SU960660A1 - Phase calibrator - Google Patents

Description

The invention relates to a measuring technique and can be used to accurately set the phase shift during testing, adjustment and calibration of phase-measuring and phase-generating equipment of the audio frequency range.

A device is known that allows discrete adjustment of a phase by a large number of bits.

The principle of operation of this device lies in the weight summation of pulses of the same frequency and different squares. As a result, a square wave signal is generated at the output of the reference phase channel and a stepwise pyramidal signal at the channel output of phase variables. At the output of each channel, there is an output filter that extracts a sinusoidal signal from. signals of the specified form 1.

Since the voltage at the output of the channels contains all even and odd harmonics, it is necessary to apply complex filters with a high slope of the frequency response in order to isolate a sinusoidal voltage with a low harmonic coefficient.

The difference in phase characteristics of the output filters in the frequency band determines the magnitude of the additional phase error of the device.

The closest to the technical essence of the invention is a phase ultrasound frequency librator, which contains a code master, low pass filters at the output of the variable and reference phase channels, a source of reference voltages, and a clock generator.

The shape of the voltage at the output of each channel is a step-sine wave, i.e. Linear-step approximation of the sinusoidal function is used in this device. With the number of steps during a period of sinusoidal voltage generated, equal to 360, the first of the higher harmonics will be a harmonic of about 359. Such

25, the composition of the harmonics greatly facilitates the filtering conditions of higher harmonics, and the output filters operate on the gentle part of the phase-frequency characteristic. The phase difference of the frequency characteristics of the filters remains almost constant in the working frequency band and can easily be eliminated by adjusting one of the filters 2. A disadvantage of the known phase calibrator is the need to distinguish the conversion factor of the counters with increasing number of bits. The phase adjustment discrete is 1. To reduce this value to 0.1 °, it would be necessary to increase the number of possible conditions to 3600, and the frequency of the clock generator 10 times. The upper limit frequency is thus limited by the speed of the elements, therefore an increase in the number of bits leads to a narrowing of the frequency range. The disadvantage of this phase calibrator is also the use of output attenuators to control the amplitude of the output voltages. In this case, strict requirements are imposed on the magnitude of the resistance and the capacitance of the load, which must be the same for each channel; otherwise, additional phase error arises. The aim of the invention is to reduce the magnitude of the discrete setting of the phase shift without narrowing the frequency range and improving the accuracy of controlling the phase shift. This goal is achieved by the fact that, in a phase calibrator containing low-pass filters, a setpoint of the code, a source of reference voltages, a clock pulse generator, the output of which is connected to the input / output of two identical variable and phase channels, each of which contains a digital signal -analog converter, the counter whose input is the channel's channel, the counter outputs are connected to the control inputs of the digital-analog converter, and the output of the digital-analog converter of the phase reference channel is connected to the input of the low-pass filter and the power inputs are connected to the outputs of the voltage source, an additional variable phase channel is added that has a common phase with the main channel, a phase variable counter, three code converters - one per each channel, between the outputs of the counter and the digital-analog outputs converter, three discrete-controlled adders, the control inputs of which are connected to the first outputs of the code setter, the transmission unit of the code, the control and information inputs of which are connected respectively to the output of one-channel ora and with the second outputs of the code master, and the outputs are connected to the installation inputs 1 of the variable phase channel counter, as well as an additional source of reference voltages connected to the power inputs of the digital-analog converters of the variable phase channels, the output of the main channel of the variable phase being connected to the first, and the output of the additional channel with the second inputs of two adders, the outputs of which are connected to the inputs of the third adder, and the output of the latter, is connected to the input of the second low-pass filter, and the input is one-shot connected to a respective output kodopreobrazovatel kaNs1la reference phase input and installation of the reference phase counter, wherein the control inputs of the reference voltage sources are connected to additional outputs of the set point code. The drawing shows a block diagram of a phase calibrator. Phase Calibrator contains a generator. 1 clock pulses, the output of which is connected to the inputs of counters 2 and 3. The inputs of the encoder 4 are connected to the outputs of counter 2, a. the outputs are connected to the control inputs of the digital-to-analog converter 5, to the output of which the input of the low-pass filter 6 is connected. Counter 2 code converter 4 and digital-to-analog converter 5 form the channel 7 of the reference phase. The main channel 8 of the variable phase contains a counter 3, a code converter 9 and a digital-to-analog converter 10. An additional channel 11 of the variable phase contains a counter 3, a ko + di-converter 12 and a digital-analog converter 13. The outputs of the counter 3 are connected to the inputs of code converters 9 and 12, the outputs of which are connected to the control inputs of the D / A converters 10 and 13, respectively. The source 14 of the reference voltages are connected to the power inputs of the D / A converter 5, and the power inputs of the D / A converters Formers 10 and 13 are connected to the outputs of the source 15 of the reference voltages. The installation inputs of the counter 3 are connected to the outputs of the code transmitting unit 16, the control input of which is connected to the output of the one-vibrator 17, and the information inputs are connected to the second outputs of the setting unit 18 of the code. The first outputs of the dial 18 of the code are connected respectively to the control inputs of the discretely controlled adders 1921. The outputs of the digital-to-analog converters 10 and 13 are connected respectively to the first and second inputs of summators 19 and 20, and the outputs of the latter are connected to the inputs of the adder 21, the output of which is connected to the input of the low-pass filter 22.

In addition, the installation inputs of the counter 2 are combined and connected to the output of the one-shot 17, and the control source inputs: 14 and 15 of the reference voltages are connected to the additional outputs of the code setter.

The outputs of the phase calibrator are the low and high frequency filter outputs b.

The principle of the phase calibrator is to form three quasi-sinusoidal stresses, one of which is the reference, and the phase of the other two changes discretely so that the phase difference between them remains constant. These two voltages are summed with weights depending on the younger phase shift bits. As a result, a variable phase voltage is generated.

The device works as follows.

The pulses from the generator output 1 clock pulses arrive at the input of channels 7, 8 and 11 of the reference and variable phases. The parallel code from the outputs of counters 2 and 3 is fed to the inputs of the corresponding code converters 4, 9 and 12, the output of which forms a parallel code fed to the control inputs of the digital-analog converters 5, 10 and 13. The bi-polar reference voltages are fed to the power inputs of the latter wives

As a result, the output of each channel is formed by a step-sinusoidal voltage, the amplitude of which is determined by the amplitude of the reference-voltage converter supplying the digital-analog converter. The step width is determined by the repetition period of the clock pulses, and the number of steps per hour, and the period of the generated voltage is equal to twice the conversion factor of counters 2 and 3. Code converters

9 and 12 are connected to the outputs of the counter 3 in such a way that the code combinations at their outputs lag one behind the other by one measure. This means that with a counter conversion factor of 18, the phase shift between the voltages at the output of channel 8 and channel 11 is constant 10. The phase shift of these voltages relative to the reference voltage at the output of channel 7 is determined by the high-order code arriving at the information inputs of the node 16 transmission code from the corresponding outputs of the unit 18 code. At the time point corresponding to the moment of the reference voltage transition from a negative to a positive value, a positive pulse appears at the input of the one-vibrator 17. The output of the code converter 4 receives a positive voltage drop, and a single pulse appears at the output of the one-vibrator allowing the writing of the code of the higher phase shift bits in counter 3. ntH, using Johnson counters may fail, so simultaneously with writing the code to counter 3, the pulse from the output of the one-shot sets counter 0 into 2.

The voltages from the outputs of the digital-to-analog converters 10 and 13 are used to form a variable-phase voltage, the discreteness of the phase change being determined by the discreteness of the change in the total summation coefficients. The weighting factors, which are summed by the named voltages in the sum: mator 19, vary according to the law

0

de i Oh, 1, ..., 9.

For adder 20, similar dependencies are

JiO-i)

5ln

1ВО

.

L

S-in 19

The phases of the first harmonics of the voltages at the outputs of the adders 19 and 20 differ by 1 °. These stresses are summed with the weight coefficients sl3 (l in adder 21, and

B, (

The value of k varies linearly from 0 to 1 with a given resolution. The phase shift of the voltage at the output of the adder 21 relative to the reference voltage is determined by the expression

f - ().

Here, the value of m is determined by the code recorded in the counter 3, i, and k depending on the size of the code fed to the control inputs of the adders 19-21.

The amplitude of the output voltages is determined by the magnitude of the reference voltages. To adjust the amplitude, the sources of the reference voltages can be made controllable from the set point of the code. This makes it possible to exclude weekend attenuators.

The phase error of the phase calibrator is mainly determined by the speed and code converters.

Claims (2)

The use of the proposed phase calibrator, in comparison with the known devices, provides the ability to adjust the phase shift with any given number of bits without narrowing the frequency range, as well as the possibility of adjusting the amplitude of the output voltages of the additional phase error due to the exclusion of output attenuators. Claim 1. A phase calibrator containing low-pass filters, a code setter, a reference voltage source, a clock generator, the output of which is connected to the inputs of two identical variable channels and a phase reference, each of which contains a digital-analogue converter, whose input counter is the channel input, the counter outputs are connected to the control inputs of the digital-to-analog converter, and the output of the digital-to-analog converter to the phase reference current is connected to the input of the filter, low frequencies, and The inputs are connected to the outputs of the source of reference voltages, characterized in that, in order to reduce the magnitude of the phase shift reference without reducing the frequency range and to control the phase shift control accuracy, an additional variable phase channel is added to it that has a common variable phase channel a counter, three code converters, one for each channel, between the outputs of the counter and the control inputs of the D / A converter, three discretely controlled adders, the control inputs to connected to the first outputs of the code setter, the code transmission node, the control and informational inputs of which are connected respectively to the one-shot output and the second outputs of the code setter, and the outputs are connected to the installation inputs of the variable-phase channel counter, as well as an additional source of reference voltages connected to the power inputs of digital-to-analog converters of variable phase channels, the output of the main channel of the variable phase is connected first, and the output of the additional channel is connected to the second inputs two adders, the outputs of which are connected to the inputs of the third adder, and the output of the latter is connected to the input of the second low-pass filter, and the input of the one-oscillator is connected to the corresponding output of the code converter of the reference phase channel and the installation input to O of the reference phase channel counter. 2. Calibrator according to claim 1, characterized in that the control inputs of the sources of reference voltages are connected to the additional outputs of the code setter. Sources of information taken into account during the examination 1. USSR author's certificate No. 229058, cl. G 06 J, 1968. 2. USSR author's certificate number 570852, cl. G 01 R 25/04, 1977.