SU1383227A1 - Amplitude modulation factor calibrator - Google Patents

Abstract

The invention relates to a radio metering technique and can be used to test and certify various types of measuring means, for example, amplitude modulation coefficient meters. The invention enhances the accuracy and speed of reproduction of calibrated amplitude modulation values by automating the calibration processes and eliminating operator errors. The device contains a modulating voltage generator 1, a modulating voltage divider 2, an amplitude-modulated signal generator 3, an input 4, a control unit 5, an electronic switch 6, an amplitude modulated signals receiver 7 mixer 8, an oscillator 9, an intermediate frequency amplifier 10 with an automatic system gain control, amplitude-modulated signal detector, 12 low-pass filter, peak detector 13, block 14, containing a signal switch 15, analog-to-digital converter 16, computational block 17 with the memory unit, a digital to analog converter 18. The figure also shows the wideband detecting section 19 and generator 20 modulated pulses. 2 Il. (g (L 00 00 oo y to

Description

The invention relates to a radio metering technique and can be used to calibrate and certify various types of measuring instruments, in particular, modulation amplitude coefficient meters (modulometers).

The aim of the invention is to improve the accuracy and speed of the reproduced calibrated values of amplitude modulation coefficients by automating the calibration process and eliminating operator errors.

FIG. 1 is a block diagram of the deviceJ in FIG. 2 - stress diagrams at characteristic points of the device. The device contains a series-connected modulating voltage generator 1, a modulating voltage divider 2, and an amplitude-modulated signal generator 3 whose output 4 is a calibrator output, control unit 5, successively connected an electronic switch 6, an amplitude-modulated signal receiver 7, including Mixer 8, local oscillator 9, intermediate frequency amplifier 10 with an automatic gain control system, an amplitude modulated signal detector 11, low pass filter 12 and Ikovy detector 13.

The device also contains a serial circuit 14 consisting of a signal switch 15, an analog-digital converter 16 (ADC), a computing unit 17c with a pa block

m, digital-analog converter 18 (CDL), as well as a broadband detector section 19 and shaper 21 modulating pulses.

The device works as follows.

The control unit 5 by means of control signals on the control inputs of the generator 1, splitter 2, generator 3, local oscillator 9 receiver 7, signal switch 15, computing unit 17c by the memory block and modulating pulse generator 20 sets the selected parameters and operating modes of the device, and also the timing of all nodes.

The required input of the modulating frequency is set at the control input of generator 1, and

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The input of divider 2 is set to the required value of the amplitude modulation factor. In the 3 AM signal generator and the local oscillator 9, the control inputs are used to simultaneously set the required carrier frequency of the amplitude-modulated signal and the frequency of the local oscillator 9, corresponding to the fine tuning of the receiver 7, on the generator frequency 3.

The time calibrator's operation can be conventionally divided into two stages. In the first stage, the transmitter gain coefficient 7 is measured by an amplitude-modulated signal with an amplitude modulation factor of M-100% and. envelope type meander. At the same time, the cri-j nusoidal signal (Fig. 2a) -c of the generator 1 is fed to the input of the modulating pulse generator 20, where a square-wave signal is formed (Fig. 26). This signal is fed to the control input of the electronic switch 6. The signal input of the switch 6 receives the unmodulated carrier signal from the generator 3. In the first stage, the divider -2 is turned off by the control signal 6 from the control unit 5, i.e. it sets the value of the amplitude modulation factor M0. At the output of the electronic switch 6, a sequence of radio pulses is generated with a meander-type envelope (Fig. 2c). With a sufficient attenuation of the signal in the pause (Fig. 2, b, c, time interval t, - 12, a radio pulse signal of the form (Fig. 2c). Has a peak value of the amplitude modulation factor M 100%. For example, with attenuation

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SRI signal in the pause

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The -70 dB error of the amplitude modulation coefficients in the signal (Fig. 2c) will be LM 0.03%. After the electronic switch 6, the radio pulse signal is fed to the input of the receiver 7, where using a mixer 8 and the local oscillator 9 is converted to a constant and relatively low intermediate frequency. In the intermediate frequency amplifier 10, the radio pulse signal is amplified to a level that provides linear detection, and is then fed to an amplitude detector 11,

where detected. At the output of the filter 12, an amplitude-modulated signal envelope is selected, the amplitude of which is converted by the peak detector 13 into a constant voltage proportional to the magnitude. Further, this constant voltage through the signal switch 15 is fed to the input of the analog-digital converter 16. and where it is converted into a digital code. Information about the value of the constant voltage in the digital code is fed to the computing unit 17c by the memory unit, where it is written to the memory unit by the command of the control unit 5. This completes the first step of the calibrator. At the second stage, the amplitude modulation coefficient is measured at the output of the generator 3 at its Sinusoidal modulation and the automatic adjustment of the amplitude modulation coefficient to a value of M 100%. To do this with

unit 5 and divider 2 switch on the transmission coefficient corresponding to 100%, and the modulating pulse driver 20 is switched to the constant control voltage shaping mode J. at which the electronic switch 6 is permanently open for the input signal. At the exit

The generator 3 will form an amplitude-modulated signal with a sinusoidal envelope (Fig. 2d) and an amplitude modulation factor M X in the general case close, but not equal to 100%. This signal through an open electronic switch 6 is fed to the input of the receiver 7 and further after detection - to the A / D converter 16, where the same operations are performed on it as for the radio pulse signal in the first stage.

The magnitude of the sinusoidal envelope of the amplitude-modulated signal in the digital code from the ADC 16 is fed to the computing unit 17c by the memory unit, it compares the amplitudes of the envelope of the meander type and sinusoidal envelope and generates an error signal proportional to the difference of the amplitudes of the envelopes in the digital code. measured in the first and second stages, i.e. proportional to the difference in MX from 1QO% o The error signal is fed to the digital-to-analog converter 18, above.

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An analog signal outputting in the form of a constant voltage proportional to the error signal. The signal from the output of block 14 is fed to the control input of generator 1, the amplitude of the modulating voltage of which varies in such a way that the amplitude modulation factor at the output of generator 3 becomes exactly 100%. This completes the calibration. Divider 2 is used to crawl the calibrated values of amplitude modulation j factors other than 100%. The computing unit 17 is switched to the memory mode and a constant output voltage level corresponding to the calibration time M 100% is fixed at the output of the DAC 18.

When changing the modulating frequency in generator 1, the calibration cycle is repeated as described above.

At high modulation frequencies (usually F 7 20 kHz), the path of the receiver 7 can introduce significant frequency and phase distortions into the envelope of the amplitude-modulated signal of the square wave type. As a result, the error in reproducing the calibrated values of the amplitude modulation coefficient may increase. To prevent this, a wideband detector section 19 is used in the device (Fig. 1).

When a high modulating frequency (F 20 kHz) is installed in the device, the DC voltage from the output of the wideband detector section 19 is proportional to the amplitude of the modulating voltage on the modular input of the generator 3, through com1 1. The 15-signal torus is fed to the ADC 16. The information on the magnitude of the modulating voltage in the digital code from block 16 is fed to the computing unit 17c by the memory block. It triggers the amplitude of the modulating voltage of the alternating modulating frequency with its value at low modulating frequencies (information about the value of the modulating voltage and low frequencies is recorded in the memory of block 17 during calibration at low modulating frequencies) and an error signal is generated, - a portion of the difference amplitudes. This error signal, through DCA 18, is the stabilization of the level of the output voltage of generator 1 at the input of generator 3.

In this way, the device is used to calibrate the amplitude modulation factor M 100% at high modulating frequencies. In this case, the frequency error of reproduction of calibrated values of the amplitude modulation coefficient, in the device, is actually determined only by the frequency distortions in the modulating path, generator 3 of the amplitude modulated signal. This error, with the proper choice of the parameters of the generator circuit, can always be made very small.

Claims (1)

Invention Formula Amplitude modulation coefficient calibrator containing a modulated voltage generator connected in series, a modulating voltage divider and an amplitude modulated signal generator, and a control unit whose outputs are connected to the control inputs of the modulating voltage generator and the amplitude generator -modulated signal, characterized by the fact that, in order to increase accuracy and speed, in addition, ktronny switch and the receiver of the amplitude-modulated signal, comprising a mixer, to which the second entry under five 0 five 0 five A local oscillator is connected, and serially connected intermediate frequency amplifiers with an automatic gain control system, an amplitude-modulated signal detector, a low-pass filter and a peak detector, the output of which is a receiver output, is a serial circuit consisting of a signal switch, analog a digital converter, a computational unit with a memory unit and a digital-analogue converter, a wide-band detector section and a shaper of modulating-current pulses, with input and the amplitude-modulated signals are connected via an electronic switch to the generator output of amplitude-modulated signals, the output of the receiver of amplitude-modulated signals is connected to the first input of the signal switch, whose second input is connected to the modulating input of the amplitude-modulated signal, the output the serial circuit is connected to the control input of the generator of modulating voltage, the output of which, in turn, is modulating via the driver x pulses is coupled to a control input of the electronic vykt lyuchatel, and respective outputs of the control unit are connected with the control input signal switch, the computer unit with a memory unit, and the pulse generator modulating the local oscillator of the receiver of the amplitude-modulated signals. .2