SU803705A1 - Acoustooptical correlator with time integration - Google Patents

Abstract

ACOUSTIC CORREL, TOR TEMPORARY INTEGRATION, containing sequentially placed on a common optical axis coherent light source *, collimator, signal ultrasonic light modulator, the electrical input of which is a correlator input, the first cylindrical lens, focal diaphragm, second cylindrical lens, third and a fourth cylindrical lens and a photodetector in the form of two linear matrices of charge-coupled devices, characterized in that, in order to increase the frequency band of the complex signals under study Alov with angular modulation, an electrically controlled transparency placed on the light source and the ultrasonic reference light modulator, harmonic signal generator, phase modulation voltage generator and matching unit the output of which is connected to the electrical input of the electrically controlled transparency, the input of the matching unit is connected to the output of the phase modulation voltage generator, the output of the garm generator connected to the signal-ethnic elements ^;. tricheskimvhodom reference ultrasonic light modulator \ o (/ > & ^ 00oso

Description

The invention relates to the field of correlation signal processing by optical methods and can be used in radar to compress pulsed radar signals with a large base. The acousto-optic corrector (AOK) is known, which contains a coherent light source, a collimator, an ultrasonic light modulator, a transparency, a lens that performs a Fourier transform, a focal diaphragm cutting the first order of the diffraction pattern, and an instant photo detector of most of the AOK can to be effectively used to compress complex radar signals, however, the duration of the latter is determined by the size of the light aperture of the light modulator along the signal propagation direction tional acoustic wave, in this case, is substantially limited. When processing broadband radiolocular signals, these restrictions are mainly related to the need to use the modulator of the modulator of various single crystals as high quality of the single crystal, which in the high-frequency region has a relatively small attenuation of the acoustic wave. The level of single-crystal injection technology makes it possible to obtain samples of such sizes that correspond to the duration of the processed radio signals, not exceeding 10-15 ISS, which in some cases is insufficient. A quadrature correlation processing device is known, built on the basis of the simplest correlator and allowing one to get a signal at its output proportional to the module of the complex envelope of the CCF, i.e. its amplitude envelope is 23. A time-integrated AOK is known, containing, consistently placed on a common optical axis, a source of coherent light, a collimator, a signal ultrasonic light modulator whose electrical input is a corrector input, a first cylindrical lens, a focal diaphragm, a second cylinder 1 | cesco lens, third and fourth cyl 1; (impurity lenses and 5J photodetector in the form of two linear matrices of charge-coupled devices. The purpose of the invention is to expand the frequency band of complex radio signals with angular modulation, processed in time-correlated correlators. This is achieved by introducing an electrically controlled transparency (EAB) and an ultrasonic reference ultrasound light into the known AFK with time integration. a light modulator, a harmonic signal generator, a phase modulation voltage generator, and a matching unit, the output of which is connected to an electrically controlled electric input ransparanta, matching block input connected to the output of the generator, the voltage of the phase modulation, and harmonic signal generator output is connected to an electrical input of the reference ultrasonic light modulator. In this case, the EUT plays the role of an input diaphragm with two regions of transparency obtained by displacing a rectangular sipe-like window oriented in the direction of propagation of the signal acoustic wave. The harmonic signal generator has a frequency of the radio signal under study. Introduction to the circuit of the known correlator of the reference ultrasonic light modulator, as well as extending it as the input aperture of the controlled transparency allows directing the input radio signal to the piezotransducer of the signal ultrasonic light modulator, which makes it possible to expand the frequency band of the radio signals being processed and increase thereby, the resolution of the correlator in range when solving radar problems. In FIG. A functional diagram of the proposed AOK is presented with temporal integration; in Fig.2, the relative position of the EUT, the reference and signal ultrasonic light modulator in a plane perpendicular to the optical axis of the device in FIG.

charge-coupled devices (CCDs) and two wide optical lenses optically coupled to the EUT transparency areas by a plane perpendicular to the direction of propagation of the acoustic wave in the signal ultrasonic light modulator, in a section.

The described AOK contains a coherent light source 1 installed on one optical axis, for example an optical quantum continuous generator, a collimator 2, an optically opaque EUT 3 placed in a plane perpendicular to the optical axis of the device, and having two regions of transparency, the shape and location of which are indicated in figure 2. In particular, controlled liquid crystal or AO transparencies, as well as transparencies based on electro-optical ceramics, can be used as EUT. The EUT 3 is connected to the voltage generator 5 of the phase modulation of the complex radio signal being processed through the matching unit 4, the locations of its transparency areas on the y axis (see Fig. 2). In addition, the AOK includes a reference ultrasonic light modulator 6, a piezo generator 7 of which is connected to a harmonic signal generator 8 with a frequency equal to the carrier of the radio signal being processed, and a signal-ultrasonic light modulator 9, which piezotransducer 10 is connected directly to the source of the radio signal being processed 11. The mutual arrangement of the reference and signal ultrasonic light modulators in a plane perpendicular to the optical axis is shown in FIG. 2. Downstream of the modulator 9 on the optical axis of the device, a cylindrical lens 12 is installed in series with a focal length F, performing a direct Fourier transform, a focal diaphragm 13, producing one first-order diffractive pattern, a cylindrical lens 14 with a focal distance Fj, performing a reverse transformation Fourier, as well as two cylindrical-lenses 15 and 16 with a focal length Fj, ° are practically associated with the projection areas.

transparency and the two lines of photodetectors 17 and 18 on the axial CCD, the relative position in the zo-j plane is explained in Fig. 3.

AOK works as follows

The input radio signal 5, (tj, D UI cos Q: f + / (t 1 + wk) comes from the signal source 11 to the piezoelectric transducer 10 and excites in the modulator 9 a signal acoustic wave propagating along the X axis. To the piezoelectric transducer 7 of the modulator 6 from A sinusoidal voltage generator is given a signal that has the form Sj (-t | "(si (, tt) 4gp). Excited in the modulator, the reference harmonic acoustic wave propagates at an angle to the x axis (see Fig. 2). For example, consider what happens in this case in one of the processing channels, corresponding to for example, the lower transparency region of the transparency (see Fig. 2). Let no signals from the matching matching unit 4 enter the transparency. The collimated light beam, corresponding to the selected transparency region, diffracts in succession on the reference and signal acoustic waves,. then undergoes a Fourier transform, implemented by a cylindrical lens 12, and spatial filtering consisting of one of the first-. the output order of the diffraction pattern with the help of the diaphragm 13. After this, the cylindrical tire 14 is made to restore one of the diaphragms of the first order, which illuminates the corresponding line of the CCD 18, and choosing F2 F, (see figure 1) this is scaling. The role of the cylindrical lens 16 reduces to focusing the diaphragm beam along axis 3. At the aperture of the PES 18 line (see Fig. 3), the region Lx can be viewed; the light aperture of the modulator 9 along the xj axis y projected on the i.th element of the CCD array, assuming that phase function 4 (tl of the signal acoustic wave over a time interval equal to its propagation delay on the dXi segment, can be considered constant and equal vf () where tj is the delay time of propagation of a signal acoustic wave from a piezo-transform l 10 to the sredina of the jth evil light aperture of the modulator 9 In this case, it is not possible to show that the intensity of the diffraction of the light of the 1. (The ES will determine the phase difference of signaling signals to acoustic waves and record the following expression:; l.) - nt-h) where Zd and L,,. J are constant. .defining with constructive: -5j pairs (-etra14 and AOK schemes, (the difference between the initial phases of the reference and the input-on signal. JlOB l) Similar correlation is also true in the absence of an égomerial rotation, the signal ultrasonic and reference ultrasonic modulus of horny light (see fig. -2), G1p: in this case, the difference between the phases of the DF phases would have a treTKHii fi-gich sense. asfazirov ke signaling to about Ornon a.kuetiche; .ukk vol1 5rasp: rostran yushnhs1g one .: n ;; In this case, the phase opening of the front of the acoustic ash film is parallel to s. but in the base evil it does not form with this axis: o yrojij, therefore, otosha.:; y. ; :: - the signal signal acoustic reference wavelength differs when the coordinates of B are different; the range of coordinates is B within the transparency region of EI1, {) y; xx relay linear changes: of the initial phase of the reference acoustic Kojveoka - along the coordinate -j, about the conditional rotation of the modulator 6 of the fire detector1; But the ZI axis will have an integral effect determined by the value of the phase; . corresponding to the average transparency area along the line at the LINE, of which “has a crust” (, indicated in figure 2. i.e., de - is a parameter, is determined by the angle of play of the modulator b, now let the gas; from the matching unit 4, the coordinate v of the lower transparency region of the EUT varies in time with respect to G1: to some law, Vo (l Considering the above, it is possible to have Ver / c that in the phase of the reference signal 5 ,, (- fc 1: D for all the elements, whether .fieiiKH PES, the variable is reduced to 4gR. (ti CHz (ij. If you move the area the opacity occurs according to the law of the phase modulus — reversal of the rear signal, ie, Ur (i) (i, then the phase of the reference acoustic wave f, (.tj, being unchanged along the length of the light aperture along the axis: transparency in this direction is defined as H -HH-b). S.; hedge15E1O5 intensity of the light flux5 incident on the i-th epept of the CCD line, type 3,, cos m; - / (ti -.- df. It follows OTivaTHTb that it is precisely the durability of the parameters of the reference automaton oscillation along the x axis, with a phono acoustic signal propagating in this direction. waves have the ability to implement multi-channel processing. 5 Scheme considered AOK source cHr-Hajia control of the EUT field of transparency is served by generator 5, modules: emergency - the radio signal phase of the function h (. Elok matching 4 under the voltage 5 from the output of the -arator 5 generates signals, y - rush-hr; pusicity areas on the axis i (.2). Tl as a result of the accumulation of intensity:; light bridges along the length of the signal to be processed. The radio signal B 1 -ii elements of the 113C line become charged Q / described |; - iie: ,, ((iy., Riie ,,, and and are constant coefficient of feeds., (L obtain an imaginary complex bend around the ACF The second radio signal in the device being described is also: 2 is the quadrature processing channel formed by the second transparency area of the EUT. However, 5 if in the prototype for the floor, 7

If the quadrature reference oscillations required a corresponding time modulation of the collimated light beams, then in the described device. The required phase shift of the reference signals, equal to (K 0,1,2 ...), is achieved by choosing the appropriate relative offset of the transparency areas of the controlled transparency to the axis l linear variation of the phase of the reference oscillation.

So, the described correlator with temporal integration allows, like the prototype, to perform frame matching correlation processing of the input radar signal with angular modulation. Like the prototype, the described correlator differs favorably from traditional radio engineering devices of the similar purpose by the simplicity of implementing multi-channel processing, which is associated with the use of promising photo detectors. In the described correlator, the longest duration of the processed radio signals is limited only by the characteristics of the CCD array, which is typical of the prototype. However, in terms of frequency properties, the proposed device significantly exceeds the prototype, since the signal modulator of the excitation light directly

but the signal being processed, i.e. the efficiency of the modulator in terms of operating frequencies and bands is used fully, not in part, as is the case in the prototype, when the input signal is fed to the light modulator as an amplitude modulation of the additional carrier frequency. The extension of the frequency band of the processed radio signals leads, as is well known, to an improvement in such an important characteristic of the Torah correspondent as its resolution in duration. In terms of frequency properties, the described correlator is equivalent to the known one with spatial integration. However, in the SCFJBaeMOM correlator, it is impossible to process radio signals from an amplitude module 1, which can be implemented in the prototype. However, it is known that the specifics of the operation of radio transmitting devices leads to the fact that the main distribution, in particular in radiolocation, was found by elephant radio signals with angular modulation, which have a right-angle bend

Thus, the correlator combines the main advantages of the known devices of correlation signal processing with temporal and spatial integration, which makes it a promising solution to radar tasks.

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Claims (1)

ACOUSTOOPTIC CORRELATOR WITH TEMPORARY INTEGRATION, containing a coherent light source, a collimator, a signal ultrasonic light modulator, whose electrical input is the input of the correlator, the first cylindrical lens, focal diaphragm, second cylindrical lens, third and fourth cylindrical lenses, sequentially placed on the common optical axis and a photodetector in the form of 'two linear arrays of charge-coupled devices, characterized in that, in order to expand the frequency band of the studied complex signals angular modulation, introduced into the correlator placed sequentially along the optical beams between the collimator and the signal ultrasonic modulator, there is an electrically controlled transparency and a reference ultrasonic light modulator, a harmonic signal generator, a phase modulation voltage generator _Λ and a matching unit, the output of which 3 is connected to an electric the input of an electrically controlled transpa-IV welt, the input of the matching unit of the plugs to the output of the voltage generator | phase modulation, the output of the harmonic signal generator is connected to the electrical input of the reference ultrasonic light modulator. I