SU1743007A1 - Device for checking communication channel quality - Google Patents

Abstract

Use: radio, in the transmission channels of discrete signals. SUMMARY OF THE INVENTION: The device comprises a band-pass filter 1, a quad 2, a low-pass filter 3, two subtractors 4 and 5, a quad 6, a divider 7. a phase locked loop unit 8, a frequency multiplier 9, a phase shifter 10, a phase detector 11, an integrator 12, an adjustable amplifier 13. 1-8-9-10-11-5-12-13-2-3-4-6-7. 1-13. 1 il.

Description

if

o2 /

 KFD - + JP cos2 / - (pc, (8)

where QFD is the conversion factor of the phase detector 11c, taking into account the series connected circuit of amplifier 13, quad 2, phase detector 11), and high-frequency components corresponding to the fourth harmonic region. The second subtractor 5 is affected by the voltage of the phase detector ifd and the subtractive voltage EI. If the level of this voltage is Cfd A2 / 2, then the output of the subtractor 5 is left with only low-frequency components due to interference (the second and third terms of expression 8) and components corresponding to the fourth harmonic regions. Since the initial phases of ipn, these components are uniformly distributed, the averaging of all components by means of the integrator 12 leads to zero voltage and as a result, the control voltage at the output of the integrator 12 will be zero. If the amplitude of the FM signal changes, then the constant component in expression (8) will not be equal to Ei, i.e. subtractor output

5 permanent component will be excellent

from zero those. Us QFD (O2-1) A2 / 2. And averaging it by the integrator 12 will lead to the formation of a non-zero regulating voltage for the amplifier 13. In this case, the control characteristic of the amplifier 13 (dependence of the transfer coefficient of the amplifier on the level of the regulating voltage) must be such that the sign of the derivative q C / d Cr (Cr is the level of the regulating voltage equal to voltage

five

0

five

0

five

0

five

where Cfdp and Kfc, 2 are the values of the conversion coefficients, respectively, before and after the change of the amplitude of the FM signal by a times.

In this case, the level of the constant component of the low-frequency voltage at the output of the 2KqA2 / 2 quadrant will be stabilized. By means of the 3-LF filter, the low-frequency part of the quadrant 11kWh (5) is separated. A differential voltage is formed by the subtractor 4, which corresponds only to the noise level, since the subtractive voltage is supplied to the subtracting input, which corresponds to the signal level, and in this case the conversion factors Knf and Kf should be equal, i.e. КНчА2 / 2 Кфд Аг / 2. By filter 3, the interference component KNch A xn (t) cos (lp + - pn) is averaged and only the voltage component due to the interference envelope Kncf (t) / 2 remains. This component is proportional to the interference power that is filtered by the bandpass filter 1, a is its level averaged by the low-pass filter 3 By means of the square root extraction unit 6, a voltage proportional to the level of interference - in (t) Knc / 2 is formed. Since the level of the signal at the output of the quad is stabilized and is known as -KfA / 2, the constant voltage level Ea will be a voltage proportional to the level of the signal -A Cf / 2. and which is the voltage divisible for divider 7 signals. Thus, at the output of the signal divider 7, a voltage will be generated proportional to the ratio of the signal level to the noise level A-in (t) de-energized on the actual communication channel. And by the value of the level of this ratio, it is possible to judge the quality of the communication channel.

Claims (1)

Invention Formula A device for controlling the quality of a communication channel, containing a bandpass filter, whose input is an input of a device, a quad, a low-pass filter, first and second subtractors, a square root extraction unit, whose input is connected to the output of the first subtractor, a signal ratio divider whose output is Output of the device, characterized in that, in order to improve the measurement accuracy, serially connected phase-locked loop, frequency multiplier by two, phase shifter, phase detector, output d which is connected to the first input of the second subtractor, the subtracting input of which is combined with the subtracting input of the first subtractor and is the input of the first constant level signal, connected in series by the integrator, the input of which is connected to the output of the second subtractor, an adjustable amplifier, the second input of which is combined with the input of the phase-locked loop and is connected to the output of the bandpass filter, and the output of the adjustable amplifier is connected to the quad input, the output of which is connected to the signal input of the phase detector and the input of the low-pass filter, the output of which is connected to the input of the first subtractor, and the output of the square root extractor connected with the first input of the signal divider, the second input of which is the input of the second constant level signal.