SU875591A1

SU875591A1 - Retunable filter on acoustic surface waves

Info

Publication number: SU875591A1
Application number: SU802882584A
Authority: SU
Inventors: Владимир Сергеевич Глушков
Original assignee: Омский политехнический институт
Priority date: 1980-02-07
Filing date: 1980-02-07
Publication date: 1981-10-23

Description

1one

Изобретение относитс к радиоэлектронике и может использоватьс в акустоэлектронных устройствах обработки сигналов.The invention relates to electronics and can be used in acoustoelectronic signal processing devices.

Известны устройства на поверхностных акустических волнах (ПАВ), содержащие встречно-штыревые прербразователи , расположенные на пьезоэлектрической подложке, в которых между входным и выходным преобразовател ми расположен фотопровод щий слой сложной конфигурации. При освещении участка поверхности подложки, покрытого слоем фотопровод щего материала , измен етс скорость распространени ПАВ на этом участке И.Surface acoustic wave (SAW) devices are known that contain interdigital converters located on a piezoelectric substrate and have a photoconductive layer of complex configuration between the input and output converters. When the surface area of the substrate coated with a layer of photoconductive material is illuminated, the rate of propagation of the surfactant in this area I.

Недостатком этих устройств вл етс невозможность перестройки амплитудно-частотных характеристик.The disadvantage of these devices is the impossibility of tuning the amplitude-frequency characteristics.

Известен также перестраиваемый фильтр на ПАВ, содержащий пьзрэлектрическую подложку с расположенными на ее поверхности в одном акустическом канале входным и выходным встречно-штыревыми преобразовател ми, отражательными структурами с переменным периодом расположени составл ющих их неоднородностей и фотопровод щим слоем, размещенный над ним источник освещени и систему управлени источником освещени . Прот женность фотопровод щего сло вдоль направлени распространени ПАВ в этом фильтре посто нна по всему фронту распространени ПАВ, а источник освещени выполнен в виде размещенного вне пьезоэлектрической подложки дискретного излучател света 2.A tunable filter on a surfactant is also known, which contains a piezoelectric substrate with input and output anti-pin converters located on its surface in one acoustic channel, reflective structures with a variable period of arrangement of the inhomogeneities constituting them and a photoconductive layer, a light source placed above it and a system light source control. The length of the photoconductive layer along the propagation direction of the surfactant in this filter is constant over the entire propagation front of the surfactant, and the illumination source is designed as a discrete light emitter 2 placed outside the piezoelectric substrate.

Недостатками известного фильтра The disadvantages of the famous filter

10 вл ютс значительные фазовые искажени сигнала на выходе и большие габариты фильтра, что св зано с различием в сдвиге фаз различных частотных компонент спектра сигнала и на15 личием объемного источника.10 are significant phase distortions of the output signal and large filter dimensions, which is due to the difference in the phase shift of the different frequency components of the signal spectrum and the lack of a volume source.

Цель изобретени - уменьшение фазовых искажений и уменьшение габаритов перестраиваемого фильтра на ПАВ.The purpose of the invention is to reduce phase distortion and reduce the size of the tunable filter on the surfactant.

20 Эта цель достигаетс тем, что перестраиваемый фильтра на ПАВ содержит дополнительный встречно-штыревой преобразователь, электрически соединенный параллельно с основным, и дополнительные отражательные структуры с переменным периодом расположени составл кнцих их неоднородностей, при этом источник освещени выполнен в виде матрицы с ветои злу чающих диодных20 This goal is achieved by the fact that the tunable filter on a surfactant contains an additional interdigital transducer, electrically connected in parallel with the main one, and additional reflective structures with a variable period of arrangement of their heterogeneities, while the illumination source is made in the form of a matrix with blunt-diode

Claims

30 structures whose columns are oriented along the SAW propagation direction, the length of the photoconductive layer along the SAW propagation direction is not constant and is chosen from the condition of compensation of the corresponding frequency components of the signal, and the ratio of the distance difference between the corresponding counter-pin converter and the near-reflection one structure to the difference in distance between the main and additional reflective structures is equal to the ratio of the rate of propagation of the surfactant. pin converters to the reflective structures and between the reflective structures in the free from the photoconductive layer of the piezoelectric substrate. Fig. 1 shows the construction of the proposed filter; in fig. 2 is an external view of a semiconductor plate with a matrix of light-emitting diode structures (view from the side of the piezoelectric substrate). The filter contains a piezoelectric substrate 1, input main 2 and additional 3 interdigital transducers located on it, output interdigital transducer 4, main reflective structures 5 and 6 and additional reflective structures 7 and 8. Reflective structures 5–8 consist of of heterogeneity 9, made in the form of grooves or strips and placed with a variable period. The substrate 1 also contains a photoconductive layer 10, the length of which along the propagation direction of the PES is not constant. It has the shape of a rectangular trapezoid. A matrix 11 of light-emitting diode structures placed on a semiconductor plate 12 is placed above the photoconductive layer with a gap with a piezoelectric substrate 1. The columns 13 of the matrix 11 are oriented along the propagation direction of the surfactant. Conclusions 14 from the semiconductor wafer 12 are connected to the outputs 15 about the electronic control system 16. The gap between the plate 12 and the substrate 1 is provided with a strip 17. The converters 2 and 3 and the reflective structures 5-8 are arranged so that condition lV) /( lane../v, where 6 is the distance between the main reflective structures 6th is the distance between the additional reflective structures; t. Is the distance between the main input transducer and the main reflective structure nearest to it; Kf is the distance between the additional t is the velocity of the surfactant propagation in the free surface of the piezoelectric substrate between the reflective structures, V is the velocity of the surfactant propagation in the free surface of the piezoelectric substrate between the input transducers and the reflective structures closest to them. layer 10 X, on the path of the SAW propagation from any frequency component of the ± signal spectrum, was selected from the condition of compensation the corresponding frequency components, which can be determined by the ratio /, AV V liV - {1 - V-) X - l. where 4V is the change in the rate of propagation of the surfactant in the plot of the piezoelectric substrate with a photoconductive coating. The electrical signal received by transducers 2 and 3 is converted into surfactants, which, propagating along substrate 1, are reflected from the heterogeneities 9 of structures 5 and 7. The surfactants reflected by structure 5 pass under the photoconductive layer 10 to the reflective structure 6. Surfactants , reflected by structure 7, passes to reflecting structure 8. Structures b and 8 re-reflect surfactant to output transducer 4. Surfactants generated by the frequency component of the input signal are effectively reflected in that region of structures 5-8, where the period of inhomogeneity 9 There is a surfactant wavelength for a given frequency f, which leads to a spatial separation of the surfactant. In the absence of a control signal at the outputs 15 of the control device 16, the light-emitting diode structures of the matrix 11 do not emit light. In this case, the photoconductive layer 10 is an insulator and the speed of propagation of the surfactant under it does not differ from the speed of propagation of the surfactant on the free areas of the substrate 1. Due to the indicated location of the transducers 2 and 3 and the reflective structures 5-8 surfactant from any frequency component f of the spectrum The input signal is fed to the output transducer 4 at the same time and in phase. When there are control signals on the part of the outputs 15, the corresponding columns 13 of the matrix 11 emit light, which illuminates the areas of the photoconductive layer 10 under them. These areas become conductive, which causes the tangential components of the electrical field of the SAW of those frequency, component f. of the input signal, which propagate along the corresponding regions of the substrate L. At the same time, the surfactant velocity is reduced by the value of fcv. With an extension of the photoconductive layer 10 selected in accordance with. the above condition, the surfactants propagating from the main input converter, reach the output converter simultaneously with the surfactants propagating from the additional input converter. As a result, surfactants from these frequency components f. The spectrum of the input signal on the output converter 4 compensates each other and is absent on the filter output. By altering the control signal, it is possible to effectively rearrange the output characteristic of the filter. The proposed filter provides simple control of the amplitude-frequency characteristics without introducing additional phase distortions. It is small in size and can be made using the methods of planar technology. Invention A tunable filter based on surface acoustic waves containing a piezoelectric substrate with input and output anti-pin converters located on its surface, and variable structures with a variable period of arrangement of components their inhomogeneities and the photoconductive layer, the source of light placed above it and the control system of the source of light, characterized in that, in order to reduce phase distortions and reduce overall dimensions, it contains an additional input interdigital transducer, electrically connected in parallel with the main transducer, and additional reflective structures with a variable period of arrangement of their irregularities, while the light source is made in the form of a matrix of light-emitting diode structures whose columns are oriented along the direction of propagation of surface acoustic waves, the length of the photoconductive layer along the direction the propagation of surface acoustic waves is not constant and is selected from the condition of compensation of the corresponding frequency components of the signal, and the difference between the corresponding input and interdigital transducer and the nearest reflecting structure to the difference between the main and additional reflective structures equal to the velocity of propagation surface acoustic waves from the entrance of the interdigital transducers to reflective structures and between with reflective structures on the photoconductive areas of the piezoelectric substrate. Sources of information taken into account during the examination 1. US patent I 3845420, cl. H 03 H 9/26, 1974.

2. The patent of France 2220930, cl. H 03 H 9/32, 1974.