SU866510A1 - Method of checking s-curve of radio engineering devices with frequency detectors - Google Patents

Description

The invention relates to radio engineering measurements, in particular, to methods for tuning and checking parameters of radio devices, to methods for controlling the symmetry of the demodulation characteristic (5-curve) of devices with frequency detectors, and can be used to configure and verify such devices in serial and mass production.

There is a method for controlling the symmetry of the $ -curve of radio devices with frequency detectors, which consists in calculating the desired parameter by the characteristic of the frequency detector, obtained by taking and plotting the dependence of the DC component of the voltage at the output of the frequency detector on. frequency of the voltage supplied to the input of the C1J device. .

There is also a known method for controlling the S-symmetry of a radio engineering device with frequency detectors, in which this parameter is controlled directly by. the oscillogram S — a curve obtained by applying to the input ^{0 of the} device under test a harmonic test signal that automatically changes in frequency in a given range of G21.

However, this method has a high complexity, which entails a decrease in the accuracy of tuning and verification, especially in conditions of mass and mass production. The increased complexity is due to the fact that this method does not give a direct readout of the measured parameter, but requires measuring the magnitude of the upper and lower (relative to the 'zero * line) halves of the 5-curve with the subsequent calculation of the desired parameter. In mass and mass production, stencils applied to the oscilloscope screen are used to reduce the complexity associated with the need for calculations, but this does not solve the problem as a whole, since instead of calculations, additional operations 866510 have to be performed related to adjusting the oscilloscope sensitivity and position zero * ”howl line 5 — curve relative to the stencil.

The purpose of the invention is to increase the accuracy of tuning-control operations in serial and mass production.

This goal is achieved by the fact that in the method of controlling the symmetry of the 6-curve radio engineering devices with frequency detectors, which consists in supplying a test signal to the input of the device and measuring the result of exposure at the output, a noise signal is used as a test signal, and the symmetry control of the 5-curve is carried out by the difference between the constant components at the output of the frequency detector, measured with a closed and open input of the device.

In this case, the obtained difference in the constant components is proportional to the difference in the area of the figures formed by the upper (P1) and lower (P2) halves of the S curve, i.e., up to a constant coefficient, the direct value is deducted as follows. The input of the tested device with the help of a switching device is alternately connected to the noise generator and to the 'case 5' of the device. At the same time, pulses appear at the output of the frequency detector of the imputed device, one vertex of which corresponds to a closed input, i.e. potential of the 'zero' line, and secondly, the deviation of the constant component from the potential of the 'zero * line under the influence of a noise signal. The amplitude of the pulses (A) at the output is directly proportional to the value of the desired asymmetry parameter ts of the 5-curve.

In FIG. 1 shows the waveforms of the test signal at the input of the device (a), the output signals of the frequency detector with an asymmetric (b, c) and 20 symmetric (d) 5-curve; in FIG. 2 is a structural diagram of connecting equipment for tuning and checking the symmetry of the B-curve.

The symmetry control of the s-curve in the process of tuning and checking is carried out as follows.

The desired parameter.

When the input of the device is shorted to frequency detectors, the output of the latter establishes a certain potential equal to the potential of the 'zero' line of the 5-curve, and there are noises due to the intrinsic noise of the device.

When a signal from a noise generator having a uniform noise spectrum in the region of the studied S-curve is applied to the input of the device, a signal consisting of a variable component, which is—, appears at the output of the frequency detector; as a result of one-time fluctuations of noise components, and a constant component, the value of which is all the more different from the potential of the 'zero * line of the © -curve; the more different is the area of the figures formed by the 'zero' line and the upper and lower halves of the “3-curve, ie ;. the greater the asymmetry.

By measuring the difference between the constant components at the output of the frequency detector, we obtain the exact value of the desired parameter - the asymmetry of the S-curve.

Moreover, the measuring device can be calibrated in units of asymmetry (%).

In conditions of serial and mass production, the process of switching the input of the tested device and measuring the difference of the constant components at the output

The signal from the noise generator 1 through a switching circuit consisting of an electric switch 2 and a pulse generator 3 is fed to the input of a tunable or verified device 4. An oscilloscope or voltmeter 6 connected to asymmetry units or having marks of acceptable asymmetry is connected to the output of device 4 through a low-pass filter 5 .

Using the tuning elements of the device to be tuned, they achieve the minimum (permissible) signal span observed on the oscilloscope screen or measured with a voltmeter.

Claims (2)

1. Sorkin I. M. Fundamentals of radio metering technology. M., Energie, 1976, with. 295-296. 2. Soboevsky, A. G. Measurements in radio equipment. M ,, Military Publishing, 1961. with. 168. Pi-PZ70 pi V g, TT BUT Pl-pz o   0 FIG.