SU1073884A1 - Band-pass surface-acoustic-wave filter - Google Patents

Abstract

BAND FILTER ON SURFACE ACOUSTIC WAVES, containing a piezo-substrate with two equidistant opposite transducers located on its working surface (IDT), one of which is made unopodied, and the other is apodized according to the aperture according to the even-nummy of the sinX pattern of a cell pattern. This is due to the fact that, in order to reduce the level of side lobes of the amplitude-frequency characteristic, two additional electrodes are inserted into the apodized IDT, on each side, connecting These are counterphased to the corresponding extremes of the IDP, while overlapping the ts of each of the electrodes corresponds to the end of the IDP of the half-wave pair of electrodes from the ratio of K.il 4t-o algebraic (taking into account the sign of the apodization function) ; the number of half-wave pairs of electrodes on one side of the center of Binn (excluding the auxiliary electrode); the level of the maximum side lobe of the amplitude-frequency characteristic of the apodized IDT (without additional electrodes).

Description

The invention relates to acoustoelectronics and can be used in various acoustoelectronic devices, in particular when creating bandpass filters on surface acoustic waves (SAWs).

A well-known SAW bandpass filter containing a piezo substrate with two interdigital transducers (IDTs) located on its working surface, one of which is made unapodized and the other apodized on the G1L aperture.

The disadvantage of this filter is low signal suppression out of bandwidth.

Closest to the proposed technical solution is a SAW bandpass filter containing a piezo substrate with two equidistant interdigital transducers (V'PP) placed on its working surface, one of which is made unapodized and the other apodized according to the law of an even function of the type sincx truncated symmetrically at any zeros [2].

A disadvantage of the known filter is the relatively high level of the side lobes of the amplitude-frequency characteristic (AFC).

The purpose of the invention is to reduce the level of the side lobes of the amplitude-frequency characteristics.

This goal is achieved by the fact that in a bandpass filter on a surfactant containing a piezo substrate with two equidistant interdigital IDT transducers placed on its working surface, one of which is non-apodized and the other is apodized according to the law of an even function of the sincx type, truncated symmetrically by at any zeros, two additional electrodes are introduced into the apodized IDT, one on each side connected to the common buses out of phase with respect to the corresponding extreme IDT electrodes, while the overlap value W _{N + 1 of} each of the additional. electrodes with the corresponding extreme electrode IDT selected from the ratio

where W _n is the algebraic (taking into account the sign of the apodization function) value of the overlap η-th from the center of the IDT half-wave pair of electrodes;

N is the number of half-wave pairs of electrodes on one side of the center of the IDT (excluding the additional electrode);

- the level of the maximum more than 10 new lobe of the amplitude-frequency characteristic of the apodized IDT (without additional electrodes).

The drawing shows the proposed band-pass filter on surface acoustic waves.

. The SAW bandpass filter contains piezo substrate 1, equidistant 2Q apodized according to the law of a clear function of the sincx type, truncated symmetrically along any paths, the input strip-picking interdigital transducer 2 and the equi-distant non-modalized interdigital interdigital transducer 3. The transducer 2 is equipped with two and two additional electrodes , one on each side, connected to the common buses b and 7 of the circuit in phase with respect to the corresponding extreme electrodes 8 and 9 of the converter.

In the proposed design of a SAW bandpass filter, two 35 (NfD-active half-wave pairs formed by additional electrodes 4 and 5 and extreme electrodes 8 and 9 of the apodized transducer 2 are introduced), which leads to a decrease of 40 by (20-25 dB) the levels closest to the main side the filter’s frequency response, without making changes to its level at frequencies corresponding to the frequency response zeros, while the level of 45 far side lobes is determined by the amplitude-frequency characteristic of the unapodized converter-3 ..

The proposed design of a SAW bandpass filter allows to reduce the level of side lobes (up to 55-65 dB) while maintaining the maximum and minimum electrode overlaps in the apodized filter converter, i.e. without changing the simplest traditional filter topology for surfactants and the accuracy requirements for its implementation ..

VNIIIPI Order 377/53

Circulation 862 Subscription

Branch of the PPP Patent, Uzhgorod, Project 4,

Claims (1)

BAND FILTER ON SURFACE ACOUSTIC WAVES, containing a piezo-substrate with two equidistant interdigital transducers (VIPs) located on its ⁴ working surface, one of which is made unapodized, and the other apodized according to the law of an even function of sink type, truncated symmetrically to any symmetric truncated symmetrically m and n and h go- tm and d with _h I that, in order to reduce the level of sidelobe amplitude-frequency characteristics, two additional 'electrode introduced into apodizovanny IDT, one on each side, Connecting to the common buses antiphase with respect to the corresponding extreme IDT electrodes, wherein the overlapping value W _{N + 1} of each of the additional electrodes to the corresponding extreme IDT electrode is selected from the relation ^{l W N + ll = L m} . . where is the algebraic (taking into account the sign of the apodization function) ’amount of overlap of the nth half-wave pair of electrodes from the center of the IDT; © N is the number of half-wave pairs of electrodes on one side of the center of the IDT (excluding the additional electrode); - the level of the maximum side lobe of the amplitude-frequency characteristic of the apodized IDT (without additional electrodes). SU 107388