SU1622850A1 - Method of determining instability of amplifier noise temperature - Google Patents

Description

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(21) 4475086/21

(22) 08.08.88

(46) 01.23.91. Bul.N 3 (72) B. R. Darchin nts

(53) 621.317.75 (088.8)

(56) Microwave devices on semiconductor devices. Ed. I.V. Malsky and B.V. Sestroretsky. M .: Owls. radio, 1969, p. 411-413.

Technical description and design for operation of the noise figure meter X5-2I, up to 1.400, 181 TO, 1977.

(54) METHOD FOR DETERMINING THE INSTABILITY OF THE NOISE TEMPERATURE OF THE AMPLIFIER

(57) The invention can be used in the design and testing of amplifiers. The purpose of the invention is to improve the accuracy of measuring the instability of the noise temperature of an amplifier, achieved by eliminating the error due to the intensity of the factor. To do this, a signal is sent from 4 to IS with a known noise signal and alternately with a sinusoidal. Output sinusoidal 4 compares a sinusoidal signal to its input. The power of the noise generator 10 from the corresponding sign is per portioned power difference of the sinusoid. The output power noise is compared to the power of the driven generator 10 and the power difference between the noise powers indicates the magnitude and sign of the noise temperature at

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due to the influence of the instability of the gain of the amplifier. To do this, the amplifier 4 is fed to the input of a noise source 8 with a known noise temperature alternately with a sinusoidal signal. The output sinusoidal signal of amplifier 4 is compared in power with a sinusoidal signal at its input. The power of the controlled noise generator 10 is changed with an appropriate sign by an amount proportional to the difference in the power of the sinusoidal signals compared. The noise output power of amplifier 4 is compared to the noise power of the adjustable noise generator 10. The magnitude and sign of the difference between the compared powers of the noise signals determine the magnitude and sign of the instability of the noise temperature of the amplifier 4. I Il.

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The invention relates to the field of radio measurements and can be used in the design and testing of amplifiers.

The aim of the invention is to improve the accuracy of measuring the instability of the noise temperature of an amplifier by eliminating errors due to the influence of the instability of the gain factor of the amplifier.

The drawing shows a block diagram of an apparatus for implementing a method for determining the instability of the noise temperature of an amplifier.

The device contains a sinusoidal microwave signal generator 1, power divider 2, first switch 3, amplifier 4 under investigation, second switch 5, variable attenuator 6, third switch 7, first adjustable noise generator 8, fourth switch 9, second adjustable noise generator 10, adder 11 voltages, first 12 and second 13 microwave amplifiers, first 14 and second 15 detectors, pulse voltage amplifier 16 with adjustable gain, pulse voltage amplifier 17, first 18 and second 19 synchronous detectors, first 20 and the second 21 indicators, the generator 22 pulse voltage in the form of a square wave, the first adjustable source

23 constant voltage, divider

24 voltage, temperature meter 25, low-noise amplifier 26, calibrated variable attenuator 27, and a second adjustable source 28 of constant voltage.

The output of the microwave signal generator 1 is connected to the input of the power divider 2, the first output of which is connected to the first input of the third switch 7. The second output of the power divider 2 is connected to the second input of the first switch 3. The output of the first adjustable noise generator 8 is connected to the first input of the first switch 3 the output of which through the analyzed amplifier 4 is connected to the input of the second switch 5. The second output of the second switch 5 through a variable attenuator 6 is connected to the second input of the third switch 7. The output of the third switch 7 through the first 12 microwave amplifier, the first detector 14, the pulse voltage amplifier 16

adjustable gain and the first synchronous detector 18 is connected to the input of the voltage divider 24

The first output of the divider 24, for example, is not connected to the first indicator 20, the second output to the first input of the voltage adder II. The output of the first adjustable voltage source 23 is connected to the second input of the voltage adder 11, the output of which is connected to the control input of the second adjustable noise generator 10. The first output of the second switch 5 is connected to the first input of the fourth switch 9. The output of the second adjustable noise generator 10 is connected to the second input of the fourth switch 9, the output of which is through the second microwave amplifier 13, the second detector 15, pulse voltage amplifier 17 and the second synchronous detector 19 are connected to indicator 21.

The first, second, third and fourth outputs of the pulse voltage generator 22 are connected respectively to the control inputs of the first 3, second 5, third 7 and fourth 9 switches. A fifth, invertible, output of the pulse voltage generator 22 is connected to the control input of the first synchronous detector 18. The sixth output of the pulse voltage generator 22 is connected to the control input of the second synchronous detector 19. The temperature meter 25 is connected to the temperature control terminals of the absorber of the first adjustable noise generator 8 . The output of the second adjustable voltage source 28 is connected to the control input of the first adjustable noise generator 8. During calibration, the output of the amplifier 4 under study is connected via a low-noise amplifier 26 and a calibrated variable attenuator 27 to the input of the second switch 5.

The method is carried out as follows.

A sinusoidal signal from the output of the generator 1 is fed to the input of the power divider 2. From the first output of the power divider 2 through the third switch 7 (at the time when the first input of this switch is connected to the output), the signal arrives at the input of the first 12 amplifier. the third switch 7 (in position 2) receives a sinusoidal signal following from the second output of power divider 2 through the first switch 3 (in position 2), test amplifier 4 and variable attenuator 6. Difference compared in power sine Shaped signals are allocated at the output of the first synchronous detector 18.

In the process of adjusting the device, the voltage at the output of the first synchronous detector 18 is set to zero using a variable attenuator 6. The signal from the output of the first adjustable noise generator 8 through the first switch 3 (in position 1), the amplifier 4, the second 5 and the fourth 9 switches (both in position 1) are fed to the input of the second amplifier 13 microwave. After half a period of the control signal, the fourth switch 9 goes to position 2 and from the second adjustable noise generator 10 the signal goes to the input of the second microwave amplifier 13. The difference in power compared noise signals is extracted at the output of the second synchronous detector 19. In the process of adjusting the device, the voltage at the output of the second synchronous detector 19 is set to zero by changing the voltage supplied from the first controlled constant voltage source 23 to the second input of the adder 11 tension In this case, the voltage at the first input of the voltage adder 11 should be equal to zero.

Consider the following specific case of the device.

Let the gain and the noise temperature of the amplifier 4 under investigation be simultaneously increased relative to the nominal values. At the same time, an increase in the gain of the investigated amplifier 4 leads to the appearance at the input of the first amplifier 12 of the microwave signal an imbalance with the envelope in the form of a square wave and to the appearance of a constant voltage with a positive sign at the output of the first synchronous detector 18 and

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the first input of the adder 11 voltage. Moreover, the magnitude of the voltage of the imbalance signal is greater, the greater the change in the gain of the amplifier under study 4.

Further, after combining with the voltage coming from the first adjustable source 23 of constant voltage, the imbalance signal is sent to the control input of the second adjustable noise generator 10. At the same time, the power of the latter also increases in proportion to the magnitude of the change in the gain of the amplifier 4 under investigation. This leads to a reduction in the difference in the noise signals compared in power to the input of the second amplifier 13 microwave due to a decrease in the contribution of the noise signal due to an increase in the gain of the amplifier under study 4. The remaining c after the correction, the difference of the noise signals compared in power has a positive sign and determines the magnitude of the change in the noise temperature Tours of the test amplifier.

In order to determine the proportionality of the change in the output power of the second controlled noise generator 10 with the change in the gain of the amplifier 4 under study, the following test is carried out.

Between the output of the amplifier 4 under study and the input of the second switch 5, a low-noise microwave amplifier 26 and a calibrated variable attenuator 27 are connected in series.

Starting with a fade on attenuator 27 equal to 1

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where Kac.t6 is the gain of amplifier 26, the b4 is changed first in the direction of increasing attenuation, and then in the direction of decreasing attenuation. In this case, a zero indication of the indicator 21 should be ensured. In the event that the indicator 21 does not have zero readings within the specified limits of variation L, then the gain of the adjustable amplifier 16 of the pulse voltage must be increased or decreased accordingly.

At the same time, the scale of the indicator 20 for changing the gain factor of the amplifier under study 4 is calibrated according to the indications of a calibrated variable attenuator 27.

In order to match the sign of the unbalance signal at the output of the first synchronous detector 18 with the sign of the change in the gain of the amplifier 4 under study, an inverted control signal is applied to the control input of the first synchronous detector 18 with respect to the control signals supplied to the control inputs of the switch 3, 5, 7 and 9 and the synchronous detector 19.

The calibration of the scale of the noise temperature change indicator 21 is performed in the mode when the output of the amplifier 4 is connected to the input of the second switch 5 and the voltage at the first input of the voltage adder 11 is zero. Calibration is performed by varying the noise temperature of the first adjustable noise generator 8 using a second adjustable constant voltage source 28. In this case, the noise temperature of the first controlled noise generator 8 is determined by the readings of the meter

25 heating (or cooling) temperature of the absorber of this generator.

Claims (1)

Invention Formula The method of determining the instability of the noise temperature of the amplifier, which consists in that the amplifier under test is given a signal with a known noise power and the power of the noise signals is compared, after which the noise temperature of the amplifier under test is instable, and that, in order to increase the accuracy of measuring the instability of the noise temperature, a signal with a predetermined noise power and a sine wave signal is alternately supplied to the perceptible amplifier, the difference of the power of the sinusoidal signal from the input and output The signals of the amplifier under test form a second noise signal whose power is changed by an amount proportional to the power difference of the sinusoidal signal from the input and output of the amplifier under test with the appropriate sign, the magnitude and sign of the power difference of the output noise signal of the amplifier and the second noise signal determine the value and sign noise temperature instability amplifier. Editor N. Yatsola Compiled by N.Mikhalev Tehred L.OleinikKorrektor M.Maksimishinets Order 1185 Circulation 422 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Subscription