RU2000655C1 - Surface acoustic wave filter for television set intermediate-frequency circuits - Google Patents

Abstract

SUMMARY OF THE INVENTION: a filter contains a sound duct placed on its working surface an apodized interdigital transducer (IDT) and IDT with weight processing with a constant length of overlapping electrodes of two different equipotential groups with a certain weighing function. 3 ill.

Description

The invention relates to acoustoelectronics and can be used as an intermediate frequency filter in television receivers.

A surface acoustic wave (SAW) filter for television receivers is known, comprising a sound duct, two apodiated interdigital transducers (IDTs) and a multiband coupler (MPO) located between the IDTs located on its working surface.

The disadvantage of the filter is the large area of the sound duct, which is necessary for realizations. 1 and filter, which leads to too high cost of filters in their industrial production.

A surfactant filter for television receivers is also known, comprising a sound duct. the epodized IDT and IDT placed on its working surface with weight processing with a constant length of overlapping electrodes of different polarity, carried out by the principle of capacitive weighing, in which the voltage is divided into peripheral sections

IDT is implemented using groups of electrodes located in an acoustic channel. The main disadvantages of this filter are the significant width of the sound duct for its implementation, which is associated with the design of a capacitive voltage divider, the presence of three buses, as well as the small technological reserves of the design due to the high requirements for topological dimensions for the efficient operation of the capacitive divider.

The purpose of the invention is to reduce the size of the sound duct and increase the technological reserves of the structure.

This goal is achieved by the fact that the proposed filter on the surfactant for the path of the intermediate frequency of television receivers, containing a sound duct, apodized IDT and IDT placed on its working surface with weight processing with a constant length of the overlapping electrodes of two different equipotential groups, in which IDT with weight processing at constant length of overlapping electrodes of different groups of the middle of the zones of overlapping electrodes

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personal groups have the following coordinates in the direction normal to the edges of the electrodes, counting from the middle of the zone of the extreme left overlap of the electrodes of various groups:

Oh, 6d, 9d. 11d, 13d, 15d. 17d, 19d. 21d, 25d are all overlaps, the left electrode, which is the electrode of the first group, and the right electrode is the second group:

4d. 8d, 10d. 12d, 14d. 16d, 18d, 20d, 23d, 29d are all overlaps, the left electrode of which is the electrode of the second group, the right electrode of the first group;

where d is the smallest distance between the middle of the zones of overlapping electrodes of different groups.

In FIG. 1 shows the proposed device; in FIG. 2 - one of the possible configurations of the proposed Converter; in FIG. 3 is a graph.

The filter on the surfactant contains a sound duct 1, on the working surface of which there is an apodized transducer 2 and IDT, weighted at a constant length of the floors 3. The filter on the surfactant barely works; - as follows. The Converter 3 excites in the sound duct 1 SAW. which propagates to the surfactant receiving transducer 2.

The surfactant converter shown in FIG. 2 contains contact bars 1,2, to which electrodes of the corresponding groups 3, 4 are connected. The transducer shown has the impulse response shown in FIG. 3, the corresponding weights are as follows:

0 ... 0-100010-101-11-11-11-11-11-11-11010-100010 ... 0

The smallest distance between the middle of the overlapping zones of the electrodes of various groups d - in the case of an equidistant IDT represents half the IDT period and is determined by the surfactant speed under the IDT and the average frequency of the converter.

To test the operability of the proposed filter device, its prototype models were created. On an YXI / 127.860 lithium lithium niobate substrate, an apodized interdigital transducer having 140 was formed

electrodes with a step of 28 microns, and IDT, containing 35 split electrodes (including empty ones) with a step of 56 microns. The aperture was 1.7 mm.

Claims (1)

Thus, the present design of the converter with weighing at a constant length of the overlapping electrodes of different polarity for television filters on surfactants allows to reduce the surface area of the sound duct and increase the technological reserves of the structure (by simplifying the topology of the converter and improving the frequency response of the filter). SUMMARY OF THE INVENTION Surface acoustic filter waves for the intermediate frequency path of television receivers, containing a sound duct, an apodized interdigital transducer (IDT) connected to the input or output of the filter, and IDT with weight processing at a constant length of the overlapping of electrodes of different equipotential groups, characterized in that that IDT with weight processing at the constant length of the overlapping electrodes of different groups has two groups of equipotential electrodes, with the middle of the zones of overlapping electrodes in which the electrode of the first group is located on the left, and of the second group, to the right of the overlap zone, are at distances of 0.6d, 9d, 11d, 13d, 15d, 17d, 19d, 21d, 25d from the middle of the zone of the extreme left overlap of the electrodes of various groups, and the middle of the overlap zones, in which the electrode of the first group is located to the right, and the second one to the left of the overlap zone, located at distances of 4d, 8d, 10d, 11d, 14d, 16d, 18d, 20d, 23d, 29d from the middle of the zone of the extreme left overlap electrodes of various groups, where d is the smallest distance between the midpoints of the overlapping zones of electrodes of various groups. cpt / & S -50fЈ Z.OL g I 39.5 br