This paper presents a new kind of differential-mode current injection test method. The equal response voltage on the cable or the antenna port of the equipment under test (EUT) is regarded as equivalent principle for radiation and injection test. The injection and radiation response analysis model and the injection voltage source extrapolation model in high intensity radiated field are established. The conditions of using differential-mode current injection as a substitute for radiation are confirmed. On the basis of the theoretical analysis, the function and structure design scheme of the directional coupling device is proposed. The implementation techniques for the single differential-mode current injection method (SDMCI) and the double differential-mode current injection method (DDMCI) are discussed in detail. The typical nonlinear response interconnected systems are selected as the EUT. The test results verify the validity of the SDMCI and DDMCI test methods.
Bulk current injection (BCI) is a kind of traditional EMC test method. Essentially, the interference current is injected into the cable of the equipment to substitute for radiation susceptibility test [
In conclusion, HIRF in large-scale test space is very difficult to simulate under the condition of laboratory. Meanwhile, there are still many insufficiencies for the traditional BCI method to carry out the injection susceptibility tests. Hence, our research team proposes a new kind of wideband differential-mode current injection test method for system level EMC test.
The theoretical equivalent principle between the injection and radiation test method is the equal response of the equipment [
In this paper, the typical interconnected system is composed of two types of equipment and the interconnected cable. It is shown in Figure
The structure of a typical interconnected system.
The equivalent circuit model for analyzing the equipment B response. (a) Radiation test. (b) Injection test.
According to the transmission line theory, the input impedance
The open-circuit voltage
In (
Therefore, in Figure
According to the above radiation analysis process, under the condition of the injection test, the equivalent circuit can be easily obtained. It is shown in Figure
According to the equivalent principle of the two test methods, that is,
Equation (
Wideband differential-mode current injection testing technique proposed in this paper is used to substitute for high intensity radiated effects test. The crucial question is how to acquire the equivalent injection voltage source
As we know, the electromagnetic radiation effects on equipment mainly include interference, degradation, failure, and damage. On the basis of theoretical analysis and experimental research for typical nonlinear systems, the action process of electromagnetic radiated energy can be divided into two subprocesses. One is the field to wire coupling process, and the other is the circuit response process of the module and device. The radiation response process is shown in Figure
Radiation response process for nonlinear interconnected system.
According to the electromagnetic field theory, the field to wire coupling is a linear process, and the circuit response of the module and device is a nonlinear process. If the excitation effects of the injection source
For the reason that
Directional coupling device (DCD) is the supporting equipment for the wideband differential-mode current injection test. The typical connection mode is shown in Figure
The sketch map of connection mode for DCD.
In order to satisfy the requirements of substituting the differential-mode current injection test for the radiation test, the DCD should contain the following ports. First, the DCD should contain the pass-through ports which are used to transmit the working signal between the interconnected equipment. It requires that the insertion loss is smaller than 0.5 dB. Second, the device should contain the injection port which is used to inject the differential-mode interference signal to the equipment B. It requires that the frequency band of the injection port is sufficient and the injection signal coupled into the equipment B is distortion-free. Third, the device should contain the monitoring port which is used to monitor the forward voltage signal on the transmission line of the interconnected system. It also requires that the frequency band is sufficient, and the monitoring signal is distortion-free.
According to the above function requirements of the DCD, the design scheme based on the directional coupler theory is confirmed. The DCD can be composed of two directional couplers. It is shown in Figure
The function and structure of the DCD.
The above six ports DCD can be regarded as lossless and reciprocal network. The scattering matrix
Port 4 is the injection port. It is used to inject differential-mode interference signal to equipment B. It requires higher injection efficiency, so the coupling coefficient should be as small as possible. However, too small coupling coefficient cannot satisfy the insertion loss requirement between port 1 and port 2; that is,
According to the transmission characteristic of the traditional symmetrical directional coupler, the phase shift between the coupling channel signal and the main channel signal is 90°. If the pulse signal transmits in the main channel, the output signal waveform of the coupling port will change obviously [
According to the unitarity of the scattering matrix
For the phase shift between the forward coupling signal and the main channel signal which is 0°, considering the energy coupling action of port 3, the parameter
From the above analysis process, the scattering matrix
Because of the directional injection characteristic of the DCD, the single differential-mode current injection (SDMCI) method is used to carry out injection test only for one end equipment in the interconnected system. The typical application is to carry out differential-mode current injection test for antenna receiving system. The test configuration of the SDMCI is shown in Figure
The typical test configuration of SDMCI test method.
The forward voltage signal extraction, interference signal injection, and normal transmission signal monitoring are realized with the support of the DCD. However, whether it satisfies the equivalent condition discussed above or not is the crucial problem, which is analyzed as follows.
The DCD can be equivalent to six ports black box network. The equivalent circuit model is shown in Figure
The equivalent circuit model when the DCD is inserted into the interconnected system.
As for the radiation test, the left part of the reference plane
The equivalent circuit model for (a) radiation test and (b) injection test.
On the basis of the equivalent source wave theory in microwave engineering [
In order to analyze the response of the equipment B, the left part of the reference plane
The further simplified circuit models for (a) radiation test and (b) injection test.
According to the equivalent source wave theorem [
It is defined that the matrix
According to the equivalent circuit model in Figure
According to the equivalent principle of the two test methods (i.e.,
If the equipment A is an antenna or a transmitter, the reflection coefficient
From the above analysis process, when the DCD is inserted into the interconnected system, under the condition of unchanged reflection coefficient
The equivalent principle for the radiation and injection test in this paper is the equal response voltage on the input port of the equipment B. However, it is very hard for us to directly monitor the input port response voltage in engineering. In order to make the SDMCI method applicable in the practical engineering test, other transmission signals which can be easily monitored should be selected as equivalent principle. The introduction of the DCD solves the problem.
The port 5 of DCD is used to monitor the forward voltage on the transmission line. In this paper, the equal response voltage on port 5 is defined as the equivalent principle for the SDMCI and radiation test. The following article proofs the correctness of using the port 5 response voltage as the equivalent principle. According to the equivalent circuit model in Figure
Assuming that the coupling coefficient of port 4 and port 5 is
Under the condition of the radiation and injection test, the response voltages
It is assumed that
It can be seen that (
Carry out the low intensity radiation pretest for interconnected systems. The radiated field intensity is selected as
Obtain the equivalent corresponding relation between injection voltage and radiated electric field intensity. The differential-mode current injection test is carried out through injection port 4 of the DCD. The output response
Finish the SDMCI test for interconnected systems. If the high intensity radiated field for ultimate examination is
In order to carry out differential-mode current injection test for two types of equipment interconnected by a cable simultaneously, the double differential-mode current injection test (DDMCI) method is proposed in this paper. The test configuration of the DDMCI is shown in Figure
The typical test configuration of DDMCI test method.
Two directional coupling devices are connected with equipment A and equipment B separately. The equivalent circuit model is shown in Figure
The equivalent circuit model of DDMCI test method.
In order to ensure that the injection response is equal to the radiation response of equipment A and equipment B, two injection voltage sources USLI and
Carry out low intensity radiation pretest for interconnected system. The radiated electric field intensity is selected as
Obtain the equivalent corresponding relation between injection voltage and radiated electric field intensity. First, the interconnected system is carried out injection test through port 4L with the left injection voltage source. The amplitude
Finish the DDMCI test for interconnected system. If the high intensity radiated field for ultimate examination is
The interconnected system under test is a typical nonlinear response system. It is composed of a receiving antenna, a coaxial cable, and RF front-end components. The RF front-end components include a clipping filter, an attenuator, a low noise amplifier (LNA), a sensitivity controller, a directional coupler, and a clipping amplifier. They are integrated together in one container. It is assumed that the receiving antenna is the equipment A1 and the container of the RF front-end components is the equipment B1. Because of the nonlinear response characteristic of the clipping filter, LNA, and so on, the above nonlinear response interconnected system is suitable to carry out the verification test.
The single frequency continuous wave radiation test and the differential-mode current injection test are carried out separately for the interconnected system. The radiation and injection configuration diagrams are shown in Figures
The configuration diagram for the radiation test.
The configuration diagram for the differential-mode current injection test.
The equal output response of equipment B1 for the radiation and injection test is regarded as the equivalent principle. According to the result of the data processing, the relation curves between the equivalent injection voltage, the output response of equipment B1, and the radiated electric field intensity are shown in Figure
The relation curves between the equivalent injection voltage and the radiated electric field intensity.
It can be seen form Figure
The interconnected system under test is also the above nonlinear response system. The validity verification for SDMCI can be conducted as follows. First, the traditional radiation test is carried out for the interconnected system. The radiation response curve of the equipment B1 from the linear region to the saturation region can be obtained. Second, according to the above SDMCI test method, the injection response curve of the equipment B1 from the linear region to the saturation region can also be abstained. Third, by calculating and analyzing the output response error of the two test methods, the validity of SDMCI method can be verified.
The response curves of the equipment B1 under the condition of radiation and the SDMCI test at the frequency point of 3.3 GHz, 4.0 GHz and 5.6 GHz are shown in Figure
Output response relative error for SDMCI test method.
Number |
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1 | 20.00 | 0.12 | 20.00 | 0.93 | 19.95 | 0.12 |
2 | 22.44 | 0.34 | 28.25 | 0.12 | 28.18 | 0.34 |
3 | 25.18 | 0.46 | 39.91 | 0.34 | 35.48 | 0.69 |
4 | 28.25 | 0.46 | 50.24 | 1.14 | 44.67 | 1.49 |
5 | 31.70 | 1.14 | 63.25 | 1.37 | 56.23 | 1.71 |
6 | 35.57 | 1.26 | 70.96 | 1.60 | 70.79 | 1.94 |
7 | 39.91 | 1.14 | 79.62 | 1.83 | 89.13 | 1.83 |
8 | 44.77 | 1.26 | 89.34 | 1.60 | 112.20 |
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9 | 50.24 | 1.37 | 100.24 | 1.60 | 141.25 | 1.49 |
10 | 56.37 | 1.14 | 112.47 | 1.83 | 158.49 | 1.03 |
11 | 63.25 | 1.14 | 126.19 | 1.83 | 177.83 | 1.14 |
12 | 70.96 | 1.03 | 133.67 | 1.71 | 188.36 | 1.60 |
13 | 79.62 | 0.92 | 141.59 | 1.60 | 199.53 | 1.14 |
14 | 89.34 | 0.92 | 149.98 | 1.60 | 211.35 | 1.03 |
15 | 100.24 | 0.92 | 158.87 | 1.37 | 223.87 | 0.80 |
16 | 106.18 | 0.92 | 168.28 | 1.37 | 237.14 | 0.69 |
17 | 112.47 | 0.69 | 178.25 | 1.26 | 251.19 | 1.03 |
18 | 119.13 | 0.57 | 188.81 | 1.14 | 266.07 | 0.34 |
19 | 126.19 | 0.46 | 200.00 | 1.03 | 281.84 | 0.35 |
20 | 133.67 | 0.46 | 211.85 | 0.80 | 298.54 | 0.69 |
21 | 141.59 | 0.46 | 224.40 | 0.69 | 316.23 | 0.81 |
22 | 149.98 | 0.34 | — | — | 334.97 | 0.81 |
23 | 158.87 | 0.00 | — | — | 354.81 | 0.23 |
24 | 168.28 | 0.12 | — | — | 375.84 | 0.46 |
25 | 178.25 | 0.12 | — | — | 398.11 | 0.12 |
The response curves under the condition of radiation and SDMCI test.
Two satellite-borne RF front-end low-noise amplifier modules are selected as equipment A2 and equipment B2 which are connected by a coaxial cable. It is important to note that this kind of interconnected system does not exist in engineering. The designed interconnected system is only for experimental verification in the extreme condition.
The radiation test configuration is shown in Figure
The configuration diagram for the radiation test.
The DDMCI test configuration is shown in Figure
The configuration diagram for the DDMCI test.
According to the test configuration in Figures
The radiation and DDMCI response curve of equipment A2.
The radiation and DDMCI response curve of equipment B2.
As can be seen from Figures
Output response relative error for DDMCI test method.
Number |
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1 | 12.62 | 0.35 | 0.35 | 14.16 | 0.34 | 0.92 | 12.62 | 1.49 |
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2 | 15.89 | 0.00 | 0.23 | 17.83 | 0.00 | 1.26 | 15.89 | 1.26 | 2.61 |
3 | 20.00 | 1.14 | 1.49 | 22.44 | 0.46 | 0.57 | 20.00 | 0.57 | 2.16 |
4 | 25.18 | 0.80 | 1.26 | 28.25 | 1.16 | 0.12 | 22.44 | 0.81 | 1.83 |
5 | 31.70 | 0.46 | 1.26 | 35.57 | 1.39 | 0.69 | 25.18 | 0.69 | 1.03 |
6 | 39.91 | 0.34 | 0.92 | 44.77 | 1.62 | 1.16 | 28.25 | 1.51 | 0.69 |
7 | 44.77 | 0.12 | 0.69 | 50.23 | 1.86 | 1.16 | 31.70 | 1.51 | 0.46 |
8 | 50.24 | 0.23 | 0.57 | 56.37 | 1.86 | 1.39 | 35.57 | 1.86 | 0.23 |
9 | 56.37 | 0.35 | 0.34 | 63.25 | 1.98 | 1.51 | 39.91 | 1.16 | 0.46 |
10 | 63.25 | 0.46 | 0.46 | 70.96 | 1.86 | 1.62 | 44.77 | 1.51 | 0.23 |
11 | 66.99 | 0.81 | 0.12 | 75.17 | 1.98 | 1.51 | 50.24 | 1.62 | 0.00 |
12 | 70.96 | 0.35 | 0.34 | 79.62 | 1.74 | 1.62 | 56.37 | 2.09 | 0.23 |
13 | 75.16 | 0.93 | 0.23 | 84.34 | 1.39 | 1.27 | 59.71 | 2.21 | 0.23 |
14 | 79.62 | 0.35 | 0.12 | 89.34 | 1.04 | 1.39 | 63.25 | 2.09 | 0.23 |
15 | 84.34 | 0.81 | 0.35 | — | — | — | 66.99 | 2.45 | 0.58 |
16 | 89.34 | 0.23 | 0.00 | — | — | — | 70.96 | 2.92 | 0.69 |
The theory, model, method, and implementation technique of the wideband differential-mode current injection test technology are systematically studied in this paper. The injection and radiation response analysis model and the injection voltage source extrapolation model in HIRF are established. The conditions of using injection as a substitute for radiation are confirmed. The equivalent injection voltage source can be obtained by the linear extrapolation. The function and structure design scheme of the directional coupling device (DCD) is proposed. The forward voltage extraction, interference signal injection, and normal transmission signal monitoring in the interconnected system are realized with the support of DCD. On the basis of the above research, the SDMCI test method and the DDMCI test method based on the DCD are summarized. The typical nonlinear response systems are selected as EUT. The test results indicate that the biggest output response relative error is smaller than 5%. They verify the validity of the SDMCI and the DDMCI test methods.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work is supported by the National Natural Science Foundation of China under Grant 61372040 and the Arm Pre-research Program under Grant 51333040101.