RU1841073C - Radar receiver noise figure meter - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to measurement engineering and can be used to monitor the noise figure of a radar receiver. The device includes a noise generator (1), a power supply (2), a switch (3), a former (4), a measurement unit (5) with a display (8), an attenuator (10), a directional coupler (11), a control unit (12) and a controlled receiver (13). The output of the power supply (2) is connected to power circuits of the noise generator (1). The outputs of the control unit (12) are respectively connected to the control inputs of the controlled receiver (13), the power supply (2) and the measurement unit (5). One of the inputs of the switch (3) is connected to the output of the controlled receiver (13) and the other (control) to the output of the former (4). The output of the switch (3) is connected to the input of the measurement unit (5). The input of the former (4) is connected to the output of the transmitter triggering synchroniser. The output of the noise generator (1) is connected through the series-connected attenuator (10) and directional coupler (11) to the input of the controlled receiver (13).

EFFECT: higher accuracy and shorter measurement time.

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Description

The proposed noise figure meter relates to the field of measurement technology and is designed to control the noise figure of the radar receiver.

Known devices for measuring noise figure can be divided into modulation and non-modulation, depending on the type of noise signal used in the measurement process.

Modulation devices (with a modulated noise generator) allow automatic measurement of the noise figure when the radar transmitter is on and with high accuracy, however, these devices are of little use in built-in control systems due to the complexity due to the large number of electrical elements and special functional units (see. U.S. Patent No. 3,794,999 of February 26, 1974).

Known non-modulation devices (with an unmodulated noise signal generator) are simple and highly reliable, however, they are characterized by low accuracy due to the impossibility of measuring the noise figure with the radar transmitter turned on, as well as the high complexity of the measurement process.

An exception is an automatic noise figure meter (see USSR author's certificate No. 306426 of 05/12/1970, G01R 27/28), which has high accuracy and low laboriousness of the measurement process, but which is not widely used in integrated radar monitoring systems due to complexity due to the presence of a large number of special devices (program unit, selective amplifier, frequency-dependent feedback, key automatic gain control with a storage element, etc.).

The closest in technical essence the prototype of the proposed meter is a non-modulation device for measuring noise figure described in the book S. M. Latin and others. ″ Technique and practice of operating radar systems ″, M., ed. ″ Soviet Radio ″, 1970, pp. 103-106.

This device contains an unmodulated noise generator, a calibrated high-precision attenuator, a waveguide switch, and a dial gauge. The measurement error with this device reaches 2.5 dB and is a consequence of the fact that measurements are made only when the radar transmitter is turned off and the value of the noise figure of the receiver fixed in this case does not correspond to the actual value with the transmitter turned on.

The measurement process using the specified device is laborious, since the operator spends considerable time on reading the readings of the pointer device and calibrated attenuator, as well as on calculating the noise figure from the readout results.

The aim of the present invention is the provision of measuring the noise figure of the receiver with the transmitter turned on to increase the accuracy of the measurement.

This goal is achieved by the fact that a key for blanking the probe pulse of the radar transmitter is inserted between the output of the monitored receiver and the input of the measuring device into the noise figure meter, containing an unmodulated noise generator, power source, measuring device and control device. The key is controlled by the driver, which is synchronized by the transmitter trigger pulse generated by the radar synchronizer.

An unmodulated noise generator is connected to the input of the receiver using a directional coupler, while between the directional coupler and the unmodulated noise generator an installation uncalibrated attenuator is included to adjust the noise figure meter in order to improve measurement accuracy.

The measuring device is made in the form of a threshold electronic circuit consisting of an integrator, a comparison circuit, a reference voltage source and an indicator that automatically displays the measurement result.

The entered key in combination with the adopted connection diagram of the unmodulated noise generator allows the measurement of the noise figure when the radar transmitter is switched on, since the probe pulse is blanked at the input of the measuring device and the unmodulated noise generator is protected from the effects of a powerful microwave probe pulse. The measured value of the noise figure of the receiver corresponds to the actual one, since its increase is taken into account when the radar transmitter is on.

The measuring device in the form of a threshold electronic circuit provides a reduction of 3 times spent on measuring time compared with the prototype.

The proposed meter combines the simplicity of functional construction with high accuracy in measuring the maximum permissible value of the noise figure.

In FIG. 1 is a block diagram of a noise figure meter.

The noise figure meter contains: an unmodulated noise generator 1, a power source 2, a key 3, a driver 4, a measuring device 5, consisting of an integrator 6, a comparison circuit 7, an indicator 8, a reference voltage source 9, an installation non-calibrated attenuator 10, a directional coupler 11, control device 12.

The noise figure is measured using the proposed meter by the method of two samples, which is implemented by preliminary normalization of the noise voltage at the output of the monitored receiver 13 with the unmodulated noise generator 1 turned off and subsequent tolerance measurement of the noise voltage with the unmodulated noise generator 1 turned on. These procedures are performed when the radar transmitter is turned on.

The noise output voltage U _{W of the} monitored receiver 13 is blanked with a key 3, which is normally open and closed for the duration of the probing signal by the pulse of the driver 4, synchronized by the start pulse of the radar transmitter. In the integrator 6 of the measuring device 5, the voltage U _{W is} integrated, then fed to the signal input of the comparison circuit 7.

At the first stage of the measurement, the voltage U _op1 is supplied to the reference input of the comparison circuit 7 from the reference voltage source 9, with which the integrated noise voltage U _{w is} compared.

The noise voltage is normalized at the output of the monitored receiver 13 at the first measurement stage by adjusting the gain of the monitored receiver 13 using the control device 12 until the voltage U _w and U _{opt1 are equal} , which is automatically fixed by indicator 8.

After normalizing the noise voltage, the power supply 2 of the unmodulated noise generator 1 and the reference voltage U _op2 instead of U _{op1 are simultaneously turned} on using the control device 12. The noise voltage U _w increased after turning on the power supply 2 is compared with the reference voltage U _op2 , and the comparison result is automatically fixed by indicator 8.

In some cases, when increased accuracy of noise figure measurement is required, a switchable attenuator can be connected between the output of the monitored receiver 13 and the input of the key 3, which is turned on by the control device 12 while the power supply 2 is turned on.

A switchable attenuator ensures a constant noise voltage at the input of the measuring device 5 during the measurement, which increases the accuracy of the measurement. It does not require the inclusion of the reference voltage U _op2 , since the noise voltage U _{w is} compared with only one reference voltage U _op1 before and after the unmodulated noise generator 1 is turned on.

An unmodulated noise generator 1 is expediently performed on an avalanche diode, and as a comparison circuit 7, an automatic parameter control device can be used according to the USSR author's certificate No. 475953 of 05.25.1973, class. G01R 31/28. In this case, the indicator 8 can be performed according to the circuit shown in FIG. 2.

The equality of voltages U _w and U _op1 during normalization is fixed in such an indicator by alternately flashing the “Norma” and “More” displays, and the result of the tolerance measurement of the voltage U _w after switching on the power supply 2 is fixed by highlighting one of these displays depending on the value of the noise figure .

Schematic design of the remaining nodes of the inventive meter is well known.

The combination in the proposed meter of simplicity of functional construction with high measurement accuracy commensurate with the accuracy of modulation devices, as well as reducing the complexity of the measurement process, distinguishes it from the specified prototype. Performed on elements of microelectronics in combination with microwave elements of a strip type (directional coupler, mounting non-calibrated attenuator), the inventive meter has lower weight and size characteristics and increased reliability at a comparable cost compared to the prototype.

Claims (2)

1. The noise figure measuring device of a radar receiver with a transmitter start synchronizer, comprising a power source, the output of which is connected to the noise generator power circuits, a control unit whose outputs are connected respectively to the control inputs of the monitored receiver of the power source and the measurement unit with an indicator, characterized in that, in order to increase the accuracy of radiation when the transmitter is running and to reduce the radiation time, it is equipped with an attenuator directed by a coupler, driver and key, input for which it is connected to the output of the controlled receiver, the control input to the output of the shaper, and the output to the input of the radiation unit, while the input of the shaper is connected to the output of the trigger synchronizer of the transmitter, and the output of the noise generator through a series-connected attenuator and directional coupler to the input of the controlled receiver . 2. The device according to claim 1, characterized in that the measuring unit is equipped with a reference voltage source and an integrator connected in series and a comparison element, the other input of which is connected to the output of the reference voltage source, the input of which is connected to the output of the control unit, while the integrator input is connected to the key output, and the output of the comparison element with the indicator input.

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