US 3571765 A
Description (OCR text may contain errors)
United States Patent lnventor App]. No. Filed Patented Assignee QUANTIZED PHASE SHlFlER UTILIZING OPEN- CTRCUITED OR SHORT-CIRCUITED 30B 56} References Cited UNITED STATES PATENTS 3,423,688 l/l969 Seidel 333/10UX 3,490,054 1/1970 Seidel 333/10 Primary Examiner-Paul L. Gensler AttorneysR. J. Guenther and Arthur J. Torsiglieri ABSTRACT: A phase shift selector which utilizes a two-stage binary fan out circuit configuration to establish phase states. The four branches of the fan out are terminated by means of either an open circuit or a short circuit to produce two reflected signals having relative phases of either 90 degrees or 180 degrees when the terminations are open-circuited, or 270 degrees or 360 degrees when the terminations are short-circuited. A selector switch then selects one of these four signals as the output signal.
QUADRATURE COUPLERS 3 Claims, 2 Drawing Figs.
US. Cl. 333/311, 333/7, 333/10 Int. Cl H0lp1/l0, l-lOlp l/18,H01p 5/14 Field ofSearch 33/7, 10, 31, 31 (A) SIGNAL m PUT 2 PORT QH 3 Ll I M. SIGNAL OUTPUT 5 PORT PATENTEU MR 2 3197! FIG.
SIGNAL I4 4 SIGNAL PORT QH i L 2 PORT v I SELECTOR QH l SWITCH 2 4 l 3 I lg \IO QH 13/ FIG. 2
B I FROM PGRT 2 I HYBRID n p I To 24 3 4 25 i To ADJLBJEIQBLE 666 gPAlgSTABLE SUPPLY SUPPLY 22 3 4 I FROMO'IEORT '2 1% *2 gbg gfi T HYBRID 12 PORT /N|/EN7OR A. N. FRIEDMAN A T TORNE V QUANTIZED PHASE SI-IIFTER UTILIZING OPEN- CIRCUITED OR SHORT-CIRCUITED 31DB QUADRATURE COUPLERS This invention relates to quantized, broadband electromagnetic wave phase shifters or producing, amongfour possible output signals, relative pulse phase shifts that are integral multiples of 90.
BACKGROUND OF THE INVENTION Digital phase shifters are known in the art. Typically, however, they include impedances or line lengths that are frequency sensitive and, as such, the desired phase shifts are produced over relatively narrow frequency bands. (See, for example, US. Pat. No. 3,423,699.) The object of the present invention is to produce quantized relative phase shifts that are integral multiples of 90 over a relatively broad range of frequencies.
SUMMARY OF THE INVENTION In accordance with the present invention, the input signal is divided into four components by means of a two-stage, quadrature hybrid-coupled fan-out. Means are provided for simultaneously terminating the four fan-out branches in either an open circuit or a short circuit, thereby reflecting the branch signals in phase or out of phase with respect to the incident branch signals. Upon reflection, pairs of reflected signal components are recombined in the second stage couplers to form two signals whose relative phases are either 90 or 180 and or 270, depending upon the branch termination. The two signals, thus produced, are coupled to a selector switch which selects the signal having the desired one of the four possible phases.
It is a feature of the invention that all phase shifts are produced by frequency insensitive terminations and by means of quadrature hybrid couplers. This avoids the use of fractional wavelength sections of transmission line, and the resulting frequency sensitivity inherent in prior art phase selectors.
These and other objects and advantages, the nature of the present invention, and its various features, will appear more fully upon consideration of the various illustrative embodiments now to be described in detail in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows, in block diagram, a quantized phase selector in accordance with the invention; and
FIG. 2 shows, in greater detail, an illustrative embodiment of a selector switch for use in connection with the phase selector of FIG. 1.
DETAILED DESCRIPTION Referring to the drawings, FIG. 1 shows, in block diagram, a quantized phase shifter'in accordance with the present invention comprising three 3 db. quadrature hybrid couplers 10, 11 and 12, arranged in a two-stage, hybrid-coupled fan-out configuration, and a selector switch 13.
The term hybrid coupler is used here in its accepted sense to describe a power dividing network having four ports, in which the ports are arranged in pairs, with the ports comprising each pair being conjugate to each other, but in coupling relationship to the ports of the other of said pairs. Being, in addition, 3 db. quadrature hybrids, the divided signal components are equal in amplitude and 90 out of phase.
Referring again to FIG. 1, the two pair of conjugate ports for each of the hybrids are identified as 1, 2 and 3, 4, of which port 1 of hybrid l0 constitutes the signal input port of the 14, l5, l6 and 17. As illustrated, the latter are represented by.
four ganged switches which, simultaneously, terminate the four ports in either an open circuit or a short circuit.
Port 2 of hybrids 11 and 12 are connected to selector switch 13 which couples the signal from one or the other of these hybrids to the signal output port of the phase selector.
In operation, the signal applied to port 1 of hybrid 1 0 is divided into two equal components in ports 3 and 4. Neglecting, for the purposes of the following discussion, phase shifts that are common to all signal components, and adopting the convention that coupling between ports 1-3, and 24 introduces no relative phase shift, whereas coupling between ports 1-4 and 2-3 introduces a relative phase shift, the phases of the signal components at ports 3 and 4, relative to the input signal, are 0 and 90, respectively.
These signals undergo a second stage of division in hybrids 11 and 12 to produce four branch signals at terminations 14, 15, 16 and 17 whose relative phases are 90, 0, degrees, 90 and respectively. Depending upon the termination, i.e., open circuit or short circuit, the branch signals are reflected with either 0 or 180 additional degrees of phase shift and recombine in ports 2 of hybrids l1 and 12 to produce two signals whose relative phases are a function of the terminations. Table I below gives the relative phases of the signals at ports 2 of hybrids 11 and 12 as a function of the termination at As can be seen from Table I, the circuit produces signals having quantized relative phase shifts of either 90, 180, 270 or 360. Switch 13 selects from among these by coupling the phase selector output port to port 2 of either hybrid 11 or 12 For example, with a short circuit termination, and selector switch 13 coupled to hybrid 11, an output signal having a 270 relative phase shift is obtained. Similarly, with an open circuit termination and switch 13 coupled to hybrid 12, a signal having a 180 relative phase shift is obtained.
Depending upon the particular application at hand, selector switch 13 and the termination selector switches can be anything from manually operated knife switches to high speed automatically operated switches. Typically, for high speed operation, ports 3 and 4 of hybrids 11 and 12 are advantageously terminated by means of PIN diodes, for example, which, when biased in their low conductivity state simulate an open circuit, and when biased in their high conductivity state simulate a short circuit. Obviously, other devices such as transistors or relays can also be used for this purpose.
FIG. 2, shows in greater detail, a selector switch comprising two, interconnected quadrature hybrid couplers 20 and 21, and switching means, shown as diodes 22 and 23, for short-circuiting the interconnecting wavepaths 24 and 25. Using-the same designations as in connection with FIG. 1, port 2 of hybrid 11 is connected to port 1 or hybrid 20; conjugate port 2 of hybrid 20 is resistively terminated. Port 1 of hybrid 21 is the selector switch signal output port. The remaining ports 3 and 4 of hybrids 20 and 21 are connected together by means of identical wavepaths 24 and 25. Switchable shorting means are connected in shunt with the latter for simultaneously shorting both wavepaths 24 and 25 at a point midway between hybrids 20 and 21.
In operation, signals are coupled into switch 13 from both hybrids 11 and 12. With diodes 22 and 23 biased in their low conductivity state, they appear as open circuits allowing free passage of signals along wavepaths 24 and 25. Accordingly, the signal from hybrid l2 propagates from port 1 of hybrid 21 to port 2 of hybrid 20 where it is absorbed in the resistive termination. The signal from hybrid 11, on the other hand, is coupled from port 1 of hybrid 20 to the signal output port 2 of hybrid 21.
When, on the other hand, the diodes are biased in their high conductivity states, the signal components derived from the signal applied to port 1 of hybrid 20 are reflected by the resulting short circuit along wavepaths 24 and 25 and are dissipated in the resistive termination connected to port 2 of hybrid 20. Similarly, the signal components derived from the signal applied to port 1 of hybrid 21 are also reflected by the short circuit along wavepaths 24 and 25, and recombine in output port 2. Thus, by switching diodes 22 and 23 between their high and low conductivity states, the selector switch signal output port is switched between the signals coming from hybrids 11 and 12.
Table II shows the relative phase of the output signal as a function of the terminations at ports 3 and 4 of hybrids 11, 12,
20 and 21.
TAB LE 11 Relative output Termination Termination signal phases, hybrids 11, 12 hybrids 20, 21
180 Open circuit Open circuit. 90,. ..d Short circuit. 360. Short circuit. Open circuit. 270 .do Short circuit.
It should be noted that, in fact, the phases of the output signals relative to the input signal also include a constant phase shift 0, which accounts for the additional phase delay the several signal components experience as they propagate through the phase shifter. This has not been included in Table II, however, since it is typically the relative phase shifts among the four output signals that is of interest. As can be seen, the relative phases among the four possible output signals are 90m degrees, where m is l, 2 or 3.
In the illustrative embodiment of FIG. 1, a short circuit and an open circuit are used to produce the desired 0 and 180 additional phase delays, and the same couplers l1 and 12 are used to recombine the reflected signal components. It is apparent, however, that other means of producing the desired 180 phase shift can be used, such as the half rotated rectangular waveguide section shown in US. Pat. No. 3,184,691. In addition, separate couplers can be used to recombine the signal components. it will also be appreciated that the particular selector switch shown is merely illustrative. Thus, in all cases it is understood that the above-described arrangements are illustrative of only a small number of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can readily be devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.
1. A quantized phase shifter for producing one of four output signals whose relative phase differences are integral multiples of degrees, comprising:
a two-stage, quadrature hybrid-coupled fan-out for dividing an input signal into four signal components;
means for simultaneously adding an additional 0 or of relative phase shift to said signal components; characterize in that:
pairs of said phase shifted signal components are combined to produce two signals whose relative phases, with respect to said input signal, differ, as a function of said means, by integral multiples of 90; and switching means for coupling to one of said two signals.
2. The phase shifter according to claim 1 wherein said switching means comprises:
first and second quadrature hybrid couplers, each having two pairs of conjugate ports;
one port of one pair of conjugate ports of each of said couplers being an input port;
the other port of said one pair of ports in said first coupler being resistively terminated;
the other port of said one pair of ports in said second coupler being the output port;
first and second identical wavepaths for coupling each port of the other pair of ports of said first coupler to a different port of the other pair of ports of said second coupler; and shorting means disposed midway along said wavepaths.
3. A phase selector comprising, in combination:
first, second and third 3 db. quadrature hybrid couplers arranged in a two-stage hybrid-coupled fan-out configuration, and a selector switch for coupling either one of two wavepaths to the phase selector output port;
each of said couplers having two pairs of conjugate ports;
one port of said pairs of ports of the first of said couplers being the input port of said phase selector;
the other port of said one pair of ports being resistively terminated;
means for coupling each port of the other pair of said first coupler to one port of one pair of ports, respectively, of said second and third couplers;
means for simultaneously terminating the other pair of ports of said second and third couplers in either an open circuit or a closed circuit; and
means for coupling the other ports of said one pair of ports of said second and third couplers to said selector switch.
227 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION nt 3571765 Dated March 2?. 1071 Inventor(s) Allen N. Friedman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column l, line 40, after "of", second occurrence, insert ports of.
This error is chargeable to the Official printer.
Signed and sealed this 22nd day of June 1 971 (SEAL) Attest:
EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, J1
Attesting Officer Commissioner of Patent