SU997231A1

SU997231A1 - Monolithic piezoelectric filter

Info

Publication number: SU997231A1
Application number: SU803211022A
Authority: SU
Inventors: Владимир Николаевич Банков; Вячеслав Иванович Бирюков; Владимир Дмитриевич Давыдов; Наталья Ивановна Изотова; Юрий Леонидович Королев
Original assignee: Предприятие П/Я Г-4149
Priority date: 1980-12-01
Filing date: 1980-12-01
Publication date: 1983-02-15

Description

(54) НОНОЛИТНИП ПЬЕЗОЭЛЕКТРИЧЕСКИЙ ФИЛЬТР(54) NON-POLITICAL PIEZOELECTRIC FILTER

1 .one .

Изобретение относитс к радиоэлектронике и можбт быть использовано в устройствах, селекции частоты.This invention relates to electronics and can be used in frequency selection devices.

Известен фильтр, содержащий пьезоподложку , на которой расположены две пары входных и выходных электродов, образующих акустически несв занные резонаторы Ц.A filter is known that includes a piezoelectric substrate on which two pairs of input and output electrodes are located, forming acoustically unrelated resonators C.

Однако известный фильтр характеризуетс недостаточно высокой избирательностью .However, the known filter is not characterized by high selectivity.

Наиболее близким к изобретению по технической сущности и достигаемому результату вл етс монолитный пьезоэлектрический фильтр, содержащий пьезоподложку и расположенные на «е поверхности две пары противолежащих электродов, образующих акустически., св занные резонаторы 2.The closest to the invention in technical essence and the achieved result is a monolithic piezoelectric filter containing a piezo-substrate and two pairs of opposite electrodes forming acoustically. Connected resonators 2 located on the surface.

Недостатком этого фильтра вл етс наличие нежелательных резонансов вблизи основного резонанса.The disadvantage of this filter is the presence of unwanted resonances near the main resonance.

Цель изобретени - ослабление нежелательных резонансов при сохранении полосы пропускани .. ,The purpose of the invention is to reduce unwanted resonances while maintaining the bandwidth ...

Цель достигаетс тем, что в монолитном пьезоэлектрическом фильт&е, содержсццем подложку и расположенные на ее поверхности две пары п1хэтиволежащих электродов, образующих акустичёски св занные резонаторы, электроды выполнены с выемками, расположенными с их внешней стороны направлени акустической св зи реэбнаторов и выемками, расположенными с внутренней стрроны электродов симметрично внешним выемкам, при этом отношение площади внешней выемки на. одном электроде к площади этого элек10 трода составл ет от 0,08 до 0,1,а плсшадь внутренней выемки составл ет 0,5-0,7 площади внешней.The goal is achieved by the fact that in a monolithic piezoelectric filter & e, there is a substrate and two pairs of these electrodes that lie on its surface and form acoustic-coupled resonators; the inner stronghold of the electrodes is symmetrical to the external grooves, with the ratio of the area of the external groove on one electrode to the area of this electrode is from 0.08 to 0.1, and the inner recess is 0.5-0.7 square to the external one.

На чертеже представлен монолитный пьезоэлектрический фильтр, выполнен15 ный согласно .данному изобретению.The drawing shows a monolithic piezoelectric filter made 15 according to this invention.

Монолитный пьезоэлектрический фильтр содержит пьезоподложку 1 с нанесенными на ее главные поверхности электродами 2 с токопровод щими The monolithic piezoelectric filter contains a piezoelectric substrate 1 with electrodes 2 with conducting

20 отводами 3, присоединенными к контактАым площадкам 4. Выемки 5 расположены с внацией стороны электродов, а выемки 6 - с внутренней стороны электродов симметрично вн.ешним. Площадь .20 by taps 3 connected to contact areas 4. The notches 5 are located on the side of the electrodes, and the notches 6 are located on the inside of the electrodes symmetrically inside. Square .

25 выемки 5 на одном электроде 2 составл ет 6,08-0,1 площади этого электрода Площадь выемки б на одном электроде составл ет 0,7-0,5 площади выемки 5. При подаче .входного сигнала на25 notches 5 on one electrode 2 is 6.08-0.1 of the area of this electrode. The area of the notch b on one electrode is 0.7-0.5 of the area of notch 5. When the input signal is applied to

Claims

30, one of the pairs of contact pads 4 in piezus 1 is excited by volume waves of shear variations in thickness. Due to the acoustic coupling between the resonators formed by pairs of counter electrodes 1 and 1 of electrodes 2, an electrical signal arises on another pair of contact pads 4, the amplitude-frequency characteristic of which has a shape corresponding to the characteristic of a band-pass filter. The presence of grooves 5 eliminates the active zones of unwanted resonance excitation, since the absence of electrode-PECELS in this area makes it difficult to excite unwanted oscillations. At the same time, the most intense unwanted oscillations experience the regions of piezo-substrate 1 located along the acoustic coupling line of the resonators at the edges of the exciting electrodes 2 from their back, i.e. from the side opposite to the area between the pairs of electrodes 2. When the ratio of the areas of the notch and electrode is less than 0.88 a decrease in the amplitude of unwanted, including anharmonic, oscillations does not occur, and if the ratio is more than 0.1, the Q of the filter is reduced. Therefore, a positive effect of the proposal is provided only when the ratio of these areas, within 0.08-0.1. The presence of grooves with the specified area and location ensures a high monofrequency of the filter and additionally increases the stability of the electrical parameters. by weakening the connection between the fundamentals. mode of oscillations and undesirable oscillations. Since the implementation of the grooves 5 with the expansion of the band pass, they are necessary to maintain its value (or contraction); n grooves b from the inside of the electrodes 5. The ratio of the areas. notches 5 and 6 are selected from the condition that the bandwidth of the filter remains unchanged by the filter in the presence of the main notches 5 and is between 0.7 and 0.5. The proposed filter suppresses unwanted resonances of more than 25 dB at a frequency that is less than half of the allowance for metallization, as well as attenuating anharmonic oscillations. Formula of the invention. coupled resonators, characterized in that, in order to attenuate unwanted resonances while maintaining the passband, the electrodes are made with grooves located on their outer side along the direction of acoustic communication of the resonators, and grooves located on the inner side of the electrodes symmetrically to the external grooves, the ratio of the area of the external groove on one electrode to the area of this electrode being from 0.08 to 0.1 and the area of the inner groove is about 0-0-0.7 in the top. Sources of information taken into account in the examination 1. US Patent 3222622, cl. 333-72, pub. 1965.

2. Patent ША № 3564463, кл. 333-72, pub. 1970.