SU761943A1 - Apparatus for measuring signal-to-noise ratio in radio receiver - Google Patents

Description

The invention relates to measuring equipment and is intended to measure the signal-to-noise ratio in coherent radio receivers. $

A device for measuring the signal-to-noise ratio is known, in which a signal is subjected to a non-linear transformation in two channels in one - with 10 to get a voltage proportional to the level of a pure signal, and the other to get a voltage proportional to a noise signal [1]. 15

However, the device has a very low accuracy in terms of interference, which is explained by the presence of two non-linear transducers.

The closest to the proposed 20 is a device for measuring the signal-to-noise ratio in a radio receiver, containing a coherent oscillator forming unit, the input of which is connected to the inputs of two phase detectors, and the output is connected to the second input of the first phase detector directly and to the second input of the second phase detector through phase shifter at an angle I / 4, two regenerants2

tori connected to the outputs of phase detectors and recorder [2],

The disadvantage is that the device does not provide the necessary accuracy of measurements.

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

The goal is achieved by the fact that in the device containing a coherent oscillator forming unit, the input of which is connected to the inputs of two phase detectors, and the output is connected to the second input of the first phase detector directly and to the second input of the second phase detector through a phase shifter through the angle β / 2, two the regenerator, connected to the outputs of the Phase detectors, and the recorder, are connected to the output of each of the phase detectors in series with a delay line and a multiplier, the second input of which is connected to the output of regenerator; out! multipliers are connected to the inputs of the summation and subtraction blocks, and the outputs of the summation and subtraction blocks are connected to the recorder inputs, respectively

3

through the first low pass filter and through the series-connected rectifier and the second low pass filter

frequencies.

The drawing shows a functional block diagram of a device for measuring signal-to-noise ratio in a radio receiver.

The device contains a receiver ^, the output of which is connected to the input of the block 2 for the formation of coherent co-. and with the inputs of two parallel branches, each of which consists of a series-connected phase detectors 3 (4), an integrator 5 (61 with a reset, and a decisive element 7 (81. '

Elements 5.7 and 6.8 form regenerators 9 and 10, connected to the bus 11 clock pulses. The output of the coherent oscillator formation unit 2 is directly connected to the second input of the phase detector 3 PD of the first branch and through the phase shifter 12 through an angle ^ 6/2 to the second input of the PD 4 of the second branch. In each branch, the output of PD 3 (41 through line 13 (1'4) delay is connected to the first input of the multiplier 15 (161, ^{and the} output of the regenerator 9 (101 "to the second input of the multiplier 15 (161. The outputs of the multipliers 15 and 16 are connected in parallel to the corresponding the inputs of the summation block 17 and the subtraction block 18. The outputs of the blocks 30

17 and 18 through the low-pass filter 19 (fnch) and through the rectifier 20 and the low-pass filter 21 are connected to the inputs of the recorder 22. · .. '

The device works as follows:

After amplification in the receiver 1, the phase-manipulated * signal is fed to the input of the coherent oscillating unit 2 and to the inputs of two PD 3 to and 4. The reference voltage from the output of block 2 is fed directly to the second input of the FDZ and through the phase shifter 12 at the angle / 2 to the second input PD 4. From the PD 3 and 4 outputs, the video signals, distorted by interference, are fed to the inputs of the integrators 5 and 6 with a reset, where the voltage accumulates during the time of the signal elementary signal,

Instead of an integrator with a reset, a matched filter may be applied. In this case, no sync pulses are applied to it. From the outputs of the integrators 5 and 6, the voltage is applied to the inputs of the decisive elements 7 and 8, respectively. . .........

By the end of the specified parcel in decisive elements 7 and 8 on the clock pulses the voltage is read and a decision is made on the sign of the parcel.

With the release of elements 7 and 8 are issued,

binary decoding signals

device (not shown) and

to the second inputs of multipliers 15 and 16

.respectively. __

761943 4

At the end of the sending in integrators 5 and 6, the received voltage is released from the clock pulses.

From the outputs of PD 3 and 4, the video signals are also fed to the first inputs of multipliers 15 and 16. These signals are preliminarily delayed. The time в "on lines 13 and 14. In this case, the signals / signals on the first and second inputs of multipliers 15 and 16 coincide in time . As a result of the multiplication of these signals, the modulation of the signal is removed at the output of blocks 15 and 16 and the constant component remains. Noise interference at the output of blocks 15 and 16 gives equiprobable emissions of opposite sign, therefore the constant component of noise interference is zero. The signals from the output of multipliers, Ϊ5 and 16 are fed to the corresponding inputs of the summation block 17, where they are added. The useful signals (constant component) are added by voltage, and the noise of quadrature channels is added by power, since they are not correlated. Therefore, at the output of block 17, the signal-to-noise power ratio P _with / Рц is two times higher than at each of its inputs. The presence of the summation unit 17 also makes it possible to increase the stability of the voltage applied to the recorder 22 until a residual phase error appears, since the output of each of the multipliers 15 and 16 in this case, the voltage changes in opposite directions, and the total voltage at the output of the unit 17 remains almost constant.

The signal from the output of blocks 15 and 16 is received in this way and to the corresponding inputs of subtraction unit 18. Since both quadrature channels are identical, the voltage of the signals at the inputs of block 18 is equal in magnitude and in sign. As a result of subtracting these signals, the DC component at the output of block 18 is equal to zero, while the noise, having equiprobable 'emissions of the opposite sign, is added in power,

After filtering in the low-pass filter 19 and 21, the signals of the constant component and interference come to the recorder 22, where the signal-to-noise ratio is determined.

The proposed scheme allows to improve the measurement accuracy, and the signal-to-noise ratio can be monitored without interrupting reception of useful information, which leads to a reduction in the time of malfunction detection.

Claims (1)

Claim Device for measuring the signal-to-noise ratio in a radio receiver, co76194.3 A coherent oscillation shaping unit, the input of which is connected to the inputs of two phase detectors, and the output is connected to the second input of the first phase detector directly and to the second input of the second phase detector - through the phase shifter at an angle ¢ / 2, two regenerators connected to the outputs of the phase detectors, and the recorder, characterized in that in order to improve the accuracy of measurements, the output of each of the phase detectors is connected The corresponding regenerator, the multiplier outputs are connected to the inputs of the summation and subtraction blocks, and the outputs of the summation and subtraction blocks are connected to the inputs of the recorder, respectively, through the first low-pass filter ⁵ and through the series-connected rectifier and the second low-pass filter.