EP0434860A1 - Circuit déphaseur en anneau commuté - Google Patents

Circuit déphaseur en anneau commuté Download PDF

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Publication number
EP0434860A1
EP0434860A1 EP89123992A EP89123992A EP0434860A1 EP 0434860 A1 EP0434860 A1 EP 0434860A1 EP 89123992 A EP89123992 A EP 89123992A EP 89123992 A EP89123992 A EP 89123992A EP 0434860 A1 EP0434860 A1 EP 0434860A1
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EP
European Patent Office
Prior art keywords
circuit
diodes
signal
transmission line
segment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89123992A
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German (de)
English (en)
Inventor
Richard W. Burns
Russell L. Holden
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Co
Original Assignee
Hughes Aircraft Co
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Filing date
Publication date
Application filed by Hughes Aircraft Co filed Critical Hughes Aircraft Co
Publication of EP0434860A1 publication Critical patent/EP0434860A1/fr
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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

Definitions

  • the present invention relates to diode phase shifters and more particularly, to a switched-ring phase shifting circuit adapted to provide large phase shifts and high peak power capability.
  • Phased array antennas are used to provide scanning flexibility in an antenna system without the need to physically move the position of the array.
  • Phased array systems typically include two dimensional arrays, such as planar arrays wherein each of the elements may be individually excited. Through individual excitation of radiating elements of the array, or individual rows or columns of elements, the scanning direction may be varied with a high degree of discrimination, providing a narrow beam that may be directed with precision.
  • the steering of the resulting beam from the antenna array is accomplished by controlling the phase of the signals applied to each element of the array relative to the other elements.
  • the "Radar Handbook” by Merrill Skolnik, (McGraw Hill 1970) provides a thorough description of contemporary phase shifting circuits.
  • phase shifters are ordinarily not required. However, if the beam is to be scanned or moved in space relative to the bore sight axis of the array, then variable or controllable phase shifters must be used to achieve such a result. Simple controllable phase shifters can be implemented by the use of different lengths of transmission line which are switched into or out of the propagation path to add delay proportional to the length of transmission line so switched. The length of the reference and delay paths are selected in view of the operating frequency range such that a desired phase shift is effected. Consequently, the propagation delay, or phase shift, corresponds to the length of transmission line switched.
  • T time division multiplexing
  • ⁇ shunt diode
  • the "T” circuit includes a pair of series diodes connecting input and output terminals and a shunt diode connected to the serial line between the series diodes.
  • the " ⁇ ” circuit includes a single series diode and a pair of shunt diodes, each connected on an opposite side of the series diode. In the contemporary circuit the series diode is either forward or reverse biased, effecting insertion of the delay line when the diode is reverse biased.
  • the input RF signal In the forward bias state the input RF signal is communicated directly to the output terminals through the series diode.
  • a portion of the input RF signal In the reverse bias state a portion of the input RF signal is communicated across the diode terminals (which acts as a capacitance in the reverse bias state), and another portion of the input RF signal passes through the delay line. Both portions are combined at the output side of the series diode producing a composite signal.
  • the effective phase shift of the circuit is the output signal when the diode is forward biased and the composite signal when the diode is reverse biased.
  • the series diode is responsive to a D.C. bias voltage across the diode electrodes.
  • the field produced by the bias voltage induces a change in electrical characteristics of the diode, which in turn affects the circuit impedance.
  • the change in impedance causes a change in phase shift through the circuit. Variations in the impedance of the diode may unfavorably impact the operating bandwidth of the circuit.
  • the series diode may limit the power handling capacity of the phase shifting circuit.
  • the power handling capacity of the diode is proportional to the square of the total voltage across the reverse biased diode. Because the series diode is located closest to the power source (the shunted diodes are spaced from the series diode by attenuating transmission line segments), the series diode is subject to greater power handling demands and may limit the power handling capacity of the circuit.
  • phase shifter circuit which incorporates the power handling and bandwidth advantages for a switched diode system, wherein the series diode is eliminated from the circuit path and phase shift may be effected without the need to drive the input RF signal through a reverse bias diode.
  • the series diode is eliminated, thereby removing operational limitations resulting from the characteristic operation of the diode.
  • a phase shifting circuit comprising a plurality of bidirectional transmission line segments serially connected to form a ring. Input and output terminals are connected to opposite ends of the first of the transmission line segments to form a first signal path through the ring. A second ring signal path, through the remainder of the serially connected transmission line segments, is selectively enabled to provide a predetermined phase shift at the output of the ring.
  • the second signal path is enabled by a pair of diodes connected to the second signal path on one end and to ground on the other.
  • the RF signal through the second signal path is shorted to ground, leaving only a signal flowing through the first signal path at the RF output.
  • the RF ground in the second signal path is removed, providing a complete second path to the input RF signal.
  • the RF output signal in that case is a composite of the signals flowing through the first and second signal paths. Because the first and second signal paths have different lengths the phase of signals at the termination of each path has a different phase. The combination of the two signals results in a composite signal having a phase distinct from the phase of the signal output from the first signal path.
  • the desired phase difference may be effected between the signal output from the first signal path and the composite signal.
  • the first signal path is formed of a transmission line segment having a length slightly less than 1/4 wavelength of the center bandwidth frequency.
  • the second path is formed to include two segments having a length of approximately 3/8 wavelength each, and an additional segment having a length of approximately 1/4 wavelength.
  • the collective length of the second signal path is approximately one wavelength.
  • FIG. 1A of the drawing illustrates a switched ring phase bit circuit in accordance with the present invention.
  • the circuit 11 functions to selectively phase shift the RF input signal by an amount corresponding to the respective lengths of the signal paths in the circuit. It is to be understood that the particular lengths and corresponding phase shifts that are discussed below are intended to be exemplary only, and are not intended to represent the only lengths or contributions that may be implemented within the scope of the invention.
  • the input to circuit 11 is provided at RF input terminal 13.
  • the output is at RF output terminal 15.
  • DC bias is provided at bias terminal 17 and is used to vary the state of shunt diodes 19 and 21.
  • Bias terminal 17 may, for example, be connected to a power source that may vary between a positive voltage (e.g., plus 100 volts) and a small negative voltage (e.g., minus 0.75 volts).
  • RF choke 23 isolates the bias supply from the RF signal passing through circuit 11.
  • Capacitors 25 and 27 isolate the RF input and output circuits, respectively, from the DC bias circuit connected to bias terminal 17.
  • circuit 11 includes transmission line segments 29, 31, 33, 35, 37 and 39.
  • the length of the various segments is selected in view of the RF signal bandwidth and the characteristic impedance that a particular length segment exhibits over the operating bandwidth.
  • Sections 51 and 53 serve as voltage transformer sections incorporated into the transmission line segments 35 and 39, to further reduce the voltage level applied to the cathode of diodes 19 and 21, thereby increasing the peak power handling ability of the circuit.
  • the transforming action of sections 51, 53 is a consequence of their size and characteristic impedance in relation to the overall size and characteristic impedance of segments 35 and 39, respectively.
  • the sections 51 and 53 may be formed to extend approximately two thirds the length of the segments 35 and 39.
  • the characteristic impedance of the segments will determine the characteristic impedance of the segments. For example, it is generally known that a short at the end of a 1/4 wavelength transmission line reflects a very high impedance (theoretically infinite) at the input to that transmission line, and that a short at the end of a 1/2 wavelength transmission line reflects a very low impedance (theoretically a short) at the input. A short at the end of a 3/8 wavelength transmission line reflects an impedance at the input that is a capacitive reactance between these extremes. As described below the present invention utilizes the characteristic impedances of different lengths of transmission line segments to provide alternate RF signal paths without the need to utilize a series diode.
  • Figure 1B illustrates the effective operation of the circuit of Figure 1A when the DC bias signal applied to bias terminal 17 is negative, effectively forward biasing diodes 19 and 21.
  • the RF signal input at terminal 13 passes through transmission line segments 29, 31 and 33.
  • the forward bias condition of diodes 19 and 21 effectively grounds the connected terminal of transmission line segments 35 and 39, respectively.
  • FIG. 2A shows the forward bias equivalent circuit representation of the conditions illustrated at Figure 1B.
  • transmission line segments 35 and 39 are grounded at one end, representative of the forward bias state of diodes 19 and 21.
  • segments 35 and 39 are implemented to have a length of approximately 3/8 wavelength at center frequency of the RF signal.
  • segments 35 and 39 exhibit a characteristic impedance that is a capacitive reactance represented by capacitors 41 and 43.
  • the segment 31 is preferably implemented to have a length of less than 1/4 wavelength, e.g. between 1/8 and 1/4 wavelength, and generates an impedance that is effectively a series inductive reactance, represented as coil 45 in the equivalent circuit shown at Figure 2A.
  • the characteristic capacitive and inductive reactances interact to form a low pass circuit, so that the input RF signal finds a low impedance path through segment 31 (represented as coil 45) and a high impedance path through segments 35 and 39 (represented as capacitors 42 and 43).
  • Figure 1C illustrates the operation of the circuit of Figure 1A when the diodes 19 and 21 are reverse biased.
  • diodes 19 and 21 no longer act as shorts, as in the forward bias condition illustrated at Figures 1B and 2A.
  • diodes 19 and 21 act as capacitors, and are therefore represented by capacitors 47 and 49 in Figure 1C. Because the ends of segments 35 and 39 are no longer an RF short to ground, the RF input signal is now provided with a pair of alternate signal paths through the circuit.
  • the first path 20, as before, is through transmission line segment 31.
  • the second path 40 is through segments 35, 37 and 39, the combined length of which is approximately one wavelength in the presently preferred embodiment.
  • Segments 35, 39 may, for example have a length between 1/4 and 3/8 wavelength, and segment 37 may have a length between 1/8 and 1/4 wavelength.
  • the RF output under those conditions is a composite signal formed of the signal flowing through the short path 20 (through segment 31) and the signal flowing through the long path 40 (through segments 35, 37 and 39).
  • the phase of the composite signal is different than the phase of the signal output from segment 31 when the diodes are forward biased. Consequently, the enablement of the alternate signal path 40 introduces a phase shift to the RF output signal.
  • the resulting phase shift that is effected by the circuit may be varied by varying the respective lengths and impedances of the signal RF transmission line segments.
  • Figure 2B illustrates the reverse bias equivalent circuit of the circuit set forth at Figure 1C. As shown in Figure 2B the diodes 19 and 21 may again be represented as capacitors 47 and 49. Segments 35, 37 and 39 collectively form a long, or delay path 40 through which the RF signal may flow without being shorted to ground
  • the present invention may be utilized to implement phase shifts in the range of up to 180 degrees. Because of the elimination of the series diode such as that incorporated in contemporary " ⁇ " phase shifter circuits, the present invention is not so constrained in its peak power capability. Due to their location in the circuit, diodes 19 and 21 are not required to withstand the same operational conditions as required of the series diode in conventional " ⁇ " circuits.
  • the invention permits wide tolerance variation in diode parameters since phase shift is implemented primarily by the proper choice of transmission line segments and impedance levels.
  • the circuit has been used in L-band applications, producing a 90 degree phase shift wherein the diode capacitance was 2.5 picofarads, segments 35 and 39 were formed to be .31 ⁇ , segment 31 was formed to be .14 ⁇ and segment 37 was formed to be .22 ⁇ .
  • Diodes with the capacitance of the order of 1.0 picofarads and a resistance on the order of 0.25 ohms are satisfactory for S-band applications.
  • Diodes with a capacitance of the order of 2.5 picofarads and a resistance of 0.25 ohms are satisfactory for L-band application.
  • Diodes with a capacitance of the order of 0.8 picofarads are satisfactory for C-band applications. Circuit bandwidth is expected to be approximately 15 to 25% of the operating frequency.
  • the particular selection of diodes and transmission line segments may be selected in view of the desired phase shift to be implemented.
  • the circuit of the present invention may be implemented in redundant parallel fashion, with each separate circuit designed to affect a particular phase shift, the selection of which may be regulated by a choice of the particular circuit. It is anticipated that other modifications and alternate applications of the present invention may be recognized and implemented by those of ordinary skill in the art without departing from the broader aspects of the invention.

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  • Waveguide Switches, Polarizers, And Phase Shifters (AREA)
EP89123992A 1988-12-21 1989-12-27 Circuit déphaseur en anneau commuté Withdrawn EP0434860A1 (fr)

Applications Claiming Priority (1)

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US28796988A 1988-12-21 1988-12-21

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EP0434860A1 true EP0434860A1 (fr) 1991-07-03

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EP (1) EP0434860A1 (fr)
CA (1) CA2004857A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015009056A1 (fr) * 2013-07-16 2015-01-22 엘지이노텍 주식회사 Déphaseur et système de transmission équipé de celui-ci

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4001734A (en) * 1975-10-23 1977-01-04 Hughes Aircraft Company π-Loop phase bit apparatus
US4238745A (en) * 1979-06-18 1980-12-09 Rca Corporation Phase shifter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4001734A (en) * 1975-10-23 1977-01-04 Hughes Aircraft Company π-Loop phase bit apparatus
US4238745A (en) * 1979-06-18 1980-12-09 Rca Corporation Phase shifter

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
1979 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM-DIGEST,30 april-2 may 1979,Orlando,US; IEEE,New York,US,1979; K.HIRAI et al.:"Practical design of C-band,MIC, PIN phase shifters" pages 229-231 *
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES. vol. 22, no. 6, June 1974, NEW YORK US pages 658 - 674; J.F.WHITE: "Diode phase shifters for array antennas" *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015009056A1 (fr) * 2013-07-16 2015-01-22 엘지이노텍 주식회사 Déphaseur et système de transmission équipé de celui-ci

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CA2004857A1 (fr) 1990-06-21

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