SU1635233A1 - Band pass filter - Google Patents

Abstract

This invention relates to a microwave technique. The aim of the invention is to increase the frequency selectivity. The band pass filter contains a rectangular substrate 2, the surfaces of which are polished and at least one of them is convex with a certain radius. On one side there is a ferrite film 1 with the first and second converters 3 and 4 of electromagnetic waves in magnetostatic (MSV), and the thickness of the rectangular substrate 2 at their locations is the same and determines the center frequency at which an elastic wave is excited in it , transferring energy to the output of the device. At other frequencies, only the MWs are excited, which transfer energy to the output of the device with significant attenuation. 1 il.

Description

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WITH

The invention relates to a microwave technique and can be applied for frequency selection in radio engineering devices.

The aim of the invention is to increase the frequency selectivity.

The drawing shows a bandpass filter.

The band-pass filter contains a ferrite film 1 placed on one side of a rectangular substrate 2. made of a non-magnetic material with two convex and polished sides, the first and second converters 3 and 4 of electromagnetic waves into magnetostatic waves placed on a ferrite film 1, magnetic system (not shown in the drawing, the arrow indicates only the direction of the field But of the magnetising ferrite film 1), moreover, the radius R of the curvature of the convexity of the sides of the rectangular substrate 2 and its thickness do in places of the positions of the first and second transducers 3 and 4 are selected from the ratios

a | 2+ n

pf and d ° T7; n

where I is the distance between the first and second converters 3 and 4;

A is the acoustic wavelength at the center frequency f0 of the passband;

vs is the speed of sound in the material of the rectangular substrate 2;

n is an integer.

Band-pass filter works as follows.

When applying a microwave signal to the first transducer 3 in the ferrite film 1, a surface magnetostatic wave (MSSW) is excited, the frequency band of which is determined by the field H0 and the structure of the first transducer 3.

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The MSSW effect due to the magnetostriction effect in those cases when the MFW frequency f is equal to the center frequency fo of the transmission band, defined by the thickness do rectangular substrate 2, in the material of the rectangular substrate 2 elastic acoustic waves are created. In the region of the first transducer 3, MSSW and the elastic acoustic wave propagate synchronously, but with increasing thickness of the rectangular substrate, the synchronism between them breaks down and the waves propagate independently. In the region of the second transducer 4, where the condition is again fulfilled, the elastic acoustic wave resonantly in the ferrite film 1 excites the MSSW, and the amplitude of this MSSW is substantially larger than the amplitude of the MSSW propagating only to the ferrite film 1. cash passed through the device.

If the frequency of the microwave signal, and hence the frequency of the MSSV excited by the first transducer 3, is not equal to f0. then the elastic acoustic wave does not excite a low level signal from the second transducer 4, due to a significant attenuation of such MSSW.

In this device, it is also possible to mechanically tune the center frequency fo by changing the distance between the first and second transducers 3 and 4, and if the first and second transducers 3 and 4 are single-ended, then

frequency gaps in a series of narrow bandwidths of the frequency response of the device will also vary.

Claims (1)

Claims A band-pass filter comprising a rectangular substrate, which is made of a non-magnetic material and on one side of which is placed a ferrite film with a first and second converter of electromagnetic waves into magnetostatic waves, a magnetic system characterized in that frequency selectivity, both surfaces of the rectangular substrate are made polished, and at least one of them is convex with a radius R of curvature equal to | 2, 12 R. where I is the distance between the transducers of electromagnetic waves into magnetostatic waves; I is the length of the acoustic wave at the central frequency fo of the bandwidth, and the thickness do of the rectangular substrate at the locations of the transducers of electromagnetic waves to magnetostatic waves is chosen from the relation n - Vs „ dop with f, i then where vs is the speed of sound in the material of the rectangular substrate; n is an integer.