RU2022286C1 - Modulator radiometer - Google Patents

Abstract

FIELD: radio measurement technology. SUBSTANCE: modulation radiometer has aerial 1, commutator 2, frequency converter 3, square-law detector 4, videoamplifier 5, restrictors 7, 10, subtracter 8, scaling amplifier 9, adders 11, 18, selective amplifier 12, sync detector 13, integrator 14, registrar 15, attenuator 16, constant voltage source 17, reference voltage source 19, reference load 20. EFFECT: improved precision of measurement. 2 dwg

Description

 The invention relates to a radio metering technique, is intended to measure the power of weak thermal radio emission against the background of pulsed noise and can be used in radio astronomy, biomedical research, in the study of the physical properties of materials and media.

 Closest to the proposed is a device containing a series-connected antenna, switch, frequency converter, intermediate frequency amplifier, quadratic detector, video amplifier, limiter, selective amplifier, synchronous detector, integrator and recorder. The reference voltage generator is connected to the reference input of the synchronous detector and to the control input of the switch, to the second signal input of which a reference load is connected.

 This device provides high measurement accuracy when exposed to uncorrelated and chaotic impulse noise, however, when exposed to pulsed interference of a small duty cycle (Q <100), the measurement accuracy decreases due to the accumulation of the power of such interference in a selective amplifier.

 The aim of the invention is to increase the accuracy of measurements by increasing the noise immunity from impulse noise of low duty cycle (Q <≈ 100).

 This is achieved by the fact that in a modulation radiometer containing a series-connected antenna, a switch, a frequency converter, an intermediate frequency amplifier, a quadratic detector, a video amplifier and a first limiter, the output of the selective amplifier through a series-connected synchronous detector and integrator is connected to the recorder, the output of the reference voltage generator is connected with the reference input of the synchronous detector and the control input of the switch, to the second signal input of which the reference load, additionally introduced is a series-connected subtractor, a scaling amplifier, a second limiter, a first adder, as well as an attenuator, a constant voltage source, and a second adder, the output of the first limiter connected to the input of the subtractor and the second input of the first adder, and the output of the synchronous detector through the attenuator connected in series, a constant voltage source and a second adder are connected to the second input of the subtractor.

 In the developed modulation radiometer, interference is selected that exceeds a predetermined threshold, the interference is scaled and compensated for while the power of the noise signal preceding the appearance of the interference is reproduced during the operation of the interference.

 Figure 1 shows the structural diagram of a modulation radiometer; in FIG. 2 - diagrams of the input signal and signals at the outputs of blocks 6, 7, 8, 11.

 The device comprises an antenna 1, a switch 2, a frequency converter 3, an intermediate frequency amplifier 4, a quadratic detector 5, a video amplifier 6, a limiter 7, a subtractor 8, a scaling amplifier 9, a limiter 10, an adder 11, a selective amplifier 12, a synchronous detector 13, an integrator 14, a recording device 15, an attenuator 16, a constant voltage source 17, an adder 18, a reference voltage generator 19, and a reference load 20.

 Modulation radiometer works as follows.

Antenna 1 provides an input signal, which is an additive mixture of the measured noise signal U ₁ (t) with temperature T ₁ and impulse noise. The switch 2 periodically with a frequency of F ₁ (where F ₁ is the frequency of the generator 19) alternately connects to the input of the frequency Converter 3 the antenna 1 or the reference load 20 with a noise temperature T ₂ . The frequency converter 3 converts the signal from the output of the switch 2 into an intermediate frequency signal. This signal is amplified by an intermediate frequency amplifier 4, detected by a quadratic detector 5, and amplified by a video amplifier 6. The signal U ₁ (t) at the output of video amplifier 6 with antenna 1 connected is proportional to the additive mixture of the useful signal power U ₂ (t) and pulsed interference U ₃ (t)
U ₁ (t) = U ₂ (t) + U ₃ (t)
When the reference load 20 is connected, the signal U ₄ (t) at the output of the video signal 6 is proportional to the radiation power of the reference load 20. The signals U ₁ (t), U ₄ (t) are shown in Fig. 2a.

The limiter 7 provides a limit on the level of U ₅ pulses of interference from the output of the video signal 6. The second signal of the limiter 7 is shown in figure 2, b.

In the absence of interference pulses at the output of the radiometer, the output of the limiter 7 alternately with the frequency F ₁ contains a useful signal U ₂ (t) and a reference signal U ₄ (t). These signals are fed to the first (inverting) input of the subtractor 8 and the first input of the adder 11. The second (non-inverting) input of the subtractor 8 receives a signal from the source 17 and adder 18, which consists of a constant threshold voltage U ₆ , which closes the limiter 10 (since U ₆ > U ₂ ), and the output voltage of the synchronous detector 13, attenuated by the attenuator 16 in K ₂ = K ₁ ^. K ₃ times, where K ₁ is the gain of the scaling amplifier 9, K ₃ is the transmission coefficient of the series-connected adder 11, the selective amplifier 12 and the synchronous detector 13.

Since the limiter 10 is locked by a positive threshold voltage K ₁ U ₆ / U ₅ > U ₆ ≥ 3v /, where v is the dispersion of the received signal at the output of video signal 6, the voltage at the second input of adder 13 is zero, and the useful and reference signals are fed to the first input of the adder 13, providing at its output an alternating voltage with a frequency F _{1 of the} reference voltage and an amplitude proportional to the temperature difference T _{1 of the} noise signal and T _{2 of the} reference radiation.

When the antenna 1 receives at the time t _{1 the} impulse noise U ₃ (t) that exceeds the threshold limit U _{5 of} duration Δt ₁ less than the half-period of the reference oscillation (Δt ₁ <1 / 2F ₁ ), to the first (integrating) input of the subtractor 8 and the first the input of the adder 11 receives an interference pulse U ₃ (t) of duration Δt ₁ and amplitude U ₅ (see Fig. 2, b).

где U₇(t) - сигнал на выходе ограничителя 7.U ₇ (t) =

where U ₇ (t) is the signal at the output of the limiter 7.

, где τ - временная задержка, возникающая при прохождении сигнала U₂(t) через сумматор 11, избирательный усилитель 12 и синхронный детектор 13.At the same time, at the moment t ₁ , the sum of the constant voltage U ₆ and the voltage from the output of the synchronous detector 13, which passed from the output of the limiter 7 through the adder 11, the selective amplifier 12, the synchronous detector 13, the attenuator 16, the source 17, and the adder 18, is present at the second input of the subtractor 8
U ₈ (t) = U ₆ (t) +

where τ is the time delay that occurs when the signal U ₂ (t) passes through the adder 11, the selective amplifier 12 and the synchronous detector 13.

The voltage U ₉ (t) at the output of the subtractor 8 during the action of the interference pulse (see figure 2, c).

-U₅ ,
(t₁< t< t₁ + Δt) .U ₉ (t) = U ₈ (t) - U ₇ (t) = U ₆ +

-U ₅ ,
(t ₁ <t <t ₁ + Δt).

The output of the scaling amplifier 9 during the Δt ₁ action of the pulsed interference voltage is present U ₁₀ (t) (see figure 2,).

(U₆-U₅)+U₂(t-τ)=
= - U₅+U₂(t-τ)
U₁₀(t)<0, так как уровень U₅ ограничения помехи U₃(t) превышает уровень полезного сигнала U₂. В этом случае ограничитель 10 открыт, и на второй вход сумматора 11 поступает сигнал U₁₀(t), а на первый вход сумматора 11 поступает напряжение U₅. Во время действия импульса помехи U₃(t) на выходе сумматора 11 формируется напряжение U₁₁(t) (см.фиг.2,д).U ₁₀ (t) = K ₁ · U ₆ + U ₂ (t-τ) -K ₁ · U ₅ =

(U ₆ -U ₅ ) + U ₂ (t-τ) =
= - U ₅ + U ₂ (t-τ)
U ₁₀ (t) <0, since the level U _{5 of the} interference limitation U ₃ (t) exceeds the level of the useful signal U ₂ . In this case, the limiter 10 is open, and the signal U ₁₀ (t) is supplied to the second input of the adder 11, and the voltage U _{5 is} supplied to the first input of the adder 11. During the action of the interference pulse U ₃ (t), the voltage U ₁₁ (t) is formed at the output of the adder 11 (see Fig. 2, d).

.U ₁₁ (t) = U ₅ - U ₅ + U ₂ (t - τ) = U ₂ (t - τ)
Thus, during the action of the impulse noise in excess of a predetermined level of restriction U ₅ , the limited impulse noise is compensated in the adder 11. The selective amplifier 12 amplifies the useful signal U ₂ (t), delayed by time τ. At the end of the action of the interference pulse at the time tt ₁ + Δt ≅ t <t _{2, the} voltage U ₁₂ (t) at the output of the subtractor 8 is
U ₁₂ (t) = U ₆ (t) +

.

Since the threshold voltage U ₆ ≥ U ₂ , then U ₁₂ (t)> 0 and the voltage from the output of the subtractor 8 does not pass through the limiter 10, then the voltage at the second input of the adder 11 is zero. At the first input of the adder 11 when the antenna 1 is connected to the modulator 2, there is a voltage U ₁₃ (t) (see Fig. 2, d).

U ₁₃ (t) = U ₂ (t), t ₁ + Δt ₁ ≅ t ≅ t ₂
The signal U ₁₃ (t) is integrated using the integrator 14 and is recorded by the registrar 15.

Similarly, the radiometer works with subsequent interference pulses that appear at time t ₃ , t ₄ ... t _n (see figure 2, a)

Claims (1)

 A MODULATION RADIOMETER comprising a series-connected antenna, a switch, a frequency converter, an intermediate frequency amplifier, a quadratic detector, a video amplifier and a first limiter, a series-connected selective amplifier, a synchronous detector, an integrator and a registrar, a reference voltage generator, the output of which is connected to the reference input of a synchronous detector and the control input of the modulator, to the third input of which a reference load is connected, characterized in that, in order to increase the accuracy For these measurements, a subtractor, a scaling amplifier, a second limiter, and a first adder are introduced in series, the second input of which is connected to the output of the first limiter and the first input of the subtractor, and the output is connected to the input of the selective amplifier, the output of the synchronous detector through the attenuator and the second adder connected in series is connected with the second input of the subtractor, a constant voltage source, the output of which is connected to the second input of the second adder.

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