EP0241380A1 - Verfahren und Vorrichtung zur Strahlfokussierung von Gruppenantennen auf einen Prüfpunkt - Google Patents

Verfahren und Vorrichtung zur Strahlfokussierung von Gruppenantennen auf einen Prüfpunkt Download PDF

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Publication number
EP0241380A1
EP0241380A1 EP87400803A EP87400803A EP0241380A1 EP 0241380 A1 EP0241380 A1 EP 0241380A1 EP 87400803 A EP87400803 A EP 87400803A EP 87400803 A EP87400803 A EP 87400803A EP 0241380 A1 EP0241380 A1 EP 0241380A1
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EP
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Prior art keywords
signal
microwave
antennas
signals
phase
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EP87400803A
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English (en)
French (fr)
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EP0241380B1 (de
Inventor
Jean-Charles Bolomey
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Centre National de la Recherche Scientifique CNRS
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Centre National de la Recherche Scientifique CNRS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
    • H01Q21/225—Finite focus antenna arrays
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/26—Sound-focusing or directing, e.g. scanning
    • G10K11/34—Sound-focusing or directing, e.g. scanning using electrical steering of transducer arrays, e.g. beam steering
    • G10K11/341—Circuits therefor
    • G10K11/346—Circuits therefor using phase variation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
    • H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays

Definitions

  • the present invention firstly relates to a method of focusing, on at least one point to be examined from a microwave radiation source, the antennas of an array of antennas receiving the radiation from the point with respective reception phase shifts .
  • Such a method is used when it is desired to obtain, from the microwave radiation coming from an object to be analyzed, a microwave image of this object.
  • a set of antennas is organized to form a network, this term being taken in a similar, but broader, sense than that which it possesses in optics, and this network of antennas is successively focused on each of the points to examine of the object, so as to build, point by point, the microwave image of this object.
  • Microwave imaging systems have, in particular, applications in biomedical engineering for the detection and treatment of tumors, for example, as well as in civil engineering, for the detection of buried objects for example, or for control of materials treated by microwave radiation (polymerization, thawing, drying ).
  • the antennas known by the name of electronically scanned antennas used for example in radar and in telecommunications, are organized in a fixed array of antennas which has maximum sensitivity in a variable direction electronically controllable, and artwork such a method, corresponding to focusing on a point located at an infinite distance, and defined only by its direction.
  • a focusing method is already known, in which the signal received by each antenna is phase-shifted in a microwave phase shifter, the phase-shifted signals are added and the summation signal subjected to microwave detection.
  • the phase law which determines the particular phase shift to be applied to each received signal, is established so that the contributions from the point on which the network is focused are in phase at the time of summation, the contributions from other points having any phases with respect to each other.
  • the signal obtained mainly represents the contribution of the focal point.
  • This known method has, on the one hand, the disadvantage of a difficult implementation from a practical point of view, because it requires the use of as many microwave phase shifters as there are antennas in the array.
  • a microwave phase shifter is a relatively complex component, with a high cost price and a large size. In cases where the number of antennas reaches several hundred, even several thousand, this solution is therefore very expensive.
  • the size of the phase shifters conditions the distance between an antenna and the neighboring antennas, that is to say the pitch of the network.
  • a not too large antenna will give a poor quality image.
  • a disadvantage of this process is that it does not allow, at a given instant, simultaneous focusing on several points.
  • each received signal is not phase-shifted, which is subjected directly to coherent microwave detection, that is to say a detection making it possible to know the signal detected in module and in phase.
  • Module and phase of each signal received are then acquired by a computer.
  • the computer performs digital processing of all of this data, in order to extract the contribution from any point of the object.
  • Such processing therefore amounts to synthetic focusing as opposed to analog focusing obtained using microwave phase shifters.
  • the applicant has sought an analog type focusing method, which can adapt to any network geometry, but does not require the use of microwave phase shifters as the only known analog focusing method. . To do this, the applicant had the idea of carrying out the phase shifts no longer on the microwave signals, but on a low frequency signal.
  • the method of the invention does not use any microwave phase shifter. It is the low frequency modulation signal which is phase shifted in low frequency phase shifters, which are very simple. This result is obtained by modulating in amplitude the signals delivered by antennas. However, as will be discussed below, it is possible to use space-saving and inexpensive microwave modulators.
  • the method of the invention being an analog type method, it can adapt to unconventional network geometries, it makes it possible to compensate for irregularities in the alignment of the antennas of the network, for example, it has a better signal ratio noise than the synthetic focusing process, and it can adapt to incoherent radiation.
  • the signals delivered by the antennas are amplitude modulated by a low frequency modulation signal of the square type, with modulation phase shifts.
  • the modulation can be carried out using microwave switches, of the PIN diode type for example, therefore with a low cost and size.
  • the invention can also be implemented for focusing the antennas of an array of transmit antennas.
  • a focusing device 30 is provided with J inputs receiving the J signals s 1 , ..., s j , ..., and s J. It is also provided with two outputs delivering two useful signals U x and V x , as well as a control input receiving, here by means of a parallel bus, a control signal ⁇ X.
  • the object 20 can itself be the source of radiation received by the antennas 1, or it can act as a secondary source, that is to say as a reflector of radiation emitted by a primary microwave source, intended to illuminate object 20, and not shown in FIG. 1 for the sake of simplicity.
  • the microwave radiation received by the antennas 1 is monochromatic of frequency f, either because the radiation source is itself monochromatic of frequency f, or because, the source emitting a radiation in a certain frequency band, a selective focusing device 30 is used, centered on the frequency f.
  • the series of J antennas 1 regularly arranged in the plane P is called, by analogy with the networks encountered in optics, antenna array.
  • the microwave image is obtained by successively focusing the array of antennas 1 on each of the points to be examined X of the object 20, during a sequential scanning, point by point, of this object.
  • focusing the antennas 1 of the antenna array on a point X is meant control of the focusing device 30 using the control signal ⁇ X so that the useful signals U x and V X at the output of the device are only representative of microwave radiation from point X.
  • a sequential scanning device not shown, generates the successive control signals A and a display device, not shown, synchronized by the sequential scanning device, collects the signals U x and V x .
  • the sequential scanning device and the viewing device are of the conventional type used in known imaging systems.
  • each signal is subjected to a microwave phase shift by a determined angle ⁇ X (j), and the J phase-shifted signals are summed.
  • the law ⁇ X (j) which determines the phase shift angle for each signal s j called the phase law for point X, is established so that the contributions coming from point X, finding themselves in phase at the time of the summation, interfere constructively, while the contributions coming from the other points, having any phases with respect to each other, interfere destructively.
  • the result of the summation mainly represents the contribution of point X.
  • the antenna array 1 is therefore focused on point X by imposing the phase law ⁇ X (j) using the signal ⁇ X.
  • the phase law ⁇ X (j) can be deduced from knowing the lengths of the paths connecting point X to each of the antennas 1.
  • each reference 2 designates a microwave switch. There are as many switches 2 as there are inputs, that is to say here J switches.
  • the switch 2 of row j is provided with a microwave input receiving the signal s j and a microwave output delivering the signal s' j , as well as a control input receiving a signal C j .
  • a microwave summing device 3 is provided with J inputs receiving the J signals s' 1 , ..., s' j , ... and s' J , and an output delivering a signal s.
  • a coherent microwave detection circuit 6 is provided a signal input receiving the signal s, a control input and two outputs delivering DA and DB signals.
  • a microwave oscillator 4 is provided with an output delivering a signal r of coherent microwave detection, connected to the control input of circuit 6.
  • the signal r is a sinusoidal signal of frequency f.
  • a low frequency coherent detection circuit 8 is provided with two signal inputs receiving the signals DA and DB, a control input and two outputs delivering the signals U x and V x .
  • a low frequency oscillator 11 is provided with an output delivering a modulation signal D, connected to the control input of circuit 8.
  • the signal D is a sinusoidal signal of frequency F, of value between substantially a few kilohertz and substantially a few megahertz.
  • a phase shift circuit 12 is provided with an input receiving the signal D, J control inputs connected to the parallel bus receiving the control signal ⁇ X , and J outputs delivering the J signals C 1 , ..., C j , ... and C J.
  • the microwave coherent detection circuit 6 comprises two mixers 61 and 62 and a phase shifter 63.
  • the mixers 61 and 62 are of the type comprising two inputs, and one output delivering a signal equal, at all times, to the produces signals received on both inputs. These are devices known to those skilled in the art as ring modulators or balanced mixers.
  • the mixer 61 receives on an input the signal to and on the other input signals r, and outputs DA signal.
  • the mixer 62 receives on one input the signal a and on the other input the signal r phase shifted by an angle equal to ⁇ / 2, in the phase shifter 63.
  • the mixer 62 outputs the signal DB.
  • the low frequency coherent detection circuit 8 comprises four mixers 81, 82, 83 and 84, two phase shifters 85 and 85 ', a subtractor 86 and an adder 88, and two low-pass filters 87 and 89 .
  • the mixers 81 to 84 are of a type comparable to that of the mixers 61 and 62.
  • the mixer 81 receives on one input the signal DA and on the other input the signal D, and it outputs a signal SA.
  • the mixer 82 receives on one input the signal DB and on the other input the signal D phase shifted by an angle equal to ⁇ / 2 in the phase shifter 85, and it outputs the signal SB.
  • the mixer 83 receives on one input the signal DA and on the other input the signal D phase shifted by an angle equal to ⁇ / 2 in the phase shifter 85 ', and it outputs the signal SC.
  • the mixer 84 receives the signal DB on one input and the signal D on the other input, and outputs the signal SD.
  • the subtractor 86 receives on its two inputs the signals SA and SB; its output is connected to filter 87, which outputs the signal U X.
  • the adder 88 receives on its two inputs the signals SC and SD; its output is connected to filter 89 which outputs the signal V X.
  • the phase shift circuit 12 includes J controllable phase shifter 121.
  • the phase shifter 121 of rank j is provided with a signal input receiving the signal D, with a control input for the angle ⁇ X (j) of phase shift, receiving a control signal also called ⁇ x (j) for the sake of simplicity, and of a signal output delivering the signal C j , phase shifted by the angle ⁇ X (j) relative to the modulation signal D.
  • the J control inputs of the J phase shifters 121 constitute the parallel bus to which the signal ⁇ X composed of the J signals ⁇ X (j) is applied.
  • the switches 2 are here PIN diode switches, well known to those skilled in the art.
  • the summator 3 and the mixers 61 and 62 are circuits of the type known by a person skilled in the art for microwave use, while the mixers 81 to 84, the subtractor 86 and the adder 88, the low-pass filters 87 and 89 and the phase shifters 121 are circuits of the type known to those skilled in the art for use at low frequency.
  • the microwave signal received by the antenna of rank j is of the form:
  • the signal s ′ j is amplitude modulated by a square type modulation signal, as shown in FIG. 10.
  • the first component of this signal is here filtered by the mixer 61. If this were not the case, a low pass filter would eliminate this component. Thus, the contribution DA j of the signal s j of the signal DA at the output of the microwave coherent detection circuit 6 is worth
  • the contributions SA j , SB j , SC j and SD j (the latter two not shown for the sake of simplicity) of the signal s j to the signals SA, SB, SC and SD are equal to:
  • phase shift ⁇ X (j) of the modulation signal is added to the phase shift ⁇ j of the microwave signal. So everything happens as if the signal s j was phase shifted by an angle ⁇ X (j) in a microwave phase shifter.
  • the angle ⁇ X (j) corresponds to the an- g of the ⁇ j so that their sum remains constant whatever j
  • U x and V signals X equal to the sum of all U Xj and V Xj respectively, are well representative of the radiation emitted by the focusing point X.
  • the focusing device 70 shown in Figure 6 allows the simultaneous focusing on two points X and Y of the object 20, to continuously observe what is happening at these two particular points without having to form a complete image, for example to follow the evolution of their temperature in the case of certain biomedical applications.
  • the focusing device 70 is provided with two buses receiving the signals ⁇ X and ⁇ Y , representative phase laws ⁇ X (j) and ⁇ Y (j) corresponding to the points X and Y to be observed.
  • the focusing device 70 is also provided with two groups of two outputs continuously delivering signals representative of the points X and Y, here for example the previously defined signals U X , V X , U y and Y Y.
  • the focusing device 70 differs from the device 30 of FIG. 2 essentially in that it comprises two oscillators 711 and 711 'delivering two signals D 1 and D 2 respectively, of frequency F 1 and F 2 respectively.
  • the two signals D 1 and D 2 are of the same type as the signal D already encountered.
  • the output signal from the oscillator 711 is applied to a phase shift circuit 712 analogous to the circuit 12 in FIG. 2.
  • the circuit 712 is controlled by the signal ⁇ X.
  • the output signal from the oscillator 711 ' is applied to a phase shift circuit 712' similar to the circuit 12 in Figure 2, controlled by the signal ⁇ Y.
  • Each circuit 712 and 712 ′ delivers a set of J modulation signals analogous to the signals C 1 , ..., C j ..., and C J of FIG. 2.
  • the two modulation signals of rank j control two switches 72 mounted in parallel downstream of an antenna 71, of row j.
  • the switches 72, 2J in number, and the antennas 71, J in number, are similar to the switches 2 and the antennas 1 in FIG. 2.
  • the J output signals of the J groups of the two switches 72 in parallel are added in a microwave summator 73, which delivers a signal
  • a coherent microwave detection circuit 76 analogous to circuit 6 of FIG. 3, receives the signal s on its signal input and delivers two signals DA and DB on its two outputs.
  • a microwave oscillator 74 analogous to oscillator 4 of FIG. 2, delivers a signal r to the control input of circuit 76.
  • Two low frequency coherent detection circuits 78 and 78 ′ are provided, analogous to circuit 8 in FIG. 4. Each circuit 78 and 78 ′ receives the signals DA and DB on its two signal inputs, and on its control input the signal D 1 and signal D 2 respectively. Circuit 78 outputs the signals U x and V X , and circuit 78 'signals U Y and V.
  • the low frequency coherent detection circuit 78 demodulates only the components of the signals DA and DB modulated at the frequency F 1 in the switches 72, c ' ie those which correspond to the phase shift law ⁇ X , determined by the phase shift circuit 712, focusing the network on point X.
  • the circuit 78 ′ demodulates only the components of the signals DA and DB modulated at the frequency F 2 , that is to say those which correspond to the phase shift law ⁇ Y , focusing the grating on the point Y.
  • the focusing method of the invention can be extended to imaging systems in which a focused antenna array is used to illuminate a point of the object to be observed and an unfocused antenna array, or even a single omnidirectional antenna, to receive radiation from the illuminated point.
  • FIG. 7 represents a device implementing such a method.
  • Block 50 represents the focusing device of a network of K transmitting antennas 51 to focus on the point X 'of the object 20'.
  • the focusing device 50 comprises a microwave oscillator 54, delivering a microwave emission signal e, of frequency f.
  • Each antenna 51 is connected to the output of the oscillator 54 by means of a microwave switch 52, of the same type as the switches 2 in FIG. 2.
  • the switch 52 of rank k is provided with an input of command receiving a signal C k .
  • a phase shift circuit 512 analogous to the phase shift circuit 12 of FIG. 5, is provided with a signal input and with K outputs delivering the signals C 1 , ..., C k , ..., and C K each signal C k being phase shifted relative to the signal received on the input of circuit 512 by an angle ⁇ X (k) controlled by the signal ⁇ X applied to the control bus of block 51 2 .
  • An oscillator 511 similar to the oscillator 11 of FIG. 2, delivers a signal of frequency modulation F, at the input of block 512.
  • a reception antenna 40 On reception, a reception antenna 40, here unique, receives the signals coming from the object 20 '. It is followed by a coherent microwave detection circuit 56, analogous to circuit 6 in FIG. 3. Circuit 56 receives, on its control input, the output signal from oscillator 54. The two outputs of circuit 56 are connected to a coherent detection circuit 58, analogous to circuit 8 in FIG. 4. The control input of circuit 58 receives the modulation signal D'. Circuit 58 outputs the signals U x and V X.
  • the operation of the focusing device 50 is similar to that of the device 30.
  • the phase shifts ⁇ X (k) introduced on the modulation signals of the microwave signals emitted produce the same effect, on the signal received and subjected to coherent microwave microwave detection.
  • f in circuit 56, and at coherent low frequency detection at frequency F in circuit 58, that phase shifts ⁇ X (k) introduced on the microwave signals transmitted. If these phase shifts ⁇ X (k) are chosen to correspond to the phasing, at point X, of the signals coming from the K antennas 51, the transmission network has therefore been focused on point X.
  • the setting of each antenna was a microwave signal guided by a guide structure of the waveguide, cable type. coaxial or ribbon line, for example.
  • the summation is carried out by a microwave summing device, like the summing device 3 of FIG. 2, provided with J inlet access and an outlet access, each access being connectable to a guide structure of the type defined here. -above.
  • FIG. 8 shows for example a device in which the reception antennas are dipole antennas 1 ′, regularly arranged on a panel 100 made of insulating material.
  • the panel 100 is disposed in front of a single antenna 41, which plays the role of summing of the microwave signals picked up and radiated again by the antennas 1 ′, these signals no longer, as before, supported by a guide structure.
  • the switches can be simple diodes 2 1 , the switching signals C 1 , ..., C j , ... and Ci being for example applied by connections 21 which are not very disturbing for the electromagnetic field.
  • connections 21 are not very disturbing for the electromagnetic field.
  • Such connections are made, for example, carbon son so as to be sufficiently - ment resistive to have only a small influence on the electromagnetic field.
  • the antenna 41 playing the role of summing device, is directly connected to a coherent microwave detection circuit, identical to the circuit 6 of FIG. 2, in the case of an array of reception antennas. The rest of the device is unchanged.
  • the focusing device 90 of FIG. 9 represents a variant of the device of the invention, using only two mixers instead of six.
  • a mixer 961 identical to the mixer 61 of FIG. 3, is provided with a first input receiving the signal s at the output of the adder 3, with a second input and with an output.
  • a mixer 981 identical to the mixer 81 in FIG. 4, is provided with a first input connected to the output of the mixer 961, a second input and an output connected to the input of a low-pass filter 987, identical to the low-pass filter 87 in FIG. 4 .
  • the output of an oscillator 94 is connected to the second input of the mixer 961 ′ via a controllable phase shifter 963.
  • the output of an oscillator 911 identical to the oscillator 11 in FIG. 2 is connected to the second input of the mixer 981 via a controllable phase shifter 985.
  • the controllable phase shifters 963 and 985 are likely to phase shift by an angle equal to 0, or equal to ⁇ / 2, as a function of a signal applied to the control input with which each of them is provided.
  • a processing and control circuit 91 for example with a microprocessor, and provided with two outputs connected to the control inputs of the phase shifters 963 and 985, an input connected to the output of the low-pass filter 987, and two outputs delivering the signals U x and V X.
  • the operation of the focusing device 90 is as follows: the processing and control circuit 91 controls the phase shifters 963 and 985 sequentially, so that the previously defined signals SA, SB, SC and SD appear one after the other the other at the input of the filter 987.
  • the circuit 91 stores the various filtered signals and processes the corresponding data to add them up and deliver the signals U x and V previously defined.
  • the signals picked up are coherent signals, that is to say periodic signals of defined phase, to which a coherent microwave detection can be applied, as in circuits 6, 76, 6 t and 961-63, as the case may be.
  • the invention is not limited to such coherent radiation and can also be applied to thermography, for example.
  • an image representative of the temperatures of the various points of the object is constructed, from microwave signals of which the object is itself the source.
  • These signals being inconsistent, that is to say of random phase, they must be detected with particular detection devices of known type, for example quadratic detection devices with or without prior frequency changes.
  • the devices of FIGS. 2, 6, 8 and 9 must therefore be modified, in this case, so that the coherent microwave detection circuits 6, 76, 6 ′ and 961-963 are replaced by suitable devices.
  • the device 70 for simultaneous focusing on several points in FIG. 6 could then be modified by placing only one modulator downstream of each antenna, and by controlling this modulator with the sum of the two corresponding signals from the phase shift circuits 712 and 71 2 '.
  • the antennas are generally organized on a surface to form an array.
  • the antennas can be organized in a line, straight or curved, to form a linear network.
  • a single switch can be used controlled by a suitable signal, for example the signal resulting from the product of the step functions relating to each of the phase shifted modulation signals.

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EP87400803A 1986-04-11 1987-04-09 Verfahren und Vorrichtung zur Strahlfokussierung von Gruppenantennen auf einen Prüfpunkt Expired - Lifetime EP0241380B1 (de)

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Application Number Priority Date Filing Date Title
FR8605205 1986-04-11
FR8605205A FR2597268B1 (fr) 1986-04-11 1986-04-11 Procede et dispositif de focalisation, sur un point a examiner, des antennes d'un reseau

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EP0241380A1 true EP0241380A1 (de) 1987-10-14
EP0241380B1 EP0241380B1 (de) 1992-01-08

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EP (1) EP0241380B1 (de)
DE (1) DE3775806D1 (de)
FR (1) FR2597268B1 (de)

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FR2694662A1 (fr) * 1992-07-20 1994-02-11 Westinghouse Electric Corp Appareil de formation de faisceau à haute résolution pour des systèmes de détection de cibles.
EP2574378A1 (de) 2011-09-19 2013-04-03 Salomon S.A.S. Bindung für einen Schuh auf einem Gleitbrett

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FR2941333B1 (fr) 2009-01-20 2012-12-14 Satimo Sa Systeme d'emission de faisceaux electromagnetiques a reseau d'antennes.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0415574A3 (en) * 1989-08-30 1991-07-17 Gec-Marconi Limited Antenna array
US5235342A (en) * 1989-08-30 1993-08-10 Gec-Marconi, Ltd. Antenna array with system for locating and adjusting phase centers of elements of the antenna array
FR2694662A1 (fr) * 1992-07-20 1994-02-11 Westinghouse Electric Corp Appareil de formation de faisceau à haute résolution pour des systèmes de détection de cibles.
EP2574378A1 (de) 2011-09-19 2013-04-03 Salomon S.A.S. Bindung für einen Schuh auf einem Gleitbrett

Also Published As

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EP0241380B1 (de) 1992-01-08
US4870423A (en) 1989-09-26
DE3775806D1 (de) 1992-02-20
FR2597268B1 (fr) 1988-06-24
FR2597268A1 (fr) 1987-10-16

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