SU1538232A1 - Device for automatic tuning of bandpass filter - Google Patents

Abstract

The invention relates to radio engineering and can be used in radio transmitting and receiving devices. The purpose of the invention is to improve the accuracy of the band passband setting. The device contains r-p1 reference frequency, amplitude modulator 2, switch 3, band-pass filter 4, envelope detector 5, phase detectors 6 and 9, adder 7, sampling-storage unit 8, r-10 modulating signal. An envelope detector 11 is entered into the device, the input of which is connected to the input of the filter 4, and the output is connected to the second input of the detector 6. The operating point of the bandwidth regulating element is set so that, when the phase difference of the envelope voltages at the inputs of the detector 6 is equal to 90 °, the passband filter 4 would be 2 times higher than the modulating frequency of r-10. When the passband of the filter 4 decreases, the output voltage of the detector 6 increases and decreases with increasing. This ensures the installation of the required bandwidth of the filter 4. 1 sludge.

Description

3 one

The invention relates to radio engineering and can be used in radio transmitting and receiving devices.

The purpose of the invention is to improve the accuracy of the band passband setting.

The drawing shows an electrical block diagram of a device for automatically adjusting a band-pass filter.

The device for automatic tuning of the bandpass filter comprises a reference frequency generator 1, an amplitude modulator 2, a switch b, a band pass filter, a first envelope detector 5, a first phase detector 6, an adder 7, a sampling-storage unit 8, a second phase detector 9, a modulating oscillator 10 signal and the second envelope detector 11.

The device for automatically adjusting the bandpass filter works as follows.

In the tuning mode, the switch 3 is supplied with a control signal and the output voltage of the amplitude modulator 2, which is an AM oscillation, is fed to the input of a band-pass filter. The second phase detector 9 performs continuous adjustment of the resonant frequency tuning the band-pass filter to the frequency of the oscillator 1.

From the outputs of the first 5 and second 11 detectors, the output voltage is fed to the inputs of the first phase detector 6. At a frequency of the output voltage of the modulating signal generator 10 equal to half the passband of the bandpass filter, the phase difference of the envelope voltages at the input and output of the bandpass filter k is 90 ° The output voltage of the first phase detector 6, corresponding to this phase shift, enters through the adder 7 and the sampling-storage unit 8 to the second control input of the band-pass filter k and controls its passband. - The reference voltage at the second input of the adder 7 provides the necessary position of the operating point of the bandwidth regulating element included in the bandpass filter b. The operating point of the bandwidth regulating element is set so that when the phase difference

382324

the envelope voltage at the inputs of the first phase detector is 90; the passband of the bandpass filter k is twice as high as the modulating frequency of the generator 10 of the modulating signal.

As the passband of the bandpass filter k decreases, the output voltage JQ of the first phase detector 6 increases and decreases as the bandwidth increases. This ensures that the required bandwidth is set.

J5 bandpass filter k.

After the end of the bandwidth adjustment process of the bandpass filter h, the device for automatically adjusting the bandpass filter

2Q goes into operating mode by turning off the control signal applied to the device control input for automatic adjustment of the bandpass filter. In this case, the input of the polio filter k is connected to the input of the device, and the sampling-storage unit 8 switches to the storage mode of the control voltage supplied to it from the output of the adder 7 in the mode

3Q settings.

In the case when the amplitude modulator 2 does not introduce a noticeable phase shift in the envelope of the input signal of the bandpass filter 4, the second detector 11 can be eliminated and the second

35 input of the first phase detector 6 can be connected directly to the output of the generator 10 of the modulating signal.

Claims (1)

Invention Formula A device for automatically adjusting a band-pass filter, comprising a series-connected band-pass filter, a first envelope detector and a first phase detector, a second phase detector, the first and second inputs of which are connected respectively to the input and output of the band-pass filter, and the input of the band-pass filter forms an input device different By the fact that, in order to increase the accuracy of the bandpass filter bandwidth setting, a second envelope detector is introduced, the input of which is connected to the input of the bandpass filter, and exit - with the second 515382326 the input of the first phase detector, the bandpass filter, and the output of the second output of the first phase detector of the phase detector to the second input are connected to the first control input of the control of the bandpass filter.