SU1709497A1 - Filter based on surface acoustic waves - Google Patents

Abstract

The invention relates to the field of radio electronics. The aim of the invention is to reduce the level of the parasitic signal of the triple passage of the filter on surface acoustic waves. The filter on surface acoustic waves contains a piezoelectric acoustic conductor 1, on the working face of which an input 2 counter-pin converter is located, at the same distance from which the main output counter is located - a pin converter 3 and two additional 6 and 11, included antiphase main counter-pin converter, as well as the main and two add equivalent loads. In this filter, when selecting, according to a certain expression, the overlap of the electrodes of the first and second additional interdigital transducers, the triple-pass signal can be fully compensated. 1 il.

Description

The invention relates to electronics and can be used in frequency selection devices for radio signals of television and communication systems.

The aim of the invention is to reduce the level of the triple-pass parasitic signal.

The filter on the surface acoustic waves (surfactants) is shown in the drawing.

The surfactant filter contains a piezoelectric sound conduit 1, an input 2 counter-wide transducer (IDT) is placed on the working section, at the same distance from which is located the main output IDT 3, made with varying overlap of electrodes connected by the first 4 and second 5 summing tires which are selected close to the shape of the envelope

electrodes overlap, And the first additional output IDT 6. whose electrodes are also made with variable overlap, are combined second 5 and third 7 summing tires antiphase electrodes of the main output IDT 3 and are located outside the overlap area of the electrodes of the main output IDT in the area adjacent to the co. the second summing bus 5, the terminals for connecting the load connected to the first 4 and second 5 summing bus 1u1i. and terminals for connecting the first load equivalent, connected to the second 5 and third 7 tires, respectively.

Terminals for connecting the second equivalent of the load 10 and the second additional output IDT 11, whose electrodes are made with

change by overlapping and are combined by the first 4 and fourth 12 summing tires antiphase to the electrodes of the main output IDT in the area adjacent to the first summing bus, and the overlap values of the electrodes of the first and second additional output IDTs. are selected in accordance with the expression

win

Sch | 21 t

Yg1 + YHl Yg2-bYH2 YO + Y

but

where Wgoi, Wgii, Wg2i - overlap of the electrodes of the main, first and second additional IDT, respectively, m;

YO, Ygi, Yg2 are the total conductivities of the radiation of the main, first and second additional IDT, respectively, sim;

Yho. YHI, YH2 are the total conductivities of the external load of the main, first and second equivalents of loads, respectively,

and terminals for connecting the second equivalent of "Agrueki are connected to the first and fourth summing tires.

The filter on the surfactant works as follows.

When an electrical signal is supplied, the input IDT 2 excites surfactant propagating along the surface of the piezoelectric sound guide 1 in the direction of the main 3, first 6 and second 11 additional output IDTs.

After reflection from each of the IDTs, the surfactants again fall on the input IDTs 2 and are summed on it with the corresponding amplitudes and phases. At the same time, the amplitude of the surfactant reflected due to regeneration from each pair of output IDT electrodes is proportional to the relative overlap of these electrodes and the effective load resistance of this pair, and the phase is determined by the polarity of connecting the electrodes to the potential bus and the relative position of the electrodes.

Since the same electrodes of each of the output transducer 3, 6. 11 are placed at the same distance from the input transducer 2, and the same electrodes of the first 6 and second 11 additional transducers are connected to the respective summing buses 4,5,7, 12 relative to each other in phase. relative to the same electrolipers of the main output IDT 3 - out of phase, then the surfactant reflected from each of the electrodes of the additional output IDT 6.11 is added to the input IDT 2 between them in phase but out of phase with the surfactant reflected from the corresponding electrode and output VSDP 3, fully or partially compensated last.

For the purpose of full mutual compensation

of reflections due to regeneration, it is necessary to ensure that the SAW amplitude reflected from each electrode of the main output ICP 3 is equal to the sum of SAW amplitudes reflected from the same electrodes of the additional output IDT 6, 11, the condition of full compensation of the regenerated surfactants and the triple passage caused by IM and MM signals depending on the specified shut off the Wgi electrodes of the main IDT 3 and the specified full. the conductivities of external loads YnoiYHl, YH2 is defined by the following expression:

-Wii

Wg2l

Yg2 + Yй2 Yo4-Y

HO

From this expression it can be seen that the ratio between the overlap of the Wgi electrodes of the additional output IDT 6, 11 and the overlapping Woi of the electrodes of the main output IDT 3 may vary depending on the ratio of the total conductivities of the external loads YHI, Yna and YHQ of these IDTs, t. e. load switching circuits and; its equivalents. By varying this ratio, it is possible to achieve compensation for the triple-pass signal with additional apertures with small apertures. IDT.

Claims (1)

Formula of the invention The filter on the surface acoustic waves (SAS), containing piezoelectric-. The skip duct, on the working face of which an input interdigital transducer (IDT) is located, at the same distance from which the main output transducer is located, filled with varying overlap of electrodes connected by the first and second summing tires, the shape of which is chosen close to the shape of the beams the electrodes overlap, and the first additional output IDT, the electrodes of which are also made with varying overlap, are combined by the second and the third by summing 1 phase antiphase electrodes of the main one IDT and located outside the zone of overlap of the electrodes of the main output IDT in the area adjacent to the second summing bus, terminals for connecting the load connected to the first and second summing tires, and the first load equivalent, connected to the second and third summing tires, characterized in , with the aim of reducing the level of the parasitic triple-pass signal, a second load equivalent and a second additional output IDT are introduced into it, the electrodes of which are made with varying overlap and combined the first and fourth summing Tires in antiphase electrodes of the main output IDT and are located outside the overlap zone of the electrodes of the main output IDT in the area, adjacent to the first Summing bus, the overlap of the riper and second electrodes of the selected IDT are selected in accordance with the expression - - -. . . willWjai wSi Ygl-hYHl Yg2 + YH2 Yo-fYl o where is wpi. Wgii, Wg2t - overlap the electrode of the main, first and second additional IDT, respectively, m; YO, Ygi, Yg2 — total conductivities of radiation of the main, first, and second additional IDT, respectively, sim; 0  yHo.YHi, YH2, are the total conductivities of the external load, first and second, about load equivalents, respectively, sim. and terminals for connecting the second load Equivalent are connected to the first and even five summing buses. 8x.