SU1257554A1 - Device for measuring non-linear distortions of envelope of amplitude-modulated signal - Google Patents

Abstract

The invention can be used to measure the non-linear distortion of the output signals of radio transmitters. The purpose of the invention, the extension of functionality, is achieved by introducing into the device for measuring nonlinear distortions ffxod .i L of the amplitude-modulated signal (AMC) envelope of two additional elements 9 and 15 of the connection, two inverters. 10 and 16, a low-frequency filter 14 and three switching devices: devices 11, 12 and 13. The device also contains a coupling element 1, a demodulator 2, peak detectors 3 and 4, a discriminator 5, an operational amplifier 7, an indicator 8. Suggested the device allows, in addition to the nonlinear distortion coefficient (K) of the AMC envelope, to automatically determine the K of the nonlinear distortion of the audio frequency amplifier, K modulation and K of the high frequency harmonics of the transmitter, which ensures the achievement of the goal. 1 il. C (/ C r t m and K a Cr j; a

Description

The invention relates to electrical measurements and can be used to measure the non-linear distortion of the output signals of radio transmitters.

The purpose of the invention is to expand the functionality.

The drawing shows a functional diagram of the device.

The device contains a communication element 1, a demodulator 2, first and second pickpoints 3 and 4, a discriminator 5, an adder 6, an operational amplifier 7, an indicator 8, the first additional communication element 9, the first inverter 10, the first, second and third blocks 11, 12 and 13 switching, low-frequency filter 14, the second additional element 15 of the communication

second inverter 16.

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The output of the communication element 1 is connected to the output of the Demodulator 2, the first output of which is connected to the first additional communication element 9, the first output of the first switching unit 11 and the input of the first inverter 10. The second output of the first switching unit 11 is connected to the output of the second inverter 16, with the first output of the second switching unit 12, the first inputs of the discriminator 5 and the adder 6 and the first output of the third switching unit 13. The third output of the first switching unit 11 is connected to the input of the first peak detector 3, the output of which It is connected with the fourth output of the first switching unit 11, the fifth output of which is connected to the input of the second inverter 16. The second output of the demodulator 2 is connected to the output of the second additional communication element 15, the input of the second peak detector 4 and the second output of the second switching unit 12, the third output of which is connected to the output of the first inverter 10, and the fourth output to the input of the low-frequency filter 14, the output of which is connected to the output of the peak detector 4, the second output of the third switching unit 13 and the second inputs of the discriminator 5 and an adder 6, the output of which is connected to the third output of the third switching unit 13 and the first input of the operational amplifier 7, the second input of which is connected to the output of the discriminator 5 and the fourth output of the third switching unit 13. Output

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the operational amplifier 7 is connected to the input of the indicator 8. The input of the communication element 1 is the device input for high frequency signals, the inputs of the additional communication elements 9 and 15 are the device inputs for low frequency signals.

The device works as follows.

In the mode of measuring the nonlinear distortions of the envelope from the transmitter output, the AM signal goes through the coupling element 1 to the demodulator 2, on the loads of which the lower and upper envelopes are allocated, respectively.

The envelope voltages are applied to the peak detectors; 3 and 4, which at the outputs cause the lower and upper amplitudes of the envelope. Then, the voltages of the lower and upper amplitudes of the envelope are fed simultaneously to the discriminator 5, where they are compared, and to the adder 6 where they are summed.

The obtained voltages from the outputs of the discriminator 5 and the adder 6 are fed to the corresponding inputs of the operational amplifier 7, operating according to the division scheme, from the output of the operational amplifier 7, the signal is fed to the indicator 8 with a symmetric reading.

The degree of deviation of the indicator arrow indicates the quantitative 5 value of the nonlinear distortion coefficient, and the direction of deviation of the arrow corresponds to the type of distortion of the amplitude (modulation) characteristics of the radio transmitter under study or RF amplifier.

When the nonlinear distortion coefficient of the audio amplifier is changed, the first and second additional communication elements 9 and 15 are connected to the output of the amplifier. The first switching unit 11 is set to a position in which the peak detector 3 is connected to the output of the low-frequency amplifier opposite the peak detector 4, the output signal proportional to the lower amplitude of the low-frequency signal of the peak detector 3 through the inverter 16 is fed to the first inputs 5 of the adder 6 and the discriminator 5 .The output signal of the peak detector 4, proportional to the upper amplitude of the low-frequency signal, arrives

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on the second inputs of the adder 6 and the discriminator 5.

In the discriminator 5 and the adder 6, the signals of the peak detectors 3 and 4 are compared and summed respectively, then the resulting signals of the discriminator 5 and the adder 6 are fed to the corresponding inputs of the operational amplifier 7 operating according to the dividing circuit, the output of the operational amplifier 7 is fed to the indicator 8 s symmetric counting.

The degree of deviation of the indicator hand will show the quantitative value of the nonlinear distortion coefficient of the audio amplifier, and the direction of the deviation will show the type of distortion of the amplitude characteristic of the amplifier.

When measuring the modulation coefficient, the coupling element 1 is connected to the transmitter output, the amplitude-modulated signal arrives at the input of the demodulator 2, the outputs of which allocate the lower and upper envelopes, respectively. Switching blocks 12 and 13 are placed in a position in which the signal from the second output of demodulator 2 passes through a low-frequency filter 14 proportional to the amplitude of the carrier signal, switching block 13 is fed to the first input of the operational amplifier 7. The signal from the first output of the demodule of the torus 2 through the switching unit 11 enters the input of the peak detector 3, the output of which extracts a signal proportional to the amplitude of the envelope AM signal, the signal from the output of the detector 3 through the switching unit 11 and the switching unit 13 goes to the second the input of the operational amplifier 7, from the output of the operational amplifier 7, the signal is fed to the indicator 8. The degree of deviation of the indicator arrow will show the quantitative value of the modulation coefficient t.

Measurement of the nonlinear distortion of the carrier signal is performed in two modes: without modulation and in AM mode.

When measuring the nonlinear distortion coefficient without modulation, the communication element 1 is connected to the transmitter output, the RF signal from the output of communication element 1 is fed to the input of the demodulator 2, the outputs of which

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signals proportional to the lower and upper amplitudes, respectively, the signal from the first output of the demodulator 2 through the inverter 10 and the switching unit 12 are supplied to the first inputs of the discriminator 5 and the adder 6, to the second inputs of which the signal goes from the filter 14 the second top: ode demodulator 2. In the discriminator 5 and the adder 6, the signals of the demodulator 2 are compared and summed.

The voltages obtained from the outputs of the adder 6 and the discriminator 5 are fed respectively to the first and. the second inputs of the operational amplifier 7, operating according to the division scheme, from the output of the operational amplifier 7, the signal is fed to the indicator 8.

The degree of deviation of the indicator hand indicates the numerical value of the nonlinear distortion coefficient of the carrier signal. When measuring the nonlinear distortion coefficient unimportant in the AM signal mode, the block

11Switches are put; similar to the measurement of the modulation coefficient, and the switch unit

12- in a position similar to the measurement of the nonlinear distortion of the envelope of the AM signal. In this case, the voltage at the outputs of the peak detectors 3 and 4 is proportional to the upper amplitudes of the upper and lower envelopes. Otherwise, the operation of the device is similar to the operation when measuring without modulation.

Thus, the proposed device allows, in addition to measuring the nonlinear distortion coefficient of the amplitude-modulated signal envelope, to automatically determine the nonlinear distortion factor of the audio amplifier, modulation factor, and coefficient of the high frequency carrier signal, which expands the functionality of the device.

Claims (1)

Invention Formula A device for measuring the nonlinear distortion of the envelope of an amplitude-modulated signal, containing a communication element, the output of which is connected to the input of the demodulator, the first peak detector, the second peak 5 12S73 / 6 the detector, the output of which is connected to the switches, and to the first inputs of the discriminator, the first input of the adder, the output of a coaxial device and from the mmator, the second inputs of the left C (; one with the first input, the operand of which is connected to the second output amplifier, switching unit, the third one is connected to the output of dnscriminal, the output of the first switching unit of the com tor, and the output of the operational amplifier is connected to the input of the first peak case with the indicator input, the vector of which is connected with the fourth terminal of the first unit for the purpose of expanding the functional connections, the fifth terminal of which is connected, two additional ones are entered into it with the input of the second inverter, additional communication elements, two in-outputs of the second additional element, low-pass filter and trit connection is connected to the second output of the switching unit, the inputs of the pre-demodulator, the input of the second peak-coupling elements are the second detector and the second output of the second input of the device for the low-15 signals of the switching unit, the third output frequency, the output of the first In addition, the first output terminal is connected to the synchronizer, and the fourth output is connected to the first, the output of the demodulator, to the input of the low-pass filter, the output of the first inverter and to the first output of which is connected to the second input of the first switching unit, the second 20 the output of which is connected to the output of which is connected to the output of the third output of the third block of the second inverter, with the first of the output key, the fourth output of which of the BTopof-o and the third block is re-connected to the output of the discriminator.