A Measurement Method for Nonlinear Distortion Components of Dual-Frequency Excitation of an Amplifier

Abstract

The present invention discloses a method for measuring the non-linear distortion components of a dual-frequency excitation of an amplifier, which includes a dual-frequency excitation signal source, an amplifier, and a spectrum analyzer. The dual-frequency excitation signal source is a dual-channel dual-frequency excitation signal source. The output end of the first channel of the dual-frequency excitation signal source is connected to the input end of the amplifier, and the output end of the amplifier is connected in series with the output end of the second channel of the dual-frequency excitation signal source and then connected to the measurement end of the spectrum analyzer. The present invention uses a dual-channel series cancellation method to enable the spectrum analyzer to measure the residual non-linear distortion components at the output end of the amplifier without dual-frequency excitation. Moreover, the cancellation method effectively reduces the signal amplitude entering the spectrum analyzer, so that the non-linear distortion generated by the spectrum analyzer can be ignored.

Description

Technical Field

[0001] The present invention relates to a method for measuring the non - linear distortion components of an amplifier under dual - frequency excitation. Background Art

[0002] The non - linear distortion of an amplifier under dual - frequency excitation is an important characteristic of the amplifier. Generally, a commercial signal source is used to generate an excitation signal containing two frequency components and input it into the amplifier. After the amplifier generates a non - linear distortion signal, a spectrum analyzer is used to measure the distortion signal. However, in the existing measurement method, the spectrum analyzer directly measures the output port of the amplifier. When the signal amplitude at the output port of the amplifier is large, after the signal is collected by the spectrum analyzer, the spectrum analyzer will further distort the signal. The distortion of the amplifier and the distortion of the spectrum analyzer are superimposed on each other, resulting in the inability to separate the two in the final measurement result; in addition, due to the impurity of the commercial excitation signal source, in addition to containing two desired main frequency components, it also contains other unnecessary frequency components. After these unnecessary frequency components pass through the amplifier, it may make it impossible for the tester to identify whether the frequency components at the output port of the amplifier originate from the amplifier or the test signal source itself. Summary of the Invention

[0003] The object of the present invention is to propose a method for measuring the non - linear distortion components of an amplifier under dual - frequency excitation, which adopts a dual - channel series cancellation method to enable the spectrum analyzer to measure the residual non - linear distortion components of the amplifier without dual - frequency excitation.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for measuring the non - linear distortion components of an amplifier under dual - frequency excitation, including a dual - frequency excitation signal source, an amplifier, and a spectrum analyzer, wherein: the dual - frequency excitation signal source is a dual - channel dual - frequency excitation signal source. The output end of the first channel of the dual - channel dual - frequency excitation signal source is connected to the input end of the amplifier, and the output end of the amplifier is connected in series with the output end of the second channel of the dual - channel dual - frequency excitation signal source and then connected to the measurement end of the spectrum analyzer; the expression of the dual - frequency excitation input signal received at the input end of the amplifier is:

[0006] V IN = E1sin ω1t + E2sinω2t

[0007] Wherein:

[0008] E1 and E2 are the amplitudes of the two frequency components;

[0009] ω1 and ω2 are the frequencies of the two frequency components;

[0010] The expression of the dual - frequency excitation output signal generated after the dual - frequency excitation signal passes through the amplifier is:

[0011] V OUT = K0 + K1(V IN ) + K2(V IN ) 2 + K3(V IN ) 3 + …

[0012] wherein,

[0013] K0, K1, K2, and K3 are non - linear coefficients;

[0014] The process by which the spectrum analyzer measures the non - linear distortion components not including the dual - frequency excitation of the amplifier is as follows:

[0015] a. When the first channel of the dual - frequency excitation signal source outputs a dual - frequency excitation signal, first, the second channel of the dual - frequency excitation signal source is operated in a short - circuit state, and no signal is generated.

[0016] b. Adjust the second channel of the dual - frequency excitation signal source to generate a dual - frequency signal including frequency components ω1 and ω2 and amplitudes E1 and E2 respectively.

[0017] c. Adjust the relative phase between the second channel and the first channel so that the ω1 and ω2 frequency components at the output end of the amplifier cancel out the ω1 and ω2 frequency components generated by the second channel, and the amplitudes E1 and E2 cancel out each other. Then, what the spectrum analyzer measures is the residual non - linear distortion components not including ω1, ω2, E1, and E2.

[0018] The further solution is: The dual - channel dual - frequency excitation signal source is a dual - channel Josephson arbitrary waveform synthesizer. Each channel of the dual - channel Josephson arbitrary waveform synthesizer includes a pulse source, a microwave amplifier, a DC blocker, a Josephson junction array, and a terminal resistor connected in series in sequence. The output of the Josephson junction array is the excitation signal output end of the channel.

[0019] The further solution is: The pulse source is an arbitrary waveform generator of model M8195A.

[0020] The further solution is: The DC blocker is a high - pass filter.

[0021] The further solution is: The Josephson junction array and the terminal resistor operate in a low - temperature environment of 4.0K to 5.0K.

[0022] The further solution is: The Josephson junction array converts the driving pulse into a flux quantum to form an excitation signal.

[0023] The beneficial effects of the present invention are:

[0024] 1. By adopting the method of dual-channel series cancellation, the spectrum analyzer measures the residual non-linear distortion component of the amplifier that does not contain dual-frequency excitation; moreover, the cancellation method effectively reduces the signal amplitude entering the spectrum analyzer, so that the non-linear distortion generated by the spectrum analyzer can be ignored.

[0025] 2. The excitation signal synthesized by the Josephson arbitrary waveform synthesizer is extremely pure and does not contain additional harmonic components, solving the problem of impurity of commercial excitation signal sources.

[0026] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the equipment connection of the measurement method of the present invention;

[0028] Figure 2 It is a schematic diagram of the dual-frequency excitation signal generated by Channel 1 of the present invention;

[0029] Figure 3 It is a schematic diagram of the non-linear distortion signal at the output end of the amplifier;

[0030] Figure 4 It is a schematic diagram of the dual-frequency excitation signal generated by Channel 2;

[0031] Figure 5 It is a schematic diagram of the residual non-linear distortion component measured by the spectrum analyzer that does not contain ω1 and ω2;

[0032] Figure 6 It is a schematic diagram of the structure of the dual-channel Josephson arbitrary waveform synthesizer of the present invention. Detailed Embodiments

[0033] A method for measuring the non-linear distortion component of dual-frequency excitation of an amplifier is a method for measuring the residual non-linear distortion component of the amplifier that does not contain dual-frequency excitation. As Figure 1 shown, the measurement method includes a dual-frequency excitation signal source 1, an amplifier 2, and a spectrum analyzer 3. The dual-frequency excitation signal source is a dual-channel dual-frequency excitation signal source. The output end of the first channel 101 of the dual-channel dual-frequency excitation signal source is connected to the input end of the amplifier, and the output end of the amplifier is connected in series with the output end of the second channel 102 of the dual-channel dual-frequency excitation signal source and then connected to the measurement end of the spectrum analyzer; the input end of the amplifier receives a dual-frequency excitation input signal expression as Figure 2 shown:

[0034] V IN = E1sin ω1t + E2sinω2t Formula 1

[0035] Where:

[0036] E1 and E2 are the amplitudes of two frequency components;

[0037] ω1 and ω2 are the frequencies of two frequency components;

[0038] The expression of the dual-frequency excitation output signal generated after the dual-frequency excitation signal passes through the amplifier is:

[0039] V OUT = K0 + K1(V IN ) + K2(V IN ) 2 + K3(V IN ) 3 +… Formula 2

[0040] Wherein,

[0041] K0, K1, K2, and K3 are nonlinear coefficients;

[0042] Substituting Formula 1 into Formula 2, the second-order nonlinear distortion of the amplifier can be obtained as:

[0043]

[0044] Correspondingly, the third-order nonlinear distortion is:

[0045]

[0046] The schematic diagram of the nonlinear distortion is as Figure 3 shown;

[0047] The process of the spectrum analyzer measuring the nonlinear distortion components of the amplifier that do not include the dual-frequency excitation is as follows:

[0048] a. When the second channel of the dual-frequency excitation signal source outputs the dual-frequency excitation signal, first operate the second channel of the dual-frequency excitation signal source in the short-circuit state, and no signal is generated;

[0049] b. Adjust the second channel of the dual-frequency excitation signal source to generate a dual-frequency signal including frequency components ω1 and ω2 and amplitudes E1 and E2 respectively, as Figure 4 shown;

[0050] c. Adjust the relative phase between the second channel and the first channel so that the ω1 and ω2 frequency components at the output end of the amplifier cancel out the ω1 and ω2 frequency components generated by the second channel, and the amplitudes E1 and E2 cancel out each other. Then, the residual nonlinear distortion components that do not include ω1, ω2, E1, and E2 measured by the spectrum analyzer are as Figure 5 shown.

[0051] The dual-channel dual-frequency excitation signal source in this embodiment uses a dual-channel pulse-driven broadband AC quantum voltage system with high-purity spectrum signal synthesis ability - Josephson Arbitrary Waveform Synthesizer (JAWS) to synthesize the dual-frequency excitation signal; as Figure 6 shown, the dual-channel dual-frequency excitation signal source is a dual-channel Josephson arbitrary waveform synthesizer. Each channel of the dual-channel Josephson arbitrary waveform synthesizer includes a pulse source 4, a microwave amplifier 5, a DC blocker 6, a Josephson junction array 7, and a terminal resistor 8 connected in series in sequence. The output of the Josephson junction array is the excitation signal output terminal of the channel.

[0052] The pulse source is an arbitrary waveform generator of model M8195A; since both the Josephson junction array and the terminal resistor are superconducting material devices of known technology, the Josephson junction array and the terminal resistor operate in a liquid helium cryogenic environment of 4.2K. The DC blocker is a DC-blocking circuit formed by a combination of capacitors, resistors, or inductors. In this embodiment, the DC blocker is a high-pass filter.

[0053] [[ID=ID=8]]Among them: for the convenience of control, two M8195A arbitrary waveform generators can be connected to a host control server 9 through an interface, and the host control server 9 coordinates and controls the two M8195A arbitrary waveform generators. The Josephson junction array converts the driving pulses generated by the pulse source into flux quanta to form an excitation signal, which can ensure the accuracy of the excitation signal quanta of the synthesized wave. The M8195A arbitrary waveform generator uses the Delta-sigma modulation algorithm to push the quantization noise in the modulation code to the high-frequency band of GHz, thereby ensuring a high signal-to-noise ratio of the synthesized excitation signal in the low-frequency region. Compared with conventional waveform synthesizers, the excitation signal of this method has the advantages of high accuracy and low harmonic distortion.

[0054] This method has two advantages compared with traditional measurement methods: (1) The excitation signal is extremely pure and does not contain additional harmonic components; (2) By means of cancellation, the signal amplitude entering the spectrum analyzer is effectively reduced, so that the nonlinear distortion generated by the spectrum analyzer can be ignored.

Claims

1. A measurement method for the non-linear distortion components of an amplifier under dual-frequency excitation, comprising a dual-frequency excitation signal source, an amplifier, and a spectrum analyzer, characterized in that, The dual-frequency excitation signal source is a dual-channel dual-frequency excitation signal source. The output terminal of the first channel of the dual-channel dual-frequency excitation signal source is connected to the input terminal of the amplifier. The output terminal of the amplifier is connected in series with the output terminal of the second channel of the dual-channel dual-frequency excitation signal source and then connected to the measurement terminal of the spectrum analyzer. The expression of the dual-frequency excitation input signal received at the input terminal of the amplifier is: V IN = E1sinω1t + E2sinω2t Where: E1 and E2 are the amplitudes of the two frequency components; ω1 and ω2 are the frequencies of the two frequency components; The expression of the dual-frequency excitation output signal generated after the dual-frequency excitation signal passes through the amplifier is: V OUT = K0 + K1(V IN ) + K2(V IN ) 2 + K3(V IN ) 3 +… Where, K0, K1, K2, and K3 are nonlinear coefficients; The process by which the spectrum analyzer measures the nonlinear distortion components not including the dual-frequency excitation of the amplifier is: a. When the first channel of the dual-frequency excitation signal source outputs a dual-frequency excitation signal, first operate the second channel of the dual-frequency excitation signal source in a short-circuit state without generating any signal; b. Adjust the second channel of the dual-frequency excitation signal source to generate a dual-frequency signal including frequency components ω1 and ω2 and amplitudes E1 and E2 respectively; c. Adjust the relative phase between the second channel and the first channel so that the ω1 and ω2 frequency components at the output terminal of the amplifier cancel out the ω1 and ω2 frequency components generated by the second channel, and the amplitudes E1 and E2 cancel out each other. Then, what the spectrum analyzer measures is the residual nonlinear distortion components not including ω1, ω2, E1, and E2.

2. The measuring method according to claim 1, characterized in that, The dual-channel dual-frequency excitation signal source is a dual-channel Josephson arbitrary waveform synthesizer. Each channel of the dual-channel Josephson arbitrary waveform synthesizer includes a pulse source, a microwave amplifier, a DC blocker, a Josephson junction array, and a terminal resistor connected in series in sequence. The output of the Josephson junction array is the excitation signal output terminal of the channel.

3. The measuring method according to claim 2, characterized in that The pulse source is an arbitrary waveform generator with the model number M8195A.

4. The measurement method according to claim 2, wherein The DC blocker is a high-pass filter.

5. The measuring method according to claim 2, characterized in that The Josephson junction array and the terminal resistor work in a low-temperature environment of 4.0K to 5.0K.

6. The measurement method according to claim 2, characterized in that The Josephson junction array converts the driving pulse into a flux quantum to form an excitation signal.

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