US3611153A

US3611153A - Balanced mixer utilizing strip transmission line hybrid

Info

Publication number: US3611153A
Application number: US876001A
Authority: US
Inventors: Cheng Paul Wen
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1969-11-12
Filing date: 1969-11-12
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05
Also published as: FR2100597B1; SE364401B; GB1322038A; DE2055710A1; FR2100597A1; NL7016487A

Abstract

A microwave hybrid in a strip transmission line configuration is provided. Two narrow striplike conductors are joined together to form a T-configuration. Another narrow striplike conductor is positioned parallel to one of the conductors along the crossed portion of the T-configuration. A ground plane is placed to form with the narrow striplike conductors a plurality of transmission lines for propagating signal energy in an electromagnetic mode.

Description

[111 3,6]1Lll53 lnventor Cheng lloul Wen Trenton, NJ.

Appl. No. $76,001

Filed Nov. 12, 11969 Patented Oct. 5, 1971 Assignee RCA Corporation BALANCED MIXER UTllLllZlNG STRIP TRANSMHSSIION LINE HYBRID [56] References Cited UNITED STATES PATENTS 3,310,748 3/1967 Putnam 325/446 3,451.015 6/1969 Heath r v 333/84(M)X Primary Examiner-Herman Karl Saalbach Assistant Examiner-Paul L. Gensler Attorney-Edward J. Norton ABSTRACT: A microwave hybrid in a strip transmission line configuration is provided. Two narrow striplike conductors 8 Claims 3 Drawing Figs are joined together to form a T-configuration. Another narrow US. Cl 325/446, striplilge conductor is positioned parallel to one of the conduc- 333/10, 333/11, 333/84 M tors along the crossed portion of the T-configuration. A Int. Cl l1-ll04b 1/26 ground plane is placed to form with the narrow striplike con- Field of Search 333/10, 1 1, ductors a plurality of transmission lines for propagating signal 84 M; 325/446 energy in an electromagnetic mode.

40 4 43 L.O. i

37: 33 [II 7 :5 Z: s9 2l I '5 Mill 2?) V- IN [V MIXER l i l 5- I l 29 mm/ll A |J| ll 1 GROUND PLANE l GROUND PLANE BALANCED MIXER UTILIZING STRIP TRANSMISSION LINE HYBRID This invention relates to microwave hybrid circuits and more particularly to a hybrid configuration employing strip transmission lines.

In the prior art, large and bulky microwave hybrids such as magic tees in waveguide and coaxial systems are known. These forms of hybrids, because of their size and structure, are not compact and do not adapt easily to microwave integrated circuit configurations. The most widely used microwave integrated circuit configuration includes a single substrate of dielectric material having a ground plane on one side thereof and a narrow striplike conductor on the opposite side. There is a new form of microwave integrated circuit proposed wherein the ground plane and the narrow striplike conductor are both on the same surface or side of the dielectric substrate. This new type of transmission line is described by the applicant C. P. Wen in lEEE 1969 G-M'l'l" international Microwave Symposium Digest of May 1969 under the title A Surface Strip Transmission Line Suitable for Nonreciprocal Gyromagnetic Device Applications."

Large waveguide magic tees or coaxial systems are difficult to couple to either of these above configurations and also add a great deal of bulk and weight that integrated circuits are intended to avoid. Although there exists a distributed-circuittype magic tee, the operating bandwidth of the distributed-circuit type is limited because of the one-quarter wavelength requirement imposed on the distributed-circuit-type magic tee.

It is therefore an object of the present invention to provide an improved microwave hybrid which is low cost, compact and adaptable for use with microwave integrated circuit configurations.

This and other objects are accomplished by at least two narrow striplike conductors fixed to one surface of a dielectric substrate. A first of the narrow striplike conductors is joined at a point along the second of the narrow striplike conductors. A substantially wider ground planar conductor is positioned on the dielectric to provide with the narrow striplike conductors a plurality of transmission lines for propagating signals in an electromagnetic mode. The second of the narrow striplike conductors is substantially in a straight line in the region of the junction thereof with the first narrow striplike conductor. A third narrow striplike conductor is fixed to the same surface of the dielectric as the other narrow striplike conductors. This third narrow striplike conductor is positioned so that a portion thereof is closely spaced and parallel to the substantially straight portion of the second narrow striplike conductor, whereby signals coupled to one end of the first narrow striplike conductor propagate in phase along the second narrow striplike conductor joined thereto and no appreciable signal is coupled to the third narrow striplike conductor. Signals coupled to the third narrow striplike conductor propagate towards each end of the second narrow striplike conductor with little or no coupling of the signals to the first narrow striplike conductor.

A further description follows along with the accompanying drawing wherein:

FIG. 1 is a balanced mixer using a microwave hybrid in accordance with a first embodiment of the present invention,

FIG. 2 is a microwave hybrid in accordance with a second embodiment of the present invention, and

FIG. 3 is a microwave hybrid in accordance with a third embodiment of the present invention.

Referring now to the particular microwave hybrid shown in FIG. 1, a dielectric substrate 11 is provided, having a plurality of narrow

striplike conductors

13, 17 and 33 thereon. The first narrow striplike conductor 13 on one surface of the substrate 11 is joined along its midpoint at point 15 to the second narrow striplike conductor 17 in a manner to form a T-shaped configuration. Substantially wider ground

planar conductors

29 and 31 are placed on the same surface of the dielectric substrate 11 to form with the narrow striplike conductor 17 a coplanar strip transmission line. This form of coplanar strip transmission line or surface strip transmission line is described in application Ser. No. 787,349 filed Dec. 27, 1969, now US. Pat. No. 3,560,893, by applicant Cheng Paul Wen. This type of transmission line has also been described by the applicant as mentioned above in the Digest of the IEEE International Microwave Symposium; Dallas, Tex.; May, 1969.

A third narrow striplike conductor 33 is fixed to the same surface of the substrate 11. This third narrow striplike conductor 33 has

opposite end portions

35 and 37 substantially parallel to one another with a middle portion 39 parallel and closely spaced in aligned relationship with the narrow striplike conductor 13. The narrow striplike conductor 33 is positioned such that

end portions

35 and 37 are aligned in a direction orthogonal to the narrow striplike conductor 13 with the ends of these

portions

35 and 37 being equally spaced from the junction 15 of narrow

striplike conductors

17 and 13.

If it is desired to use the hybrid arrangement to provide a balanced mixer configuration, one end or port 19 of transmission line 13 is coupled to a diode mixer 23 and the opposite end 21 of transmission line 13 is coupled to a second diode mixer 25. The free end 27 of transmission line 17 is coupled to a source of RF (radio frequency) carrier signal energy, not shown, and a local oscillator 41) is coupled across

portions

35 and 37 of narrow striplike conductor 33.

In the operation of the balanced mixer arrangement shown in FlG. l, signals such as RF signals received at port 27 at one end of narrow striplike conductor 17 propagate in the coplanar transmission line made up of narrow striplike conductor 17 and ground

planar conductors

29 and 31 to the junction 15 of the narrow striplike conductor 13 and conductor 17. At this point, the power of the: applied RF signal divides equally and in phase and propagates along the transmission line formed by the narrow striplike conductor 13 and ground planar conductor 31 to mixer 25 at port 21 and propagates along the transmission line formed by the narrow striplike conductor 13 and ground planar conductor 29 to mixer 23 at port 19. If the lengths from junction 15 to

mixers

25 and 23 are equidistant, the signal levels arriving at the respective mixers are equal and the signals are in phase. Although the narrow striplike conductor 33 is spaced a short distance from conductor 13, little or no coupling is provided to narrow striplike conductor 33 because the phase of the applied RF signal is the same at opposite ends of the T-junction 15 of narrow striplike conductor 13.

If, as suggested above, a local oscillator is coupled across the ends 41 and 413 ofconductor 33 or at port 40 of the hybrid, the signals from the local oscillator at port 40 travel along the parallel narrow

striplike portions

35 and 37 in the manner of a parallel-conductor transmission line with a shorted portion 39 parallel to the narrow striplike conductor 13. At this shorted region 39, coupling of the local oscillator signal is provided to the narrow striplike conductor 13. Since the

portions

35 and 37 of the parallel-conductor transmission line are at opposite ends of narrow striplike conductor 13 with respect to junction 15, the local oscillator signals are coupled to transmission line 13 with the signal at one end of conductor 13 being out of phase with respect to the signal at the other end and little or no coupling of the oscillator signal to the narrow striplike conductor 17 at the center 15 of conductor 13 occurs. By providing the arrangement described herein, one mixer is responsive to the input RF carrier and a local oscillator signal 180 out of phase with respect to the oscillator signal at the other mixer. It is known that when combiningthe mixer output signals, even order harmonic distortion from the local oscillator is suppressible.

A microwave hybrid in accordance with another embodiment of the present invention is shown in H6. 2. The narrow striplike conductor 53 is substantially the same as narrow striplike conductor 33 in FIG. 1. ln the arrangement of FIG. 2, the narrow

striplike conductors

55 and 57, as well as the conductor 53, are placed on one surface of the dielectric substrate 51 in much the same manner as

conductors

13 and 17 of FIG.

l. The opposite surface of the dielectric substrate is provided with a ground planar conductor 52. The narrow

striplike cond uctors

55 and 57 provide with ground planar conductor 52 two microstrip transmission lines propagating microwave signal energy in the approximate transverse electromagnetic (TEM)I'J'IOdg; Conductor 57 is joined at the middle of conductor 55 at point 61 'to form a T-configuration of two transmis sion lines. The narrow striplike conductor 53 is positioned so that at the coupling and termination region, portion 59 is closely spaced and parallel-to the conductor 55 so as to be in the electromagnetic coupling region of narrow striplike conductor 55.

The operation of the configuration shown in FIG. 2 is like that of FIG. 1. Signals traveling along narrow striplike conductor 57 are power split and arrive at opposite ends 56 and 58 of narrow striplike conductor 55 in phase with little or no appreciable coupling to the narrow striplike conductor 53. Signals coupled across the ends of narrow striplike conductor 53 are coupled across the closely spaced region of

conductors

55 and 59 to the opposite ends 56 and 58 of narrow striplike conductor 55. The power of a signal applied across the ends of conductor 53 divides and appears at the opposite equidistant ends of the narrow striplike conductor 55 180 out of phase. No appreciable coupling to the narrowstriplike conductor 57 occurs.

A narrow band microwave hybrid is provided by a third embodiment of the present invention shown in FIG. 3. In FIG. 3 there is provided a dielectric substrate 7 l with a ground planar conductor 73 on one surface of substrate 71. Again two narrow

striplike conductors

75 and 76 are joined together at junction point 74 such as to form a T-configuration with narrow striplike conductor 76 at the midpoint of narrow striplike conductor 75. Narrow striplike conductor 75 and the ground planar conductor 73 provide a transmission line which propagates signals in a transverse electromagnetic (TEM) mode. Likewise signals are propagated in the transverse electromagnetic (TEM) mode between the narrow striplike conductor 76 and ground planar conductor 73.

A one-half wavelength resonator section 70 which is open circuited at both ends is closely spaced adjacent to narrow striplike conductor 75. The resonator section 70 is formed of narrow striplike conductor 77 and the ground planar conductor 73. The narrow conductor 77 is placed with respect to the narrow striplike conductor 75 such that the center 78 of the narrow conductor 77 is adjacent to the junction 74. A narrow striplike conductor 79 is spaced a short distance from one end 81 of narrow striplike conductor 77 so as to be in capacitycoupling relationship with narrow strip conductor 77. A narrow band mixer is provided by positioning mixer diodes, not shown, at the

ends

85 and 87 of narrow striplike conductor 75. An RF carrier signal is applied to the free end 89 of the conductor 76. A local oscillator signal is applied to the end 91 of the conductor 79.

In the operation of the hybrid as a balanced mixer, RF carrier signals applied between narrow striplike conductor 76 and ground conductor 73 at point 89 are propagated along the transmission line comprising narrow striplike conductor 76 and ground planar conductor 73 to the junction 74. At this point as per the previous arrangements, the RF carrier signal divides and appears at the

equidistant points

87 and 85 in phase with little or no coupling to the narrow strip 77 because, as in the previous embodiments, the phase of the signal is the same at the opposite equidistant points from the junction 74.

The combination of the narrow striplike conductor 79, ground planar conductor 73 and the resonant narrow strip conductor 77 in the arrangement described, provides a form of directional coupler. If the length of the resonator section 70. composed of narrow conductor 77 and ground conductor 73 is one-half wavelength at the local oscillator frequency, oscillator signals applied at point 91 of narrow striplike conductor 79 are capacitively coupled to the narrow striplike conductor 77. The local oscillator signals are coupled from the striplike conductor 77 to the closely spaced narrow striplike conductor 75. The local oscillator signals arrive at opposite ends 87 and 85 of narrow striplike conductor 75, l80 out of phase with respect to each other. This difference in phase and the fact that little or no coupling is provided to conductor 76 results from the location of junction 74 of narrow

striplike conductors

75 and 76 at the midpoint 78 of the one-half wavelength along conductor 77.

What is claimed is:

l. A hybrid comprising in combination:

a dielectric substrate,

a first narrow striplike conductor fixed to one surface of said substrate, a second narrow striplike conductor joined along a portion 1 5 of its length to one end of said first narrow striplike conductor in a manner to form three conductors radially extending from the junction of said first and second conductors, said second narrow striplike conductor fixed to said one surface of said dielectric substrate,

2 relatively broad conductive means spaced with respect to said first and second narrow striplike conductors to form with said first and second narrow striplike conductors three transmission lines radially extending from said junction, said lines being arranged for propagating signals in an electromagnetic mode, whereby first signals received at one end of said first narrow striplike conductor propagate in phase toward opposite ends of said second narrow striplike conductor,

a third narrow striplike conductor fixed to said one surface of said substrate with a portion of said third conductor closely spaced and parallel to the portion of said second conductor in the region of the junction of said first and second conductors so as to be electromagnetically coupled to each other,

means by which second signals are applied to said third conductor to cause said second signals coupled therefrom to said second conductor to power divide and propagate said second signals to the opposite ends of said second conductor 180 out of phase without any significant coupling of said second signals from said second conductor to said first conductor.

2. The combination as claimed in claim 1 wherein said conductive means is a wide ground planar conductor fixed to the surface of said substrate opposite that to which said narrow striplike conductors are fixed.

3. The combination as claimed in claim 1 wherein said conductive means includes at least two ground planar conductors fixed to the same surface of said substrate as said striplike conductors.

4. The combination as claimed in claim 1 wherein the mid point of the length of said third conductor is at a point adjacent to said region of said junction of said first and second conductors.

5. The combination as claimed in claim 1 wherein said lastmentioned means comprises a parallel-conductor transmission line terminated by said third conductor connected across the parallel-conductor transmission line.

6. The combination as claimed in claim 2 wherein said third conductor is about one-half wavelength long at the midoperating frequency of said propagating therealong.

7. The combination as claimed in claim 6 wherein said lastmentioned means comprises a fourth narrow striplike conductor with one end closely spaced to one end of said third narrow striplike conductor.

8. A balanced mixer responsive to an RF microwave signal and a locally generated microwave signal comprising in combination:

a substantially flat dielectric substrate,

a first narrow striplike conductor fixed to one surface of said substrate,

a second narrow striplike conductor joined along a portion of its length to said first conductor in a manner to form three radially extending conductors extending from the junction of said first and second conductors. said second narrow conductor fixed to said one surface of said dielectric substrate,

relatively broad conductive means spaced with respect to said first and second conductors to form with said first and second conductors three radially extending transmission lines for propagating said microwave signals in an electromagnetic mode,

a first mixer coupled to one end of said second conductor,

a second mixer coupled to the opposite end of said second conductor,

the transmission line formed by said first conductor and said conductive means serving to support said RF microwave signal which is power divided at the junction of said first and second conductors and fed in phase to said first and second mixer at opposite ends of said second conductor,

a third narrow striplike conductor fixed to said one surface of said substrate with a portion of said third conductor closely spaced and parallel to the portion of said second conductor in the region of the junction of said first and second conductors so as to be electromagnetically coupled to each other, and

means by which said locally generated microwave signals are applied to said third conductor to cause said locally generated signals coupled therefrom to said second conductor to power divide and propagate said locally generally signals to the opposite ends of said second conductor out of phase without any significant coupling of said locally generated signals to said first conductor.

Claims

1. A hybrid comprising in combination: a dielectric substrate, a first narrow striplike conductor fixed to one surface of said substrate, a second narrow striplike conductor joined along a portion of its length to one end of said first narrow striplike conductor in a manner to form three conductors radially extending from the junction of said first and second conductors, said second narrow striplike conductor fixed to said one surface of said dielectric substrate, relatively broad conductive means spaced with respect to said first and second narrow striplike conductors to form with said first and second narrow striplike conductors three transmission lines radially extending from said junction, said lines being arranged for propagating signals in an electromagnetic mode, whereby first signals received at one end of said first narrow striplike conductor propagate in phase toward opposite ends of said second narrow striplike conductor, a third narrow striplike conductor fixed to said one surface of said substrate with a portion of said third conductor closely spaced and parallel to the portion of said second conductor in the region of the junction of said first and second conductors so as to be electromagnetically coupled to each other, means by which second signals are applied to said third conductor to cause said second signals coupled therefrom to said second conductor to power divide and propagate said second signals to the opposite ends of said second conductor 180* out of phase without any significant coupling of said second signals from said second conductor to said first conductor.

4. The combination as claimed in claim 1 wherein the midpoint of the length of said third conductor is at a point adjacent to said region of said junction of said first and second conductors.

5. The combination as claimed in claim 1 wherein said last-mentioned means comprises a parallel-conductor transmission line terminated by said third conductor connected across the parallel-conductor transmission line.

7. The combination as claimed in claim 6 wherein said last-mentioned means comprises a fourth narrow striplike conductor with one end closely spaced to one end of said third narrow striplike conductor.

8. A balanced mixer responsive to an RF microwave signal and a locally generated microwave signal comprising in combination: a substantially flat dielectric substrate, a first narrow striplike conductor fixed to one surface of said substrate, a second narrow striplike conductor joined along a portion of its length to said first conductor in a manner to form three radially extending conductors extending from the junction of said first and second conductors, said second narrow conductor fixed to said one surface of said dielectric substrate, relatively broad conductive means spaced with respect to said first and second conductors to form with said first and second conductors three radially extending transmission lines for propagating said microwave signals in an electromagnetic mode, a first mixer coupled to one end of said second conductor, a second mixer coupled to the opposite end of said second conductor, the transmission line formed by said first conductor and said conductive means serving to support said RF microwave signal which is power divided at the junction of said first and second conductors and fed in phase to said first and second mixer at opposite ends of said second conductor, a third narrow striplike conductor fixed to said one surface of said substrate with a portion of said third conductor closely spaced and parallel to the portion of said second conductor in the region of the junction of said first and second conductors so as to be electromagnetically coupled to each other, and means by which said locally generated microwave signals are applied to said third conductor to cause said locally generated signals coupled therefrom to said second conductor to power divide and propagate said locally generally signals to the opposite ends of said second conductor 180* out of phase without any significant coupling of said locally generated signals to said first conductor.