CN102128990A - Method for judging power amplifier saturation in electromagnetic radiation sensitivity automatic test - Google Patents

Abstract

The invention discloses a method for judging the saturation of a power amplifier in an automatic electromagnetic radiation sensitivity test, belonging to the field of electromagnetic compatibility sensitivity testing. The method increases the output amplitude of a signal source and calculates the standard limit value E and the actually measured electric field strength value. The difference Δ between E ₀ , when the difference Δ does not meet the threshold X, adjust the signal source output amplitude increment according to the difference Δ while comparing the relationship between the difference Δ and the signal source output increment, Determine whether the power amplifier has gain compression, so as to judge whether the power amplifier enters the nonlinear saturation region, so as to determine whether the output of the power amplifier can meet the standard limit value requirements while dynamically adjusting the amplitude increment to determine the output amplitude of the signal source Purpose. The method for judging the saturation of the power amplifier of the present invention saves test time, improves test efficiency, and prolongs the service life of the power amplifier; at the same time, it ensures the accuracy of electromagnetic compatibility test results.

Description

A Method for Judging Power Amplifier Saturation in Automatic Electromagnetic Radiation Sensitivity Test

technical field

The invention relates to the field of electromagnetic compatibility automatic testing, in particular to a method for judging the saturation of a power amplifier in the automatic testing of electromagnetic radiation sensitivity.

Background technique

According to GJB151A-97 "Requirements for Electromagnetic Emission and Susceptibility of Military Equipment and Subsystems", electromagnetic compatibility testing includes two parts: electromagnetic interference (EMI) testing and electromagnetic susceptibility (EMS) testing, and electromagnetic susceptibility testing includes conduction sensitivity. Accuracy and radiation susceptibility testing. The basic principle of the sensitivity test is that the interference generating equipment produces a certain level of electromagnetic interference, and it is very time-consuming to manually adjust the signal source, so the EMC automatic test system is used to test the amplitude of the signal source for each frequency point of the tested product. Automatic adjustment of the value. As shown in Figure 1, the electromagnetic radiation susceptibility automatic test system generally consists of a signal source, a power amplifier, a radiation antenna, a field sensor, monitoring equipment, and a PC. The output signal of the signal source is transmitted to the input terminal of the power amplifier through the radio frequency cable, and the output terminal of the power amplifier outputs a high-power signal to the excitation terminal of the radiation antenna. The radiation antenna generates a certain intensity of interference signal under the excitation of the high-power signal, and the monitoring equipment collects and displays the The strength of the external interference signal received by the sensor at the location of the tested product, the PC is respectively connected to the control port and the signal source of the monitoring equipment, on the one hand, it collects and processes the external electromagnetic radiation field received by the monitoring equipment and controls the instrument of the monitoring equipment Parameter setting; on the other hand, it also controls the instrument parameter setting of the signal source. According to the provisions of the GJB151A-97 standard on the field strength limit value, the output amplitude of the signal source is adjusted to make it reach the limit value required by the GJB151A-97 standard.

In the electromagnetic radiation susceptibility test, it is necessary to apply an external electromagnetic radiation field of a certain intensity to the tested product in a wide frequency range to investigate the electromagnetic sensitivity of the tested product. The strength of the applied electromagnetic radiation field at the location of the tested product must meet the limit value requirements of certain test standards. Therefore, when interference is applied to each frequency point, it is necessary to set an initial amplitude for the signal source, and adjust the signal source output based on this. Amplitude, so that the field strength of the applied electromagnetic radiation received by the field sensor reaches the strength (limit value) specified in the test standard, and then it can step to the next test frequency point to continue the test. In the automatic test of electromagnetic radiation sensitivity, it is necessary to judge whether the power amplifier enters the nonlinear saturation region while adjusting the output amplitude of the signal source. As shown in Figure 2, when the input signal does not enter the nonlinear saturation region of the power amplifier, the power amplifier The characteristic curve has better amplification characteristics, and the input signal strength can continue to increase until the output meets the standard limit value requirements; if the input signal enters the nonlinear saturation region of the amplifier, continuing to increase the input signal strength will not change the output signal strength of the power amplifier. If the limit value required by the standard cannot be reached, the power amplifier may be burned out. Gain compression in the nonlinear saturation region of the power amplifier is an inherent property of the power amplifier, which is unavoidable, but the location of the nonlinear saturation region cannot be precisely located. Therefore, while increasing the input signal amplitude of the power amplifier (that is, the output amplitude of the signal source), it is necessary to judge whether to enter the nonlinear saturation region of the power amplifier.

Existing methods for judging the saturation of power amplifiers are all judged by the number of empirical control cycles. As shown in Figure 3, E in Figure 3 is the standard electric field strength. During the test, when the difference Δ between the standard limit value and the field strength value at the test position does not meet the threshold X requirement, but in a small range Z( When Z>X), that is, |Δ|<Z, start counting cycles. When the number of cycles reaches an empirical value, generally 6 times, it is considered that the power amplifier has entered the nonlinear saturation region, and it is judged that the output of the power amplifier cannot meet the standard limit value. request, exit the program.

Judging whether the power amplifier is saturated according to this method has the following disadvantages:

1. This method adopts the number of empirical cycles, which may be repeated many times in the saturation region of the power amplifier, which takes a lot of time and reduces the efficiency of the test.

2. Continuously increasing the input signal amplitude in the saturation region of the power amplifier may cause damage to the power amplifier and reduce the performance of the power amplifier.

Contents of the invention

In order to judge whether the power amplifier enters the nonlinear saturation region by observing whether the power amplifier has gain compression, to determine whether the output of the power amplifier can meet the standard limit value requirements, and to protect the power amplifier at the same time, a method for quickly judging the saturation of the power amplifier is adopted. . By comparing the relationship between the field strength increment at the test position and the signal source output signal amplitude increment, it is judged whether the power amplifier enters the nonlinear saturation region.

A method for judging the saturation of a power amplifier in an automatic electromagnetic radiation susceptibility test, comprising the following steps:

Step 1. Set the initial cycle count value to i=1, and set the output amplitude S of the signal source at the same time. The output amplitude S of the signal source at different test frequency points is set according to the antenna coefficient of the antenna used;

Step 2. Read the electric field strength value E ₀ at the test position, and the unit of the electric field strength value E ₀ is dBμV/m;

Step 3: Determine the number of cycles i, and perform different operations according to the number of cycles i:

a. If i=1, execute the fourth step;

b. If i>1, and the distance between the electric field strength increment (E ₀ -E ₁ ) at the test position and the signal source output amplitude increment (αΔ) satisfies 0.8<(E ₀ -E ₁ )/αΔ<1.25, If the power amplifier does not enter the nonlinear saturation region, perform the fourth step; otherwise, the power amplifier enters the nonlinear saturation region, record the output amplitude of the signal source and adjust the next frequency point.

Step 4: Calculate the difference Δ between the standard limit value E and the actual measured electric field strength value E ₀ , at this time, the standard limit value E also uses dBμV/m, and the unit of the difference Δ is dB, Δ=EE ₀ ;

Step 5. Determine whether the difference Δ satisfies |Δ|<X. If the difference Δ meets the requirements, record the output amplitude of the signal source and adjust the next frequency point; if the difference Δ does not meet the requirements, go to step 6; X Generally, the value is 0.1-0.5, preferably 0.1.

Step 6. Adjust the signal source output amplitude S=S+α·Δ, and add 1 to the number of cycles at the same time, that is, i=i+1, and set E ₁ =E ₀ ; where α is the adjustment coefficient, generally taken as 0.5≤α ≤0.9, preferably 0.8.

Step 7. Repeat steps 2 to 6 until the difference Δ satisfies |Δ|<X, then the signal source adjustment of the current frequency point is completed, and the amplitude adjustment of the next frequency point is continued.

The advantages of the present invention are:

1. Reduce test time and improve test efficiency.

2. Make the field strength value of the test position close to the standard limit value in a step-by-step manner, which not only protects the test equipment, but also ensures the accuracy of the test.

3. By quickly judging whether the power amplifier has entered the nonlinear saturation region, reducing the number of times the input signal is increased in the nonlinear saturation region, protecting the power amplifier and prolonging the life of the power amplifier.

Description of drawings

Fig. 1 is a radiation sensitivity test block diagram in the prior art;

Fig. 2 is a power amplifier characteristic curve;

Fig. 3 is a flow chart of an existing method for judging power amplifier saturation;

Fig. 4 is a flowchart of the method of the present invention.

Detailed ways

The method of the present invention will be described in detail below in conjunction with the accompanying drawings.

A method for judging the saturation of a power amplifier in an automatic electromagnetic radiation susceptibility test, as shown in Figure 4, has the following steps:

The first step is to set the initial cycle count value as i=1, and set the initial amplitude S of the signal source at the same time;

The output amplitude S of the signal source at different test frequency points is set according to the antenna factor of the antenna used.

The second step is to read the electric field strength value E ₀ at the test position, and the unit of the electric field strength value E ₀ is dBμV/m, which is convenient for subsequent calculations;

The third step is to judge the number of cycles i, and perform different operations according to the number of cycles i:

a. If i=1, execute the fourth step sequentially;

b. If i>1, first compare the electric field strength increment at the test position with the signal source output amplitude increment to determine whether the power amplifier has entered the nonlinear saturation region. If the power amplifier enters the nonlinear saturation region, then If the output signal strength of the power amplifier at the test frequency cannot meet the standard requirements, record the output amplitude of the signal source and adjust the next frequency point; if the power amplifier does not enter the nonlinear saturation zone, perform the fourth step in sequence;

Compare the electric field strength increment (E ₀ -E ₁ ) at the test position with the signal source output amplitude increment (αΔ), considering the unsatisfactory linearity within the dynamic range of the power amplifier, use the discriminant formula 0.8<(E ₀ -E ₁ )/αΔ<1.25 to determine whether the power amplifier has gain compression, wherein α is an adjustment coefficient, generally set at 0.5-0.9. If 0.8<(E ₀ -E ₁ )/αΔ<1.25 holds, the power amplifier does not enter the nonlinear saturation region; otherwise, the power amplifier enters the nonlinear saturation region.

The fourth step is to calculate the difference Δ between the standard limit value E and the actual measured electric field strength value E ₀ , Δ=EE ₀ , at this time, the standard limit value E also uses dBμV/m, and the unit of the difference Δ is dB;

The fifth step is to judge whether the difference Δ satisfies the requirement of the threshold X, that is, |Δ|<X, where X generally takes a value of 0.1-0.5, preferably 0.1. If the difference Δ meets the requirements of the threshold X, record the output amplitude of the signal source and adjust the next frequency point; if the difference Δ does not meet the requirements of the threshold X, enter the sixth step;

The actual measured electric field strength value is obtained by monitoring equipment.

The difference Δ is used to estimate the distance between the tested electric field strength value and the standard limit value, which is the basis for adjusting the amplitude increment of the signal source in the next step.

Step 6: Adjust the output amplitude of the signal source S=S+α·Δ, and add 1 to the number of cycles at the same time, that is, i=i+1, and set E ₁ =E ₀ ; where α is the adjustment coefficient, generally taken as 0.5≤ α≤0.9, preferably 0.8.

The seventh step, repeat the second step to the sixth step until the difference Δ meets the requirements of the threshold X, that is, |Δ|<X, then the signal source adjustment of the current frequency point is completed, and the amplitude adjustment of the next frequency point is continued .

Claims (4)

1. a method for judging power amplifier saturation in an electromagnetic radiation susceptibility automatic test, is characterized in that comprising the steps: Step 1. Set the initial cycle count value as i=1, and set the output amplitude S of the signal source at the same time; The output amplitude S of the signal source at different test frequency points is set according to the antenna coefficient of the antenna used; Step 2, reading the electric field strength value E ₀ at the test position; The unit of electric field strength _E0 is dBμV/m; Step 3: Determine the number of cycles i, and perform different operations according to the number of cycles i: a. If i=1, execute the fourth step; b. If i>1, and the electric field strength increment (E ₀ -E ₁ ) at the test position and the signal source output amplitude increment (αΔ) satisfy 0.8<(E ₀ -E ₁ )/(αΔ)< 1.25, the power amplifier does not enter the nonlinear saturation zone, go to the fourth step; otherwise, the power amplifier enters the nonlinear saturation zone, record the output amplitude of the signal source and adjust the next frequency point; where α is the adjustment coefficient; Step 4. Calculate the difference Δ between the standard limit value E and the actually measured strength E ₀ of the interference signal, Δ=EE ₀ , the unit of the standard limit value E is dBμV/m, and the unit of the difference Δ is dB; Step 5. Determine whether the difference Δ satisfies |Δ|<X. If yes, record the output amplitude of the signal source and adjust the next frequency point; if not, perform step 6; where the threshold value X is 0.1≤X ≤0.5; Step 6. Adjust the signal source output amplitude S=S+α·Δ, and add 1 to the number of cycles at the same time, that is, i=i+1, and set E ₁ =E ₀ ; where α is the adjustment coefficient, which is taken as 0.5≤α≤ 0.9; Step 7. Repeat steps 2 to 6 until the difference Δ satisfies |Δ|<X, then the signal source adjustment of the current frequency point is completed, and the amplitude adjustment of the next frequency point is continued. 2. the method for judging power amplifier saturation in a kind of electromagnetic radiation susceptibility automatic test according to claim 1, is characterized in that: the actually measured electric field strength value described in step 2 obtains by monitoring equipment. 3. The method for judging power amplifier saturation in a kind of electromagnetic radiation susceptibility automatic test according to claim 1, characterized in that: the threshold value X is 0.1. 4. The method for judging the saturation of a power amplifier in an automatic electromagnetic radiation sensitivity test according to claim 1, wherein the adjustment coefficient α is 0.8.

Images