RU140482U1 - PULSE-PHASE DISCRIMINATOR - Google Patents

Abstract

A pulse-phase discriminator comprising a phase comparison unit and a sampling-storage unit, the inputs of the phase comparison unit are connected to the sources of the reference and controlled frequencies, an RC isolation circuit, the input of which is connected to the output of the phase comparison unit, the output of the RC isolation circuit is connected to the information input sampling-storage unit, and the control input of the sampling-storage unit is connected to a source of controlled frequency, characterized in that, in order to improve the accuracy of demodulation of the output pulse-width modulator of the input signal, the second sampling-storage unit and a computing device are introduced, the information input of the second sampling-storage unit is connected to the output of the first sampling-storage unit, the control input of the second sampling-storage unit is connected to a source of controlled frequency, the first summing input of the computing device is connected to the output the second sampling-storage unit, the second summing input is connected to the output of the first sampling-storage unit, the input of the low-pass filter is connected to the output of the computing device, the output which is the output of the pulse-phase discriminator.

Description

The utility model relates to the field of automation and computer technology and can be used as a logical element for comparing the pulse repetition rate of the master oscillator, which determines the engine speed in discrete astatic electric drives, and the pulse repetition rate of the feedback sensor located on the motor shaft, as well as in other phase synchronization systems.

Known pulse-phase discriminator (Bubnov A, B, Questions of theory and design of precision synchronous common-mode DC electric drives: Monograph - Omsk, 20005. - S. 151-153), containing a logical comparison device, a functional converter and a sample-storage unit, moreover, the inputs of the logical comparison device are connected to the terminals of the sources of the controlled and reference frequencies, and the output is connected to the control input of the functional converter, the measuring input of the functional converter is connected to move the sample-and-hold unit, which is an output device, a control input of the sample-storage is connected to the terminal reference frequency source, and measuring input connected to the output of the function converter, wherein the function generator may be configured as a series-connected voltage adder and the integrator.

The disadvantage of this device can be considered a narrow range of compared frequencies due to the presence of the dependence of the transient conversion process on the change in phase error and the ratio of the quantization period T _e to the integrator time constant T.

The closest technical solution to the claimed device is a pulse-phase discriminator (AS USSR No. 1688381 class. H03T) 13/00, 1991) containing a phase comparison unit, an RC isolation circuit and a sampling-storage unit, the inputs being the phase comparison unit is connected to the terminals of the sources of the reference and controlled frequencies, and the output through the RC isolation circuit is connected to the information input of the sample-storage unit, the control input of which is connected to the terminal of the source of the controlled frequency, and the output of the sample-storage unit is the output of the device, while the sample-storage unit consists of a storage unit and a pulse shaper, while the first input of the storage block is the information input of the sample-storage block, and the second input is connected to the output of the pulse shaper, the input of which is the control input of the sample-storage block, and the output of the fetch-storage unit is the output of the storage unit.

The disadvantage of this device is the presence of an error in the measurement of the phase mismatch of the controlled f _to and the reference f _e frequencies, manifested in the time delay of the discriminator output signal.

The technical result of the utility model is to increase the speed of demodulation of the output pulse-width modulated signal.

The specified technical result is achieved by the fact that in the known pulse-phase discriminator containing a phase comparison unit, the first and second inputs of which are respectively the first and second inputs of the pulse-phase discriminator, the output of the phase comparison unit through an RC isolation circuit is connected to the information input of the sample unit -storage, the control input of which is connected to the second input of the phase comparison unit, according to the claimed technical solution, the second sampling-storage unit is introduced and calculate device, while the information input of the second sample-storage unit is connected to the output of the first sample-storage unit, the control input of the second sample-storage unit is connected to a source of controlled frequency and the output is connected to the first input of the computing device, in addition, the second input of the computing device is connected to the output of the first sampling-storage unit, while the output of the computing device is the output of the device.

The essence of the technical solution is illustrated by drawings, where in FIG. 1 shows a functional electrical diagram of the proposed device, FIG. 2 shows the timing diagrams of the pulse phase discriminator.

The pulse-phase discriminator comprises a phase comparison unit 1, an RC isolation circuit 2, sample-storage units 3 and 4, and a computing device 5.

The first and second inputs of the phase comparison unit 1 are the first and second inputs of the pulse-phase discriminator and are connected respectively to the sources of the reference f _e and the controlled f _{to the} frequencies. The output of the phase comparison unit 1 through an RC isolation circuit 2 is connected to the information input of the sample-storage unit 3, the control input of which is connected to the terminal of the source of the controlled frequency f _to . The information input of the fetch-storage unit 4 is connected to the output of the fetch-storage unit 3, the control input of which is connected to the terminal of the source of the controlled frequency f _to , and the output is connected to the first input of the computing device 5, the second input of which is connected to the output of the fetch-storage unit 3. The output of the computing device 5 is connected to the input of the low-pass filter 6, the output of which is the output of the pulse-phase discriminator.

The pulse phase discriminator operates as follows.

The pulses of the reference f _e and the controlled f _{to the} frequencies are fed to the input of the phase comparison unit 1. The phase comparison unit 1 generates a sequence of pulses whose repetition period is equal to the period T _{e of the} reference frequency, and the duration is proportional to the phase mismatch of the compared frequencies. If the parameters of the RC isolation circuit 2 are selected so that

, где

where

R is the resistance of the RC isolation circuit;

C is the capacitance of the RC isolation circuit; then the isolation circuit does not distort the input waveform, as its frequency lies behind the cutoff frequency of the transfer function of the RC circuit (USSR AS No. 1688381 class. H03B 13/00, 1991). In this case, the constant component in the output signal is U _p . a dividing circuit 2 is absent and the amplitude of the negative pulse U _{2 of the} output signal is equal to the average voltage of the input signal over a period

where U _cf is the average voltage at the output of the phase comparison unit;

U is the amplitude of the output pulses of the phase comparison unit;

τ ₁ - the duration of the output pulses of the phase comparison unit;

T _e - the period of the output pulses of the phase comparison.

Since the DC component in the output signal of the RC isolation circuit is absent, then

From here

Substituting (2) in (4), we obtain

.

.

The output signal of the RC isolation circuit 2 is fed to the information input of the sample-storage unit 3, in which the amplitude of negative pulses U _{2 is} stored along the leading edge of the pulses of the controlled frequency. Thus, a step voltage U _i is formed at the output of the sample-storage unit 3, from which a slowly changing component U _Ф proportional to the phase mismatch Δφ (U _ВХ ) of the compared pulse sequences can be extracted using a low-pass filter.

In transient conditions, Δφ is a variable, as a result of which a step voltage U _i is formed at the output of the sample-storage unit 3, from which a slowly changing component U _Ф proportional to the phase mismatch Δφ (U _ВХ ) of the compared pulse sequences can be extracted using a low-pass filter, but having a time delay τ _s approximately equal to half the period of the reference frequency (Fig. 2). To exclude the time delay, a second sampling-storage unit 4 and a computing device 5 are introduced. Information from the first sampling-storage unit 3 corresponding to the previous value of the phase error is copied to the second sampling-storage unit 4 along the leading edge of the pulses of the controlled frequency, and the output is generated voltage U _i-1 (Fig. 1).

The output signals of the sample-storage blocks 3 and 4 are fed to the first and second inputs of the computing device 5. The output signal of the computing device is formed in accordance with the expression:

,где

,Where

U _i is the output signal of the first sampling-storage unit (output signal of the closest technical solution to the claimed device);

U _i-1 is the output signal of the second sampling-storage unit.

In this case, the output signal of the first sample-storage block U _i is adjusted by an amount equal to half the difference between the present U _i and the previous U _i-1 values of the output signal of the demodulator.

The low-pass filter allows you to select from the step signal U a slowly changing component proportional to the phase error of the compared frequencies.

As a result, the time delay present in the output signal U _{Φ of the} known device is eliminated in the output signal of the pulse-phase discriminator.

This allows you to improve the quality of demodulation of the output pulse-width modulated signal of the pulse-phase discriminator, through the use of a correction signal proportional to the difference between the present and previous values of the output signal of the demodulator.

Claims (1)

A pulse-phase discriminator comprising a phase comparison unit and a sampling-storage unit, the inputs of the phase comparison unit are connected to the sources of the reference and controlled frequencies, an RC isolation circuit, the input of which is connected to the output of the phase comparison unit, the output of the RC isolation circuit is connected to the information input sampling-storage unit, and the control input of the sampling-storage unit is connected to a source of controlled frequency, characterized in that, in order to improve the accuracy of demodulation of the output pulse-width modulator of the input signal, the second sampling-storage unit and a computing device are introduced, the information input of the second sampling-storage unit is connected to the output of the first sampling-storage unit, the control input of the second sampling-storage unit is connected to a source of controlled frequency, the first summing input of the computing device is connected to the output the second sampling-storage unit, the second summing input is connected to the output of the first sampling-storage unit, the input of the low-pass filter is connected to the output of the computing device, the output which is the output of the pulse-phase discriminator.

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