SU1764138A1 - Surface acoustic wave operating device - Google Patents

Abstract

The invention relates to electronics. The aim of the invention is to increase the attenuation in the retention band of a surface acoustic wave device. The device contains two pairs of cascade-connected, pairwise connected main directional couplers 2, 5 main acoustic waveguides with a reflecting grid 3, 6 located in each of the HVIX, respectively, as well as K pairs pairwise connected To additional directional couplers 9 additional acoustic waveguides with a reflecting grid 10 located in each of them. An auxiliary reflecting structure 4.7 is introduced into each of the main and additional acoustic waveguides. Reflecting gratings 3, 6, 10 in pairwise connected main and additional acoustic waveguides are offset from one another. The magnitude of this displacement, the number of reflective elements in the reflective gratings, the number of reflective elements in the auxiliary reflecting structures, the width of the acoustic waveguides and the distance between them are chosen in accordance with certain expressions. 9 il. sl C

Description

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The invention relates to electronics and can be used in acoustoelectronic devices for signal processing on surface acoustic waves (SAW).

A surfactant device is known that contains a piezoelectric substrate, on the working face of which are input and output interdigital transducers (IDT), and a surfactant waveguide intersecting both IDT. A large number of electrodes having an increased thickness to provide the necessary reflection coefficient allows creating a standing wave mode. Such a device performs the functions of a resonator. The disadvantage of the device is a small out-of-band suppression in the delay band.

The closest to the invention is a device containing input and output interdigital transducers placed on the working face of the piezoelectric substrate and two pairs of cascade connected, coupled by the main directional couplers of the acoustic waves of the main waveguides with the reflecting grid located in each of them . In such a device, it is not possible to obtain a large attenuation of the signal in the delay band. This is due to the fact that the amplitude-frequency characteristic in it is formed by reflective gratings located in the coupled waveguides. The resulting transfer characteristic coincides in appearance with the function

(sinx / x) 2.

The sidelobe level of this function is 26 dB.

The aim of the invention is to increase the attenuation in the delay band.

This is achieved by introducing into the device K pairs which are pairwise connected to K by additional directional couplers of additional acoustic waveguides with a reflecting grid located in each of them, and an auxiliary reflecting structure introduced into each of the main and additional acoustic waveguides. located in the acoustic waveguide, combined with the input IDT, placed between the respective directional coupler and the IDT inputs, auxiliary reflective structure located in addition

solid acoustic waveguide; combined with the output IDT, placed between the corresponding directional coupler and the output IDT, the auxiliary reflective structures in the other main and additional acoustic waveguides are placed between the respective directional couplers and each of them is common for each of the two cascade-connected corresponding acoustic waveguides, reflecting grids pairwise connected main and additional acoustic waveguides are offset one relative to another in the direction of propagation of the PA a distance selected from the expression

L Ni Do / 6,

where L is the distance between the beginnings of reflecting arrays located in pairwise connected main and additional acoustic waveguides, m;

Up to the length of the surfactant at the center frequency of the device on the surfactant, m;

NI is the number of reflecting elements in the reflecting grid, which is a multiple of three and satisfies the condition

th (Nin) 0.96,

where n is the reflection coefficient of the surfactant from the Individual reflecting element of the reflecting lattice,

the number of reflective elements in the auxiliary reflective structures satisfies the condition

th (N2r2) 0.3,

where N2 is the number of reflective elements in the auxiliary reflecting structures;

G2 is the reflection coefficient of the surfactant from a separate reflective element of the auxiliary reflecting structure, and the width of each main and additional acoustic waveguides and the distance between them in the directional link section are related by the expression

pa

P

Col 4

where d is the width of each main and additional acoustic waveguides, m;

a is the distance between the corresponding acoustic waveguides in the directional communication area, m,

p, g - external and internal transverse wave numbers, respectively;

LCB is the length of the directional link section, expressed in lengths of surface acoustic waves.

FIG. 1 shows the frequency dependences: 1 — reflections from a separate reflecting structure; II is a multiplier resulting from the mutual shift of two reflecting structures by the distance L: 111 — the resulting reflection from a pair of reflecting structures shifted one relative to the other; in fig. 2 shows the calculated frequency dependencies of the coupling coefficient between the waveguides; in fig. 3 - dependence of the squares of the amplitudes and the parameter KceLcB on the frequency in two coupled waveguides; in fig. 4 — device topologies: 1 — input interdigital transducer; 2 - directional coupler; 3, 4 - reflecting structures; 5 - directional responder; 6, 7 - reflecting structures; 8 - output interdigital transducer; 9 - directional coupler; 10 - reflecting structure; in fig. 5-9 - diagrams of transfer characteristics in various places of the device on surfactant.

The surfactant device (Fig. 4) contains a piezoelectric substrate (not shown), an input interdigital transducer 1, surfactant waveguides connected by directional couplers 2, S, 9, combined with surfactant waveguides reflecting structures 3, 6, 10 , 4, 7 output counter-pin converter 8.

The device on surfactant works as follows

The signal to be processed is fed to the input IDT 1 and is converted into the main waveguide wave type (Fig. 5, AFC plot at point a) Part of the energy of the waveguide mode is reflected back to one of the auxiliary reflecting structures 4 (Fig. 5, AFC plot point b) - The transmitted wave is divided equally in power by the directional coupler 2. The phase difference of two waves in coupled waveguides is l / 2. Reflected from a pair of reflecting structures 3, the waves pass through a three-digit directional coupler twice and in-phase fold in the second waveguide (Fig. 7, frequency response plot at point c). Since in the cavity of the resonator formed by the reflecting structures 4 and 3, a mode close to the standing wave mode arises, the type of diagrams in FIGS. 6, 7 depends on the location of the registration point

waves. The curves shown in these figures correspond to the point of the antinode. At the synchronization frequency, the acoustic energy reflected by the reflecting structures 3 branches into the next pair of connected waveguides (Fig. 8, frequency response plot at point d) The cascade connection of the connected waveguides increases out-of-band suppression and leads to bifurcation of the central lobe at point g. As is well known, out-of-band suppression in Fabri-Pero resonators is limited to direct passage from the input transducer to the output Pedestal of the resonator type eristiki serves AFC converters The proposed device is a pedestal frequency dependence of the reflection structures 3, 6, 10.

The proposed design can be performed by a two-layer technology, as shown in FIG. 4, or by a single layer using focusing IDTs. The material for waveguides can be germanium monoxide, selenium on niobate lithium, silicon monoxide on Y-quartz, and other materials resulting in a decrease speed Rayleigh waves. Diffusion of metals into the substrate or proton exchange can be used to fabricate waveguides.

A surfactant device made in accordance with the invention makes it possible to obtain high attenuation in the delay band (10 to 20 dB more compared with similar devices).

Claims (1)

Invention Formula A device on surface acoustic waves (SAW) containing input and output counter-pin transducers (IDT) placed on the working face of the piezoelectric substrate, two pairs of cascade connected, connected in pairs by the main directional couplers of the main acoustic waveguides with a reflecting grid located in each of them , with the fact that, in order to increase the attenuation in the delay band, pairs of pairs are connected to it in pairs with additional directional couplers kusticheskih waveguides disposed in each of the reflective grating, and in each of the main and additional acoustic waveguides introduced auxiliary reflecting structure, wherein the auxiliary reflective structure disposed mainly acoustic waveguide, blended with an input IDT,, arranged between the respective directional coupler and an input B SL, an auxiliary reflecting structure located in the sub-. The complementary acoustic waveguide, combined with the output transducer, is placed between the corresponding directional retransmitter and the output LBP, the auxiliary and reflecting structures of the remaining main and additional acoustic waveguides are located between the corresponding directional branches and each of them is common for each of the two cascade connected corresponding acoustic waveguides, reflecting gratings of pairwise connected main and additional acoustic waveguides another in the direction of the surfactant propagation to the distance L chosen from the expressions v / 6, L: ;;: /; t; where To is the length of the surfactant at the Central frequency of the device on the surfactant, m; / ;; NI is the number of reflective elements in the reflecting grid, which is a multiple of three and satisfies the condition th (Nin) 0.96 ,: where n is the reflection coefficient of the surfactant from a separate reflective element of the reflecting grid, the number of reflective elements in the auxiliary reflective structures satisfies the condition tn (N2r2) SO, 3, where Na is the number of reflective elements in the auxiliary reflecting structures gk- - G -; - -; -....: -:, -: -; ha-coefficient of reflection of surfactant from a separate reflective element of an auxiliary reflective structure and the width d of each main and additional acoustic waveguides and the distance a between them in the directional communication area are related by the expression cos (-f -) (p 2 ()  Ra 1 Lee p a where p, g are the external and internal transverse wave numbers correspondingly; The UB is the length of the directional link segment, expressed in the lengths of the surfactant.  Јin & Ni + Ј / 3u f - to & vi b $ / io i V vBV 3 v-i Ш  x Co $ & tflbЈ / $ JD Fi-nd. i   :: N - V 4 RSA; AJ C .., - Jl Wjf -7- - .--. l t Kea 0.05 i 0.04 I о.оз -3 0.02 1 o.oi -3 0.00 о.bo 20.00 cho.oo 60.00 fio.bb iooloo 120: 00 uM Fyg.2 four, 2.00-C 1.50 and 1,000 .50 N 0.00 0.60 20.00 4b.bb 60.bb eb.bb i bb: ob 120: 00 FIG. 2 : 00 uM 0  mg FIG. five Fi, G. (B FIG. B