SU1345146A1 - Device for measuring signal-to-noise ratio - Google Patents

Abstract

The invention relates to radio engineering. A device for measuring the signal-to-noise ratio in radio communication systems contains a mixer 1, a frequency-modulated local oscillator 2, band-pass filters 3, 4, accumulating meters 5, 6, keys 7-10, 14, 15, adders 11, 12, subtracting element 13 , transducer 16, synchronous detector 17, a recording device 18. The invention increases the sensitivity while limiting the measurement time by more fully using the measurement period. 7 il. WITH SL 42 Oi Figure 1

Description

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

The aim of the invention is to increase the sensitivity with a limited measurement time by more fully utilizing the measurement period.

FIG. 1 shows a block diagram of the device; in fig. 2 is a structural diagram of an instantaneous POWER accumulating meter; in fig. 3 is a block diagram of a synchronous detector; in fig. 4 is a block diagram of the control unit; in FIG. 5, time diagrams of the operation of the device; in fig. 6 - timing diagrams of the synchronous detector; in fig. 7 - timing charts of the control unit.

The device contains a mixer 1, a signal input connected to the input terminal of the device, a reference input to the output of the frequency-modulated local oscillator 2, and an output to the inputs of the first and second band-pass filters 3 and 4, the outputs of which are connected through the first and second accumulating meters 5 and 6 instantaneous power (Н№1М) to the signal inputs of the first and second 7 8 and the second and fifth 9, 10 keys “Outputs. keys 7 and 8 are connected to the second, and the outputs of keys 9 and 10 - to the first inputs of the second and first adders 11 and 12. The outputs of the adders 11 and 12 are connected to the non-inverting and inverting inputs of the subtracting element 13. The output of the adder 12 is connected to the signal input of the fourth key 14, and the output of the subtractive element 13 to the signal input of the third key 15. The outputs of the keys 14 and 15 are connected via a logarithmic converter 16 to the signal the input of the synchronous detector 17, the output of which is connected to the input of the recording device 18.

The control unit 19 is connected: a Bbw output to the input of the local oscillator 2, a second output to the second control input of the NIMM 5 and a control input of the key 7, a third output with the second control input of the NIMM 6 and the control Rout of the key 8, the fourth output - to the control inputs of the key

0

0

five

9, 14 and the synchronous detector 17, the fifth output to the control inputs of the keys 10 and 15, the sixth to the first control input of the HHMf-l 5, the seventh to the first control input of the NIMM 6.

The instantaneous power accumulator 5 (Fig. 2) contains a key 20, a signaling input connected to the signal one, and a control input - to the first control inputs of the meter, the output of the key 20 via a quadratic detector 21 is connected to the signal input of the synchronous detector 5 22, controlling the input of which is connected to the first control input of the meter. The output of the synchronous detector 22 is connected to the signal input of the synchronous integrator 23. The first control input is the synchronous integrator 23 connected directly, and the second through the inverter 24 to the second control input of the meter. The output of the synchronous integrator is connected to the output of the accumulating instantaneous power meter.

The synchronous detector 17 (Fig. 3) contains a key 25, the signal and control inputs of which are connected to the signal and control inputs of the synchronous detector 17, and the output connected to the integrator signal input 26. The output of the integrator 26 is connected to the output of the synchronous detector 17..

The control unit 19 (FIG. 4) comprises a master oscillator 27 connected to the input of a divider at ten 28 and to the pinch and seventh outputs of the control unit 19. The output of divider 28 is connected to ten through a scale amplifier 29 with the first, and through an inverter 30 with the third and fourth outputs of the control unit, as well as directly with the second and fifth outputs of the control unit 19.

The device works as follows.

At the first output of the control unit 19, a signal is generated (FIG. 5a) with

0

five

0

five

0

a period of 20 T ,, (T., is the period of the pulses of the master oscillator 27 of the control unit 19) by which the signal of the local oscillator 2 is modulated, as a result of which a signal is produced at the output of the band-pass filter 3 (FIG. 56), and the signal of the output of the band-pass filter 4 (Fig. 5c). In the time interval (tp -t) at the output of the bandpass filter,

pa 3 we have an additive mix signal plus noise with power level P + P, and in the time interval (t, t) only noise with power level P. At the output of the bandpass filter 4 we have: in the time interval (t, -t) - power noise P, (t, 2- power of the additive mixture signal + noise (Pj, +

+ RSH) in NIMM 5 and 6 is produced modulation (interruption) with a period T of the input signal or a mixture of a signal plus noise using a key 20, the selection of a square voltage proportional to the power level using a quadratic detector 21 and further synchronous detection using synchronous detector 22. Synchronous integrator 23 provides averaging of the power supplied to it Pf + Psc in the interval (tp-t) (in block 5) and P | in (t - t j) (in block 5) under the action of control signals supplied from the second and third outputs of control block 19 with a period of T 20 TO. As a result, at the outputs of the first and second meters 5 and 6, alternating sequences of voltage levels (Fig. 5e, e), proportional to the power levels of PC + RS and Pc, are obtained. These voltage levels through the keys 8, 7, 9 and 10 are fed to the inputs of the adders 11 and 12. The keys 8, 7, 9 and 10 control the signals with a period T 20 TQ (Fig. 76, c) from the second, third, fourth and the fifth outputs of the control block 19. At the same time, the first and second inputs of the sum-mountain 11 from the outputs of the first and second; 1 meters 5 and 6 receive the voltage corresponding to the power level of the mixture signal + noise P + P, and the first and second inputs of the adder 12 receive the noise power. As a result, at the output of adders 11 and 12, we have constant voltages (Fig. 5k) and (Fig. 5l), proportional, respectively, to the power level of the mixture signal + sound (Pj. + P) and noise power (Rsch). On the output of the subtracting element 13, there is a signal equal to the difference (+ - Pj) - P, i.e. its level corresponds to the signal power of the R. Sigchal from the output of the subtracting element 3, corresponding to the power P ,, through the) key 15, and the signal from the output of the adder 12, corresponding to the power

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PJJI noise through switch 14 is transmitted through a logarithmic converter to the signal input of the synchronous detector 17 (Fig. 5m), controlled by a signal with a period of T-20 T, from the fourth output of the control unit (Fig. 7c). As a result of the synchronous detection of the signal supplied from the output of the logarithmic converter, a voltage is formed that corresponds to the level of Ig -. it

Ui

the voltage is formed as follows: when the control signal is turned on (fig. 6b), the control input of the switch 25 (fig. 3) of the synchronous detector 17 results in the formation of a zero level, i.e. in time intervals t 1 s. 20, etc. the voltage level corresponding to Pw (Fig. 6a) is fixed to zero (Fig. 6c). The constant voltage component corresponding to 25p is restored by the integrator.

Ig P, - Ig P Ig (Fig. 6d).

 sh

from the output of the synchronous detector 17, this voltage is applied to the input of the recording device 18, a reading of 30

which is proportional to the ratio

signal / noise in decibels.

The control unit 19 (FIG. 4) operates as follows.

The master oscillator 27 generates

video pulses of the type meander with a period of Tjj. These pulses are fed to the input of the divider 28 to the ten and simultaneously to the sixth and seventh outputs of the control unit 19 (Fig. 7a). From the output of divider 28, ten video pulses (Fig. 7c) with a period T 20 T are applied to the input of the scale amplifier, to the input of the inverter 30, and to the second and fifth outputs of the control unit 19. From the inverter output, video pulses (Fig. 7c) are fed to the third and fourth outputs, and from the output of the scale amplifier - to the first output (Fig. 7d) of the control unit 19.

Claims (1)

Invention Formula A device for measuring the signal-to-noise ratio containing the sm-tel, the signal input of which is connected to the input terminal of the device, the reference stroke - to the output of the local oscillator, and the output - to the first bandpass filter, the first and second accumulating instantaneous power meters, six keys five whose subtractive element, the output and the inverting input of which are connected via the third and fourth keys respectively to the input of a logarithmic converter; six keys, characterized in that, in order to increase the sensitivity with a limited measurement time, a second and first pass band filter is inserted into it th adders and a synchronous detector, the output of the mixer through a second bandpass filter and the second accumulating instantaneous power meter is connected to the input signal- fifth and sixth keys whose outputs are respectively cos 466 dinene with the first inputs of the first and second adders, and the output of the first bandpass filter through the first accumulating meter of instantaneous power connected to the signal inputs of the first and second keys, the outputs of which are respectively connected to the second inputs of the second and first adders 5 while inverting and non-inverting inputs of the subtracting element, respectively connected to the outputs of the first and second adders, a synchronous detector is connected between the output of the logarithmic converter and the input of the registering device pa, and the outputs of the control unit are connected; the second and third respectively to the second control inputs of the first and second accumulating instantaneous power meters, and the fourth to the control input of the synchronous detector. ABOUT ABOUT 25 . 26  (of R