SU1691784A1 - Meter of accompanying deviation of frequency of amplitude-modulated oscillation - Google Patents

Abstract

The invention relates to a radio metering technique, in particular, to devices for measuring the distortion of modulated oscillations. The purpose of the invention — improving measurement accuracy — is achieved by introducing a reference pulse generator, a pulse counter, three permanent memories, a digital-to-analog converter, two multiplying digital-analog converters, two low-pass filters, a dual two-channel analog demultiplexer, four storage units , two arithmetic units, two-channel analog multiplexer, voltmeter effective voltage value, two control pulse generators, single bratora control unit and the local oscillator. In addition, the meter contains an amplitude modulated oscillator, a mixer, a frequency modulated receiver, and a local oscillator. 1 il. (Ls

Description

The invention relates to a radio metering technique, in particular, to devices for measuring the distortion of modulated oscillations, and can be used to certify standard signal generators and to improve their quality.

The purpose of the invention is to improve the measurement accuracy ..

The drawing shows a structural diagram of the proposed meter. The circuit includes a reference pulse generator 1, a pulse counter 2, the first 3, the second 4 and the third 5 permanent storage devices, a digital-to-analog converter 6, the first 7 and second 8 multiplying digital-to-analog converters 9, an amplitude-modulating generator 9, a mixer 10, FM receiver 11, local oscillator 12, first 13 and second 14 low-pass filters, dual dual-channel analog de-multiplexer 15, first, second, third and fourth sample storage blocks 16-19, arithmetic blocks 20, 21, dual-channel analog multiplexer 22, vol 23 meter effective voltage value, the first 24 and second 25 control pulse generator, a monostable multivibrator 26, the control unit 27, the local oscillator.

The meter works as follows.

In the pulse counter 2, a linearly increasing code is generated using the reference pulse generator 1. When the counter overflows, it is automatically reset, i.e. the exit code

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the pulse counter is periodic. The frequency division factor of the pulse counter 2 is chosen such that the repetition period of the linearly increasing code at its output is equal to the period of the modulating oscillation. In the permanent storage device 3, this code is converted into a harmonic code. In this case, the sine or cosine function (one period) is recorded in the persistent storage device 3. The digital-to-analog converter 6 converts the code into an analog harmonic signal, which is fed to the modulating input AM of the generator 9, where the test signal is generated. The mixer 10 performs frequency conversion of the AM test signal using a local oscillator 12. The FM receiver 1t tunes to the difference frequency between the signal and the local oscillator, selects and detects the transformed test oscillation in frequency. Since AM generator 9, mixer 10 and FM receiver 11 have amplitude-phase conversion, the useful amplitude modulation of the test oscillation is converted to accompanying frequency modulation with frequencies that are multiples of the modulating frequency AM oscillation, which is separated at the output of the FM receiver 11 The permanent memory devices 4 and 5 record the functions of the harmonics under study (as a rule, 2-3 harmonics are sufficient for the study), and in the ROM 4 the function of the sine is recorded, and in the ROM 5 the function of the cosine is written. In the device, the measurements are performed separately on each of the harmonics studied. At the same time, the functions of the sine and, sine of the harmonic under investigation are selected using the enable input to ROM 4 and 5. In multipliers 7 and 8, the output oscillation of the FM receiver 11 is multiplied by the sine and cosine functions of the harmonic under study. At the same time, the constant components of the voltages at the outputs of the multiplying digital-analogue converters 7 and 8 are directly proportional to the projections of the vector of the investigated harmonic to the orthogonal coordinate axes. These voltages are extracted using low-pass filters 13 and 14 and are recorded in sample storage blocks 1, 6, 18. Selection of storage units 16-19 sampling is carried out using a dual dual-channel analog demultiplexer 15. If the signal O is present at its address input, it connects the output of filter 13 to the input of block 16 and the output of filter 14 to the input of block 18. If address

Signal 1 is present at the input, it connects the output of filter 13 to the input of block 17 and the output of filter 14 to the input of block 18. The moment of voltage recording in blocks 16-1 $ is set by means of a single vibrator 26 connected to the enabling input of the demultiplexer 15.

The proposed meter allows you to measure separately the accompanying frequency deviation of the AM oscillation that occurs in the AM oscillator, mixer, transmission path and FM receiver. This uses the property of the frequency converter (mixer) to invert the law

5 of the frequency modulation of its input junction of the bath when it is tuned to the mirror channel.

When measuring the concomitant frequency deviation in the AM generator 9 using the 25 pulse generator and the heterodyne control unit 27, the frequency of the local oscillator 12 is switched to twice the input frequency

5 oscillations of the FM receiver 11, i.e., the mixer 10 is rearranged to the mirror channel. The same pulses from the output of the pulse generator 25 change the signal at the address input of the demultiplexer lexor 15, which in connection with this describes the switching of blocks 16-19. When the mixer 10 is rearranged to the mirror channel, the accompanying frequency modulation, occurring in AM generator 5, is inverted, and the accompanying frequency modulation, occurring in mixer 10 and FM receiver 11, remains unchanged; therefore, the difference of the vectors of the studied hermonics at two frequencies, the local oscillator 12 is equal to twice the magnitude of the accompanying frequency deviation arising in the AM generator 9. Voltages directly proportional to the projections of the vector of the harmonic to the orthogonal axes

5 coordinates at the first setting of the local oscillator 12, are recorded in blocks 16 and 18, and at the second setting of the local oscillator - in blocks 17 and 19, Known, the well-known rule of subtracting two vectors using their projections on orthogonal axes

0 coordinate allows to perform the required vector subtraction operation using arithmetic units 20 and 21, the output of which is proportional to the difference of the projections of the two vectors

5 investigated harmonics. Using a pulse generator 24 and a multiplexer 22, these voltages are alternately supplied to the input of an effective voltage value of the voltmeter 23. In this voltmeter, the voltage is alternately squared, their sum is integrated, the square root is extracted from the result, and the resulting value is displayed on the indicator. Thus, the rule of subtracting two vectors is realized and their voltage directly proportional to the frequency deviation arising from AM generator 9.

When measuring the concomitant frequency deviation arising in the FM receiver 11, the measurement process is similar to that described, except that the measured value is determined by adding the two vectors along their projections.

When measuring the concomitant frequency deviation in mixer 10 or the transmission path at the mixer output (assuming that the distortions introduced by the mixer are significantly less than the distortions of the path under test), the frequency modulation law is additionally inverted using a local oscillator 12 meter 11 frequency deviation, which must be tuned to the mirror channel at the same time as the local oscillator 12 is tuned. In this case, the associated frequency modulation. arising in AM generator 9, is inverted twice, i.e. remains unchanged, the attendant frequency modulation occurring in meter 11 of frequency deviation 11, as well as in mixer 10 (or transmission path), is inverted in mixer FM receiver 11. Therefore, the difference of two vectors at the first and second settings allows you to determine the measured value. In the afOM case, blocks 20 and 21 should be subtracted.

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A concurrent frequency deviation meter for amplitude-modulated oscillation, containing successively connected amplitude-modulated oscillator, mixer, and frequency-modulated receiver, as well as a local oscillator, the output of which is connected to the second input of the mixer, characterized in that. in order to increase accuracy, the reference pulse generator, the pulse counter, the first memory device and the digital-analog converter, the second permanent memory device, the first multiplier

a digital-to-analog converter and a first low-pass filter connected in series to a third permanent storage device, a second multiplicative digital-to-analog converter and a second low-pass filter, as well as a dual dual-channel analog de-multiplexer. four sample storage units, two arithmetic units, a series-connected dual-channel analog multiplexer and a voltmeter of the effective voltage value, two control pulse generators, a single-oscillator and a local oscillator control unit, the first and second outputs of which are connected to the frequency-modulated input, respectively receiver, the output of which is connected to the second inputs of the first and second multiplying digital-to-analog converters; the output of the second pulse generator control is connected to the input of the local oscillator control unit, to the address input of a dual dual-channel analog demultiplexer and through a one-vibrator to its enable input; the outputs of the first and second low-pass filters are connected to the first and second inputs of the dual dual-channel analog de-multiplexer, the first to fourth outputs, respectively which are connected to the inputs, respectively, of the first to fourth storage units of the sample, the outputs of the first and second storage units of the sample are connected respectively to the first and second at the inputs of the first arithmetic unit, and the outputs of the third and fourth storage units of the sample are connected respectively to the first and second inputs of the second arithmetic unit, the outputs of the first and second arithmetic blocks are connected respectively to the first and second inputs of a two-channel analog multiplexer, the address input of which is connected to the output of the second generator control pulses, the inputs of the second and third permanent storage devices are connected to the second output of the pulse counter, the output of the digital and th transducer is connected to the input amplitude- modulated oscillator

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Claims (1)

Claim. A meter for concomitant frequency deviation of amplitude-modulated oscillations, containing a series-connected amplitude-modulated oscillator, mixer, and frequency-modulated receiver, as well as a local oscillator, the output of which is connected to the second input of the mixer. characterized in that, with the aim of increasing accuracy, 45, a reference pulse generator, a pulse counter, a first memory device and a digital-to-analog converter, series-connected a second permanent memory, a first multiplier digital-to-analog converter and a first low-pass filter, connected in series with a third read-only memory, a second multiplier digital-to-analog converter and a second low-pass filter, as well as a double two-channel analog demultiplexer. four sample storage blocks, two arithmetic blocks, a two-channel analog multiplexer and an effective voltage voltmeter connected in series, two control pulse generators, a single vibrator and a local oscillator control unit, the first and second outputs of which are connected respectively to the local oscillator input and the second input of the frequency-modulated receiver, output which is connected to the second inputs of the first and second digital-to-analog converters, the output of the second control pulse generator connected to the input of the local oscillator control unit, to the address input of the dual two-channel analog demultipleik25 sora and through the single-vibrator to its enable input, the outputs of the first and second low-pass filters are connected respectively to the first and second inputs of the dual two-channel analog demultiplexer, the first and fourth outputs of which are connected to the inputs respectively, the first and fourth blocks of sample storage, the outputs of the first and second blocks of sample storage are connected 35, the terms respectively to the first and second input I will give the first arithmetic block, and the outputs of the third and fourth blocks of sample storage are connected respectively to the first and second inputs of the second arithmetic block, the outputs of the first and second arithmetic blocks are connected respectively to the first. and second inputs of the two-channel analog multiplexer, the address input of which is connected to the output of the second pulse generator control, the inputs of the second and third permanent storage devices are connected to the second output of the pulse counter, the output of digital-analog eob50 verters connected to the input amplitudnomodulirovannogo generator.