SU1022294A1 - Pass-band filter on surface acoustic waves - Google Patents

Abstract

STRIP FILTER ON SURFACE ACOUSTIC WAVES, containing an input strip-cutting partitioned counter-pin converter and an output counter-pin converter. A Shi-Rocon converter is used, the electrode pitch in which differs from that of the electrodes in the input stripe, sectioned counter; A pin converter and is selected from the following ratios. Р e where LP is the spatial period of the section of the input strip-creating partitioned interdigital transducer (IDT); 6. - spacing of electrodes in the input strip-sectioning section (LH bathing; Kj-ftiar electrodes in the output wideband IDT; K: integers. In GT // l And y. 0tft.f

Description

The invention relates to radio electronics and can be used for frequency selection of signals in television radar and associated receivers. The surface acoustic wavelength i (surfactant) filter containing a strip-guiding and wide-band anti-whip: transducers (IDT) is known. Due to surfactant surfactant in the multielectrode structure of the bandwidth of the IDT, significant spurious signals occur, causing, in turn, distortions of a given amplitude-frequency characteristic. (AFC) of the filter. in which the sections of the electrodes are arranged periodically with a different spatial period, and the steps of the electrodes in both converters are chosen to be identical. The disadvantages of such a filter are limited operating frequency range. The upper limit of the working frequency range is determined by the resolving power of the technological process of manufacturing transducer structures, especially multielectrode banding, and the lower one is limited by the actually possible (up to 200 mm) size of piezoelectric substrates on which filter converters are placed. The purpose of the invention is to expand the operating frequency range. The goal is to achieve that in a band-pass filter on surface acoustic waves containing an input strip-creating partitioned anti-whip transducer and an output counter-extending transducer, a wide-band transducer is used as the output anti-pin transducer partitioned anti-pin converter and is selected from the following ratio the spatial period tion input guide polosozada sectional interdigital converters are (IDTs); t is the step of the electrodes in the input section of the sectionalized IDT; - step electrodes in the output broadband IDT; - integers. In FIG. 1 shows the structural scheme of the proposed filter; in fig. 2 and 3 are graphs that show his work. The filter contains a stripped sectionalized transducer 1 and a broadband transducer 2 located in the general acoustic flow, sections 3 of which are placed with a spatial period Up. In the simplest case, each section 3 can be formed by only one pair of electrodes 4 and 5. The pitch t of the electrodes of the transducer 1 and the pitch of the electrodes of the transducer 2 are selected unequal, i.e. C-j With or,. wP-te if, 2, 1 1 / if 6 K where K is an integer. In this case, t, e V / fo; e, V / $ v, where b | p is the number of pairs of electrodes in the partitioning period of converter 1; fo and fk are respectively the frequencies of acoustic synchronization of transducers 1 and 2; V- surfactant velocity. The filter works as follows. impulse response, 4ip (t) of the strip-generating partitioned converter 1 can be represented as a sequence of pulses. hv) i (-t-ti, which are the impulse characteristics of each section and are shifted relative to each other by the time period Tp Lp / V. m. Thus, Lp (t) is Z b (-b-ty). I where M is the number of sections in converter 1, tv,. The frequency response of such a converter has a number of harmonic responses (Fig. 2), repeated with a frequency {pe V / lp-r 2 o / Np, resulting from vector addition individual sections, ie, Ap () (f). | - where Ay (t) and & UU / $) are the frequency response and phase response of each section, respectively. The anharmonic responses in the AFC of the converter are as below. and Above the acoustic frequency of the chronism to /. When executed, condition Lp K e 6 (.), I.e. when, the maximum frequency response A ({) of the broadband converter 2 coincides with the anharmonic response to at high frequency (Fig. 2), and under the condition -, i.e. with anharmonic response with response K at a low frequency of fc-4o p (phi1 3). As in the first (E-) 7Ca) and in the second (J -cIji) cases, all the anharadonic responses, except for the response at the frequency {, are significantly weakened, therefore in the resulting frequency response of the filter AjCi) -Ap (t) AC (4b only One required response at frequency ix-f о. When using converter 1 in each section only one pair of electrodes and in the case of the minimum possible spatial period of sections.Up - 1.5 N, the nearest anharmonic responses in its frequency response Ap () are located at frequencies f -x-1.66 Jo and (, $ 33 0. Highlight these responses using a broadband transform 2, you can expand the working frequency range of the filter up to at least 1.66 times, without changing the electrode pitch. Bandwidth of the converter 1. If necessary, unnecessary anharmonic responses in the frequency response can be further suppressed by using matching filter circuits or completely destroy when they are combined with the middle frequencies of the zeroes of the frequency response of the AN () wideband converter 2. Thus, the proposed filter design provides an extension of the working frequency range through the use of high near-frequency or low-frequency anharmonic responses in the frequency response of a strip-locking partitioned IDT.

M

Lg (fJ

, t

f, f -ffft

F1a.1

A (f}

„(F) --l

/ f

-JdLUL / LULh

0t№.J

Claims (1)

BAND FILTER ON LOCAL ACOUSTIC WAVES, a live input stripe-onirovanny onirovanny interdigital transducer and an output interdigitated transducer. ! of the transducer used shigde Lp - the spatial period ^and sections of the input stripe sectionalized interdigital transducer (IDT); Ff is the electrode pitch of the • stripe bath of IDT; Fj- Electrode pitch of broadband number. in the input section - integers in the output IDT ?. > g