SU790108A1 - Switchable two-frequency piezoelectric band-pass filter - Google Patents

Description

(54) SWITCHABLE PLASTIC ELECTRIC PIEZOELECTRIC

STRIP FILTER

I

The invention relates to the field of radio electronics and can be used in frequency selection devices.

Closest to the present invention is a switchable two-frequency piezoelectric bandpass filter containing an input differential transformer, the middle point of the secondary winding of which is connected to a common bus, connected between the antiphase terminals of the secondary winding and a capacitor, connected to its antiphase shoulders, two piezoelectric resonators connected by one of the terminals to the output resonant circuit and switching system 1. The switching system at the same time ensures switching on of one or the second akogo same filter having a different center frequency.

A disadvantage of the known filter is a change in its electrical characteristics — amplitude and phase-frequency, temporal and temperature stability, and transmission coefficient when switching from one center frequency to another.

The purpose of the invention is to ensure the immutability of the electrical characteristics at

switching from one medium frequency to another.

This is achieved by the fact that a switchable two-frequency piezoEv is an electrical band-pass filter containing an input differential transformer, the middle point of the secondary winding of which is connected to a common thickness, connected between the antiphase terminals of the secondary winding and the two piezoelectric resonators connected to its antiphase shoulders resonant circuit, and the switching system, contains two additional piezoelectric resonators, one of the conclusions of which is connected to the corresponding output of the secondary winding, and the other with the anti-phase output of the output circuit; the switching system is designed as two three-contact two-position switches, the middle contacts of which are connected to a common thickness,

Claims (1)

The 20 extreme contacts of one are connected to additional capacitors, the second output of which is connected to the corresponding output of the secondary winding, and the second - to the corresponding conclusions of the output resonant circuit and other additional capacitors, the second output of which is connected to the common bus. The drawing shows the electrical circuit of the proposed filter. The filter contains a differential transformer 1, a capacitor 2 connected between the antiphase terminals of the secondary winding 3 of transformer 1, additional capacitors 4 and 5, switch 6, piezoelectric resonators 7 and 8, additional piezoelectric resonators 9 and 10, switch 11, output resonant circuit 12 and additional capacitors 13 and 14. The middle point of the transformer 3 and the middle contacts of the switches 6 and 11 are connected to the common bus. Resonators 7 and 8 are included in the antiphase shoulders of transformer 1. Additional resonators 9 and 10 are connected by one output to the corresponding output of the secondary winding 3, and the other to the antiphase (with respect to the output of the secondary winding) output of circuit 12. Parallel to the resonators 7 and 8 connected correction capacitors. In the antiphase arms of the transformer 1, several parallel-connected resonators can be switched on, while a corresponding number of resonators are also connected parallel to the resonators 9 and 10 (not shown). The filter works as follows. When installing the switches 6 and 11 in the upper position between the transformer 1 and the circuit 12 included resonators 8 and 10, forming a band-pass differential bridge filter. The average frequency of the differential transformer is determined by the capacitance of the capacitors 2 and 4, and the tuning frequency of the output resonant circuit 12 is determined by the capacitance of the capacitors 12 and 14. In this case, the resonators 7 and 9 act as notch resonators. When switches 6 and 11 are placed in the lower position, one of the outputs of the output circuit 12, previously being potential, is connected to a common thickness, and resonators 7 and 9 are connected to its second output, forming a band-pass filter with a different center frequency. Resonators 8 and 10 in this case have resonant frequencies located in the delay band and act as notch resonators. At the same time, the frequencies of transformer 1 and circuit 12 are also rebuilt by connecting to them capacitors 5 and 13 c. Instead of capacitors 4 and 14. The proposed filter provides almost identical electrical characteristics at both middle operating frequencies. Claims of the invention A switchable two-frequency piezoelectric bandpass filter containing an input differential transformer, the middle point of the secondary winding of which is connected to a common length, a capacitor connected between the antiphase terminals of the secondary winding, two piezoelectric resonators connected to its antiphase shoulders, and switching system, characterized in that, in order to ensure constant electrical characteristics when switching from one center frequency to another, it contains two additional piezoelectric resonators, one of the terminals of which is connected to the corresponding output of the secondary winding, and the other with the antiphase output of the output circuit, and the switching system is designed as two three-contact two-position switches, the middle contacts of which are connected with a total thickness, the extreme contacts of one connected to additional capacitors, the second output of which is connected to the corresponding output of the secondary winding, and the second - with the corresponding conclusions of the output resonant circuit and other additional capacitors, the second output of which is connected to the total length. Sources of information taken into account during the examination 1. Ya. I. Velikin and others. Pzoelectric filters. M., “Svy, 1966, p. 210. nn -h