SU720697A1 - Tracking filter - Google Patents

Description

(54) FOLLOWING FILTER

I

This invention relates to a measurement technique.

A prior art filter comprising a serially connected input driver, gtr of coal pulses, a band-pass filter with a controlled resonant frequency and an output square-wave driver, a control input of a band-pass filter with a controlled resonant frequency through a low-pass filter connected to the output of the phase detector, one from the inputs of which is connected to the output of the input, and the other to the output of the output formers of rectangular pulses 1.

However, the lime filter has a significant probability of tuning to the second harmonic of the input signal.

The purpose of the invention is to reduce the likelihood of tuning to the second harmonic of the input signal. To do this, in the following filter, which contains series-connected input shaper of square pulses, a band-pass filter with controlled resonant frequency and an output shaper of square pulses, the control input of the band-pass filter with controlled resonant frequency is connected to the output of the phase detector through a low-pass filter, one phase from the inputs of which is connected to the output input, and on the other to the output of the output rectangular pulse shapers, the schun is switched on parallel to the output of the low-pass filter The switching key between the output of the output square-wave pulse former and the control input of the key is connected in series with the pulse-driver and the coincidence element, the other input of which is connected to the output of the second polar-pulse generator.

The drawing shows a structural electrical circuit of the proposed device.

The following filter contains an input shaper I of rectangular pulses, a band-pass filter 2, with a controlled resonant frequency, an output shaper of 3 rectangular pulses, a phase detector 4, a low-pass filter 5, an element 6 of coincidence, a shaper of 7 pulses, a bypass switch 8.

The following filter works as follows.

The input shaper 1 generates rectangular pulses of the input frequency, which are fed to the band-pass filter 2 and to the input of the phase detector 4. From the output shaper 3, the pulses go to the second input of the phase detector 4 and to the input of the shaper 7 pulses. A voltage proportional to the phase mismatch of the output signal from the input signal, separated by the phase detector 4, which tunes the bandpass filter 2 to the input frequency, is transmitted to the control input of the low pass filter 5. the input element b pulses from the output shaper 3 and from the shaper 7 pulses. The duration of the pulses at the input of the driver 7 pulses is selected from the condition: /

Bc / -r-t

j.t ver

where t ver; (- upper limiting frequency of the filter operating range. - When setting the tracking filter to the second harmonic of the input signal, i.e. when the frequency of the pulses arriving at the pulse shaper 7 is shorter than the duration of the pulses being generated, simultaneously to both inputs element 6 pulses from the output shaper 3 and shaper 7 pulses.

When element 6 is triggered, the signal from its output goes to the bypass switch 8, which “zeroed the low-pass filter 6, which results in the rearrangement of the band-pass filter 2 to the lower limit of the operating range. After the termination of the signal from element 6, the voltage at the output of low-pass filter 5 begins to increase from a constant filter time from zero to a voltage corresponding to the setting of the band-pass filter 2 to the first

input harmonic. Since the zeroing of the low-pass filter 5 occurs on the leading edge of the signal from element b, the pulse duration from element b does not affect the effect of tuning. 5 The feasibility of the following filter is to reduce the likelihood of tuning to the second harmonic of the input signal.

Claims (1)

Invention Formula A trailing filter containing series-connected input shaper of rectangular pulses a filter with a controlled resonant frequency and an output shaper of rectangular pulses, while the control input of a bandpass filter with a controlled resonant frequency is connected via a low-pass filter to the output of the phase detector, one of the inputs of which is connected to the output of the input, and the other to the output of the formers rectangular pulses, characterized in that, in order to reduce the likelihood of tuning to the second harmonic of the input signal, a bypass switch is connected parallel to the output of the low-pass filter, you have a rectangular pulse shaper and the control input of the switch are connected in series and the coincidence pulse shaper element, the other input of which S9edinen yield a second straight -mougolnyh pulse shaper. Sources of information taken into account in the examination Mr. Coordon Deboo, Roger S. Hedlund. “Automatically tuned filter uses 4C operational amplifiers EDN / EEE, Fab., 1, 1972 (prototype).