SU1173354A1 - Device for measuring signal-to-noise relation - Google Patents

Abstract

A DEVICE FOR MEASURING THE RELATIONSHIP SIGNAL / NOISE, containing successively connected generator, multiplier and integrator, a band-pass filter whose input is the input of the device, and the output is connected to the first input of the dividing unit, so as to improve the accuracy measurements, a notch filter, a differentiator and a high-pass filter connected between the integrator's output and the second input of the dividing unit are entered into it, while the input of the band-pass filter is connected through a series of notch filter The transducer and the differentiator are connected to the second input of the multiplier.

Description

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The invention relates to a radio measuring technique and can be used to measure the signal-to-noise ratio (SNR) in radio devices.

The aim of the invention is to improve the accuracy of the SNR measurement by converting the noise voltage, which takes into account the shape of its frequency spectrum and at the same time eliminates the effects of interference and signal harmonics by selecting a frequency so that noise samples are in the frequency intervals between interference and harmonics. signal

The drawing shows a block diagram of the proposed device.

. The device contains a generator 1, a multiplier 2, an integrator 3, a band-pass filter 4, a separating unit 5, a notch filter 6, a differentiator 7, a high-pass filter 8, while the multiply-connected multiplier, an integrator and a high-pass filter are connected to the input of a separating unit, another the input of which, combined with the input of the notch filter, is the input of the device, the output of the notch filter being connected through a differentiator to another input of the multiplier.

Consider the functions performed by the basic structural elements of the device.

The generator 1 forms a rectangular, multiplier-shaped reference voltage. The integrator 3 suppresses the high-frequency components of the alternating voltage, which are bbmie frequencies defined by the time constant of the integrating circuit. The band-pass filter 4 passes a continuous signal to the input of the dividing block 5. The notch filter 6 suppresses the useful signal and passes the noise voltage to the input of the differentiator 7, which performs a differentiation operation on the noise voltage. The high-pass filter does not pass the low-frequency components of the output voltage of the integrator 3. The dividing unit 5 performs the operation of calculating the value of the voltage ratio of the useful signal from the output of the band-pass filter 4 to the voltage coming from the high-pass filter code 8,

The device works as follows.

The input signal and noise mixture is separated by a bandpass filter 4 and a notch filter 6 into signal and noise voltages, respectively. The voltage of the signal goes directly to the divider unit 5, and the noise voltage is differentiated in time by the differentiator 7, and then multiplied with the reference voltage of the generator I in multiplier 2. From the output voltage of multiplier 2, the frequency band is separated using an integrator 3 and an upper filter frequency 8, This voltage, equivalent to the input noise voltage, enters the splitter unit, where the SNR is calculated,

The introduction of a notch filter, a differentiator and a high-pass filter can significantly improve the accuracy of measuring the SNR value,

The transmission coefficient of the part of the device producing the processing noise voltage can be recorded

Koksch, 1

where K, K2, Kj and Kg - respectively

Differential gains 7, ne-t Repair factor 2, integrator 3 and high pass filter 8.

Differential Transmission Factor

where s is the current frequency value; d pole frequency.

In practice, the frequency response section is usually much smaller than oL, i.e. (.. Then | K, (and) | Ratio of the multiplier operating with a rectangular control (reference) voltage of one polarity

K., (T) Koj (1 + sign Sin Wont),

where Kf, is the multiplication factor; The signSinWp t-signum function, which is either +1 or -I, according to the voltage sign Sinw Wgn, is the frequency of the first harmonic of the reference voltage. By expanding the signum function in the Fourier series, H S op Trra5 .., we can write the expression for the multiplier transfer coefficient 2 M n (j4,3, S ... Representing the noise voltage at the input of the differentiator 7 in the form of Oo Ujtl - Zu. sm (u) .tl, you can find the voltage at the output of the multiplier 2 UjU) U (t) K, K, Zu, 5in (c..b) K. sinKu) Z. 1 KHi, .- 2u) K „and,. . . , .. f.-Ku3, t) -cos (u ,, t.4, Ku, t), 544 Considering the fact that integrator 3 and high-pass filter 8 attenuate high and low frequencies, forming a band-pass filter with transmission (u1) | part of the terms can be neglected N at Т1о6К, 3, S14. .-Kw.i). Proceeding from the fact that K - u (,. Quotes.,., 3, S.,. I4) -. The last expression is a recording of the noise voltage, taking in the form of narrow bands (samples) of noise near the odd harmonics of the frequency Shdpi transferred to the frequency domain bounded by the frequency characteristics of the integrator 3 and the high-pass filter 8 (LR). This - -: is proportional to the level of the input noise voltage with a proportionality factor of 2u) onKaU, | K3.8M (

Claims (1)

DEVICE FOR MEASURING SIGNAL / NOISE RELATIONSHIP, comprising a series-connected generator, multiplier and integrator, a band-pass filter, the input of which is the input of the device, and the output is connected to the first input of the dividing unit, characterized in that, in order to increase the accuracy of measurement, they are introduced into it a notch filter, a differentiator and a high-pass filter, connected between the output of the integrator and the second input of the dividing unit, while the input of the bandpass filter through a follower * · but connected by a notch filter and the differentiator is connected to the second input of the multiplier. S2 m GO GO SP