GB2462870A

GB2462870A - Method of and device for producing phase-shifts in a beam of microwave electromagnetic waves

Info

Publication number: GB2462870A
Application number: GB8205303A
Authority: GB
Inventors: Jacques Saint; Gerard Collignon
Original assignee: RADANT ETUDES
Current assignee: RADANT ETUDES
Priority date: 1981-04-30
Filing date: 1982-02-25
Publication date: 2010-03-03
Anticipated expiration: 2002-02-25
Also published as: GB2462870B; GB8205303D0; FR2734409B1; FR2734409A1

Abstract

A network of wires 8 can be made continuous or discontinuous by means of diodes disposes on said wires and controllable as required. According to the invention, an electronic lens is divided into parallel channels 21, 22....., in which the phase-shift wires are disposed, said channels being seperated by metal plates 11,12,......, which form wave-guides. In this way most of the interference coupling phenomena are eliminated and the lens deflection properties are improved.

Description

TITLE

"NETHOD OF AN]) DEVICE FOR PRODUCING PHASE-SHIFTS IN A BEAM OF MICROWAVE ELECTROMAGNETIC WAVES"

DESCRIPTION

The invention relates mainly to a method and device for electronic scanning in the plane perpendicular to the electric field of a beam of microwave electromagnetic Waves.

In an earlier patent specification No. 2 026 967

filed on 15 October 1969, a description has already been given of a method of electronically scanning an aforementioned beam of waves by using networks of electrically conductive wires parallel to the electric field vector of the microwave wave and bearing spaced-apart controllable switches, inter alia diodes, for making the wires continuous or discontinuous and consequently introducing a phase-shift of the micro-wave wave which differs depending on whether the diodds are transmitting or blockd. A number of the resulting networks can be disposed one behind the other for the purpose of electronic scanning of the beam by increments.

However, electronic scanning lenses constructed in the aforementioned manner and based on dielectric panels bearing diodes and wires have certain disadvantages, more particularly the following: 1. The phase laws to be applied to the lens by polarizing a number of diode wires agree only approximately with the theoretical laws. To obtain acceptable side radiation, it is therefore necessary to modify the theoretical linear phase law, which means that each desired aiming of the beam has to be brought about experimentally and each phase state hs t be stored in the control computer memories. This procedure is long and expensive.

2. After experimental optimization of the phase laws in the aforementioned manner, the experimentally-obtained radiation diagrams are degraded compared with the theoretical diagram. More particularly the antenna gain falls more steeply than expected when the antenna is out of aim, and the resulting secondary radiation is her than exoected.

The invention relates to a method and device for producing electronic scanning in the plane perpendicular to the electric field of a beam of microwave electromagnetic waves, using networks of wires parallel to the electric field vector and bearing diodes, but free from the afore-mentioned disadvantages and difficulties.

The method according to the invention, in contrast to the kiown prior art, is characterised in that the network of wires bearing controllable switches, inter alia diodes, is divided into elementary adjacent channels separated by metal surfaces forming waveguides and the conductive wires are grouped in the channels so as to prevent interfering coupling between a channel and the nearest adjacent channels4 the channels having a width substantially equal to bail the wavelength of the beam of electromagnetic waves under consideration (the distance being measured in free space: dielectric constant 1).

When the networks are organized in this manner, the aforementioned difficulties are obviated, the phase laws to S. be applied ar near the expected theoretical laws and the radiation diagrams are only slightly degraded, even when the antenna beam is considerably off the aim.

The invention and the manner of working it will be understood more clearly from the following description with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic perspective view of part of a device forming an electronic scanning lens according to the invention; Fig. 2 is a view corresponding to Fig. 1 but showing only one channel and one manner of disposing the networks of phase-shifting wires therein; Fig. 3 is a top view in the direction of arrow III of Fig. 2 of a manner of dispoping phase-shifting wires grouped by increments in a channel; Fig. 4 shows the phase-shifts obtained in dependdnce on frequency around a wavelength under consideration (3100 iz), and Figs. 5, 6 and 7 are three curves illustrating the radiation diagrEits obtained at a given frequency (3100 when the antenna is off the aim by three different amounts.

In the embodiment illustrated in Figs. 3. to 3, the device forming art elecronic scanning lens is divided into channels by metal or metal-coated plates parallel to one another and parallel to the electric field vector E of the electromagnetic waves in the beam. The plates 1.

12 l........ co-operate to bound channels 2, 22....... -, 1

inside which the waves propagate in a guided wave mode.

According to an essential feature of the invention, the space e between adjacent plates l, l2Is* is substantially equal to half the length of the electromagnetic wave to be guided.

Advantageously, more particularly if it is desired to move the beam off the aim by a considerable amount.

e.g. above 300. dielectric plates 2'*****'* made of an appropriate material are disposed in each channel 2i.

22.......

In the chosen example, where the operating frequency band is between 2 900 and 3 300 MHz, corresponding to wavelenVths of the order of 10 centimetres, the width of the channels has been made eoual to 47 rrn. The dielectric plates used have a thickness of 8 nn and are made of a complex glass and polyester resin material having a dielectric constant of 4.2 and a very low loss coefficient. An experimental lens corresponding to the curves given hereinafter was made up of 3Q adjacent channels having a height h of cm and a depth p of 25 cm. Of course these dimensions can vary,more particularly the height of the stack which is unlimited.

The diode wires used are mounted one behind the other in each channel.

Fig. 3 shows a satisfactory arrangement of the wires in the chanel. In the illustrated example, the diodds used are PIN type diodes having an inverse capacitance of 0.2 pF. They are mounted in series on continuous wires at intervals of 10.16 mm. The phase shift provided by each diode.l is adjusted by the position of the wire in the channel cross-Section ( , Fig. 3) Thus, the group 4 of two wires 5, 6 forming an elementary phase-shifter produces a phase shift of 11.25°.

The distance between the two wires is such that the group is adapted to transmitting the microwave wave as known in the art.

The group 7 of two diode wires 8 and 9, which forms a second elementary phase-shifter. is placed in the channel behind group 4 and produces a phase shift of 22.5°, the difference in phase-shift being due to the difference in the Dositioning of wires 5, 6 and 8, 9 respectively in the channel. Advan1eously the adjustments are made experi-menta]]y.

The group 10 of three diode wires 11, 12, 13 similarly produces a phase shift of 45.

The group 14 of four diode wires 15 -18 produces a phaee shift of 90°.

Finally, the last group 19 of five wires 20 -24 produces a phase shift of 1800. Thus, by supplying the diodes in the conductive direction or by blocking them, any phasd shift of the microwave wave can be obtained from 00 to 348.750 by successive increments of 11.250.

by forming discontinuities in the wires of all or only some of the groups of diode wires 4, 7, 10, 14 and 19.

In order to facilitate the construction, the diode wires are advantageously mounted as shown in Fig. 2 on printed circuit strips made e.g. of epoxy glass 0.8 nun thick secured between a dielectric plate 3 arid an adjacent metal or metal-coated wall 1. Thus, each strip 25 engages in its channel e.g. by sliding in grooves formed on the facing walls of the dielectric plates 3 and the metal plate 1.

The diodes for controlling the blocking (discontinuous wire) or unbiocking (continuous wire) of the diodes are advantageously energized arid electrically controlled in a similar manner to that in French patent specification 2 395 620 filed on 24 June 1977 in the name of the predent applicants by grouping the diodes on each wire in small sets of diodes mounted in opposition. For example, the diodes on each wire can be grouped in parallel associations of 7 diodes in series. If 8 such associations are mounted on each wire, 8 x 7 56 diodes can be ptioned so that blocking or unbiocking thereof can be controlled by a relatively small control voltage of the order of 350 V (i.e. 7 x 50 V in inverse operation). chen the wires have to be continuous (transparent network) the diodes are controlled in direct operation by supplying them with a current of 240 milliamperes, i.e. 8 x 30 mA in direct operation.

In Fig. 2, references 26 and 27 denote the wires supplying diodds grouped on a strip in accordance with the principle described in the aforementioned specification 2 395 620.

In the aforementioned patent, however, the wires supplying the diodes must be taken into account in the total definition of the panel. which complicates the construction.

S

ccording to the invention, the wires are advan-ageously all disposed against the metal walls forming wave guides. In the aforementioned position, they have no microwave influence, whicli facilitates the construction.

To this end, wire 26 is placed against one surface of strip towards its edge 28 in *contact with plate 1, and wire 27 is disposed on the other surface of strip 25, likewise towards its edge 28 in contact with plate 1, wires 26 and 27 being separated only by the thickness of the strip.

Contact between wire 27 and the associations of diodes is obtained by forming a inetallized hole across the strip at the reouircd places for obtaining a junction with wire 27 mounted on the other sufface of the strip. (This embodiment has not been illustrated).

ReferrIng to the curves in Fig. 4, we see that the curves for the phase shift are very flat in a frequency band -of more than 15% around the average frequency of.3100 Iz in question. This means that the radiation diagram remains adequate over a wide frequency range.

Similarly, the curves in Figs. 5, .6 and 7 show that in the example under consideration of a lens mn.de up of 32 channels constructed in the aforcmsntioned manner, the antenna radiatbn diagram i rc-latively well preserved, which is shown in that the main lobe is preserved when successively out of aim by 20, 40 and 600 in the cases under consideration. ,jhe side lobes of the beam remain within acceptable limits at around -40 dB and rena1n below -30 dB.

Numerous variants can mde to the embodiment S. illustrated and described, inter alia with regard to the mechanical construction and the arrangement of the diode wires in the channels.

Thus, other assemblies could be used instead of printed circuit strips and the structure could be reinforced e.g. by the known method of cellular sandwich panels. In addition, the metal plates 1 forming wave guides can be metal-coated plastics sheaths instead of metal sheets, inter alia in order to reduce the weight of the structure.

The invention therefore comprise3 all technical eQuivalents of the described means arid combinatiOnS thereof, if made in accordance with its spirit and embodied in conformity with the claims hereinafter. Jo

Claims

CLAIMS1, An electronic method of changing the pha$e-shift of a wave transmitted by a microwave radiating source, the method being of the kind in which at least one network oriented substantially parallel to the electric field of the incident wave is interposed in the path of the beam, phase-shifting wires capable of being made continuous or discontinuous by means of controllable switches, more particularly diodes, being placed on the wires and control-lable as rec!uired, the method being characterised in that the network is divided into elementary adjacent channel.2is 22, separated by metal surfaces lii la..... forming wave guides and the conductive wires 5, 6, 8, 9, 1]. -13, -18, 20 -24 ar grouped in the channels so as to prevent interfering coupling between a channel and the nearest adjacent channels, the channels having a width substantially equal to half the wavelength of the beam measured in free space.
2. A method according to claim 1, characterised in that each channel comprises identical groups 4, 7, 10, 14, 19 of conductive wires capable of inducing the same phase-shift values for each channel.
3. vice for working the method according to claim 1 or claim 2, characterised in that it comprises networks of parallel conductive wires 5, 6, 8, 9, 11 -13, -18, 20 -24 in which controllable switches, more particularly diodes, are mounted, the wires being disposed one behind the other in juxtaposed channels 2i. 22.....SUformed between metal surfaces 1, l2**S* parallel to the networks and, in the general direction of the incident beam, forming waveguides spaced apart by substantially half the wavelength of the beam.
4. A device according to claim 3, characterised in that dielectric plates l' 2* are disposed substantially in the central plane of the channels.
5. ddvicc according to claim 3 or claim 4, characterieca in that the controll.ble switches such as diodes are groued and electrically energized in small groups inich in turn ar grouped and supplied in parallel / in known manner.
6. a device according to an\' of claims 3 to 5, characterised in that the controllable switches such as diodes are mounted on printed-circhit strips 25 oriented in accordance with the height of the channels.
7. :-. device according to any of claims 3 to 6, charactersed in that the number and oositioning of the wires in the channels deend on the rhase shift which it is desired to introduce.
8. A device according to any of claims 3 to 7, characterised in that the wires are regrouped in each charrEl so that each group 4, 7, 10, 14 and 19, when actuated in inverse operation, introduces a phase-shift of the wave eual to an integral multiple of a given value, e.g. 11.25°.
9. . device according to claim 8, characterised in that each group of wires 4, 7, 10, 14, 19 introducingSa phase-shift of the wave comprises at least two parallel wires.
10. Electronic scanning device substantially as herejnbefore described with reference to the accompanying drawings.IAmendments to the claims have been filed as follows 1. An electric method of changing the phase-shift of a wave transmitted by a microwave radiating source, in which at least one network of wires oriented substantially parallel to the electric field of the incident wave is Interposed in the path of the beam, said wires being capable of being made continuous or by means of controllable switches, being placed on the wires and Controllable as required, the method being characterised in that each network is divided along its width (w) measured parallel to the plane of the network and Perpendicularly to the direction of the wires into elementary adjacent channels separated by metal surfaces forming wave guides and the conductive wires are grouped in the channels so as to prevent interfering coupling between a channel and the nearest adjacent channels, the channels having a width substantially equal to half the wavelength of the beam measured In free space.2. A method according to Claim 1, characterlsed In that each channel comprises Identical groups of conductive wires capable of Inducing the same phaseshift values for each channel. (, Lt:3. A device for use in the method according to Claim 1 or Claim 2, characterlsed in that it comprises networks of parallel conductive wires in which controllable switches, are mounted, the wires of each successive network being disposed one behind the other in juxtaposed channels formed between metal surfaces parallel to the wires and, in the general direction of the incident beam, forming waveguides spaced apart by substantially half the wavelength of the beam and means for controlling said controllable switches.A device according to Claim 3, characterised in.that dielectric plates are disposed substantially in the central plane of the channels.5. A device according to Claim 3 or Claim L3, characterised in that the controllable switches are grouped and etrically energized in small groups which in turn are grouped and supplied in parallel in known manner.6. A device according to any of Claims 3 to 5, characterised in that the controllable switchesI iSare mounted on printed-circuit strips oriented In accordance with the height of the channels.7. A device according to any of Claims 3 to 6, characterlsed in that the number and positioning of the wires in the channels depend on phase shift wh!ch it Is desired to Introduce.8. A device according to any of Claims 3 to 7, characterlsed. In that the wires are regrouped in each channel so that each group, when actuated In inverse operation, introduces a phase-shift of the wave equal to an Integral multiple of a given value, e.g.
11.250.9. A device according to ClaIm 8, characterised In that each group of wires introducing a phase-shift of the wave comprises at least two parallel wires.10. Electronic scanning device substantially as hereirjbefore described with reference to the accompanying drawings.