DIRECTIONAL COUPLER

Abstract: Cut-away portions (17a,17b) are provided in the grounded conductor at portions where the coupling conductors are opposed to each other. The coupling conductors are electromagnetically coupled to each other via the cut-away portions. Therefore, no interference takes place between the transmission lines on both sides of the grounded conductor.

Description: The present invention relates to a directional coupler device. Fig. 3 shows a circuit diagram showing a multi terminal directional coupler having four input terminals and four output terminals. In Fig. 3, the signals input to signal input terminals 1 and 2 input to a hybrid directional coupler 9a of 3dB of degree of coupling (referred to as coupling degree hereinafter) and each of the signals is divided into two parts in the directional coupler 9a and the divided signals are coupled. The divided and coupled signals are respectively input to hybrid directional couplers 9c and 9d. The signals input to the signal input terminals 3 and 4 are input in hybrid directional couplers 9b with a 3dB coupling degree and each of the signals is divided into two parts in the directional coupler 9b and coupled and the divided and coupled signals are input in the hybrid directional couplers 9c and 9d of 3 db coupling degree. The signals input in the directional coupler 9c are respectively divided in two parts and coupled and the divided and coupled signals are output at signal output terminals 5 and 6. The signals input in the directional coupler 9d are respectively divided into two parts and coupled and the divided and coupled signals are output at the signal output terminals 7 and 8. In the multi terminal directional coupler constructed as mentioned above, each signal having 1/4 power of the input power of the signals input in the input terminals 1 to 4 is output at the output terminals 5 to 8. The multi terminal directional coupler can be applied to a butler matrix which controls the directionality of the radiation beam and the available scope of the coupler is wide. In Figs. 4(A) and 4(B), there is provided a branch line directional coupler 9a on the top surface of a left upper portion of a dielectric substrate 10 of a rectangular shape having its entire reversed surface formed with a ground conductor plate 11. The branch line directional coupler 9a comprises strip conductors 21 and 22 of a rectangular shape and width d1 and λg/4 long and strip conductors 23 and 24 of a rectangular shape and width d2 and λg/4 long and the strip conductors 21, 22 and the strip conductors 23 and 24 are respectively parallelly formed on the dielectric substrate 10 so as to provide a rectangular shape by the respective strip conductors 21 to 24. λg is a wave length in the wave guide. Respective conductors on the connection point of the strip conductors 21 and 23, connection point of the strip conductors 22 and 24, connection point of the strip conductors 21 and 24 are respectively indicated by the numerals 25 to 28. As known in the prior art, in the branch line directional coupler 9a, a microwave line of a specific impedance Z₀ may be coupled to the conductors 25 to 28 by defining the widths dl and d2 of the strip conductors 21 to 24 in a suitable width and there can be obtained 3 db coupling degree in a circuit formed by the conductors 25 to 28 of the connection points. Branch line directional couplers 9b, 9c and 9d are formed on the left bottom portion, right top portion and right bottom portion in the drawing of the top surface of the insulator substrate 1 in the same manner as the branch line directional coupler 9a. For the convenience, the reference numerals 21 to 28 of the directional coupler 9a are used in the directional couplers 9b, 9c and 9d. The respective conductors 25, 26, 27 and 28 at the connection points of the directional coupler 9a are connected to the signal input terminals 1 and 2 and the connection points 25 of the respective directional couplers 9c and 9d through the connection strip conductors 31, 32, 35 and 36 of width d. The respective conductors 25, 26, 27 and 28 at the connection points of the directional coupler 9b are connected to the signal input terminals 3 and 4 and the connection points 26 of the respective directional couplers 9c and 9d through the connection strip conductors 33, 34, 37 and 38 of the width d. It is noted that the strip conductors 36 and 37 are formed in a solid crossing shape, that is the conductor 37 is laid over the conductor 36 through a insulator 43 at a solid cross portion 30. The conductors 28 and 27 at the connection points of the directional coupler 9c are respectively connected to the signal output terminals 5 and 6 through the strip conductors 39 and 40. The conductors 28 and 27 at the connection points of the directional coupler 9d are respectively connected to the signal output terminals 7 and 8 through the strip conductors 41 and 42. In order to transfer 1/4 power of the signals input in the signal input terminals 1 to 4 to the output terminals 5 to 8 with predetermined phase difference, the respective lengths of the connection strip conductors 31 to 34, 35 to 38 and 39 to 42 are made equal. In the multi terminal directional coupler constructed as mentioned, the connection strip conductors 31 to 42 act as micro strip lines in association with the ground conductor 11 and operates in a similar manner as the directional coupler shown in Fig. 3. When the specific impedance of the micro strip line is given, the width of the strip conductors 31 to 42 can be selected in a known manner. In the conventional directional coupler shown in Figs. 4(A) and 4(B), the signal which propagates along the strip conductor 36 and the signal which propagate along the strip conductor 37 interfere each other at the cross point 30 of the connection strip conductors 36 and 37, whereby there can not produce equivalent signals at the signal output terminals 5 to 8. In the multi terminal directional coupler, it is required to coincide the electrical length of the signals which progagate the connection strip conductors 31, 35 and 39; 32, 36 and 41; 33, 37 and 40; 34, 38 and 42 from the terminals 1 to 4 to the signal output terminals 5 to 8. However, in the conventional structure as shown in Figs. 4(A) and 4(B), it is necessary to adjust the length of the strip conductors 31 to 42 corresponding to the shape of the solid crossing 30, resulting in difficulty of the manufacturing of the coupler. Furthermore, in order to decrease the electrical coupling among the connection strip conductors 31 to 42 other than the hybrid couplers 9a to 9d, it is necessary to make the line distance width. However, in the conventional structure shown in Fig. 4, there must be provided eight input and output strip conductors 31 to 34 and 39 to 42 and four strip conductors 35 to 38 for connecting the directional couplers on the substrate 10, whereby the size of the directional coupler is bulky. The precharacterizing part of claim 1 refers to a multi terminal direction coupler device as disclosed in DE-A-3 435 583. The known coupler device comprises 64 input and 64 output terminals and 192 branch line coupler means. In order to reduce the number of connections between the coupler means the device is divided into two parts. Every part consists of eight identical structures, each defining a 8 x 8 matrix having eight input and eight output terminals. Two of said 8 x 8 matrices are coupled together respectively, such that the first half of coupler means are disposed on a front board and the second half of coupler means of said matrix is disposed on a back board. Due to this configuration the number of coaxial feed-throuth elements connecting the coupler means on both sides is reduced. However, it is difficult to make electrical length between the input and output terminals coincident with high accuracy. Further the manufacturing of the known device is very complicated. US-A-3 575 674 describes a microwave directional coupler on microstrip having high directivity. The known coupler has an iris between two lines separated by a common ground plane, such that each line forms a separate transmission line with the common ground plane and is completely isolated from each other, beyond the open portion of the iris. Both even- and odd-mode fields are substantially contained within the dielectric, thereby eliminating the phase unbalance common to other types and permitting greater directivity. Furthermore, an amplifier in strip line technique with branch couplers and additional active and passive elements is disclosed in D3 = THE TRANSACTIONS OF THE I.E.C.E. OF JAPAN vol. E63, no. 12, December 1980; T. NOGUCHI et al.: "Microwave integrated circuits with high-dielectric constant substrate for UHF transistor amplifier", pages 842 - 848. It is the object of the present invention to provide a multi terminal directional coupler device and a microwave device comprising directional coupler means, in which interference of the signals propagating in the strip conductors is prevented and which can be manufactured easily. The problem is solved according to the invention with the features of claim 1 or 2 respectively. The present invention is characterized in that in a multi terminal directional coupler comprising N input terminals, wherein N is 2 ℓ but more than 4 and ℓ is natural number, N output terminals and ℓx 2 ℓ-1 directional couplers, to output signals having 1/N power from the input signals which are input to the N input terminals, each of said ℓx 2 ℓ-1 directional couplers is formed in such a manner that two coupling conductors forming the output or input terminals are formed on opposite two sides of a ground conductor through dielectric substrates and the opposite two coupling conductors are electromagnetically coupled through an opening defined in the ground conductor. By the arrangement mentioned above, strip conductors for connecting the input terminals, the output terminals, coupling conductors of the directional couplers and for connecting the respective terminals and coupling conductors and for connecting the respective coupling conductors can be separately formed on the respective dielectric substrates situated on both sides of the ground conductor. Accordingly, the size of the multi terminal directional coupler may be decreased to about 2/3 of the conventional directional coupler of the kind, whereby it is possible to decrease the size and weight of the directional coupler. Moreover, since the solid crossing can be eliminated, it is possible to prevent the interference between the signals propagating the strip conductors. Therefore, there can be provided multi terminal directional couplers which is able to divide the power of the input signals with a good electrical property. Moreover, according to the present invention, there is provided a microwave signal processing circuit which comprising a directional coupler formed in such a manner that a pair of coupling conductors forming input and output terminals are formed on both sides of a ground conductor through substrates so that said coupling conductors are electromagnetically coupled through an opening defined on a ground conductor formed between the coupling conductors and microwave signal processing circuit disposed on the substrates connected at the front stage or rear stage to the directional coupler. By the arrangement mentioned above, there may be divided the coupling conductors of the directional coupler, the microwave signal processing circuits and connecting lines for connecting the coupling conductors and the microwave signal processing circuits in two parts on both sides of the two substrates. Accordingly, the size of the microwave device can be decreased into 1/2 compared to the conventional device and it is possible to decrease the size and weight of the microwave device. In addition, since the device according to the present invention can be made without ridge coupling as used in the conventional device, it is possible to prevent the interference between the signals propagating the various circuits or lines in the device. Therefore, there can be provided microwave devices which can process the input signals with a good electric property. Fig. 1(A) is a top plan view showing an example of four input four output directional coupler according to the present invention, Fig. 1(B) is a plan view showing the directional coupler shown in Fig. 1(A) viewed from below, Fig. 1(C) is a top plan view showing a ground conductor used in the directional coupler shown in Fig. 1(A), Fig. 1(D) is a cross sectional view taken along the lines A-A′ in Fig. 1(A) and Fig. 1(B), Figs. 2(A) and 2(B) are vertical cross sectional views showing electric field distribution of even mode and odd mode in vertical mode drive at the connecting potion of B-B′ line in Figs. 1(A) and 1(B), Fig. 3 is a circuit diagram of the four input four output multi terminal directional coupler shown in Figs. 1(A) and 1(B), Fig. 4(A) is a top plan view showing four input and four output multi terminal directional coupler using four branch line directional couplers, Fig. 4(B) is a vertical cross sectional view taken along the line C-C′ shown in Fig. 4(A), Fig. 5(A) is a top plan view showing an example of the four input and four output multi terminal directional coupler according to the present invention, Fig. 5(B) is a bottom plan view of the multi terminal directional coupler shown in Fig. 5(A), Fig. 5(C) is a vertical cross sectional view taken along the line A-A′ shown in Figs. 5(A) and 5(B), Fig. 5(D) is a vertical cross sectional view taken along the line B-B′ shown in Figs. 5(A) and 5(B), Fig. 6(A) is a top plan view showing the multi terminal directional coupler shown in Fig. 5(A), Fig. 6(B) is a top plan view of a grand conductor used in the multi terminal directional coupler shown in Fig. 5(A), Fig. 6(C) is a top plan view showing conductor patterns of the bottom surface of the multi terminal directional coupler shown in Fig. 5(A), Fig. 7(A) is a top plan view showing another example of the directional coupler forming the rear part of the eight input eight output multi terminal directional coupler, Fig. 7(B) is a top plan view showing a grand conductor of the directional coupler shown in Fig. 7(A), Fig. 7(C) is a top plan view of the conductor patterns of the directional coupler shown in Fig. 7(A), Fig. 8(A) is a circuit diagram of the multi terminal directional coupler shown in Figs. 5(A) to 5(D), Fig. 8(B) is a circuit diagram showing a modification of the multi terminal directional coupler shown in Figs. 5(A) to 5(D), Fig. 9 is a circuit diagram showing the multi terminal directional coupler shown in Figs. 7(A) to 7(C), Figs. 10(A) and 10(B) are vertical cross sectional views showing the even mode and odd mode by the vertical mode drive at the connecting potion on the line F-F′ of Figs. 5(A) and 5(B), Fig. 11 is a circuit diagram showing in the conventional four input four output multi terminal directional coupler, Fig. 12 is a circuit diagram showing the conventional eight input eight output multi terminal directional coupler, Fig. 13 is a circuit diagram showing the conventional 16 input 16 output multi terminal directional coupler, Fig. 14(A) is a top plan view showing the four input four output multi terminal directional coupler using four branch line directional coupler, Fig. 14(B) is a vertical cross sectional view taken along the line E-E′ in Fig. 14(A), Fig. 15(A) is a top plan view showing a microwave balanced amplifier according to the present invention, Fig. 15(B) is a top plan view of the ground conductor used in the microwave balanced amplifier shown in Fig. 15(A), Fig. 15(C) is a top plan view showing the conductor patterns used in the microwave balanced amplifier shown in Fig. 15(A), Fig. 15(D) is a vertical cross sectional view taken along the line A-A′ in Fig. 15(A), Fig. 15(E) is a vertical cross sectional view taken along the line B-B′ in Fig. 15(A), Figs. 16(A) and 16(B) are vertical cross sectional views showing the electric field distribution of the odd mode and even mode by the vertical drive at the connecting portion of the line B-B′ in Fig. 15(A), Fig. 17 is an embodiment of a four input four output multi terminal amplifier according to the present invention, Fig. 18(A) is a top plan view of the multi terminal amplifier for showing the practical feature of the multi terminal directional coupler shown in Fig. 17, Fig. 18(B) is a top plan view of the ground conductor 12 of the multi terminal amplifier shown in Fig. 17, and Fig. 18(C) is a top plan view showing the conductor patterns on the dielectric substrate 10by used in the multi terminal amplifier shown in Fig. 17. Referring to Figs 1(A) to 1(D) there are defined coupling openings 17a and 17b which penetrate a ground conductor 11 and has a length W of the short side and λ g/4 of the long side in the upper right portion and lower right portion of an elongated ground conductor 11 with to thick, the coupling openings 17a and 17b are filled by coupling insulation materials 10ca and 10cb. The ground conductor 11 is provided between dielectric substrates 10a and 10b with a thickness of t. In the upper right portion in Fig. 1(A) above the dielectric substrate 10a, a coupling conductor 18a of a rectangular shape with a length S on the short side and a length λg/4 on the long side is formed above the coupling insulation material 10ca. On the other hand, another coupling conductor 19a similar to the conductor 18a is formed below the coupling insulation material 10ca on the upper left portion of Fig. 1(B) on the lower surface of the dielectric substrate 10b. In order to provide input terminals and output terminals of the multi terminal directional coupler on the same side and to equalize the electrical length between the input terminal and output terminal, the coupling conductors 18a and 19a are formed so that the longitudinal directions of the coupling conductors 18a and 19a extend in parallel with the longitudinal direction of the dielectric substrates 10a and 10b. When microwave signal is applied to the ends of the short sides of the coupling conductors 18a and 19a, there is developed a mode coupling between the coupling conductors 18a and 18b and the ground conductor 11 through the coupling insulation material 10ca in the coupling opening 17a. Then the input power is divided into two equivalent parts and coupled, thereby outputting at the other end of the short side of each of the coupling conductors 18a and 19a. Referring to Figs. 1(A) and 1(B) the positions of the coupling openings 17a and 17b are indicated by dotted lines. The respective short sides of the coupling opening 17a of the ground conductor 11 and the short sides of the coupling conductors 18a and 19a are coincided each other. The dielectric substrates 10a and 10b and coupling insulation material 10ca are formed in one body and have the same dielectric constant. Figs. 2(A) and 2(B) are respectively vertical cross sectional views showing the electric field distribution of the odd mode and even mode by the known vertical mode driving at the coupling portion on the B-B′ line in Fig. 1. In the even mode shown in Fig. 2(A) there are developed electric force lines between the coupling conductors 18a and 19a and the ground conductor 11, whereby the opening acts as the magnetic wall. On the other hand, in the odd mode shown in Fig. 2(B) there are developed electric force lines between the coupling conductors 18a and 19a and the ground conductor 11, whereby the opening acts as the electric wall. Accordingly, there is formed a directional coupler 9ca having a predetermined coupling degree by the ground conductor 11 and the coupling conductors 18a and 19a formed on the dielectric substrate 10a and 10b. Therefore, there can be provided a four terminal directional coupler 9ca having a coupling degree of 3dB by selecting the dielectric constant of the dielectric substrate 10a, the width S of the coupling conductors 18a and 19a and the width W of the coupling opening 17a. It is noted that the coupling degree is 3dB. In order to increase the coupling degree, the width W of the coupling opening 17a is made large. There is formed a coupling conductor 18b having the same shape of the conductor 18a directly above the coupling insulation material 10cb at the lower right portion in Fig. 1 (A) on the dielectric substrate 10a, while there is formed a coupling conductor 19b having the same shape of the conductor 19a directly below the coupling insulation material 10cb at the lower left portion in Fig. 1 (B) on the lower surface of the dielectric substrate 10b. Accordingly, there can be provided a directional coupler 9da having 3dB coupling degree in a similar manner as the directional coupler 9ca by the ground conductor 11 and the coupling conductors 18b and 19b. There is formed a branch line directional coupler 9a having 3dB coupling degree similar to the conventional one at the central portion in Fig. 1 (A) on the upper surface of the dielectric substrate 10a, while another branch line directional coupler 9b having 3dB coupling degree similar to the conventional one at the central portion in Fig. 1.(B) on the lower surface of the dielectric substrate 10b. On the upper surface of the dielectric substrate 10a the signal input terminals 1 and 2 are connected to the conductors 25 and 26 disposed at the connection points of the directional coupler 9a through connection strip conductors 31 and 32 of the width d. The connection conductors 27 and 28 of the directional coupler 9a are connected on the lower end of the short side of the coupling conductor 18a of the directional coupler 9ca and the short side of the coupling conductor 18b of the directional coupler 9da through connecting strip conductors 36 and 35. The upper end portion of the short side of the coupling conductor 18a of the directional coupler 9ca and the lower end portion of the short side of the coupling conductor 18b of the directional coupler 9da are connected to the signal output terminals 5 and 7 through connecting strip conductors 39 and 41. On the lower surface of the dielectric substrate 10b, the signal input terminals 3 and 4 are connected to conductors 25 and 26 at the connection point of the directional coupler 9b through the connection strip conductors 33 and 34 of the width d. Conductors 27 and 28 at the connecting point of the directional coupler 9b are connected to the upper end potion of the short side of the coupling conductor 19a of the directional coupler 9ca and the lower end portion of the short side of the coupling conductor 19b of the directional coupler 9da through the connection strip conductors 38 and 37 of the width d. The lower end portion of the short side of the coupling conductor 19a of the directional coupler 9ca and the upper end portion of the short side of the coupling conductor 19b of the directional coupler 9da are connected to the signal output terminals 6 and 8 through the connection strip conductors 40 and 42. In the arrangement mentioned above the signal input terminals 1 and 2 and the signal output terminals 5 and 7 are formed on the outer parts of the left and right side of the dielectric substrate 10a, while the signal input terminals 3 and 4 and the signal output terminals 6 and 8 are formed on the outer parts of the left and right sides of the dielectric substrate 10b. Therefore it is advantageous that, when lead wires are connected to the signal input terminals and signal output terminals, the work of connecting the lead wires is easy since the connecting positions are not overlapped. Moreover, in order to transmit 1/4 power of the input signals entered at the signal input terminals 1 to 4 to the signal output terminals 5 to 8 with the same phase difference of the input signals, the electric length of the parts beginning from the signal input terminals 1 to 4 to the input ends of the respective directional couplers 9ca and 9da including connection strip conductors 31 and 35, connection strip conductors 32 and 36, connection strip conductors 33 and 37 and connection strip conductors 34 and 38 is equivalent while the electric length of the parts beginning from the output ends of the directional couplers 9ca and 9da including the connection strip conductors 39 to 42 is equivalent. The multi terminal directional coupler arranged as mentioned above has a circuit equivalent to the circuit shown in Fig. 3 and can act similar to the circuit shown in Figs. 4 (A) and 4 (B). Although in the embodiment mentioned above, the terminals 1 to 4 are used as the signal input terminals and the terminals 5 to 8 are used as the signal output terminals, the multi terminal directional coupler can act as a reversible circuit, therefore the terminals 1 to 4 can be used as the signal output terminals with the terminals 5 to 8 used as the signal input terminals. In the arrangement shown in the present arrangement, it is possible to decrease the sides of the device to about 1/2 compared to the conventional device shown in Figs. 4 (A) and 4 (B). In addition since the solid crossing part 30 formed by the strip conductors 37 as shown in Figs. 4 (A) and 4 (B) is unnecessary, the input signal can be divided into two parts with equivalent power with a good equivalency. In addition in the present embodiment since the solid crossing part 30 is unnecessary, it is possible to form the conductor patterns accurately, whereby the electric lengths between the respective input terminals and output terminals can be made uniformly. Accordingly, the accurate phase relation can be assured between the input terminal and output terminal. In the embodiment mentioned above although the branch line hybrid directional couplers 9a and 9b are used for dividing and coupling the power of the signal on the same plane the present invention is not limited to the embodiment, for example there may be used various hybrid directional coupler such as inter digit type, tandem connection type hybrid directional coupler for dividing and coupling the power of the signal. In this case it is possible to decrease the sides of the device compared to the device using the branch line hybrid directional coupler. In the embodiment mentioned above, although explanation is made with respect to the case having four input and output terminals, the present invention is not limited to this embodiment and the present invention can be applied to the case having the multi terminals more than five and there may be arranged such a multi terminal directional coupler having more than three known directional couplers 9a, 9b and 9c and more than three directional couplers 9ca and 9da. Moreover, in the embodiment mentioned above, although the shape of the coupling conductors 18a, 18b, 19a, 19band the coupling openings 17a and 17b are rectangular, they are not limited to those shown in the embodiment, it is possible to form them in such a manner that among the coupling conductors 18a, 19a, 18b and 19b, the coupling opening may be formed so as to couple the mode coupling conductors 18a, 19a, 18b and 19b. In the present invention there are provided a plurality of first directional couplers on both sides of the ground conductor through the dielectric substrate, forming two coupling conductors which are connected with the first directional couplers on both sides of the ground conductor through the dielectric substrate in addition the ground conductor provided between the coupling conductors is provided by the opening and moreover there are provided the second directional couplers to couple the coupling conductors, whereby the second directional couplers act in a similar manner as the conventional branch line directional couplers as shown in Figs. 4(A) and 4(B), so that there are provided two known first directional couplers and the second directional couplers, therefore the multi terminal directional coupler according to the present invention can act in a similar manner as the conventional directional coupler. As mentioned above, the first directional couplers are provided on both sides of the ground conductors through the dielectric substrates and the coupling conductors of the second directional coupler are provided on the dielectric substrates there can be formed a multi terminal directional coupler with 1/2 size of the conventional multi terminal directional coupler and it is possible to eliminate the solid crossing. Accordingly, the conductor patterns of the directional coupler can be formed accurately, it is advantageous that the signals can be output with a good electric property preventing the interference of the signals at the solid crossing part. A further embodiment of the pressing invention is explained hereinafter. Referring to Figs. 5(A), 5(B), 6(A) and 6(B), there are defined coupling openings 52ax to 52dx which penetrate a ground conductor 11x and has a length W of the short side and λg/4 of the long side in the upper left portion, lower left portion, central portion and central right portion of an elongated ground conductor 11x with t0 thick, the coupling openings 52ax to 52dx are filled by coupling insulation materials 10cax, 10cbx, 10ccx and 10cdx. The ground conductor 2 is provided between dielectric substrates 10ax and 10bx. In the upper right portion in Fig. 5(A) above the dielectric substrate 10ax, a coupling conductor 51aax of a rectangular shape with a length S on the short side and a length λg/4 on the long side is formed above the coupling insulation material 10cax. On the other hand, another coupling conductor 51abx similar to the conductor 51aax is formed below the coupling insulation material 10cax on the upper right portion of Fig. 5(B) on the lower surface of the dielectric substrate 10bx. In order to provide input terminals and output terminals of the multi terminal directional coupler on the same side and to equalize the electrical length between the input terminal and output terminal the coupling conductors 51aax and 51abx are formed so that the longitudinal directions of the coupling conductors 51aax and 51abx extend in parallel with the longitudinal direction of the dielectric substrates 10aax and 10abx. When microwave signal is applied to the ends of the short sides of the coupling conductors 51aax and 51abx, there is developed a mode coupling between the coupling conductors 51aax and 51abx and the ground conductor 11x through the coupling insulation material 10cax in the coupling opening 52ax. Then the input power is divided into two equivalent parts and coupled, thereby outputting at the other end of the short side of each of the coupling conductors 51aax and 51abx. Referring to Figs. 5(A) and 5(B) the positions of the coupling openings 52ax and 52dx are indicated by dotted lines. The respective short sides of the coupling opening 52ax of the ground conductor 11x and the short sides of the coupling conductors 51aax and 51abx are coincided each other. The dielectric substrates 10ax and 10bx and coupling insulation material 10cax are formed in one body and have the same dielectric constant. The same structure may be employed in the directional couplers 50bx to 50dx. Figs. 10(A) and 10(B) are respectively vertical cross sectional views showing the electric field distribution of the odd mode and even mode by the known vertical mode driving at the coupling portion on the F-F′ line in Fig. 5. In the even mode shown in Fig. 10(A) there are developed electric force lines between the coupling conductors 51aax and 51abx and the ground conductor 11x, whereby the opening acts as the magnetic wall. On the other hand, in the odd mode shown in Fig. 10(B) there are developed electric force lines between the coupling conductors 51aax and 51abx and the ground conductor 11x, whereby the opening acts as the electric wall. Accordingly, there is formed a directional coupler 50ax having a predetermined coupling degree by the ground conductor 11x and the coupling conductors 51aax and 51abx formed on the dielectric substrate 10ax and 10bx. Therefore, there can be provided a four terminal directional coupler 50ax having a coupling degree of 3dB by selecting the dielectric constant of the dielectric substrates 10ax and 10bx, the width S of the coupling conductors 51aax and 51abx and the width W of the coupling opening 52ax. It is noted that the coupling degree is 3dB. In order to increase the coupling degree, the width W of the coupling opening 52ax is made large. There is formed a coupling conductor 51bax having the same shape of the conductor 51aax directly above the coupling insulation material 10cbx at the lower left portion in Fig. 5 (A) on the dielectric substrate 10ax, while there is formed a coupling conductor 51bbx having the same shape of the conductor 51abx directly below the coupling insulation material 10cbx at the lower right portion in Fig. 5 (B) on the lower surface of the dielectric substrate 10bx. Accordingly, there can be provided a directional coupler 50bx having 3dB coupling degree in a similar manner as the directional coupler 50ax by the ground conductor 11x and the coupling conductors 51bax and 51bbx. There is formed a coupling conductor 51cax having the same shape of the conductor 51aax directly above the coupling insulation material 10ccx at the central portion in Fig. 5 (A) on the dielectric substrate 10ax, while there is formed a coupling conductor 51cbx having the same shape of the conductor 51abx directly below the coupling insulation material 10ccx at the central portion in Fig. 5 (B) on the lower surface of the dielectric substrate 10bx. Accordingly, there can be provided a directional coupler 50cx having 3dB coupling degree in a similar manner as the directional coupler 50ax by the ground conductor 11x and the coupling conductors 51cax and 51cbx. There is formed a coupling conductor 51dax having the same shape of the conductor 51aax directly above the coupling insulation material 10cdx at the right central portion in Fig. 5 (A) on the dielectric substrate 10ax, while there is formed a coupling conductor 51dbx having the same shape of the conductor 51abx directly below the coupling insulation material 10cdx at the left central portion in Fig. 5 (B) on the lower surface of the dielectric substrate 10bx. Accordingly, there can be provided a directional coupler 50dx having 3dB coupling degree in a similar manner as the directional coupler 50ax by the ground conductor 11x and the coupling conductors 51dax and 51dbx. On the upper surface of the dielectric substrate 10ax, the signal input terminal 1x is connected to the connection terminal 56ax on the upper portion of the coupling conductor 51aax of the directional coupler 50ax through a connection strip conductor 61x, while the connection terminal 57ax of the lower portion of the coupling conductor 51aax of the directional coupler 50ax is connected to the connection terminal 56cx of the upper portion of the coupling conductor 51cax of the directional coupler 50cx through a connection strip conductor 63x having S character shape. The connection terminal 57cx on the lower portion of the coupling conductor 51cax of the directional coupler 50cx is connected to the signal output terminal 5x through the connection strip conductor 65x. The signal input terminal 2x is connected to the connection terminal 56bx on the upper portion of the coupling conductor 51bax of the directional coupler 50bx through the connection strip conductor 62x. The connection terminal 57bx on the lower portion of the coupling conductor 51bax of the directional coupler 50bx is connected to the connection terminal 57dx of the coupling conductor 51dax of the directional coupler 50dx through the connection strip conductor 64x having a zigzag shape. The connection terminal 56dx on the upper portion of the coupling conductor 51dax of the directional coupler 50dx is connected to the signal output terminal 6x through the connection strip conductor 66x. On the lower surface of the dielectric substrate 10bx, the signal input terminal 3x is connected to the connection terminal 59ax on the lower portion of the coupling conductor 51abx of the directional coupler 50ax through the connection strip conductor 71x and the connection terminal 58ax on the upper portion of the coupling conductor 51abx of the directional coupler 50ax is connected to the connection terminal 58dx on the upper portion of the coupling conductor 51dbx of the directional coupler 50dx through the connection strip conductor 73x having a zigzag shape. The connection terminal 59bx on the lower portion of the coupling conductor 51dbx of the directional coupler 50dbx is connected to the signal output terminal 7x through the connection strip conductor 75x. The signal input terminal 4x is connected to the connection terminal 59bx on the lower portion of the coupling conductor 51bbx of the directional coupler 50bx through the connection strip conductor 72x and the connection terminal 58dx on the upper portion of the coupling conductor 51bbx of the directional coupler 50bx is connected to the connection terminal 59cx on the lower portion of the coupling conductor 51cbx of the directional coupler 50cx through the connection strip conductor 74x having a S character shape. The connection terminal 58cx on the upper portion of the coupling conductor 51cbx of the directional coupler 50cx is connected to the signal output terminal 8x through the connection strip conductor 76x. the width of the respective connection strip conductors 61x to 66x and 71x to 76x is defined according to the characteristic impedance. As shown in Figs. 5(A) and 5(B) the signal input terminals 1x to 4x and the signal output terminals 5x to 8x are formed so that they are located alternatively on the dielectric substrate 10ax and 10bx with the different position of one side of the dielectric substrates 10ax and 10bx. Accordingly in order to connect a lead wire to the respective signal input and output terminals 1x to 8x, the respective connection points are not overlapped, therefore, the work of the connection is easy. In order to output the signal having 1/4 power of the input signal applied to the signal input terminals 1x to 4x at the respective output terminals 5x to 8x with the same phase difference, the electric length of the connection strip conductor beginning from the respective signal input terminals 1x to 4x and ending at the signal output terminals 5x to 8x through the respective directional couplers, that is the total electric length of the connection strip conductors 61x, 63x and 65x; the total electric length of the connection strip conductors 62x, 64x and 66x; the total electric length of the connection strip conductors 71x, 73x and 75x; and the total electric length of the connection strip conductors 72x, 74x and 76x are made uniform. The multi terminal directional coupler as mentioned above is equivalent to the circuit 100x shown in Fig. 11, and can operate in the same manner as shown in Figs. 14(A) and 14(B). In the embodiment mentioned above the terminals 1x to 4x are used as the signal input terminal and the terminals 5x to 8x are used as the output terminals, however, the multi terminal directional coupler according to the present invention is a reversible circuit, therefore 1x to 4x may be used as the signal output terminals and 5x to 8x may be used as the signal input terminals. In the arrangement of the embodiment, there are used four directional couplers 50ax to 50dx with the two directional couplers 50ax and 50bx juxtaposed on the upper portion and lower portion in Figs. 6(A) to 6(C) and two directional couplers 50cx and 50dx juxtaposed on the left portion and right portion in Figs. 6(A) and 6(C), therefore the size of the multi terminal directional coupler 60x can be decreased about 2/3 compared to that of the conventional one shown in Figs. 14(A) and 14(B). Since the solid crossing 30x formed by the strip conductor 37x as shown in Figs. 14(A) and 14(B) can be eliminated the input signal can be divided into equivalent power with a good uniformity. In the embodiment, since the solid crossing 30x is eliminated, the circuit patterns can be made accurately and the electric lengths between the input and output terminal can be made uniform. Therefore there can be obtained accurate phase relation at the input terminal and the output terminal. The conductor patterns on the dielectric substrate shown in Fig. 5(A) is equivalent to that reversed by 180° from the conductor pattern on the dielectric substrate 10b whereby the two conductor patterns can be formed by the same pattern. Fig. 8(A) is a circuit diagram of the multi terminal directional coupler 60x wherein the connection strip conductors formed on the top surface and lower surface of the multi terminal directional coupler 60x shown in Figs. 5(A) to 5(B) are separately shown. In Fig. 8(A) the real lines in the connection line and the directional coupler show the connection conductors 51aax, 51bax, 51cax and 51dax formed on the dielectric substrate 10ax and the connection strip conductors 61x to 66x, while the dotted lines in the connection lines and the directional coupler show the connection conductor 51abx, 51bbx, 51cbx and 51dbx and the connection strip conductors 71x to 76x. As shown in Fig. 8(A), there may be located the directional coupler 50cx as shown in Fig. 8(B) at the solid crossing position 77x on which the connection strip conductors 65x and 76x cross in solid manner. The multi terminal directional coupler 61x arranged as mentioned above can act in the same manner as the multi terminal directional coupler 60x with the same advantage as the multi terminal directional coupler 60x. Fig. 9 is a further example of the multi terminal directional coupler having 8 input terminals and 8 output terminals according to the present invention. The multi terminal directional coupler comprises two multi terminal directional couplers 60x and 60′x having four input and four output terminals and a directional coupler 80x having 8 input terminals and 8 output terminals. The multi terminal directional coupler 60′x is formed in the same manner as the multi terminal directional coupler 60x shown in Figs. 5(A) to 5(D) and comprises four signal input terminals 1′x to 4′x and four signal output terminals 5′x to 8′x. The directional coupler 80x comprises four directional couplers 50ex to 50hx having the same structure of the directional couplers 50ax to 50dx, and act as the conventional directional coupler 118x as shown in Fig. 8. The signal output terminals 5x to 8x and 5′x to 8′x are connected to the signal input terminals 81x to 88x and the multi terminal directional coupler shown in Fig. 9 acts as the conventional multi terminal directional coupler 120x as shown in Fig. 12. Figs. 7(A) to 7(C) show the specific structure of the directional coupler 80x shown in Fig. 9. In Figs. 7(A) to 7(C) although there is shown only one directional coupler 80x, the directional coupler 80x is formed integrally with the two multi terminal directional couplers 60x and 60′x on the dielectric substrate 10ax and 10bx. The structure of the directional coupler 80x is explained hereinafter. In Figs. 7(A) to 7(C), four coupling conductors 51eax, 51fax, 51gax and 51hax having the same shape of the conductor 51aax are juxtaposed in left and right direction with the predetermined space on the central portion of the upper surface of the dielectric substrate 10ax directly above the coupling dielectric materials 10cex, 10cfx, 10cgx and 10chx. In Figs. 7(A) to 7(C), four coupling conductors 51ebx, 51fbx, 51gbx and 51hbx having the same shape of the conductor 51abx are juxtaposed in left and right direction with the predetermined space on the central portion of the upper surface of the dielectric substrate 10bx directly below the coupling dielectric materials 10cex, 10cfx, 10cgx and 10chx. Accordingly there is formed a directional coupler 50ex having 3dB coupling degree same as the directional coupler 50ax by the coupling conductors 51eax and 51ebx and ground conductor 11x. There is formed a directional coupler 50fx having 3dB coupling degree same as the directional coupler 50ax by the coupling conductors 51fax and 51fbx and ground conductor 11x. There is formed a directional coupler 50gx having 3dB coupling degree same as the directional coupler 50ax by the coupling conductors 51gax and 51gbx and ground conductor 11x. There is formed a directional coupler 50hx having 3dB coupling degree same as the directional coupler 50ax by the coupling conductors 51hax and 51hbx and ground conductor 11x. On the top surface of the dielectric substrate 10ax, as shown in Fig. 7(A) the signal input terminal 81x is connected to the connection terminal 56hx on the upper portion of the coupling conductor 51hax of the directional coupler 50hx through a connection strip conductor 201x having a zigzag shape. The connection terminal 57hx on the lower portion of the coupling conductor 51hax of the directional coupler 50hx is connected to the signal output terminal 89x through the connection strip conductor 202x. The signal input terminal 82x is connected to the connection terminal 56gx on the upper portion of the coupling conductor 51gax of the directional coupler 50gx through a connection strip conductor 203x having a zigzag shape. The connection terminal 57gx on the lower portion of the coupling conductor 51gax of the directional coupler 50gx is connected to the signal output terminal 90x through the connection strip conductor 204x. The signal input terminal 83x is connected to the connection terminal 57ex on the lower portion of the coupling conductor 51eax of the directional coupler 50ex through a connection strip conductor 205x having a zigzag shape. The connection terminal 56ex on the upper portion of the coupling conductor 51eax of the directional coupler 50ex is connected to the signal output terminal 91x through the connection strip conductor 206x. The signal input terminal 84x is connected to the connection terminal 57fx on the lower portion of the coupling conductor 51fax of the directional coupler 50fx through a connection strip conductor 207x. The connection terminal 56fx on the upper portion of the coupling conductor 51fax of the directional coupler 50fx is connected to the signal output terminal 92x through the connection strip conductor 208x. As shown in Fig. 7 (C), on the lower surface of the dielectric substrate 10bx, the signal input terminal 85x is connected to the connection terminal 58fx on the upper portion of the coupling conductor 51fbx of the directional coupler 50fx through a connection strip conductor 209x. The connection terminal 59fx on the lower portion of the coupling conductor 51fbx of the directional coupler 50fx is connected to the signal output terminal 93x through the connection strip conductor 210x. The signal input terminal 86x is connected to the connection terminal 58ex on the upper portion of the coupling conductor 51ebx of the directional coupler 50ex through a connection strip conductor 211x. The connection terminal 59ex on the lower portion of the coupling conductor 51ebx of the directional coupler 50ex is connected to the signal output terminal 94x through the connection strip conductor 212x. The signal input terminal 87x is connected to the connection terminal 59gx on the lower portion of the coupling conductor 51gbx of the directional coupler 50gx through a connection strip conductor 213x having a zigzag shape. The connection terminal 58gx on the upper portion of the coupling conductor 51gbx of the directional coupler 50gx is connected to the signal output terminal 95x through the connection strip conductor 214x. The signal input terminal 88x is connected to the connection terminal 59hx on the lower portion of the coupling conductor 51hbx of the directional coupler 50hx through a connection strip conductor 215x having a zigzag shape. The connection terminal 58hx on the upper portion of the coupling conductor 51hbx of the directional coupler 50hx is connected to the signal output terminal 96x through the connection strip conductor 216x. The width of the respective connection strip conductors 201x to 216x is determined corresponding to the characteristic impedance. It is noted that the respective signal input terminals 81x to 84x and the signal output terminals 89x to 96x are formed alternatively on the dielectric substrates 10ax and 10bx as shown in Figs. 7 (A) and 7 (C) with the different positions on one side of the dielectric substrates 10ax and 10bx. Accordingly in case of connecting the lead wires to the signal input and output terminals 81x to 96x, since the connection points are not overlapped the work of the connection of the lead wire is easy. In order to output the signal corresponding to the input signal applied to the signal input terminals 81x to 88x at the respective output terminals 89x to 96x with the same phase difference, the electric length of the connection strip conductor beginning from the respective signal input terminals 81x to 88x and ending at the signal output terminals 89x to 96x through the respective directional couplers, that is the total electric length of the connection strip conductors 201x and 202x; the total electric length of the connection strip conductors 203x and 204x; the total electric length of the connection strip conductors 205x and 206x and the total electric length of the connection strip conductors 207x and 208x are and the total electric length of the connection strip conductors 209x and 210x; the total electric length of the connection strip conductors 211x and 212x; the total electric length of the connection strip conductors 213x and 214x; and the total electric length of the connection strip conductors 215x and 216x are made uniform. The directional coupler 80x mentioned above is connected to the multi terminal directional couplers 60x and 60′x forming them integrally, it is possible to provide the 8 input and 8 output multi terminal directional coupler 118x as shown in Fig. 12 and the directional coupler 80x operates in the same manner as the known multi terminal directional coupler 120x shown in Fig. 12. The multi terminal directional coupler 120x is the reversible circuit same as the multiple directional coupler 60x. The multi terminal directional coupler arranged using the directional couplers 50ax to 50hx has the same advantage as the multi terminal directional coupler 60x shown in Figs. 5 (A) to 5 (B). Although, in the embodiments shown in Figs. 7 and 9, the respective directional couplers 50ex and 50fx are located at positions shown in Fig. 9, the directional coupler 50ex may be located at the solid crossing portion between the input terminals 83x, 86x and the output terminals 91x, 94x, that is the directional coupler 50ex may be located at the position of the directional coupler 50ex as presently shown in Fig. 9 or a position 302x where the connection strip conductors 206x and 212x cross in a solid manner. The directional coupler 50fx further may be located at the solid crossing portion between the input terminals 84x, 85x and the output terminals 92x, 93x that is at the present -position a position where the connection strip conductors 208x and 210x cross in the solid manner. In addition the directional couplers 50ex and 50fx may be located at any one of four positions mentioned below. (1) The directional coupler 50ex is located at a position 303x where the connection strip conductors 206x and 209x cross in a solid manner, while the directional coupler 50fx is located at a position 304x where the connection strip conductors 207x and 212x cross in a solid manner. (2) The directional coupler 50ex is located at a position 305x where the connection strip conductors 206x and 210x cross in a solid manner, while the directional coupler 50fx is located at a position 306x where the connection strip conductors 208x and 212x cross in a solid manner. (3) The directional coupler 50ex is located at a position 303x while the directional coupler 50fx is located at a position 306x. (4) The directional coupler 50ex is located at a position 304x while the directional coupler 50fx is located at a position 305x. Although, in the embodiments shown in Figs. 7 and 9, the respective directional couplers 50gx and 50hx are located at positions shown in Fig. 9, the directional coupler 50gx may be located at the solid crossing portion 307x where the connection strip conductors 201x and 214x cross in a solid manner, while the directional coupler 50hx may be located at the solid crossing position 308x where the connection strip conductors 204x and 215x cross in a solid manner. Although the embodiment is explained with respected to the directional coupler having four or eight input and output terminals, the present invention is not limited to the embodiment and for example the present invention may be applied to the multi terminal directional coupler having more than 16 terminals. In general the present invention may be applied to the multi terminal directional coupler comprising: first input terminals, the number of which is N/2 wherein N is 2 n (n is natural number) and N/2 first output terminals respectively juxtaposed on one side of the ground conductor through the first dielectric substrate; N/2 second input terminals and N/2 second output terminals juxtaposed on another side of the ground conductor through the second dielectric substrate; the first multi terminal directional coupler comprising n x 2 n-1 directional couplers formed on the first dielectric substrate and connected to the N/4 first input terminals and the N/4 second input terminals, the N/4 third output terminals formed on the first dielectric substrate and the N/4 fourth output terminals formed on the second dielectric substrate; the second multi terminal directional coupler comprising n x 2 n-1 directional couplers formed on the first dielectric substrate and connected to the N/4 first input terminals and the N/4 second input terminals, the N/4 fifth output terminals formed on the second dielectric substrate and the N/4 sixth output terminals formed on the second dielectric substrate; N/4 first directional couplers connected to either one of the N/4 third output terminals of the first multi terminal directional coupler and one of the N/4 sixth output terminals of the second multi terminal directional couplers without overlapping and connected to either one of the N/4 first output terminals and one of the N/4 second output terminals without overlapping; N/4 second directional couplers connected to either one of the N/4 fourth output terminals of the first multi terminal directional coupler and one of the N/4 fifth output terminals of the second multi terminal directional couplers without overlapping and connected to either one of the N/4 first output terminals and one of the N/4 second output terminals without overlapping; whereby the first multi terminal directional coupler, the second multi terminal directional coupler, the N/4 first directional couplers and the N/4 second directional couplers and two coupling conductors in which the respective opposite ends form the input terminals and output terminals are formed on both sides of the ground conductor through the first dielectric substrate and the second substrate, so that the respective coupling conductors are coupled electromagnetically through the opening defined in the ground conductor. In the present embodiment the respective coupling conductors 51aax, 51abx, 51bax, 51bbx, 51cax, 51cbx, 51dax, 51dbx, 51eax, 51ebx, 51fax, 51fbx, 51gax, 51gbx, 51hax, 51hbx and the coupling openings 52ax to 52hx are elongated rectangular shape, the shape of them may be selected as desired so far as there are formed openings in the ground conductor 11x between the respective pairs of conductors 51aax and 51abx; 51bax and 51bbx; 51cax and 51cbx; 51dax and 51dbx; 51eax and 51ebx; 51fax and 51fbx; 51gax and 51gbx and 51hax and 51hbx so that there are formed electromagnetic mode coupling between the pairs of two coupling conductors. As mentioned above, in the present invention, there are provided N input terminals and N output terminals (wherein N is 2 ℓ ( ℓ is natural number)) and ℓx 2 ℓ-1 directional couplers so that signals having 1/N power of the input signals applied to the N input terminals can be output at the N output terminals and the respective ℓx 2 ℓ-1 directional couplers are formed on both sides of the ground conductor through the first and second dielectric substrates with the two coupling conductors having their opposite ends formed input terminals and output terminals so that the respective coupling conductors can be electromagnetically coupled through the opening defined on the ground conductor formed therebetween, therefore, the input terminals, output terminals, the coupling conductors of the respective directional couplers and strip conductors for connecting the respective terminals and coupling conductors and for connecting the respective coupling conductors may be formed being divided into two parts on the two dielectric substrates formed on both sides of the ground conductor. Accordingly, the size of the multi terminal directional coupler becomes 2/3 compared to that of the conventional directional coupler so that it is possible to decrease the size and weight. By the arrangement mentioned above the multi terminal directional coupler can be formed without solid crossing, therefore it is possible to form the circuit patterns accurately and to prevent the interference among the signals propagating the strip conductors. therefore it is possible to provide a multi terminal directional coupler in which the power of the signals can be divided with a gooa electric property. Referring to Figs. 15(A) to 15(E) showing a further embodiment of the present invention, there are defined coupling openings 22ay and 22by which penetrate a ground conductor 12y and has a length W of the short side and λg /4 of the long side in the upper right portion and lower right portion of an elongated ground conductor 12y with t0 thick, the coupling openings 22ay and 22by are filled by coupling insulation materials 10cay and 10cby. The ground conductor 12y is provided between dielectric substrates 10ay and 10by with a thickness t. In the upper left portion in Fig. 15(A) above the dielectric substrate 10ay, a coupling conductor 21aay of a rectangular shape with a length S on the short side and a length λg/4 on the long side is formed above the coupling insulation material 10cay. On the other hand, another coupling conductor 21aby similar to the conductor 21aay is formed below the coupling insulation material 10cay on the central left portion of Fig. 15(C) on the lower surface of the dielectric substrate 10by. The coupling conductors 21aay and 21aby are so formed that the longitudinal direction of the coupling conductors 21aay and 21aby is parallel to the respective short sides of the dielectric substrate 10ay and 10by. When the microwave signals are applied to the ends of the short sides of the coupling conductors 21aay and 21aby, a mode coupling is developed between the coupling conductors 21aay and 21aby and the ground conductor 12y through the coupling insulation material 10cay filled in the coupling opening 22ay so that the power of the signal is divided into two parts and the divided signals are input to another terminal and coupled with the other divided signal then the coupled signals can be output on the respective ends of the short sides of the coupling conductors 21aay and 21aby. In Fig. 15(A) the dotted lines indicate the position of the coupling openings 22ay and 22by. in one directional coupler 20ay, the respective short sides of the coupling opening 22ay of the ground conductor 12y and the short sides of the coupling conductors 21ay and 21aby coincide each other. The dielectric substrates 10ay and 10by and the coupling insulation material 10cay are made of dielectric material having the same dielectric constant. The directional coupler 20by is formed in the same manner as mentioned above. Figs. 16(A) and 16(B) are respectively vertical cross sectional views showing the electric field distribution of the odd mode and even mode by the known vertical mode driving at the coupling portion on the B-B′ line in Fig. 15. In the even mode shown in Fig. 16(A) there are developed electric force lines between the connecting conductors 21aay and 21aby and the ground conductor 12y, whereby the opening acts as the magnetic wall. On the other hand, in the odd mode shown in Fig. 16(B) there are developed electric force lines between the connecting conductors 21aay and 21aby and the ground conductor 12y, whereby the opening acts as the electric wall. Accordingly, there is formed a directional coupler 20ay having a predetermined coupling degree by the ground conductor 12y and the connecting conductors 21aay and 21aby formed on the dielectric substrate 10ay and 10by. Therefore, there can be provided a four terminal directional coupler 20ay having a coupling degree of 3dB by selecting the dielectric constant of the dielectric substrates 10ay and 10by, the width S of the connecting conductors 21aay and 21aby and the width W of the coupling opening 22ay. It is noted that the coupling degree is 3dB. In order to increase the coupling degree, the width W of the coupling opening 22ay is made large. There is formed a coupling conductor 21bay having the same shape of the conductor 21aay directly above the coupling insulation material 10cby at the central right portion in Fig. 15 (A) on the dielectric substrate 10ay, while there is formed a connecting conductor 21bby having the same shape of the conductor 21aby directly below the coupling insulation material 10cby at the central left portion in Fig. 15 (B) on the lower surface of the dielectric substrate 10by. Accordingly, there can be provided a directional coupler 20by having 3dB coupling degree in a similar manner as the directional coupler 20ay by the ground conductor 12y and the connecting conductors 21bay and 21bby. A hybrid amplifier 5y having a known structure with a predetermined amplification factor is formed at the central portion of the upper surface of the dielectric substrate 10ay, while a hybrid amplifier 6y having a known structure with a predetermined amplification factor is formed at the central portion of the lower surface of the dielectric substrate 10by. In the upper surface of the dielectric substrate 10ay, the signal input terminal 1y is connected to the connection terminal 23ay on the upper portion of the coupling conductor 21aay of the directional coupler 20ay through a connection strip conductor 131y. The connection terminal 24ay on the lower portion of the coupling conductor 21aay of the directional coupler 20ay is connected to the signal input terminal 5ay of the amplifier 5y through the connection strip conductor 133y. The output terminal 5by of the amplifier 5y is connected to the connection terminal 23by on the upper portion of the coupling conductor 21bay of the directional coupler 20by through a connection strip conductor 135y. The connection terminal 24by on the lower portion of the coupling conductor 21bay of the directional coupler 20by is connected to the non reflective terminating device 8y through the connection strip conductor 138y. In the lower surface of the dielectric substrate 10by, the connection terminal 26ay on the lower portion of the connection conductor 21aby of the directional coupler 20ay is connected to a non reflective terminating device 7y through the connection strip conductor 132y and the connection terminal 25ay on the upper portion of the connection conductor 21aby of the directional coupler 20ay is connected to the amplifier 6y through the connection strip conductors 134y. The output terminal 6by of the amplifier 6y is connected to a connection terminal 26by on the lower portion of the connection conductor 21bby of the directional coupler 20by through the connection strip conductor 136y. The connection terminal 25by on the connection conductor 21bby of the directional coupler 20by is connected to the signal output terminal 2y through the connection strip conductors 137y. The connection strip conductors 131y to 138y have respectively desired width which is defined by the characteristic impedance. In order to match the impedance of the signal input terminal 1y and the signal output terminal 2y, two amplifiers 5y and 6y have the same input and output impedance with the same amplification and gain property. The microwave signal entered in the signal input terminal 1y is input to the connection terminal 23ay of the directional coupler 20ay, in which the input signal is divided in to two parts and one part of the divided signal is entered to the input terminal 5ay of the amplifier 5y through the connection terminal 24ay situated on the same plane of the connection terminal 23ay and further through the strip conductor 133y. Another part of the divided signal divided in the directional coupler 20ay is entered to the input terminal 6ay of the amplifier 6y through the connection terminal 25ay which is located on a plane opposite to the plane on which the connection terminal 23ay is located and further through the connection strip conductor 134y. The respective signals output from the output terminal 5by of the amplifier 5y and the output terminal 6by of the amplifier 6y are respectively input to the connection terminals 23by and 26by of the directional coupler 20by through the connection strip conductors 135y and 136y. The respective signals input to the directional coupler 20by are composed or coupled and the composed signals is output at the signal output terminal 2y through the connection terminal 25by and connection strip conductor 137y. In the microwave balanced amplifier mentioned above, two amplifiers 5y and 6y are located on the dielectric substrates 10ay and 10by and since the two amplifiers are separated by the ground conductor, there does not occur any interference of the signals of the amplifiers 5y and 6y. Accordingly, the signal entered in the signal input terminal 1y can be processed with a good electrical property. Moreover since two amplifiers 5y and 6y and the connection strip conductors are located on both size of the dielectric substrates 10ay and 10by, it is possible to decrease the size of the microwave balanced amplifier about 1/2 of the size of the conventional device and therefore the weight of the amplifier device. Moreover, in the present embodiment it is not necessary to couple the signals by way of ridge coupling using wire or ribbon conductors as employed in the interdigit directional coupler whereby the circuit patterns can be accurately formed and the work of the production of the device is simple compared to the work of the production of the conventional device. In addition since the conductor patterns of the dielectric substrate 10ay shown in Fig. 15 (A) is the same as the conductor patterns on the dielectric substrate 10by shown in Fig. 15 (C), it is an advantage that two conductor patterns can be produced using the same pattern. Fig. 17 is a circuit diagram showing an embodiment of the four input four output multi terminal amplifier according to the present invention. In Fig. 17, four amplifiers 31y to 34y are connected between the first and second multi terminal directional couplers 201y and 202y, each having four inputs and four outputs. The multi terminal directional couplers 201y and 202y comprises four directional couplers 40ay to 40dy and 40ey to 40hy each having 3dB coupling degree, whereby four output signal each having 1/4 power of the input signals applied to the four input terminals can be output at the four output terminals. Accordingly by changing the amplification factor of the amplifiers 31y to 34y, there can be obtained at the output terminals 55y to 58y the output signals each having a desired power level which has been coupled from the input signals entered at the input terminals 51y to 54y with a predetermined power level and amplified. Figs. 18 (A) to 18 (C) are circuit diagrams showing specific structure of the multi terminal amplifier shown in Fig. 17 and Fig. 18 (A) is a top plan view of the multi terminal amplifier, Fig. 18 (B) is a plan view showing the ground conductor 12y of the multi terminal amplifier shown in Fig. 18 (A) and Fig. 18 (C) is a plan view showing conductor patterns on the dielectric substrate 10by of the multi terminal amplifier shown in Fig. 18 (A). In Figs. 18 (A) to 18 (C), the like parts are designated with like reference numerals. The multi terminal amplifier comprises a first directional coupler 201y having four directional couplers 40ay to 40dy, an amplifier formed by four amplifiers 31y to 34y and a second multi terminal directional coupler 202y having four directional couplers 40ey to 40hy. In Fig. 18 (A) there are defined coupling openings 42ay to 42dy which penetrate a ground conductor 12y and has a length W of the short side and λg /4 of the long side in the upper left portion, lower left portion, central portion and central right portion of the multi terminal directional coupler 201y of an elongated ground conductor 12y with t0 thick, the coupling openings 42ay to 42dy are filled by coupling insulation materials 10cay and 10cby, 10ccy and 10cdy. On the left central portion, the right central portion, upper right portion, lower right portion of the multi terminal directional coupler 202y of the ground conductor 12y The ground conductor 12y, there are defined coupling openings 42ey to 42hy penetrating the ground conductor 12y with short sides of length of W and long sides of λg/4 and the respective coupling openings are filled by the coupling insulation materials 10cey, 10cfy, 10cgy and 10chy. The ground conductor 12y is provided between two dielectric substrates 10ay and 10by. On the top surface of the dielectric substrate 10ay, there are formed rectangular coupling conductors 41aay, 41bay, 41cay, 41day, 41eay, 41fay, 41gay and 41hay each having short sides of length S and long sides of length of λg/4. On the lower surface of the dielectric substrate 10by shown in Fig. 18 (C), coupling conductors 41aby, 41bby, 41cby, 41dby, 41eby, 41fby, 41gby, and 41hby having the same shape as the conductor 41aay are respectively formed directly below the coupling insulation materials 10cay to 10chy. The respective input terminals and output terminals of the multi terminal amplifier are formed on one side of the multi terminal amplifier. In order to form the same electric length between the respective input terminals and output terminals, the coupling conductors 41aay to 41hay and 41aby to 41hby are formed in such a manner that the longitudinal direction of the conductors 41aay to 41hay and 41aby to 41hby are parallel to the short side direction of the dielectric substrates 10ay and 10by. Accordingly, similar to the directional couplers 20ay and 20by, there is formed a directional coupler 40ay having 3dB coupling degree by the coupling conductors 41aay and 41by and the ground conductor 12y. In a similar manner there are formed directional couplers 40by to 40hy having 3dB coupling degree. On the top surface of the dielectric substrate 10ay, the signal input terminal 51y is connected to the connection terminal 43ay on the upper portion of the coupling conductor 41aay of the directional coupler 40ay through a connection strip conductor 61y. The connection terminal 44ay on the lower portion of the coupling conductor 41aay of the directional coupler 40ay is connected to the connection terminal 43cy on the upper portion of the coupling conductor 41cay of the directional coupler 40cy through the connection strip conductor 62y of a S character shape. The connection terminal 44cy on the lower portion of the coupling conductor 41cay of the directional coupler 40cy is connected to the input terminal 31ay of the amplifier 31y through a connection strip conductor 63y. The signal input terminal 53y is connected to the connection terminal 43by on the upper portion of the coupling conductor 41bay of the directional coupler 40by through the connection strip conductor 67y. The connection terminal 44by on the lower portion of the coupling conductor 41bay of the directional coupler 40by is connected to the connection terminal 44by on the lower portion of the coupling conductor 41day of the directional coupler 40dy through the connection strip conductor 68y of a zigzag shape. The connection terminal 43by on the upper portion of the coupling conductor 41day of the directional coupler 40by is connected to the input terminal 32ay of the amplifier 32y through the connection strip conductor 69y. The output terminal 31by of the amplifier 31y is connected to the connection terminal 44ey on the lower portion of the coupling conductor 41eay of the directional coupler 40ey through the connection strip conductor 64y. The connection terminal 43ey on the upper portion of the coupling conductor 41eay of the directional coupler 40ey is connected to the connection terminal 43gy on the upper portion of the coupling conductor 41gay of the directional coupler 40gy through the connection strip conductor 65y of a zigzag shape. The connection terminal 44gy on the lower portion of the coupling conductor 41gay of the directional coupler 40gy is connected to the signal output terminal 55y through the connection strip conductor 66y. The output terminal 32by of the amplifier 32y is connected to the connection terminal 43fy on the upper portion of the coupling conductor 41fay of the directional coupler 40fy through the connection strip conductor 70y. The connection terminal 44fy on the lower portion of the coupling conductor 41fay of the directional coupler 40f is connected to the connection terminal 43hy on the upper portion of the coupling conductor 41hay of the directional coupler 40hy through the connection strip conductor 71y of a S character shape. The connection terminal 44hy on the lower portion of the coupling conductor 41hay of the directional coupler 40hy is connected to the signal output terminal 56y through the connection strip conductor 72y. On the lower surface of the dielectric substrate 10by, the signal input terminal 52y is connected to the connection terminal 46ay on the lower portion of the coupling conductor 41aby of the directional coupler 40ay through a connection strip conductor 73y. The connection terminal 45ay on the upper portion of the coupling conductor 41aby of the directional coupler 40ay is connected to the connection terminal 45dy on the upper portion of the coupling conductor 41dby of the directional coupler 40dy through the connection strip conductor 74y of a zigzag shape. The connection terminal 46dy on the lower portion of the coupling conductor 41dby of the directional coupler 40dy is connected to the input terminal 33ay of the amplifier 33y through a connection strip conductor 75y. The signal input terminal 54y is connected to the connection terminal 46by on the lower portion of the coupling conductor 41bby of the directional coupler 40by through the connection strip conductor 79y. The connection terminal 45by on the upper portion of the coupling conductor 41bby of the directional coupler 40by is connected to the connection terminal 46cy on the lower portion of the coupling conductor 41cdy of the directional coupler 40cy through the connection strip conductor 80y of a S character shape. The connection terminal 45cy on the upper portion of the coupling conductor 41cby of the directional coupler 40cy is connected to the input terminal 34ay of the amplifier 34y through the connection strip conductor 81y. The output terminal 33by of the amplifier 33y is connected to the connection terminal 46fy on the lower portion of the coupling conductor 41fby of the directional coupler 40fy through the connection strip conductor 76y. The connection terminal 45fy on the upper portion of the coupling conductor 41fby of the directional coupler 40fy is connected to the connection terminal 46gy on the lower portion of the coupling conductor 41gby of the directional coupler 40gy through the connection strip conductor 77y of S character shape. The connection terminal 45gy on the upper portion of the coupling conductor 41gby of the directional coupler 40gy is connected to the signal output terminal 57y through the connection strip conductor 78y. The output terminal 34by of the amplifier 34y is connected to the connection terminal 45ey on the upper portion of the coupling conductor 41eby of the directional coupler 40ey through the connection strip conductor 82y. The connection terminal 46ey on the lower portion of the coupling conductor 41eby of the directional coupler 40ey is connected to the connection terminal 46hy on the lower portion of the coupling conductor 41hby of the directional coupler 40hy through the connection strip conductor 83y of a zigzag shape. The connection terminal 45hy on the upper portion of the coupling conductor 41hby of the directional coupler 40hy is connected to the signal output terminal 58y through the connection strip conductor 84y. The width of the connection strip conductors 61y and 84y is determined corresponding to the characteristic impedance. Each of the signal entered to the signal input terminals 51y to 54y is processed in the multi terminal amplifiers shown in Figs. 18 (A) and 18 (C) and in order to output the processed signals to the signal output terminals 55y to 58y with the same phase difference against the input signals, the electric length of the connection strip conductor beginning from the respective signal input terminals 51y to 54y and ending at the signal output terminals 55yx to 58y through the respective directional couplers and the amplifiers, that is the total electric length of the connection strip conductors 61y, 66y and; the total electric length of the connection strip conductors 67y to 72y; the total electric length of the connection strip conductors 73y to 78y; and the total electric length of the connection strip conductors 79y to 84y are made uniform. The multi terminal directional coupler arranged as mentioned above is equivalent to the circuit shown in Fig. 17 and by changing the amplification factors of the amplifiers 31y to 34y, it is possible to obtain the coupled and amplified signals with desired power level at the signal output terminals 55y to 58y from the signal input at the signal input terminals 51y to 54y which are coupled with the same degree. As mentioned above, since the signal input terminals 51y to 54y, signal output terminals 55y to 58y, amplifiers 31y to 34y and the connection strip conductors 61y to 84y for connecting the respective terminals are divided to two parts on both sides of the dielectric substrate 10ay and 10by employing the directional couplers 40ay to 40hy in place of using the interdigit directional coupler, the size of the four input or output multi terminal amplifier may be decreased to 1/2 of the conventional multi terminal amplifier using inter digit directional coupler. In the present embodiment, since it is not necessary to provide a ridge coupling by the wire or ribbon conductor as used in the inter digit directional coupler, the circuit patterns can be accurately made and the work of manufacturing the device can be easier than the work of manufacturing the conventional device. The conductor patterns on the dielectric substrate 10ay shown in Fig. 18 (A) is the same as the patterns which are rotated by 180° from the patterns of the dielectric substrate 10by shown in Fig. 18 (C) around the center of the dielectric substrate 10by, whereby the respective conduction patterns can be made by the same pattern. Although in the present embodiment the hybrid amplifiers 5y, 6y, 31y to 34y are formed on the dielectric substrate 10ay and 10by, the present invention is not limited to the embodiment, it may be possible to replace the dielectric substrates by semiconductor substrates and the hybrid amplifiers 5y, 6y, 31y to 34y may be replaced by various types of the amplifier such as MMIC formed on the semiconductor substrate. In this case the coupling insulation material may be replaced by semiconductor material. Although the coupling conductors 21aay, 21aby, 21day, 21bby, 41aay, 41aby, 41bay, 41bby, 41cay, 41cby, 41day, 41dby, 41eay, 41eby, 41fay, 41fby, 41gay, 41gby, 41hay and 41hby and coupling openings 22ay, 22by, 42ay to 42hy are respectively formed as the rectangular shape, the shape is not limited to the rectangular shape, provided that there are formed openings between the coupling conductors of the directional coupler so that the mode coupling can be electromagnetically developed between each pair of the coupling conductors. Although the explanation made with respect to the device having four signal input and output terminals, there may be used more than 16 multi terminal device in the present invention. In place of the amplifiers 5y, 6y, 31y and 34y, various microwave signal processing device such as attenuator, phrase shifter, modulator and/or frequency converter may be used. Accordingly in the present invention by providing at least one of the directional couplers 50ay and 50by and said microwave signal processing device, the present invention can be applied to the various type of the microwave device. Accordingly it is possible to provide microwave devices which are able to process input signals with a good electric property preventing the interference between the signals propagating in the lines and which are small in size and light in weight and able to be manufactured easily. In case where the phase shifters are used in place of the amplifiers 5y and 6y shown in Fig. 15 (A) and 15 (C), by changing the amount of phase shift in the phase shifters it is possible to take attenuated microwave signals from the output terminals 2y using the input microwave signals at the input terminal 1y. In the present invention, since there are provided one or more directional couplers comprising directional coupler formed in such a manner that two coupling conductors forming input and output terminals are disposed on both sides of the ground conductor through the substrates so that the coupling conductors can be electromagnetically coupled through openings defined in the ground conductor between the coupling conductors and microwave signal processing device disposed any one of the front stage or rear stage of the directional coupler, said coupling conductors of the directional coupler, said microwave signal processing device and various lines for connecting the coupling conductors and the microwave processing device may be formed on both sides of the two substrates being separated into two parts. Accordingly the size of the microwave device is about 1/2 of the conventional device and it is possible to provide a light and small sized device. Since the device according to the present invention can be provided without using wire and ribbon coupling conductor to develop the ridge coupling, the interference among the signals can be prevented. Therefore there can be provided the microwave device which is able to process the microwave signal with a good electric property.

Claims: A multi terminal directional coupler device comprising N input terminals (1x to 4x) and N output terminals (5x to 8x) and n x 2 n - 1 directional coupler means (50ax to 50dx), wherein N = 2 n ≧ 4 (n is a natural number), so that signals of 1/N power of input signals are output at the respective N output terminals, characterized in that at least two of said directional coupler means (50ax to 50dx) consist each of a pair of coupling conductors respectively, one coupling conductor (51aax to 51dax) of each of said pairs being disposed on the upper surface of a first dielectric substrate (10ax) and the other coupling conductor (51abx to 51dbx) of each of said pairs is disposed on the lower surface of a second dielectric substrate (10bx), and a ground conductor (11) being disposed between the lower surface of said first (10ax) and the upper surface of said second substrate (10bx), said pair of coupling conductors being coupled through corresponding coupling openings (52ax to 52dx) defined in the ground conductor (11) between said pairs of coupling conductors. A microwave device comprising directional coupler means (40ay to 40hy) and microwave signal processing means (31y to 34y) connected with the front stage or rear stage of the directional coupler means, characterized in that said directional coupler means (40ay to 40hy) consist of a pair of coupling conductors respectively, one coupling conductor (41aay to 41hay) of said pair being disposed on the upper surface of a first dielectric substrate and the other coupling conductor (41aby to 41hby) of said pair is disposed on the lower surface of the second dielectric substrate, and a ground conductor (12y) being disposed between the lower surface of said first and the upper surface of said second substrate, said pair of coupling conductors being coupled through a respective coupling opening (42ay to 42hy) defined in the ground conductor between said pair of coupling conductors.

Inventors: AIKAWA MASAYOSHI, TANAKA TOSHIAKI, AIKAWA, MASAYOSHI, TANAKA, TOSHIAKI
Applicants: ATR OPTICAL AND RADIO COMMUNIC, ATR OPTICAL AND RADIO COMMUNICATIONS RESEARCH LABORATORIES
Application year: 1988
Main classification: H01P5
IPC codes: H01P5