding to the FET  28 , and through-holes  64 ,  65  and  66  connected to the conductor patterns  61 ,  62  and  63  are provided in the drain connection electrode  23  and the micro strip lines  36  and  24 . By stacking the dielectric sheet  2  on the dielectric plate  1 , the drain, source and gate of the FET  28  are connected to a predetermined conductor pattern on the dielectric sheet  2 . 
     Next, FIG. 8 is a partial exploded perspective view showing the construction of a part of a high frequency module according to the fourth embodiment of the invention. While in the first and second embodiments holes are formed in the dielectric sheet, in this fourth embodiment, electronic parts, such as a thin-film inductor and a thin-film resistor, are directly formed on the dielectric plate  1 , and the connection to the circuit on the dielectric sheet is effected through a through-hole provided in the dielectric sheet. With reference to FIG. 8, a thin-film inductor  30  has at one end a conductor pattern  67  provided on the upper side of the dielectric plate  1 . A micro strip line  25  has at one end a through-hole  68  provided on the dielectric sheet  2 . By stacking them together, the thin-film inductor  30  is electrically connected to the end portion of the micro strip line  25 . Due to this arrangement, there is no limitation due to the material of the dielectric sheet  2 , whereby it is possible to easily form an arbitrary minute conductor pattern on the dielectric plate  1  side. 
     While in the above-described embodiments a dielectric sheet is used, it is also possible to use a dielectric plate thinner than the dielectric plate used as the base material. Further, while in the above-described embodiments a dielectric sheet is used, it is also possible to use an insulating sheet material or a plate material having a low dielectric constant. 
     Further, while the above embodiments have been described as applied to a voltage control oscillator, the present invention is naturally also applicable to other high frequency modules, such as a filter, an antenna combier, and an antenna module. 
     According to the present invention, an electronic part is directly mounted or formed on a base material having a high frequency ground surface, so that the ground connection of the electronic part is reliably effected, and there is no adverse influence on the high frequency characteristic due to the increase in the length of the grounding path. Further, since the heat generated by the electronic part is directly conducted to the base material, a high level of heat radiation property is obtained, and there is no adverse influence on the electronic part and the peripheral members. Further, since the electronic part is provided on the base material, the height (thickness) dimension of the entire structure is reduced, and the height of the entire high frequency module can be reduced. Further, the electronic part does not protrude from the surface of the dielectric sheet, or, if it does, it does so only to a small degree, whereby the electronic part is mechanically protected. 
     Further, in the aspect of the invention, an electronic part can be directly formed on the base material, so that it is possible to use a sheet material or a plate material on which such an electronic part cannot be directly formed. 
     Further, in the high frequency module, it is possible to easily obtain a high frequency module including a dielectric resonator. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.