SU792553A1 - Band-pass filter based on surface acoustic waves - Google Patents

Description

The invention relates to the field of acoustoelectronics and can be used in devices for processing signals on surface acoustic waves (SAS).

A surpass filter is known in which excitation and reception of a wave are carried out by interdirectional transducers located in a common acoustic flow on the surface of the acoustic duct l.

The disadvantage of such a filter is the relatively high level of spurious signals and, above all, body waves and direct electromagnetic pickup from input to output.

Closest to the invention in technical essence and the achieved result is a band-pass filter on surface acoustic waves, which are placed on. a piezoelectric evukoprovod input and output interdigital transducers in parallel acoustic channels and a multi-band coupler located between them 27. In such a filter, parasitic body waves excited by an input counter-inverter do not fall on a receiving transducer located in another acoustic channel.

However, in this design, the electromagnetic pickup associated with the pass-through capacity of the filter remains at a high level and leads to undesirable distortions of its characteristics.

The aim of the invention is to reduce distortion.

The goal is achieved by a temr that in a band-pass filter on surface acoustic waves containing placed on a piezoelectric

5 acoustic conduit input and output interdigital transducers in parallel acoustic channels, a multi-strip coupler located between them is made of several sections that are in a common acoustic flow with a shift in the direction of propagation of surface acoustic waves, and the number of sections and the distance between 25 back proportional to the filter passing capacity. Embodiments of the image involve placing one between the sections of the multi-strip coupler. grounded electrodes, as well as the equality of the distances between

thirty

the edges of the grounded electrodes and the adjacent electrodes are the gaps between the electrodes of the multi-strip coupler.

. The drawing shows a block diagram of the filter.

The surface acoustic wave band filter contains input 1 and output 2 interdigital transducers located on the surface of the sound input 3 and acoustically connected using a multi-strip coupler 4, divided into sections, between which additional grounded shielding electrodes 5 are placed.

The input electrical signal applied to converter 1 excites a surface alstatic wave, which is reemitted to the adjacent channel using a partitioned multi-band coupler 4 and is received by output converter 2. The sectioning of a multi-band coupler and the inclusion of additional screening electrodes reduce the electromagnetic pickup signal by reducing the transit signal filter capacity.

The implementation of the band-pass filter on surface acoustic waves in accordance with the invention makes it possible to reduce the level of the spurious signal of the electromagnetic pickup by 10-20 dB.

Claims (3)

1. The band-pass filter on surface acoustic waves containing four L1 Placed on the piezoelectric duct, the input and output interdigital transducers in parallel channels and a multi-band coupler located between them, characterized in that, in order to reduce distortion by reducing the pass-through capacity of the filter, the multi-band coupler performs several sections, in the common acoustic flow with a shift in the direction of propagation of surface acoustic waves, the number of sections and the distance between them being inversely proportional to the passage capacitance filter. 2. A bandpass filter according to claim 1, characterized in that grounded electrodes are placed between the sections of the multi-strip coupler. 3. Bandpass filter on PP. 1 and 2, so that, in order to increase the efficiency of surface waves re-emission, in it the distances between the edges of the grounded electrodes and the adjacent electrodes are equal to the gaps between the electrodes of the multiband response. Sources of information taken into account in the examination 1. US Patent No. 3582840, cl. 332-72, 11.06.71. 2. Holland M. and Clayborn L. Devices on surface acoustic waves. M., Mir, TIIER, t. 62 1974, No. 5, pp. 74-75. f four ±. 13-i one.