US2973512A

US2973512A - Electromagnetic wave switching arrangements

Info

Publication number: US2973512A
Application number: US755772A
Authority: US
Inventors: Walsh Arthur Stephen
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1957-08-20
Filing date: 1958-08-18
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28
Also published as: GB848113A

Description

ELECTROMAGNETIC WAVE SWITCHING ARRANGEMENTS M w T N M w 2 w W W E Q m w s L h R w W a T M m w a u m m w M8302 5 5; in 9 AV N 1&2; s V H 8 P LliLrLrlll l\IL & 558 BED 5232?. 56:8 MMEEZE 525% oiazoz 2255a T m. mi A m .m

Feb. 28, 1961 Feb. 28, 1961 A. s. WALSH ELECTROMAGNETIC WAVE SWITCHING ARRANGEMENTS 3 Sheets-Sheet 2 Filed Aug. 18, 1958 ToK M/HLSH- M 2 m; M 4 n a w Feb. 28, 1961 A. s. WALSH 2,973,512

ELECTROMAGNETIC WAVE SWITCHING ARRANGEMENTS Filed Aug. 18, 1958 3 Sheets-Sheet 3 F l T I CHANGE OVERH 2A [am/ nc INVEN TOR ELECTROMAGNETIC WAVE SWITCHING ARRANGEMENTS Arthur Stephen Walsh, Watford, England, assignor to The General Electric Company Limited, London, England Filed Aug. 18, 1958, Ser. No. 755,772

Claims priority, application Great Britain Aug. 20, 1957 5 Claims. (Cl. 343-16) This invention relates to electromagnetic wave switching arrangements.

According to the present invention, an electromagnetic wave switching arrangement comprises first and second transmission paths, first and second directional couplers which are each associated with both the transmission paths and which are arranged, at the frequency of operation, each to divide substantially equally between the two paths the enerby of an electromagnetic wave fed to the coupler in either direction along either path, each of these couplers being of the kind in which the wave coupled from. either path to the other is effectively subjected to a phase-shift of substantially 90, and a nonreciprocal phase-shift device which is provided in one of the two transmission paths between the two directional couplers and which has associated control means to cause the device selectively to have, at the firequency of operation, one of two ditierent phase-shift conditions in the first of which the device introduces substantially zero phase-shift to an electromagnetic wave travelling in one direction through the device and substantially 180 phaseshift to a wave travelling in the opposite direction while in the second condition these phase shifts are interchanged, the arrangement being such that, during operation, when the said device is operating in the first phase-shift condition, substantially all the energy of an electromagnetic wave fed to the first directional coupler over a first portion of the first transmission path which is on the side of that coupler remote from the second directional coupler is passed to a second portion of that path which is on the side of the second directional coupler remote from the first directional coupler, substantially all the energy of an electromagnetic wave fed to the second directional coupler over the second portion of the first transmission path is passed to a portion of the second transmission path which is on the side of the first directional coupler remote from the second directional coupler, and substantially hi the energy of an electromagnetic wave fed to a second portion of the second transmission path which is on the side of the second directional coupler remote from the first directional coupler is passed to the first portion of the first transmission path, while when the said device is operating in the second phase-shift condition energy is transferred in the manner stated in connection with the first condition with the references to the said second portions of the two transmission lines interchanged. Preferably an isolator is provided in the first portion of the firsttransmission line, this isolater being arranged to pass without appreciable attentuation an electromagnetic wave fed over that portion to the first directional coupler 2,973,512 Patented Feb. 28, 1961 but to absorb substantially all the energy of a wave travelling in the opposite direction.

In a radar system of the kind utilising a non-resonant directional aerial system which requires a resistive termination connected to the aerial system for correct operat-ion thereof, an electromagentic wave switching arrangement as set out above may be provided between the trans mitter, the receiver and the aerial system, the transmitter being arranged to supply an electromagnetic wave to the first portion of the first transmission path, the receiver being arranged to be supplied with an electromagnetic wave by the first portion of the second transmission path, and the aerial system being connected between the second portions of the two paths so that, during operation and for both phase-shift conditions of the said device, an electromagnetic wave is supplied to the aerial system over one of the second portions of the two paths while the other effectively constitutes the required termination, whereby the direction in which the aerial system is beamed may be changed by operation of the said control means.

When the phase-shift device is operating in the first phase-shift condition, an electromagnetic wave from the transmitter is passed to the aerial over the second portion of the first t-ranmission path while the necessary resistive termination is effectively provided by the second portion of the second transmission path since the electromagnetic wave passed thereto by the aerial system is passed through the switching arrangement and is arranged to be absorbed by the said isolator or otherwise. Similarly, when the device is operating in the second phase-shift condition, the two connections to the aerial system are effectively interchanged, the aerial system being such that this results in a change in the direction in which the aerial system is beamed. It will be realised that in this condition, the unradiated wave passed by the aerial system to the second portion of the first transmission path is again absorbed after passing through the switching arrangement to the first portion of that path. In both conditions of the phaseshift device the switching arrangement, in addition to its switching function, acts as a duplexer.

According, therefore, to another aspect of the present invention, a radar system has a switching arrangement provided between a radar transmitter and a radar receiver on the one hand and a non-resonant aerial system on the other hand, this switching arrangement being formed by two directional couplers in combination with a non-reciprocal phase-shaft device which has associated control means to vary the operating conditions of the device whereby beam switching of the radar system may be effected by operation of the said control means while the said switching arrangement, in addition to its switching function, acts as a duplexer.

One example of a C.W. radar system which incorporates a switching arrangement in accordance with the present invention will now be described with reference to the accompanying drawings in which Figure 1 diagrammatically shows the radar system including the switching arrangement;

Figure 2 shows a perspective view of the aerial system of the radar system; t

Figure 3 shows in more detail the construction of the switching arrangement;

Figure 4 shows a sectional elevation through part of 3 the switching arrangement, the section being taken at the lines IV-IV in Figure 3, and

Figure shows a plan view of the part shown in Figure 4.

Referring now to Figure 1, the radar system comprises a radar transmitter 15, a radar receiver 16 and a nonresonant aerial system 17. A switching arrangement 18 is connected between the transmitter 15 and the receiver 16 on the one hand and the aerial system 17 on the other hand, this switching arrangement being arranged to effect beam switching of the aerial system 17 and also to act as a duplexer. Referring now to Figure 2 of the accompanying drawings, the aerial system 17 comprises a main length of waveguide 19 to which four further waveguides 20 are connected by means of coupling slots 21. The longitudinal axes of the

waveguides

19 and 20 all lie in the same plane while the longitudinal axes of the waveguides 20 lie parallel to one another and perpendicular to the axis of the waveguide 19. A plurality of radiator slots 22 are provided in a narrow wall of each of the waveguides 20 while the end 23 of each of these waveguides is short-circuited. The slots 22 in the walls of all the waveguides 20 together make up the aerial array. Although the aerial system shown diagrammatically in Figure 2 has only sixteen slots 22, there may in practice be more slots. In that case the aerial system may comprise more than four waveguides 20 each of which has more than four slots 22. During operation of the aerial system 17, an electromagnetic wave is supplied to one end of the waveguide 19 while a resistive termination is required to be connected to the other end so as to prevent any portion of the original wave reaching that end of the waveguide 19 being reflected back along that waveguide. Beam switching is effected merely by interchanging (in the manner subsequently described) the ends of the waveguide 19 to which the electromagnetic wave is supplied and the end to which the resistive termination is connected.

Referring again now to Figure 1 of the drawings, the

switching arrangement 18 comprises two

waveguides

1 and 2 which are both of rectangular cross-section, different portions of these two waveguides being referenced in this figure 'by the appropriate numeral with the addition of a letter suflix. Two like directional couplers 3 and 4 are provided, each of these directional couplers being awbranched-guide coupler which is arranged to divide the energy of a wave travelling in either direction along either of the

waveguides

1 or 2 between the two waveguides. A feature of this construction of directional coupler is that in the event of a wave being supplied to the directional coupler 3 along the waveguide portion 1A, for example, the energy transferred in the waveguide 2 is subjected to a 90 phase-shift so that the wave developed at the point 6 is lagging by 90 on the wave at the .point 5. The waveguide portions 1B and 2B between the directional couplers 3 and '4 are of equal length. The waveguide portion lB however includes a non-reciprocal phase-shift device 7 which is capable of being operated in either one of two conditions, the manner in which it is caused to change from'one condition to the other being subsequently described. In one of the conditions the device 7 introduces into the waveguide portion 1B a phase-shift of 180 to a wave travelling in the direction of the arrow 8 and zero phase-shift to a wave travelling in the opposite direction while in the other condition, the device 7 introduces zero phase-shift to a wave travelling in the direction of the arrow 8 and 180 to a wave travelling in the opposite direction.

An isolator 9 is provided in the waveguide portion 1A between the directional coupler 3 and the radar transmitter 15 while the waveguide portion 2A is connected directly to the radar receiver 16. The isolator 9 presents no appreciable attenuation to a wave being supplied 4 from the transmitter 15 to the directional coupler 3 but absorbs any wave travelling in the opposite direction.

The waveguide portions 1C and 2C are connected to the two ends respectively of the waveguide 19 (Figure 2) of the aerial system 17.

Consider now the conditions when the device 7 is arranged to introduce a phase-shift of 180 to a wave travelling in the direction of the arrow 8 and no phaseshift to a wave travelling in the opposite direction. A wave supplied by the transmitter over the waveguide portion 1A is divided by the directional coupler 3 between the Waveguide portions 1B and 2B, virtually no energy being transferred into the portion 2A. As previously explained the wave developed at the point 6 is lagging by 90 on the wave at the point 5. Since the device 7 introduces a phase-shift of 180 to a wave travelling along the waveguide portion 1B in the direction of the arrow 8, the wave at the point 10 is leading by 90 the wave at the point 11. The energy of the wave passed to the directional coupler 4 over the waveguide portion 2B is transferred into the waveguide portion 1C with a further phase-shift of 90 so that it is then in phase with that portion of the wave which is passed from the waveguide portion 13 to the waveguide portion 1C. The portion of the wave fed to the directional coupler 4 over the waveguide portion 13 which is coupled into the wave guide 2, is equal in magnitude and opposite in phase to that portion of the wave fed over the waveguide portion 2B which passes straight through the directional coupler 4 so that there is no resultant wave at the point 12.

Substantially all the energy supplied by the transmitter 15 is thus passed to the aerial system 17 by way of the waveguide portion 1C. The energy that is not radiated by the aerial system 17 is returned to the switching arrangement 18 by way of the waveguide portion 2C which energy is divided between the waveguide portions 1B and 2B by the directional coupler 4. The wave at the point 11 is lagging on the wave at the point 10 but since in this case the device 7 introduces no phase-shift, the wave at the point 5 is lagging by 90 on the wave at the point 6. The directional coupler 3 serves to combine the waves passed thereto over the waveguide portions 1B and 2B so that substantially all the energy of the wave passed to the switching arrangement 18 by the aerial system 17 is combined and passed to the waveguide portion a 1A, virtually no portion of this energy being passed to the receiver 16 over the waveguide portion 2A. The isolator 9 is arranged to absorb the energy supplied thereto in this manner without reflection.

Any received signal picked up by the aerial system 17 is passed to the switching arrangement 18 over the waveguide portion 10. It will be appreciated that such a wave is passed through the switching arrangement 18 to the waveguide portion 2A and thus to the receiver 16 With substantially no attenuation.

When it is required .to change the direction in which the aerial system is beamed, the condition of the device 7 is changed so that the device 7 introduces substantially zero phase-shift to a wave travelling in the direction of the arrow 8 and phase-shift to a wave travelling in the opposite direction. Under this condition a wave fed to the switching arrangement 18 from the transmitter 15 is passed with substantially no loss of energy to the aerial system 17 by way of the waveguide portion 20. The unradiated energy is returned over the waveguide portion 10 and is again absorbed by the isolator 9. In this case any signal picked up by the aerial system 17 is fed to the switching arrangement 18 over the waveguide portion 20 and is passed through the switching arrangement so as to appear on the waveguide portion 2A which passes it-to the radar receiver 16.

The manner in which the

waveguides

1 and 2, the

couplers 3 and 4, the phase-shift device 7 and the' iso-v lator 9 are arranged in the switchingarrangement 18 Rd is shown in Figure 3 which is a cross-section through the switching arrangement.

Referring now also to Figures 4 and 5, the phase-shift device 7 is of known form and comprises a ferrite member 24 mounted asymmetrically in the waveguide 1 while an associated electromagnet 25 (which is only shown as a broken outline in Figure 3) is provided to set up a transverse magnetic field in the region of the member 25. The operating winding of this electromagnet 25 is arranged to be energised through a change-over switch 26 (Figure 4) from an electric supply line 27. The changeover switch 26 is a double-pole double-throw switch and each position of this switch causes the phase-shift device 7 to have one of the operating conditions previously discussed. The change-over switch 26 may conveniently be formed by change-over contacts of an electromagnetic relay.

The ferrite member 24 does, of course, have some effect on the electrical length of that portion of the waveguide 1 in which it is provided and in order to ensure that the portions of the

waveguides

1 and 2 connecting the couplers 3 and 4 have the same electrical lengths, a dielectric member 28 is provided in the waveguide 2.

The isolator 9 is also of known form and comprises a ferrite member 29 (Figure 3) which is mounted asymmetrically in the waveguide 1 together with a permanent magnet or electromagnet which is shown diagrammatically by the broken line Si in Figure 3 and which is arran ed to provide a transverse magnetic field so that the isolator operates in the manner previously described.

It will, of course, be understood that the directional couplers 3 and 4 need not be branched-guide couplers but in an alternative construction of switching arrangement may, for example, be long slot couplers. An essential feature of each of these couplers is that it is capable of dividing equally between the two

waveguides

1 and 2 the energy of an electromagnetic wave fed thereto in either direction along either waveguide while the Wave coupled from either of the

waveguides

1 and 2 to the other waveguide is effectively subjected to a phase-shift of substantially 90.

It will be also realised that although the radar system described above is a C.W. radar system, the switching arrangement may equally well be applied to a pulsed radar system, TR. and A.T.R. switches then being provided between the switching arrangement and the radar transmitter and radar receiver in known manner.

Although the example described above makes use of waveguides, it is to be understood that the present invention is not so restricted and may, for example, be applied to switching arrangements which utilise co-axial transmission lines.

What I claim is:

1. An electromagnetic wave switching arrangement comprising first and second transmission paths, first and second directional couplers which are each associated with both the transmission paths and which are arranged, at the frequency of operation, each to divide substantially equally between the two paths the energy of an electromagnetic wave fed to the coupler in either direction along either path, each of these couplers being of the kind in which the wave coupled from either path to the other is efiectively subjected to a phase-shift of substantially 90, and a non-reciprocal phase-shift device which is provided in one of the two transmission paths between the two directional couplers and which has associated control means to cause the device selectively to have, at the frequency of operation, one of two different phase-shift conditions in the first of which the device introduces substantially zero phase-shift to an electromagnetic wave travelling in one direction through the device and substantially 180 phase-shift to a Wave travelling in the opposite direction While in the second condition these phase-shifts are interchanged, the arrangement being such that, during operation, when the said device is operating in the first phase-shift condition, substantially all the energy of an electromagnetic wave fed to the first directional coupler over a first portion of the first transmission path which is on the side of that coupler remote from the second directional coupler is passed to a second portion of that path which is on the side of the second directional coupler remote from the first directional coupler, substantially all the energy of an electromagnetic wave fed to the second directional coupler over the second portion of the first transmission path is passed to a portion of the second transmission path which is on the side of the first directional coupler remote from the second directional coupler, and substantially all the energy of an electromagnetic wave fed to a second portion of the second transmission path which is on the side of the second directional coupler remote from the first directional coupler is passed to the first portion of the first transmission path, While when the said device is operating in the second phase-shift condition energy is transferred in the manner stated in connection with the first condition with the references to the said second portions of the two transmission lines interchanged.

2. A switching arrangement according to claim 1 wherein an isolator is provided in the first portion of the first transmission line, this isolator being arranged to pass without appreciable attenuation an electromagnetic wave fed over that portion to the first directional coupler but to absorb substantially all the energy of a wave travelling in the opposite direction.

3. A radar system comprising a non-resonant aerial system which comprises a first transmisison path having two ends and a plurality of radiating elements coupled to the first transmission path, a radar transmitter, a radar receiver, a second transmission path having first and second end portions and a center portion between the two end portions, a third transmission path having first and second end portions and a center portion between the two end portions, means to connect the first end portions of the second and third transmission paths, one to the radar transmitter and one to the radar receiver, means to connect the second end portions of the second and third transmission paths to the two ends respectively of the first transmission path, first and second directional couplers which are connected between the center portions of the second and third transmisison lines, each of these directional couplers dividing substantially equally between the second and third transmission paths the energy of an electromagnetic Wave fed to the coupler in either direction along either of those paths while the wave coupled from either of these paths to the other is effectively subjected to a phase-shift of substantially and a non-reciprocal phase-shift device which is provided in the center portion of the second transmission path between the two directional couplers and which has associated control means to cause the device selectively to have, at the frequency of operation, one of two different phase-shift conditions in one of which the device introduces substantially zero phase-shift to an electromagnetic wave travelling in one direction through the device and substantially phase-shift to a wave traveling in the opposite direction while in the other condition these phase-shifts are interchanged, the arrangement being such that, during operation, when said device is operated in a first of said two phase-shift conditions, substantially all the energy of an electromagnetic wave fed to the first directional coupler by the radar transmitter is passed to the aerial system by way of the second end portion of the second tnansmission path, substantially all the energy of an electromagnetic wave fed to the second directional coupler from the aerial system over the second end portion of the second transmission path ispassed to the radar receiver, and substantially all the energy'of an'electromagnetic wave fed to the second directional coupler over the second end portion of the third transmission path is passed to the first end portion of the second transmission path, while when said device is operated in a second of said two phase-shift conditions energy is transferred in the manner stated inconnection with the first condition with the references to the second end portions of the second and third transmission paths interchanged.

4. A radar system as set forth in claim 3 wherein an isolator is provided in the first end portion of the second References Cited in the file of this patent UNITED STATES PATENTS 2,849,685 Weiss Aug. 26, 1958