US3721922A

US3721922A - Composite digital logic microwave phase shifter

Info

Publication number: US3721922A
Application number: US00094510A
Authority: US
Inventors: D Boensel
Original assignee: Deutsche ITT Industries GmbH
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1970-12-02
Filing date: 1970-12-02
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20

Abstract

A microwave phase shifter comprising a strip transmission or meander line associated with a ferrimagnetic toroid or ferrimagnetic substrate divided into discrete operative regions. These discrete operative regions form the magnetic memory elements of a digital logic function. The device thus operates as a digitally controlled phase shifter in which the ferrimagnetic elements serve the dual purpose of operating on the digital control code signals as memory elements, while simultaneously effecting stage-by-stage phase shift of the microwave energy in the said meander line or strip-line.

Description

United States Patent 1 Boensel COMPOSITE DIGITAL LOGIC MICROWAVE PHASE SHIFTER [75] Inventor: Donald W. Boensel, La Canada,

Calif.

[73] Assignee: International Telephone and Telegraph Corporation, New York, N.Y.

[22] Filed: Dec. 2, 1970 [21] App]. No.: 94,510

[52] US. Cl. ..333/24.l, 333/84 M [51] Int. Cl. ..I-I0lp 1/32 [58] Field of Search ..333/24.l

[56] References Cited UNITED STATES PATENTS 3,478,283 11/1969 Simon et a1 ..333/24.l X 3,274,521 9/1966 Nourse ..333/24.1 3,332,042 7/1967 Farris ..333/24.l X 3,371,293 2/1968 Jones et al ..333/24.1

3,418,605 12/1968 Hair etal ..333/24.l

Primary Examiner-Paul L. Gensler Attorney-C. Cornell Remsen, Jr., Walter J. Baum, Paul W. l-lemminger, Charles L. Johnson, Jr. and

Thomas E. Kristofferson [57] ABSTRACT A microwave phase shifter comprising a strip transmission or meander line associated with a ferrimag netic toroid or ferrimagnetic substrate divided into discrete operative regions. These discrete operative regions form the magnetic memory elements of a digital logic function. The device thus operates as a digitally controlled phase shifter in which the ferrimagnetic elements serve the dual purpose of operating on the digital control code signals as memory elements, while simultaneously effecting stage-by-stage phase shift of the microwave energy in the said meander line or strip-line.

6 Claims, 4 Drawing Figures COMPOSITE DIGITAL LOGIC MICROWAVE PHASE SI'IIFTER BACKGROUND OF THE INVENTION 1. Field of The Invention The present invention relates to radio frequency phase shifters, and more particularly, to microwave phase shifters which are digitally controllable.

2. Description of The Prior Art In the prior art there have been a number of microwave phase shifters developed and produced for particular applications. Among the mechanically operated versions are the so-called variable a dimension waveguide, the rotary waveguide phase shifter, the helical-line trombone phase shifter, and many others.

In the field of electrically controlled phase shifters, the generic category to which the present invention belongs, there may be found both analog and digitally controlled devices. A very complete and current reference describing the state of this art, in particular relation to the more immediate background of the present invention, is Radar Handbook by Merrill I. Skolnik, a McGraw Hill book, (1970). In particular, Chapter 12 of that reference discusses the theory and various structures for electrically controllable phase shifters. The term ferrimagnetic, as it applies to materials of the families of both ferrites and garnets (magnetic ceramics) is extensively used in the present application. The definitions and description of the characteristics of those materials contained in the aforementioned reference are pertinent to the present invention, and the meaning of terms used herein, which are also found in that reference, are the same.

The so-called Reggia-Spencer phase shifter shown in the reference is a prime example of a high powered inherently analog type controllable phase shifter mounted within a waveguide. Other types of digital and analog shifters all employing transmission lines of one type or another, are discussed.

The reference also shows and describes strip-transmission-line, slow-wave phase shifters using the socalled meander line. In that particular prior art device, ferrite elements in the form of hollow rectangular guides envelop the meander line which is emplaced as the center conductor strip of a transmission line. The ferrite element is broken into discrete lengths axially and these are subject to control by latching wires. That prior art structure is adaptable to digital control of the phase shift from the outputs of an external digital device, such as a multibit digital shift register or memory device connected thereto. Thus the source of digital control would be separate except for the interconnection wires.

One important disadvantage of these prior art and digital type phase shifters structures, has been the size and amount of equipment involved to accomplish the objective. The manner in which the present invention contributes to this art in providing a more economical, simpler and more reliable structure will be seen as this description proceeds.

SUMMARY OF THE INVENTION It may be said to have been the principal object of the present invention to develop a composite digital logic microwave phase shifter, controllable and combining the magnetic memory media of the shift register digital control device with the ferrimagnetic material used in connection with a strip or meander line for the actual control of phase shift of a microwave signal through the transmission line.

The preferred instrumentation of the present invention involves a series of discrete phase shifter stages constructed of microwave strip on ferrite substrates. The devices are nonreciprocal and are actuated by switching the material between a positive and a negative state of flux saturation.

Alternatively, the structure may involve a ferrimagnetic toroid arrangement in connection with a symmetrical strip-line, although the meander line on a ferrimagnetic substrate produces the most compact and practical structure in low and moderate power situations.

Separation of the line into n digital stages is accomplished either by physical separation, barrier techniques or actual division of the ferrite substrate into independent platelets. Thus, each stage corresponds to a region of the magnetic ceramic substrate and operates discretely to provide a predetermined phase shift. The meander line traverses all of the said regions, and therefore, the total phase shift through the meander line is equal to the sum of the shifts provided in the individual stages. Since the said regions each serve the dual purpose of influencing the corresponding meander line section to produce phase shift and also acting as, for example, the digital memory in a serially operated shift register arrangement, each successive region is constructed to provide double the phase shift provided by the preceding stage (a standard digital 'bit progressive significance). While the structure of a shift register has been selected as the logical configuration for detailed description hereinafter, it is to be understood that generalized digital logic functional circuitry is instrumentable alternatively and with equal ease. For example, rather than operating as a shift register, the design could be such as to make the logic combination operable as a counter (accumulator),an adder, digital comparator, or other arrangement.

In the configuration to be described, the first stage, corresponding to the least significant digit, provides 22 A" phase shift. A four-bit embodiment, as is illustrated herein and to be discussed in detail hereinafter, provides 45, and in the second through fourth stages.

Externally provided digital control pulses and shift pulses effect-operation of the specific aforementioned overall device, and since the phase shift provided by each succeeding digital stage is greater, the length of meander line affected increases in each succeeding (more significant) stage. Referring again to the aforementioned Radar Handbook reference, the device depicted on page l2 23, FIG. 19, illustrates a comparable situation (in that particular detail only) in that the ferrimagnetic materials sections are of progressively variable size.

The definitions, materials selection criteria, and other considerations such as power handling capability, magnetostriction and temperature stabilization, etc., as set forth in Chapter l2 I of the aforementioned reference, are all pertinent to the detailed design of a structure according to the present invention.

A more detailed description of one embodiment of the present invention, taken with the drawings, follows hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a circuit for an instrumentation of the present invention in the meander line and ferrite substrate form.

FIG. 2 is a functional waveform chart, including both electrical pulse relationships and magnetic condition relationships.

FIG. 3 is a cross-section detail illustrating the manner of instrumenting individual phase shift regions of the present invention in a symmetrical strip transmission line using a ferrim agnetic toroid.

FIG. 4 is a typical microstrip meander line phaser stage where the meander line is on a flat ferrimagnetic platelet. This figure also illustrates flat toroidal material geometry typically.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIGS. 1 and 2, the waveforms of FIG. 2 will be identified and related to FIG. 1.

At the outset it will be observed that although a fourbit logic and phase shift configuration is illustrated in FIG. 1, it was considered necessary to depict only the first three stages insofar as the waveforms of FIG. 2 are concerned.

The first line, I, on FIG. 2, depicts the transfer (shift) signal fed to the

B windings

10, 13, 16 and 19 in FIG. 1. The second line of FIG. 2 depicts the somewhat delayed current pulse I fed to the A winding at 9 for the first stage of the overall circuit.

The ferrimagnetic regions represented by 5, 6, 7 and 8 will be generally referred to as the identifications for the 4 stages of the overall four-bit device. Accordingly, the currents I I, and I:, are the C winding output current pulses from 11, 14 and 17, respectively. Similarly, I I, and I are the comparable currents after passage through the intervening delay circuits. These currents 1,, I, and I, pass through windings l2, l and 18, respectively, and as such, preset the shifting action effected by I,.

Between stages 5 and 6 it will be noted that the interconnections from 11 to 12 include a diode 22, capacitor 23 and resistor 24. The diode 22 insures that the priming action or the set-up" of the succeeding stage effected by C winding output pulses in each case, is unilateral, so that no reverse interaction is extant.

The capacitor 23 and resistor 24 act as a delay filter affecting the pulse shape, as well as delaying the succeeding A winding current pulses, was will be seen in FIG. 2. The function of

diodes

25 and 28 are analogous to diode 22, and similarly,

capacitors

26 and 29 perform functions analogous to that of capacitor 23. Obviously, also resistors 27 and 30 perform the same function between stages 6 and 7 and 7 and 8, respectively as performed by resistor 24 between stages 5 and 6. The total meander line comprises the sections 1, 2, 3 and 4, which are shown in substantially the same length in FIG. I for convenience. It is to be understood however, that stages producing the larger incremental phase shift A dz, would normally be constructed with longer sections of meander line. This follows from the previous discussion of least and most significant digital stages and their respective incremental contributions to the overall phase shift. The microwave signal input to the meander line circuit begins at 20, the output being depicted at 21.

In FIG. 2, the lines 1, and d), and will be seen to depict the magnetic latched condition of either d or 4),. In each case, the conditions depicted on these last three lines of FIG. 2 are arbitrarily selected but are consistent with the controlling current pulse waveforms above in FIG. 2. From this showing it will be understood that the respective flux or saturation states may be caused to shift from left to right, the pattern being incremented one position with each clock pulse, I,. At this point, it will also be realized that, since the square-loop ferrimagnetic material latches, the currents that produce the changes need not be sustained, and accordingly, in the absence of further pulsing, will remain in their last condition. The foregoing follows from the known characteristics of latching type (square-hysteresis-loop) retentive materials extant in this art.

The meander line and ferrimagnetic substrate device of FIG. 1 is inherently nonreciprocal.

The convention assumed for the purpose of explanation is that a positive state of magnetic material saturation (plus 41),) produces a phase shift of Ad) equals 0, where 0 is 22 It", for example. Similarly, the second, third and fourth stages 6, 7 and 8, respectively, produce 20, 40 and 80, respectively. It is also assumed in the understanding of FIG. 1, taken with FIG. 2, that current, or current pulse flowing into the dots will set the magnetic material in the condition. A change from 4:, to (I), will produce a current flow out of the dot of the corresponding C winding in each case. As previously discussed, C winding output currents are delayed for purposes already obvious from the previous discussion. Accordingly, it will be understood that the ferrimagnetic material saturation condition is switched so that the states of flux shift from left to right, the pattern being incremented one position with each clock pulse I, (a normal shift register function).

Referring now to FIG. 3, one form of arrangement by which the ferrimagnetic material cooperates with a transmission line structure to produce the effects in each of the stages, is shown. The detail structure of FIG. 3 is known and used with a single latching wire (typically 9) as an externally controlled element in a digital phase shifting system of a prior art type. A socalled symmetrical strip-line is illustrated in cross-sec tion in FIG. 3, the center conductor 36 being placed between two ground planes 30 and 31. The ferrimagnetic toroid 34 is held in its position against the edge of the center conductor strip 36 and is insulatingly emplaced symmetrically between the said two ground planes by insulating members 32 and 33. These insulating materials 32 and 33 may be foamed plastic or other known low loss microwave transmission line insulating material. Two magnetizing wires 9 and 11 are shown as they might correspond to A and C windings of a typical stage in FIG. 1. Similarly, an orthogonally placed magnetic excitation wire (winding) is illustrated at 10. The wire 10 could be regarded as corresponding to a B type winding in a given stage. A flux path indicating arrow is shown M35 as it relates to the field produced by 9 and 11.

Referring now to FIG. 4, a flat toroid configuration is shown for an understanding of the general form required for a discrete meander line ferrimagnetic region, such as one of those depicted at 5, 6, 7 or 8 in FIG. 1. The meander line itself is shown at 41, lying on the ferrimagnetic substrate 40. The latching wire 9 may actually be two independent windings, in effect, and would be a typical placement for A and C windings (as schematically depicted in FIG. 1). The line 10, although not truly orthogonal, in its magnetic effect, is located to minimize interaction with the lines at 9 and 11. The flux arrow 44 indicates a type of circular field polarization, which is of itself known and corresponds to one of the theories discussed in the aforementioned Radar Handbook concerning the interaction of the ferrimagnetic material and the meander or strip-line with which it cooperates, to produce the phase shift effect.

From an understanding of the nature of the present invention, various modifications and variations will suggest themselves to those skilled in this art. Different ways of producing the interstage delay are, of course, readily possible. To mention one additional possible variation, it will be realized that the B windings of FIG. 1 might be isolated by means of electrical circuitry connected in the series path between them obviating the requirement that the B fields be located orthogonally oriented to avoid interactions with the other windings. The basic functioning of the system insofar as the phase shifting effect of magnetic saturation in the ferrimagnetic substrate is concerned, is not dependent on the exact orientation of the granular structure of the magnetic material itself or on the exact magnetization vectors applied. The factors relating to orientation of magnetic fields are also discussed as a matter of prior art knowledge in the aforementioned Radar Handbook reference.

Accordingly, it is to be understood that the drawings and description herewith presented are to be regarded as typical and illustrative and not as limiting the scope of the present invention.

What is claimed is:

l. A latching multi-stage digital microwave phase shifter in which the microwave phase influencing ferrimagnetic material is also used to register the digital control signals, comprising:

an electromagnetic energy transmission line associated with said ferrimagnetic material, said line being divided and arranged into a plurality of serial stages each including an independent operatively associated magnetically responsive region of said ferrimagnetic material, to introduce a phase shift of the microwave energy flowing in said transmission line which is the sum of the individual phase shifts provided by each of said stages, said stages each providing a discrete corresponding phase shift in accordance with one of first and second magnetic conditions of the corresponding magnetically responsive region;

means for applying externally generated first control pulses to a first input of the first of said stages in a direction to produce said first magnetic condition in the corresponding region of said first stage;

means comprising interstage coupling means for applying interstage control pulses delayed with respect to said first control pulses to each succeedmg stage from each stage exhibiting said first magnetic condition at any time, thereby to provide for operation of said serial stages as a digital logic circuit, the magnetic conditions of the said stages providing a corresponding phase shift through said transmission line;

and means for applying a magnetic flux transfer pulse at a second input to all of said stages substantially contemporaneously, said transfer pulses operating to transfer said first magnetic condition from each of said stages in said first condition at any time to the following stage.

2. Apparatus according to claim 1, in which said transmission line is a balanced strip type line having a center conductor symmetrically spaced between two ground planes, said ferrimagnetic material is in the form of a ferrimagnetic toroid for each of said stages insulatingly mounted between said ground planes and in lateral juxtaposition with said center conductor.

3. Apparatus according to claim 1 in which said transmission line includes a meander line on a ferrimagnetic substrate and said independent regions are formed therein by separation of said substrate into discrete ferrimagnetic platelets.

4. Apparatus according to claim 1 in which said transmission line includes a meander line on a ferrimagnetic substrate and said independent regions are formed therein by physical isolation between regions to provide substantial magnetic isolation.

5. Apparatus according to claim 4 in which said digital logic circuit is a shift register circuit comprising input and output windings associated with each of said independent regions of said stages for applying said externally generated first control pulses and for passing said interstage control pulses on to the next stage, respectively, each of said stages also including a transfer winding arranged to form a magnetic flux substantially orthogonal with said input and output windings to minimize interaction, and in which means are included for connecting said transfer windings for all of said stages in series.

6. Apparatus according to claim 5 in which said interstage coupling means includes an RC delay network and diode means connected between said output winding of each of said stages and said input winding of the next stage, thereby to apply said delayed interstage control pulses to said next stage input winding.

III i i

Claims

1. A latching multi-stage digital microwave phase shifter in which the microwave phase influencing ferrimagnetic material is also used to register the digital control signals, comprising: an electromagnetic energy transmission line associated with said ferrimagnetic material, said line being divided and arranged into a plurality of serial stages each including an independent operatively associated magnetically responsive region of said ferrimagnetic material, to introduce a phase shift of the microwave energy flowing in said transmission line which is the sum of the individual phase shifts provided by each of said stages, said stages each providing a discrete corresponding phase shift in accordance with one of first and second magnetic conditions of the corresponding magnetically responsive region; means for applying externally generated first control pulses to a first input of the first of said stages in a direction to produce said first magnetic condition in the corresponding region of said first stage; means comprising interstage coupling means for applying interstage control pulses delayed with respect to said first control pulses to each succeeding stage from each stage exhibiting said first magnetic condition at any time, thereby to provide for operation of said serial stages as a digital logic circuit, the magnetic conditions of the said stages providing a corresponding phase shift through said transmission line; and means for applying a magnetic flux transfer pulse at a second input to all of said stages substantially contemporaneously, said transfer pulses operating to transfer said first magnetic condition from each of said stages in said first condition at any time to the following stage.