US3919670A - Microwave phase shifter - Google Patents

Microwave phase shifter Download PDF

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Publication number
US3919670A
US3919670A US432373A US43237374A US3919670A US 3919670 A US3919670 A US 3919670A US 432373 A US432373 A US 432373A US 43237374 A US43237374 A US 43237374A US 3919670 A US3919670 A US 3919670A
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United States
Prior art keywords
phase shifter
microwave
circuit means
varactor diodes
circular waveguide
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Expired - Lifetime
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US432373A
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English (en)
Inventor
Gerald I Klein
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CBS Corp
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Westinghouse Electric Corp
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Priority to US432373A priority Critical patent/US3919670A/en
Priority to BG30203A priority patent/BG22809A3/xx
Publication of USB432373I5 publication Critical patent/USB432373I5/en
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Publication of US3919670A publication Critical patent/US3919670A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/18—Phase-shifters
    • H01P1/185—Phase-shifters using a diode or a gas filled discharge tube
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/18—Networks for phase shifting
    • H03H7/185—Networks for phase shifting comprising distributed impedance elements together with lumped impedance elements

Definitions

  • the four sets of varactor diodes [5 ll '2" H0113) 1H8; HOlP 9/00 are synchronously driven in a manner to cause the relsgl held of Search 333l-l 31 sultant or effective obstacle plane to continuously ro- 333/7 D, 7 R, 98 R 98 S, 33. /l6 R 9 R, tate between 0 and 360 within the waveguide in re- 30 307/34) sponse to control voltage inputs applied to the four sets of varactor diodes.
  • This invention relates generally to phase shifters of electromagnetic energy and more particularly to an electrically controlled phase shifter having birefringent properties.
  • phase changers by means of which the phase of an output wave is shifted with respect to the input wave are well known components in the art of microwave transmission.
  • One such phase changer consists of a mechanically rotated half wave plate coupled between two quarter wave plates which act as polarization converters wherein linearly polarized waves are first converted to circularly polarized waves, applied to the rotating half wave section and then reconverted to linearly polarized waves with the instantaneous phase shift introduced being dependent on the instantaneous angular relationship of a thin slab of dielectric material relative to a fixed reference estab' lished by the input polarization converter.
  • Such apparatus is shown and described in detail in US Pat. No. 2,858,512 issued to RF. Barnett.
  • a magnetically controlled ferrite phase shifter is furthermore disclosed in US. Pat. No. 2,787,765, A.G. Fox wherein an electrically controlled rotating magnetic field is applied to a ferromagnetic material in the presence of the magnetic field is utilized for varying the angular relationship of the applied field to the polarization of the wave energy for varying the phase shift in the manner previously described but removing the limitations imposed by mechanically moving parts.
  • microwave digital phase shifter requires a six bit unit with one-half least significant bit accuracy at all phase states capable of switching between each state in the order of 3/5 nanoseconds seconds) including settling time to within one-half least significant bit at a peak switching rate in the order of 200MHz.
  • the present invention is directed to an improved phase shifter of the type including a half wave plate operable upon circularly polarized waves wherein the angular relationship of a shunt susceptance obstacle plane relative to a fixed reference is electrically controlled and rotated by means of the operation of four sets of varactor diodes (voltage variable capacitors) mounted inside of a circular waveguide and being spaced every 45 therein and covering a span of 120.
  • the four varactor sets are synchronously driven by cyclically varying, e.g.. sinusoidal control signals such that the first and third sets have signals applied which are l out of phase with one another as does the second and fourth sets; however. a phase difference of exists between adjacent sets.
  • Each varactor diode set comprises at least one but preferably a plurality of equally spaced varactor diodes aligned in a linear fashion extending longitudinally within the waveguide and substantially parallel to the central axis thereof.
  • FIG. I is a perspective view generally illustrative of a typical prior art rotary phase shifter utilizing a mechanically rotated half wave plate;
  • FIG. 1 is a perspective view further illustrative of a prior art half wave plate including a dielectric element
  • FIG. 2 is an axial cross sectional view of the preferred embodiment of the subject invention
  • FIG. 3 is a partial longitudinal sectional view further illustrative of the preferred embodiment of the subject invention shown in FIG. 2;
  • FIG. 4 is a diagram illustrative of the cyclic capacitance/susceptance variation of the four varactor sets being illustrative of operation of the embodiment shown in FIGS. 2 and 3;
  • FIG 5 is a diagram illustrative of the driver control voltage signal pattern applied to the four sets of varactor diodes.
  • a mechanically rotatable phase shifter is basically comprised of a rotatable half wave plate 10 located between input and output transitions to circular waveguide which typically converts TE rectangular mode waves to the TE mode and quarter wave plates 12 and 14, respectively, which converts the linearly polarized TE mode waves into a circularly polarized TE mode waves and vice versa.
  • Reference numerals I6 and I8 refer to the input and output rectangular waveguide section for coupling linearly polarized waves to and from the phase shifter.
  • Intermediate the input rectangular waveguide section and the first quarter wave plate 12 is the rectangular to circular waveguide transition section 20.
  • a second waveguide transition section 22 couples the quarter wave plate 14 to the output rectangular waveguide section 18.
  • the rotary half wave plate It] is additionally shown in FIG. Ia and typically consists of a section of circular waveguide 24 having a slab 26 of dielectric material of a length L axially mounted across the diameter of the waveguide.
  • a linearly polarized electric field E is converted to a polarized wave consisting of two components E and E at right angles to one another.
  • the diagram in FIG. la illustrates the condition where the electric field vector E is perpendicular to the slab 26 while the field vector E lies in the plane of the slab.
  • the electric field vector E will experience a minimum retardation while the field E will experience a maximum retardation.
  • the propagation constant B, for the field vector E is greater than the propagation constant B for the field Ill vector E. in the slab 26. Passing of the electric field vectors E and B; through the circular waveguide 24 having a dielectric slab 26 of a length L can be expressed as:
  • the length L of the dielectric slab 26 is chosen toobtain a differential phase change. [3.1. 3 L I 180.
  • a circular polarized electric wave is introduced into a section of waveguide such as shown in FIG. 1a, it emerges with circular polarization in an opposite sense. i.e.. from a clockwise to a counter clockwise sense.
  • the circular waveguide 24 containing the slab 26 is physically rotated by an angle d) relative to a fixed reference such as that provided by the dielectric 21 in the input quarter wave plate section 12 shown in FIG. I, the emergent circular wave from the circular waveguide 24 will have its phase shifted through an angle 2d). Further. the passage of the emergent circularly polarized wave from the half wave plate through the output quarter wave plate 14 shown in FIG.
  • a rotary phase shift additionally normally includes means 28 and 30 in the waveguide transitions 20 and 22 to absorb the small amount of improperly polarized energy present therein. Typically. these may comprise horizontally oriented film loads. The absorption of improperly polarized energy effects energy loss but not forward phase shift. Also when desirable. the dielectric slab elements may be contoured to minimize reflections. i
  • the same class of device can be designed for operation in connection with coaxial or other TEM mode transmission systems by the use of transitions to rectangular waveguide or by direct launching of circularly polarized waves in circular guides from the coaxial line employing a helical coupler. thus eliminating the need for quarter wave plates.
  • the inherent mechanical limitation in the rotation rate at which the phase can be varied is overcome by effecting an electrical rotation of the half wave plate member, thereby realizing phase scanning rates in the megahertz (MHz) range.
  • the aforementioned Fox patent obtains electrical rotation by generating a rotating magnetic field around a ferrite element and thus provides one means for obtaining fast scanning rates.
  • the present invention is directed to still an improved control phase shifter having birefringent properties. i.e.. producing 180 differential phase shift along two orthogonal principal axes. Accordingly. the present invention is directed to a controlled varactor half wave plate. the preferred embodiment of which is shown in FIGS. 2 and 3. Directing attention now to the preferred embodiment.
  • the four sets 32, 34, 36 and 38 of linearly aligned varactor diodes are mounted inside of a section of circular waveguide such that the four sets of varactor diodes are adapted to form four obstacle planes 33, 35, 37 and 39 spaced apart inside of the waveguide.
  • the four sets of varactor diodes are identical in construction and number and are axially oriented within the waveguide 40 and operate as variable shunt susccptances across the waveguide when respectively operated by suitably applied electrical control voltages.
  • Each plurality (n) of varactor diodes forms N 11-] sections providing a length L.
  • the varactor diodes. moreover. are desirably spaced apart one quarter wavelength N4) of the mean operating frequency of the microwave energy propagated through the waveguide 40.
  • the plurality of varactor diodes may consist of equal susceptances or be configured to exhibit a taper wherein the first and last susceptance 42 and 42,, have one half the value of the intermediate susceptances. This can easily be accomplished by proper sclection of the diodes themselves or in any other known fashion such as by paralleling diodes. Also the same result can be effected by suitable biasing techniques well known to those skilled in the art. It has also been observed that an odd number of sections (N 3 to 7) provide the best operating characteristic.
  • the varactor capacitances be selectively varied generally as shown by the diagram in FIG. 4. It can be observed that alternate sets of diodes operate as opposing pairs of susceptances with a 90 shift between adjacent sets.
  • time related e.g.. sinusoidal control voltages such as shown in FIG. 5
  • the susceptance pattern is varied substan tially as shown by FIG. 4 resulting in an effective or resultant obstacle plane 60 corresponding to the dielectric plate 26 shown in FIG. 2 which rotates within the waveguide 40.
  • the control voltages applied to the varactor diode sets vary si nusoidally the effective obstacle plane 60 will exhibit a rotation angle (b of l80 for each cycle of the applied control voltage.
  • control voltages applied to the first and third set of varactor diodes 32 and 36 are 180 out of phase with respect to one another. The same may be said for the control voltages applied to the third and fourth set of varactor diodes 34 and 38.
  • a simplification in the drive circuit connection to the varactor diodes immediately becomes evident by considering varactor diode sets 46 and 36 operated as mutually opposite pairs and varactor diode sets 34 and 38 operated as a second mutually opposite pair. By selectively choosing one set of diodes in each pair to have inverse characteristics or simply by inverting their connections. sets 46 and 36 can be commonly driven by a first control signal from a driver circuit 50 while the second pair of diodes 34 and 36 can be driven by a second control signal 90 out of phase with respect to the first.
  • the apparatus thus described comprises a microwave analog phase shifter which provides the capability for smooth and continuous phase change over a 360 range by 90 phase shifted variation of control voltage inputs applied to four cumulative shunt susceptances spaced 45 in a circular waveguide.
  • a digital processor employing control data stored in programmable semiconductor memories in conjunction with available integrated circuit digital to analog convertors can also be used to obtain the desired phase control.
  • the present invention moreover. is inherently a molulo 211 phase shifter requiring no reset since the control inputs for 360 are identical to those for 0 and since a unique combination of a con- Ill 6 trol voltage input corresponds to each phase angle be tween 0 and 360.
  • a microwave phase shifter comprising in combination:
  • electrical circuit means coupling respective mutually synchronized control signals to said at least four variable capacitance means for selectively varying the capacitance value thereof and providing a varying resultant shunt susceptance therefrom which generates an effective rotatable obstacle plane for said circularly polarized waves. thereby imparting a phase shift thereto which is a function of the angle of said obstacle plane relative to a fixed reference.
  • microwave phase shifter as defined by claim I wherein said electrical circuit means coupling respective mutually synchronized control signals to said four variable capacitance means comprises circuit means generating four sinusoidal control voltages consecutively phased 90 apart. and wherein said four control voltages are respectively applied to said four variable capacitance means.
  • said at least four electrically controlled variable capacitance means comprises four sets of axially aligned varactor diodes and wherein said electrical circuit means coupling control signal to said four sets of varactor diode means comprises circuit means for varying the capacitance of each set of diodes in cyclic fashion such that the variation between adjacent varactor diode sets is shifted 90.
  • phase shifter as defined by claim I and additionally including microwave circuit means coupled to one side of said circular waveguide section for coupling circularly polarized waves thereto;
  • second microwave circuit means coupled to the opposite side of said circular waveguide section for coupling circularly polarized waves therefrom.
  • phase shifter as defined by claim I wherein said at least four electrically controlled variable capacitance me ans each comprises respective sets of varactor diode means.
  • each set of varactor diode means comprises a plurality of spaced apart varactor diodes linearly aligned along the longitudinal direction of said circular waveguide section.
  • N is an odd number including the numbers 3 and 7.
  • microwave phase shifter as defined hy claim 1 and additionally including first microwave circuit means coupled to one side of said circular waveguide section for converting linearly polarized way es to circularly polarized waves.
  • second microwave circuit means coupled to the other side of said circular waveguide section for converting circularly polarized waves to linearly polarized waves.
  • phase shifter as defined by claim 10 wherein said first and second microwave circuit means comprises quarter wave plate microwave circuit means.
  • both quarter wave plate microwave circuit means includes a circular waveguide portion
  • first and second waveguide transition elements respectively coupled to the first quarter wave plate microwave circuit means for providing a transition from rectangular waveguide to circular waveguide. and to said second quarter 8 wave plate circuit means for providing a transition from circular waveguide to rectangular waveguide.
  • microwave phase shifter as defined by claim 12 and wherein said electrical circuit means coupling respective mutually synchronized control signals to said four sets of varactor diodes comprises circuit means coupling a like cyclically variable control signal to each set of varactor diodes with each control signal being phased 90 apart such that the first and third set of varactor diodes receive a first pair of signals 180 apart and wherein said second and fourth set of varactor diodes receive a second pair of signals 180 apart.

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  • Waveguide Switches, Polarizers, And Phase Shifters (AREA)
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US432373A 1974-01-10 1974-01-10 Microwave phase shifter Expired - Lifetime US3919670A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4595890A (en) * 1982-06-24 1986-06-17 Omni Spectra, Inc. Dual polarization transition and/or switch
US6853343B2 (en) * 1999-03-12 2005-02-08 Harris Corporation Polarization plate
US20100171674A1 (en) * 2009-01-08 2010-07-08 Thinkom Solutions, Inc. Low cost electronically scanned array antenna

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3790908A (en) * 1972-12-29 1974-02-05 Hughes Aircraft Co High power diode phase shifter

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3790908A (en) * 1972-12-29 1974-02-05 Hughes Aircraft Co High power diode phase shifter

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4595890A (en) * 1982-06-24 1986-06-17 Omni Spectra, Inc. Dual polarization transition and/or switch
US6853343B2 (en) * 1999-03-12 2005-02-08 Harris Corporation Polarization plate
US20100171674A1 (en) * 2009-01-08 2010-07-08 Thinkom Solutions, Inc. Low cost electronically scanned array antenna
US8362965B2 (en) 2009-01-08 2013-01-29 Thinkom Solutions, Inc. Low cost electronically scanned array antenna

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USB432373I5 (me) 1975-01-28
BG22809A3 (me) 1977-04-20

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