SU1215064A1 - Apparatus for measuring signal-to-noise ratio - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to simplify and increase the accuracy of the device. The device contains a mixer 1, a band-pass filter 2, keys 3 and 7, accumulating gauges 4 and 8 of instantaneous power, a subtractor 5, a frequency-modulated local oscillator 6, a control unit 9, a differential logarithmic converter 10 and a recording device 11. 2 or . yu SP Od

Description

one

The invention relates to a measurement technique and can be used to measure the signal-to-noise ratio of an additive mixture of signal and noise in radio communication systems.

The purpose of the invention is to simplify and improve the accuracy of the device.

1 shows a block diagram of the device; 2 shows timing diagrams for the operation of the device.

The device contains a series-connected mixer 1, a bandpass filter 2, the first key 3, the first accumulating meter 4 of instantaneous power and the subtractive element 5, the frequency-modulated local oscillator 6, the second key 7, the second accumulating meter 8 of instantaneous power, control block 9, differential logarithmic converter 10, the registering device 11 and the terminal 12 of the device for connecting the receiver under study (not shown).

The device works as follows.

The mixture of signal and noise, the ratio of which must be measured, from the output of the receiver under study goes through terminal 12 of the device to the signal input of the mixer 1, to the reference input of which the signal of the local oscillator 6 goes. Mixer 1 and the local oscillator 6 transfer the spectrum of the input signal mixture with noise the passband frequency region of the filter 2. According to the modulating signal from the first output of block 9, the local oscillator 6 provides the tuning of the received mixture for the transparency band of the filter 2.

The bandwidth q f and the center frequency f of filter 2 are chosen from the condition

D f S 1,1 DE, fo 30 d,

where & E is the width of the signal spectrum.

The key 3 performs gating of the signal and noise mixture, and the key 7 gates the noise in the case of detuning the frequency of the received signal and noise mixture for the transparency band of the filter 2.

The meter 4 provides a measurement of the power of the signal mixture and

2150642

noise (PP + RS), and meter 8 - measurement of the power of the noise PS.

At the first output of the control unit 9, a signal is generated (FIG. 2cx),

5 by which the signal of the local oscillator 6 is modulated, with the result that at the output of the filter 2 a signal (Fig. 25) forms an additive mixture of the signal and noise with a power level. Key 3,

 O controlled by the signal from the second output of block 9, ensures the passage of a mixture of signal and noise to the gauge 4 (Fig. 2b). Key 7, controlled by a signal from the third output

 5 of the block 9, ensures that only noise passes to the meter 8 (FIG. 2d). Meters 4 and 8 integrate instantaneous signal and noise mix power

20 PC + RS and noise PS, respectively. The signals from the output of the meters 4 and 8 are fed to the direct and inverting inputs of the subtracting element 5, respectively, at the output of which

25, a signal is generated that is proportional to the power of the PC signal. Thus, at the outputs of meters 4 and 8 and element 5, signals are formed that are proportional to the powers of the mixture of the signal with the PC + RS noise, the PC noise and the PC signal.

Next, the signals from the outputs of the subtracting element 5 and the meter 8 are fed respectively to the direct 35 and inverting inputs of the differential logarithmic converter 10. The latter generates a signal and, proportional to the logarithm of the ratio of signals received at its inputs

U6v ,, K k tog 1. sh

where k is the transfer coefficient of the converter 10.

The output signal of converter 10 is fed to the input of a recording device 11, whose readings are proportional to the 50 signal-to-noise ratio in decibels.

Claims (1)

Invention Formula A signal-to-noise ratio measurement device containing a series-connected mixer, a band-pass filter, a first switch, a first accumulating instantaneous power meter and a subtractive element, a frequency-modulated local oscillator, the output of which is connected to the reference input of the mixer, the second switch whose signal input connected to the output of the bandpass filter, the second accumulator measuring instantaneous power, the signal input of which is connected to the output of the second key, and the output to the second input of the subtracting element, the block systematic way, the first, second, third, fourth and fifth outputs of which are connected to respective control inputs of a frequency-modulated oscillator, the first and second keys. Editor E. Kopcha fig 2 Compiled by L. Muranov Tehred O. Niece Proofreader T. Kolb Order 904/54 Circulation 730 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Branch PPP Patent, Uzhgorod, st. Project, 4 The first and second instantaneous power accumulation meters, a logarithmic converter and a recording device, characterized in that, in order to improve the accuracy and simplify the device, the logarithmic converter is differential, its first input connected to the output of the subtracting element, and the second input connected to the output of the second the instantaneous power accumulator, the output of the logithmic converter is connected to the input of the recording instrument.