RU95926U1 - PHASE ROTATOR ON SURFACE (SURFACE) ACOUSTIC WAVES - Google Patents

Abstract

 Phase shifter on surface (near-surface) acoustic waves containing a piezoelectric sound duct, on the working surface of which two acoustic channels are placed parallel to each other, each of which contains an input and output interdigital transducers (IDT) located at the same distance "L" from each other , and between which there is a shielding element, characterized in that all IDTs are implemented as broadband dispersion ladder-type converters with split electrodes, following which λ (1) / 4, λ (2) / 4, ... λ (i) / 4, ... λ (n) / 4 (where n is the number of split electrodes), and the input IDTs of both channels are identical, that is, the location electrodes and their connection to buses having identical shapes, the same way, the output IDTs of both channels, having the same bus shape and electrode location, are made with different connection of electrodes to the buses, namely with the connection offset in one of the channels to one split electrode, except In addition, an absorber of surface waves is applied to the ends of the sound duct.

Description

The utility model relates to the field of radio engineering and can be used in devices for frequency selection of a radio signal, in particular, in antenna compensators of active interference.

Known acoustic phase shifter [1], containing a piezoelectric sound guide with located on its surface in a common acoustic stream n-section input and common output transducers. The sections of the input transducer are placed on the sound duct with a spatial shift equal to 1 / n of the period of the acoustic surface wave. Moreover, in series with each section of the input converter, a controlled resistance is included, with the help of which the phase shift is smoothly adjusted.

The disadvantage of this device is the presence of external control circuits and low temperature stability. In addition, this phase shifter is relatively narrowband, since the nominal value of the phase shift is obtained only at frequencies close to the center frequency.

Also known is a discrete phase shifter [2], made in the form of a piezoelectric delay line of elastic surface waves, in which emitting and receiving transducers are located on the surface of the sound duct, and a step-shaped metal film is deposited between them in a common acoustic stream. The film provides the required phase shift due to a discrete change in the step step by ΔL.

This phase shifter does not provide high accuracy of setting the phase shift between the outputs, has a low temperature stability and is also relatively narrowband.

The closest adopted for the prototype is a phase shifter with a fixed phase shift [3], containing a piezoelectric sound duct, on the working surface of which two channels are parallel to each other. Each channel contains an input and output interdigital converters (IDT), which are located at the same distance "L". Both channels are identical in all respects, except that in one of them the surface of the sound duct between the IDT is covered with a thin metal film.

The phase difference is measured between the signals at the output of the first and second channels and is determined by the difference in the time the signals travel the distance “L” with different speeds “V” and “V + ΔV”.

The disadvantage of this device is the receipt of a given phase shift only in a relatively narrow, 1-2%, frequency band (close to the center frequency), the difficulty of accurately performing the required phase shift rating (due to a change in the speed rating V) and a change in the phase shift rating itself when changes in ambient temperature (due to changes in the speed of the surfactant and the linear dimensions of the device).

The technical result of the utility model is to obtain a fixed phase shift of 90 ° between the output channels of the device in a wide relative passband when operating in a wide range of temperature changes.

The specified technical result is achieved by the fact that in the phase shifter on the surfactant containing a piezoelectric sound duct, on the working surface of which two acoustic channels are placed parallel to each other, each of which contains the input and output IDTs located at the same distance “L” from each other, and between by which the shielding element is located, all IDTs are implemented as broadband dispersion ladder-type converters with split electrodes (4 electrodes per period), and the input IDTs of both channels identical, i.e., the location of the electrodes and their connection to the buses having identical shapes is the same, the output IDTs of both channels, having the same bus shape and the location of the electrodes, are made with different connections of the electrodes to the buses, namely, with the connection offset in one of the channels on one split electrode, in addition, an absorber of surface waves is applied to the ends of the sound duct.

The inventive utility model is illustrated by the drawings shown in figures 1-5.

Figure 1 shows the structure of a broadband quadrature phase shifter on a surfactant;

Figure 2 shows fragments of the beginning and end of the topology of the output IDT of the first channel with an odd number of half-periods;

Figure 3 shows fragments of the beginning and end of the topology of the output IDT of the second channel with an odd number of half-periods;

Figure 4 presents the amplitude-frequency characteristics of the two channels of the phase shifter;

Figure 5 presents the difference phase-frequency characteristic (between the outputs of the channels) of the phase shifter.

The proposed phase shifter is a piezoelectric sound pipe 1, on the working surface of which are parallel to each other acoustic channels "A" and "B".

In each channel, at the same distance “L”, the input and output converters are located, which are implemented as wideband dispersive IDT 2, 3, 4, 5 ladder-type with split electrodes (4 electrodes per period), the step of which λ (1) / 4, λ (2) / 4, ... λ (i) / 4, ... λ (n) / 4 (n is the number of split electrodes).

Between the transducers, in the channels “A” and “B”, there are screens 6. In order to eliminate unwanted reflections of the surfactant from the ends of the sound duct 1, an absorber of surface waves 7 is applied to the ends (Figure 1).

Input IDTs 2, 4 of both channels are identical, namely, the location of the electrodes and their connection to the buses 8, 10 and 9, 11 (respectively), having identical shapes, is the same.

The output IDTs 3, 5 of both channels, having the same bus shapes 12, 14 and 13, 15 (respectively) and the location of the electrodes, are made with different connections to the buses. For example: the electrodes of the output IDT 3 are connected to the buses 12 (+) and 13 (-) with alternating ++ - ... - ++ (Figure 2), and the electrodes of the output IDT 5 are connected to the buses 14 (+) and 15 ( -) already with a shift by one split electrode, following the alternation - ++ - ... ++ - + (Figure 3), or + - ++ ... - ++ - (with an odd number of half-periods). With an even number of half-periods, the alternation will be ++ - ... ++ - for one channel and + - ++ ... ++ - + or - ++ - ... - ++ - for the second channel.

For experimental verification of the claimed technical solution, samples of a phase shifter were made on a YX / 128 ° LiNbO ₃ slice duct. Product specifications were measured using an Agilent E5071C network analyzer.

Figure 4 shows the amplitude-frequency characteristics (AFC) of the first and second channels of the phase shifter, differing only in the presence of antiphase pulsations formed due to false signals of triple passage.

Figure 5 shows the phase-frequency characteristic (PFC), measured between the outputs of the first (A) and second (B) channels of the phase shifter. The phase difference between the channels is 90 ° with a spread of peak values of 3.5 ° in a wide relative passband. Reducing the level of false signals will reduce the spread of the peak values of the phase difference from the nominal value.

Since the distance “L” between the input IDT 2 and the output IDT 3 of channel “A” is identical to the distance between the input IDT 4 and the output IDT 5 of channel “B”, acoustic waves propagate at the same speed and reach the output IDT 3 and 5 with the same initial phase in each channel. And since the split electrodes follow with a period ^of _1/4 wavelength (which corresponds to a phase change of 90 ° on each electrode) and the connection of the electrodes to the buses of the output converters 3, 5 is performed with a shift by one split electrode, the phase difference between output 1 and output 2 the device is exactly 90 ° at each frequency f (1), f (2), ... f (i), ... f (n) the passband formed by the transducer electrodes.

Therefore, a change in the speed of the acoustic wave V or the distance between the transducers L does not lead to a change in the difference in the delay time and the phase difference between the outputs of the channels when the velocity spread in different sound ducts or when the temperature changes.

The claimed technical solution allows to obtain the exact nominal value of the phase shift of 90 ° between the output channels of the phase shifter in a wide relative passband up to 30%. The magnitude of the deviation of the phase difference is not more than 3.5 °.

In addition, this phase shifter has thermal stability, i.e. the nominal value of the phase shift does not depend on the material used in the piezoelectric sound duct (its thermal stability, strong or weak electromechanical coupling) and the type of acoustic wave (surface or near-surface) when operating in a wide temperature range. In the manufacture of an ST-cut piezoelectric device, the phase shifter obtains the property of thermal stability.

LITERATURE

1. A.S. 509977 (USSR), MKI ² H03H 7/18. Acoustic phase shifter / S.S. Karinsky, V.G. Komarov, V.I. Rechitsky. - No. 2009177 / 40-23; declared 03/22/74; publ. 04/05/76, Bull. 13.

2. A.S. 364077 (USSR), MKI N03NN 7/18. Discrete phase shifter / S.S. Karinsky, V.V. Zelenin. - No. 1688431 / 26-9; application 07/26/71; publ. 12/25/72, Bull. 4.

3. Karinsky S.S. Signal processing devices for ultrasonic surface waves. - M .: Soviet Radio, 1975, p.131, p.156.

Claims (1)

Phase shifter on surface (near-surface) acoustic waves containing a piezoelectric sound duct, on the working surface of which two acoustic channels are placed parallel to each other, each of which contains an input and output interdigital transducers (IDT) located at the same distance "L" from each other , and between which there is a shielding element, characterized in that all IDTs are implemented as broadband dispersion ladder-type converters with split electrodes, following which λ (1) / 4, λ (2) / 4, ... λ (i) / 4, ... λ (n) / 4 (where n is the number of split electrodes), and the input IDTs of both channels are identical, that is, the location electrodes and their connection to buses having identical shapes, the same way, the output IDTs of both channels, having the same bus shape and electrode location, are made with different connection of electrodes to the buses, namely with the connection offset in one of the channels to one split electrode, except In addition, an absorber of surface waves is applied to the ends of the sound duct.