RU2393502C1 - Two-channel null radiometre - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: proposed radiometre comprises matched load, first and second noise generators, attenuator, HF modulator, antenna, first and second directed couplers, first and second receivers, first and second LF preamplifiers, first and second homodyne filters, first and second LF amplifiers, first and second HF filters, LF and HF modulators, comparator connected, on one side, with radiometer common bus, control unit, dynamic integrator with its output making radiometer digital bus, and first and second current sources. Note here that matched load, first and second directed couples, first and second noise generators, first and second current sources, attenuator and HF modulator are arranged on temperature-controlled p.c.b. and stay in thermal contact therewith.

EFFECT: expanded performances in operation in null measurements mode.

2 cl, 6 dwg

Description

The invention relates to passive radar and can be used to measure the power of noise signals in remote sensing systems of the Earth, various natural environments, in industry.

Known zero radiometer [Filatov A.V., Bordonsky G.S. // Zero radiometer. A.S. USSR N1704107, G01R 29/08, G01S 13/95], the structural diagram of which is shown in figure 1, containing a series-connected antenna 1, directional coupler 2, modulator 3, receiver 9, low-frequency amplifier 10, high-pass filter 11, synchronous filter 12, a comparator (zero-organ) 13, a control unit 14, at the fourth output of which a digital code of the measured antenna signal is generated, which is sent to the bus 15. The circuit for automatically inputting the reference signal of the noise generator 5 to the directional coupler 2 starts from the first output of the control unit 14. Impulse ny signal includes a constant current source 4. The source 4 feeds Controlled noise generator whose output signal via an attenuator 6 is supplied to the directional coupler 2. The noise signal produced by the generator 5, for the radiometer is the first reference signal. The second reference noise signal is generated by the coordinated load 7, which is at the temperature of the thermostated board 8. To increase the stability of the radiometer, a modulator 3, a directional coupler 2, an attenuator 6, a noise generator 5, and a controlled current source 4 are installed on the same board.

A feature of the operation of this radiometer is that the processing of the envelope of modulated signals at the output of the receiver (at a low frequency) consists in the operation of eliminating the constant component by a high-pass filter 11, which does not require the use of synchronous detection operations. After eliminating the DC component, the voltage polarity is analyzed at the input of the comparator during the period when a matched load is connected to the input of the receiver. Since there are no signal shape transformations in the low-frequency part of the radiometer in order to isolate informative voltage levels, there are no errors associated with these transformations. The principle of zero measurements is fulfilled in the radiometer, and as a result, the radiometer becomes insensitive to changes in the transmission coefficient of the measuring path.

The described radiometer, selected as an analogue, is single-channel (single-receiver) and therefore its sensitivity is √2-fold lower than that of two-channel (two-receiver) circuits (Graham radiometers).

Known two-channel zero radiometer [publication RU 2003115658 from 11/20/2004], which includes (figure 2) antenna 1, an input unit, two identical measuring channels, a low-frequency signal processing unit. The input unit includes a directional coupler 2, a high-frequency modulator 3, a matched load 4, an attenuator 5, a noise generator 6, a high-frequency switch 27 installed on a thermostated board 7. The first and second measuring channels consist of receivers 8 and 13, low-frequency pre-amplifiers 9 and 14 synchronous filters 10 and 15, low-frequency amplifiers 11 and 16, high-pass filters 12 and 17, respectively. The low-frequency part includes a low-frequency modulator 18, a comparator 19, a control unit 20, a dynamic type integrator 21, from the output of which a signal is fed to the output digital bus 22.

In the input unit of the radiometer, the signals are modulated. In the directional coupler 2, a reference signal is added to the signal of the antenna 1, which is generated by the semiconductor noise generator 6 using an avalanche-span diode, attenuated in the attenuator 5 to the required value (tuning occurs when calibrating the radiometer) and through the high-frequency switch 27 enters the directional coupler. The closed state of the high-frequency key is determined by the control pulse-width signal _tsh , coming from the fifth output of the control unit 20. Thus, the noise generator signal is modulated according to the pulse-width law before it enters the antenna path. The second reference signal in the radiometer is generated by the coordinated load 4, which is at the temperature of the input node of the radiometer.

The antenna path of the measured signal and the coordinated load path are connected respectively to the inputs 1 and 2 of the high-frequency modulator 3, which connects them to the inputs of the two measuring channels of the radiometer. Modulator 3 has a two-input-two-output configuration (2 × 2). Depending on the pulse signal t _mode at the modulator control input coming from the first output of the control unit, if the antenna path is connected to the first measuring channel (modulator output 1), the matched load at this point in time is connected to the second measuring channel (output 2), and vice versa.

Each measuring channel has a radiometric receiver with a linear transfer characteristic and a band of received frequencies df. Synchronous filters reduces the fluctuation component, thereby eliminating the overload of the amplifiers following them and, on the whole, increase the accuracy of the radiometer. They consist of three single-link RC integrating circuits in which the resistor is common, and the constant components of three modulated input signals (antenna, antenna + noise generator, matched load) are accumulated on three capacitors by synchronously connecting them to a common point in the circuit via a controlled electronic key.

The high-pass filter is assembled according to the scheme of a single-link first-order CR filter with a cutoff frequency f _cp << 1 / 2t _modes , designed to eliminate the DC component in the signals with minimal distortion of the pulse shape.

The outputs of the measuring channels are alternately, with a modulation frequency of t _mode signals, through a low-frequency modulator 18 with a 2 × 1 configuration connected to the first input of the comparator 19, the second input of which is connected to a common point in the circuit.

The output signal of the comparator, presented in levels of logical zero and one, is fed to the input of a digital control unit 20, which has one input and five outputs, with the help of which the radiometer as a whole is controlled. From output 1, a pulse signal with a duration of t _modes implements symmetric modulation in the radiometer, synchronously controlling high-frequency and low-frequency modulators. Zero balance in the radiometer is achieved by additional pulse-width modulation of the noise generator by the signal t _chis from the fifth output of the control unit. The second and third outputs of block 20 are used to control the corresponding synchronous filters of the measuring channels. From the fourth output of the control unit, the digital code of the antenna signal is fed to the input of the dynamic integrator 21. In the dynamic integrator, digital codes of the measured antenna signal are accumulated over a certain time interval and averaged.

The considered radiometer, selected as a prototype, has limitations on the range of measured signals. The upper limit of the measuring range is fixed and is determined by the equivalent temperature of the agreed load.

The present invention solves the problem of expanding the functionality of the radiometer over the range of the measured antenna signals while maintaining the ability of the radiometer in zero measurement mode.

To achieve this technical result, in a radiometer containing a matched load, the first noise generator, the output of which is connected to the input of the attenuator, a high-frequency modulator, to the first input of which are connected a series-connected antenna and a first directional coupler, to the first output are a series-connected first receiver, the first preliminary low-frequency amplifier, first synchronous filter, first low-frequency amplifier, first high-pass filter, the output of which is connected to the first input m of a low-frequency modulator, to the second output - a second receiver, a second pre-amplifier of a low frequency, a second synchronous filter, a second low-frequency amplifier, a second high-pass filter, the output of which is connected to the second input of the low-frequency modulator, and the output of the low-frequency modulator is connected to the first input a comparator, the second input of which is connected to the common bus of the radiometer, and the output is connected to the input of the control unit, the first output of which is connected to combined control by their inputs of high-frequency and low-frequency modulators, the second and third outputs are connected to the control inputs of the first and second synchronous filters, respectively, and the fourth output is connected to the input of a dynamic type integrator, the output of which is the digital output bus of the radiometer, and the load is matched, the first directional coupler, high-frequency modulator , the attenuator, the first noise generator are installed on the thermostated board and are in thermal contact with it, the ones installed on the thermostat are introduced In this case, the second directional coupler, the second noise generator, the first and second noise sources, the outputs of which are connected to the inputs of the first and second noise generators, respectively, the control input of the attenuator is connected to the fifth output of the control unit, the outputs of the attenuator and the second generator noise are connected to the second inputs of the first and second directional couplers, respectively, the output of the second directional coupler is connected to the second input of the high-frequency modulator, and the first nth input - to the output of the agreed load.

To the control unit, which contains a reversible binary counter, binary counter, register, code comparison circuit, first and second triggers, first and second decoders, first and second power amplifiers, driver, clock generator, the output of which is connected to the input of the binary counter, first the output of which is connected to the second input of the code comparison circuit, and the second output is connected to the input of the shaper and the second input of the reversible binary counter connected together, the first input of which is the input of the control unit and the output of the binary reversible counter is connected to the first input of the register, the output of which is connected to the first input of the code comparison circuit, the output of which is connected to the first input of the first trigger, the second input of which is connected to the output of the driver and combined with the second input of the register and the input of the second trigger, the output of the first trigger is connected to the first inputs of the first and second decoders and combined with the input of the first power amplifier, the output of which is the fifth output of the control unit, the output of the second trigger is connected to w the other inputs of the first and second decoders and combined with the input of the second power amplifier, the output of which is the first output of the control unit, the first and second outputs of the first decoder are connected together and with the third and fourth outputs of this decoder make up the second output of the control unit, the third and fourth outputs of the second decoder connected together and with the first and second outputs of this decoder make up the third output of the control unit, the fourth output of which are the outputs of the reversible binary counter and forms rovatelya, entered calibration unit, first and second outputs of which are connected to third and fourth inputs of the first flip-flop, respectively.

Figure 1 presents the structural diagram of a radiometer - analogue.

Figure 2 presents the structural diagram of the radiometer prototype.

Figure 3 presents the structural diagram of the proposed two-channel zero radiometer.

Figure 4 shows timing diagrams explaining the principle of operation of a two-channel zero radiometer.

Figure 5 presents the structural diagram of the control unit of the radiometer.

6 shows a map of measuring ranges.

The composition of the radiometer (Fig. 3) includes antenna 1, an input unit, two identical measuring channels, a processing unit. The input unit includes a high-frequency modulator 3 installed on a thermostatic board 7, first 6 and second 24 noise generators, attenuator 5, first 2 and second 23 directional couplers, first 26 and second 25 current sources, matched load 4. Each measuring channel consists of receivers 8 and 13, preliminary low-frequency amplifiers 9 and 14, synchronous filters 10 and 15, low-frequency amplifiers 11 and 16, high-pass filters 12 and 17. The processing unit includes a low-frequency modulator 18, comparator 19, control unit 20, integrat dynamic type 21, whose output signal is supplied to the output line 22.

The first 6 and second 24 noise generators are made using semiconductor avalanche-span diodes, through the active zone of which the currents generated by the corresponding first 26 and second 25 current sources flow. By changing the current, the output noise power of the generators and, therefore, the reference signals are tuned.

In the input unit of the radiometer, the signals are modulated. Signal paths of the antenna and matched load are subjected to amplitude pulse modulation. Modulation occurs in the high-frequency modulator 3 according to the symmetric law and includes two equal half-periods with a duration of t _modes . The input signal of the antenna is supplied to the first input of the modulator 3 through a directional coupler 2, in which the signal of the first noise generator 6, previously modulated according to the pulse-width law, is added to the antenna signal. Latitudinal modulation is performed by a discrete change in the absorption coefficient of the attenuator 5 by the control signal t _chis coming from the fifth output of the control unit. Two levels α and α + Δα of reducing the signal of the noise generator T _{GSh1 by the} attenuator 5 are adjusted during the calibration operation, which is described below. The first level α defines the upper limit of the measurement range, the second α + Δα - the range span. Accordingly, the first reference signal T _op1 , which determines the upper limit of the measuring range, arriving at the first input of the high-frequency modulator 3 through the first directional coupler 2 and attenuator 5, is

T _op1 = [(T _rsh1 -T ₀ ) α + T ₀ (1-α)] β ₁ + T ₀ (1-β) -T ₀ ,

where T ₀ is the physical temperature of the thermostatically controlled board 7 of the input unit, β ₁ is the transfer coefficient of the first directional coupler, α is the attenuation coefficient of the signal, varying from 0 (full signal suppression) to 1 (full transmission).

Upon receipt from the fifth output of the control unit of the signal t _chis at the control input of the attenuator 5, in the latter the coefficient α increases by Δα, which leads to an increase in the reference signal at the first input of the modulator 3 to the value of T _add , which is equal to

T _add = [(T _rsh1 -T ₀ ) (α + Δα) + T ₀ (1-α-Δα)] β ₁ + T ₀ (1-β) -T ₀ .

The condition is imposed on the change in the signal reduction coefficient by the attenuator: α and the sum α + Δα during regulation should not exceed unity. If the condition is not met during the calibration of the radiometer, the current of the source 26, which feeds the first noise generator, is regulated.

Matched load path includes a second directional coupler 23, wherein the signal to matched load T _cN accrue reference signal T _OP2 second noise generator 24, input to the second input of the RF modulator 3. The signal T _OP2 is adjusted by adjusting the output signal of the second generator T _NH2 noise at step calibration and also, like the signal T _op1 , determines the upper limit of the range of measured signals. The reference signal T _op2 is _changed not by attenuation in the attenuator, but by a change in the current of the source 25 supplying the noise generator 24. The reference signal T _op2 is

T _op2 = (T _rsh2 -T ₀ ) β ₂ + T ₀ (1-β ₂ ) -T ₀ ,

where β ₂ is the transmission coefficient of the second directional coupler 23.

The principle of operation of the radiometer is as follows. The modulation control signals supplied to the modulator 3 from the first output of the control unit 20 are a periodic sequence of rectangular pulses following with a duty cycle of two. One modulation period consists of two equal half-periods with durations of t _modes (Fig. 4). In the first half-cycle, when at the output 1 of the control unit the signal t _mod has a low level corresponding to a logic zero, in the modulator 3 the inputs and outputs are switched as follows: input 2 is connected to output 1 (see figure 3), input 1 is connected to output 2. That is, the coordinated load signal 4 equal to T _cn and the signal of the second reference noise generator 24, at the output of the directional coupler 23 equal to T _op2 , are fed to the input of the first measuring channel (receiver 8). The signal of the antenna 1 with an effective temperature T _α and the signal of the first reference noise generator 6, at the output of the directional coupler 2, is equal to T _add or T _opt1 , depending on the signal at the control input of the attenuator 5, is fed to the input of the second measuring channel (receiver 13).

In the second modulation half-cycle, when the t _mode signal has a high logic level, in modulator 3, input 1 is connected to output 1, input 2 to output 2. Thus, the antenna path is connected to the receiver of the first channel and the matched load path to the receiver of the second channel. In each half-period of modulation at the fifth output of the control unit, a pulse-width signal is generated with a duration of t _sys (Fig. 4).

From the outputs of both channels, a periodic sequence of modulated signals amplified at a high frequency, detected and amplified at a low frequency, is fed to the input of the comparator 19 through a low-frequency modulator 18, which, like the modulator 3, is controlled by t _mod signals. As a result of the synchronous operation of both modulators, only matched load signals, which appear at the output of the first measuring channel in the first half-period of modulation and at the output of the second channel in the second half-period of modulation, are alternately passed to the input of the comparator.

Figure 4 shows the timing diagrams of the signals at the outputs of the measuring channels (corresponding to the outputs of the high-pass filters 12 and 17) when the zero balance is set in the radiometer. The zero balance for each measuring path is considered established if, during the half-period of modulation with the matched load connected to the input of the receiver, the channel output voltage is zero, and this case is fixed by a comparator 19 operating in the zero-organ mode. The zero balance for each measuring channel when the radiometer is turned on is established and then, when the antenna signal is changed, it is regulated by the corresponding change in the pulse width of the pulse-width signal t _n . Since the output signals of the channels are periodic in nature and they exclude a constant component, then for one period the equality of the volt-second areas of the positive and negative pulses is performed. Since the voltage at the input of the comparator is equal to zero during the half-period of modulation with the matched load connected, therefore, the equality of the volt-second areas of the positive and negative pulses is performed in another half-period of the modulation when the antenna receivers are connected to the input.

So, for the first channel, according to figure 4, we have

where U ₊ and U _- are the amplitudes of the positive and negative pulses equal to

where G ₁ is the coefficient of proportionality between the input signals T _α , T _add , T _sn , T _op1 , T _op2 and the voltage at the output of the high-pass filter of the first channel, which includes high and low frequency amplification factors, the transfer coefficient of the quadratic detector, k is the Boltzmann constant, df ₁ is the frequency band received by the first channel, T _W1 is the effective temperature of the noise of the receiver of the first channel.

Substituting (2) in (1), we obtain

G ₁ kdf ₁ (T _α + T _add + T _but1 -T _sn -T _op2 ) t _chis =

= G ₁ kdf ₁ (T _cn + T _op2 -T _α -T _op1 ) (t _mod -T _s ).

Where from

From the formula (3) follows a linear dependence of the duration t _SHIS and the input signal of the antenna T _α . Therefore, through this duration, the antenna signal can be indirectly determined. It also follows from formula (2) that the width of the pulse-width pulse signal t _{chis is} not affected by changes in the transmission coefficient of the measuring path (coefficient G ₁ ) and the receiver's own noise (T _sh1 ). Elimination of the influence of these two main destabilizing factors indicates that the radiometer works on the principle of zero measurements. However, changes in the amplification factors of the amplifiers included in the receiver should not exceed the limit beyond which the measuring channel begins to work in nonlinear mode. The signal transformations by the quadratic detector of the receiver should take place in the quadratic region of the current-voltage characteristics of the diode.

For the second measuring channel, after similar calculations, we obtain a similar formula (3) for finding the duration t _chis .

The antenna signal is determined from (3)

The values of the maximum and minimum signals of the antenna can be found from formula (4) by substituting into it the durations of _tshiss equal to zero and the duration of t _modes : T _{α, max} = T _cn + T _op2 -T _op1 ; T _{α, min} = T _cn + T _op2 -T _op1 -T _add .

Thus, by changing the signals T _op1 and T _op2, you can adjust the upper limit of the measurement range, by changing the signal T _add - the lower boundary, i.e. arbitrarily determine the measuring range.

The block diagram of the control unit is presented in figure 5. The control unit generates all the necessary signals for the functioning of the radiometer. It also generates a digital code that goes to the dynamic type integrator 21 (Fig. 3) and then, after averaging, to the output bus 22. This digital code is the digital equivalent of the measured antenna signal. The control unit consists of digital logic elements and it includes: binary counter 28, reversible binary counter 29, temporary data storage register 30, binary code comparison circuit 31, triggers for generating a pulse-width signal 32 and symmetric modulation 33, pulse shaper 38, two decoders 36 and 37 for controlling synchronous filters of the measuring channels, two power amplifiers 34 and 35 of the output signals of the triggers, a clock generator 39. The principle of operation of the control unit corresponds to the principle of work oty prototype. The reverse counter 29 stores a code corresponding to the width of the pulse width signal. Therefore, in the formula (3), we can make the transition from durations to their digital equivalents

where N _Rsch is the code of the reverse counter, N _max is the code of the reverse counter, when in all its digits it is one.

To set the measuring range, a calibration unit 40 has been introduced into the radiometer control unit. This unit is a three-position switch. Using this switch, two operating modes of the radiometer “work” and “calibration” are set. The first two positions of the switch "min" and "max" correspond to the calibration mode. In the "min" position, the logical unit signal is received from the first output of switch 40 to the third input of the first trigger 32 of the control unit and this trigger, regardless of the signals at inputs 1 and 2, is set to unity. Thus, at the output 5 of the control unit, the signal t _chis is constantly acting. When the switch is "max", the signal of the logical unit from its second output is fed to the fourth input of the first trigger 32 and holds it in the reset state, regardless of the signals at inputs 1 and 2. As a result, the signal t _will not be generated. The third position of the "work" switch provides the potentials of logical zero at the outputs "min" and "max" of the switch and the first trigger of the control unit operates in normal mode.

The setting of signals T _op1 , T _op2 , T _{add is} carried out during the calibration of the radiometer. Five measurement ranges are shown in FIG. 6. For the first three cases (Fig.6 a, b, c) the minimum T _{α, min} and maximum T _{α, max} antenna signals correspond to the inequalities: T _{α, min} and T _{α, max} <T _sn ; T _{α, min} <T _sn , T _{α, max} > T _sn ; T _{α, min} and T _{α, max} > T _sn . The last two cases (Fig. 5 g, d) are particular and occur if T _{α, min} = T _sn and T _{α, max} = T _sn .

Calibration for all five cases involves two stages (performed by the point-to-point method).

The first stage begins by setting the switch of block 40 in the control unit 20 to the “max” position (the t _{signal is} not generated and T _{add is} disabled during the entire calibration step) and connecting the radiator input instead of the antenna of the reference emitter determining the upper limit of the measurement range T _{floor max} At this stage, you configure either the reference signal T _op1 or T _op2 . If the measuring range shown in _{Fig. 6a is} necessary, for which the antenna signal is always smaller than the matched load signal, T _{op1 is adjusted by a} corresponding change in the absorption coefficient α of the attenuator 5. For this measuring range, the second reference signal T _op2 = 0. This condition is achieved by turning off the second current source 25 supplying the second noise generator 24 in the input unit of the radiometer. The reference noise signal is adjusted for this case and all subsequent ones until the zero voltage is obtained at the first input of the comparator 19 of the radiometer, which is similar to the work of the known radiometers on the zero method with analog zero balance control, described, for example, in [Gevorkyan V.G. Kislyakov A .G. Mirzabekyan E.G. Automatic zero radiometer of a wavelength range of 3-4 mm // News of universities. Radiophysics. 1979.V.22, No. 2. S.240-242]. The adjustment is completed when the signal with the modulation frequency disappears at the input of the comparator and this moment is recorded by an oscilloscope connected to the first input of the comparator.

For the measurement ranges in FIG. 5b, at the first stage, T _{op2 is} adjusted by adjusting the output current of the source 25. T _{op1 is} turned off as a result of setting the coefficient α = 0 in the attenuator 5 (total signal absorption). In special cases, to tune to the range shown in FIG. 5g, T _op2 and T _op1 are turned off, since T _{et, max} = T _sn . For the range in FIG. 5d, adjustment according to the maximum standard is carried out as well as for the range in FIG. 5b, c.

The second stage, as a result of which the lower limit of the range is adjusted, begins by connecting to the input of the radiometer the standard T _{et, min} defining the lower limit, and switching the unit 40 to the "min" position. Then installing _SIS t = t _mod for all five bands considered adjusts the T Δα _additional change in the absorption coefficient of the attenuator 5. Adjustment takes place analogously to adjust the first phase (recorded signal at the first input of the comparator 19, adjustment is made until the disappearance of the modulation frequency).

After two calibration steps, the radiometer is adjusted to the specified measurement range from T _{et, min} to T _{et, max} .

In the radiometer, the control unit 20 and the dynamic integrator 21 are made on digital CMOS logic integrated circuits. The dynamic type integrator circuit is described in [a.s. No. 1409953. Volokhov S.A., Korsakov S.Ya., Kochetov A.A. Modulation radiometer. G01R 29/08. BI No. 26, 1988, p. 155]. In the literature, the structures of the high-frequency modulator 3, attenuator 5 with electronic adjustment of the absorption coefficient, directional couplers 2 and 23 are quite adequately described [Bakharev SI, Volman VI, Lib Yu.N. et al. Ed. Volman V.I. A guide to the calculation and design of microwave strip devices. M .: Radio and communication, 1982; Bogdanov A.M., Davidovich M.V., Katz B.M. et al. Ed. A.P. Krenitsky and V.P. Meshchanov. Ultra-wideband microwave devices. M .: Radio and communication, 2001]. In this radiometer, these nodes are made on microstrip waveguide structures. Precise adjustable current sources 25 and 26 are made using integrated analog circuitry and provide current control in the range from 0.01 to 10 mA. In the receivers of the measuring channels, transistor amplifiers are used. Band-pass filters are made on oncoming rods [Mazepova OI, Meshchanov VP, Prokhorova NN et al. Ed. Feldstein A.A. Guide to the elements of strip technology. M .: Communication, 1979]. Synchronous filters 10 and 15 are described in [Freiter. Synchronous integrator and demodulator // Devices for scientific research. 1965. V. 36, No. 5. P.53]. The low-frequency modulator 18, the analog comparator 19 are applied in an integrated design.

Unlike the prototype, this radiometer can measure signals in any measurement range, while maintaining the operation of the radiometer in zero measurement mode, which increases the stability of its operation. The adjustment to the selected measuring range occurs during the calibration operation.

Claims (2)

1. A two-channel zero radiometer containing a matched load, a first noise generator, the output of which is connected to the input of the attenuator, a high-frequency modulator, to the first input of which are connected a series-connected antenna and a first directional coupler, to the first output are a series-connected first receiver, the first low pre-amplifier frequency, the first synchronous filter, the first low-frequency amplifier, the first high-pass filter, the output of which is connected to the first input of the low-frequency mode a second receiver, a second low-frequency pre-amplifier, a second synchronous filter, a second low-frequency amplifier, a second high-pass filter, the output of which is connected to the second input of the low-frequency modulator, and the output of the low-frequency modulator is connected to the first input of the comparator, the second input of which is connected to the common bus of the radiometer, and the output is connected to the input of the control unit, the first output of which is connected to the combined control inputs of high-frequency of the second and third frequency modulators, the second and third outputs are connected to the control inputs of the first and second synchronous filters, respectively, and the fourth output is connected to the input of a dynamic type integrator, the output of which is the digital output bus of the radiometer, the load being matched, the first directional coupler, high-frequency modulator, attenuator , the first noise generator is installed on the thermostatic board and are in thermal contact with it, characterized in that the thermostat mounted the circuit board and the second directional coupler, the second noise generator, the first and second noise sources, the outputs of which are connected to the inputs of the first and second noise generators, respectively, the control input of the attenuator is connected to the fifth output of the control unit, the outputs of the attenuator and the second generator noise are connected to the second inputs of the first and second directional couplers, respectively, the output of the second directional coupler is connected to the second input of the high-frequency modulator, and the first input - output to the termination. 2. The two-channel zero radiometer according to claim 1, the control unit of which contains a reversible binary counter, a binary counter, a register, a code comparison circuit, first and second triggers, first and second decoders, first and second power amplifiers, a shaper, a clock generator, an output which is connected to the input of the binary counter, the first output of which is connected to the second input of the code comparison circuit, and the second output is connected to the input of the shaper and the second input of the reverse binary counter connected together, the first input is an input of the control unit, and the output of the binary reversible counter is connected to the first input of the register, the output of which is connected to the first input of the code comparison circuit, the output of which is connected to the first input of the first trigger, the second input of which is connected to the output of the driver and combined with the second input of the register and the input of the second trigger, the output of the first trigger is connected to the first inputs of the first and second decoders and combined with the input of the first power amplifier, the output of which is the fifth output of the unit is controlled second output of the second trigger is connected to the second inputs of the first and second decoders and combined with the input of the second power amplifier, the output of which is the first output of the control unit, the first and second outputs of the first decoder are connected together and with the third and fourth outputs of this decoder make up the second output of the control unit , the third and fourth outputs of the second decoder are connected together and with the first and second outputs of this decoder are the third output of the control unit, the fourth output of which are the outputs a reversible binary counter and shaper, characterized in that a calibration unit is introduced into it, the first and second outputs of which are connected to the third and fourth inputs of the first trigger, respectively.

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