Lightning protection module design method of communication system transmitting channel and protection module

Abstract

The invention discloses a lightning protection module design method of a communication system emission channel and a protection module, and relates to the technical field of lightning protection, and the method comprises the following steps: selecting a sensitive device to simplify the emission channel; performing simulation verification on the simplified transmitting channel; the method comprises the following steps: carrying out model selection on a gas discharge tube GDT and a transient voltage suppressor TVS of lightning protection devices, and designing a transient protection circuit to discharge most of energy of lightning electromagnetic pulses; fourier transform is carried out on the 8 / 20 us lightning current, and energy accumulative distribution is carried out; according to the lightning protection module designed through the design method, the peak power in a lightning electromagnetic pulse intrusion test and a simulation experiment is far smaller than the minimum value of the tolerable peak threshold power range of a power amplifier, meanwhile, before and after a lightning stroke experiment is carried out, data shows that the gain at the center frequency of the amplifier is not compressed, and the gain at the center frequency of the amplifier is not compressed. And a transmitting channel of a communication system is ensured not to be interfered, and sensitive elements of the system are effectively protected.

Description

Technical Field

[0001] The present invention relates to the technical field of lightning protection, and in particular to a lightning protection module design method and a protection module for a transmission channel of a communication system. Background Art

[0002] Lightning is a common discharge phenomenon in nature. Lightning strikes that affect lines can generate sufficiently high overvoltage surges in the power system. Depending on the application and equipment location, the pulse amplitude ranges from hundreds of volts to tens of thousands of volts. The communication system plays a vital role in modern society. It is not only a tool for information exchange, but also one of the important infrastructures to promote social progress and development. Modern communication systems generally use low power for electronic circuits. If the devices are not protected, the energy of lightning pulses can cause partial damage or slow degradation of electronic components, or even permanent damage to the equipment, which can seriously paralyze the communication system. Therefore, in the process of lightning protection, the communication network needs a reliable lightning protection system to deal with device damage or destruction caused by surges caused by lightning or overvoltage and overcurrent.

[0003] The development and implementation of lightning protection systems, including line lightning rods, grounding systems, surge protectors (SPDs), and overhead grounding wires, have undergone continuous improvement and have gained wide recognition in the global power industry. Continuous efforts to reduce the frequency of lightning strikes on transmission lines and reduce the incidence of lightning-induced faults are key goals for scientists, engineers, and practitioners in the global power sector. Jiang Yijin et al. studied a new type of overhead transmission line lightning protection system based on external grounding wires, using grounding wires placed on both sides of the top of independent external towers as protection wires to replace standard grounding wires and protect short overhead transmission line sections under special circumstances such as highly endangered lightning strikes. Hu Haize et al. studied and adopted lightning protection frames and upper lightning protection nets to replace lightning rods to protect against direct lightning strikes, and used lightning protection wires between frames to protect against lightning shielding strikes. At the same time, an external ring grounding network was used to optimize the grounding network and perform special local impact optimization. Yang Dasheng et al. analyzed and calculated the two-stage protection circuit, and proposed a quantitative design algorithm based on the transient response index of this circuit to optimize the system power supply lightning protection design. Wang Q et al. designed a radio frequency front-end electromagnetic pulse protection module using multiple lightning protection devices to study the insertion loss based on the different characteristics and performance differences of the electronic devices themselves. Although the above protection module can discharge most of the energy of lightning, there will be residual pressure and the influence of low-frequency components of lightning current in the follow-up, and no effective protection measures are taken for sensitive components of the system. Therefore, a lightning protection module design method and protection module for the transmission channel of the communication system are needed to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a lightning protection module design method and a protection module for a transmission channel of a communication system, so as to solve the problems existing in the prior art mentioned in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The design method of the lightning protection module of the transmission channel of the communication system includes the following steps:

[0007] S1: Understand the transmission channel principle of typical communication systems and select sensitive devices to simplify the transmission channel;

[0008] S2: Simulate and verify the simplified transmission channel;

[0009] S3: Select the lightning protection devices gas discharge tube GDT and transient suppression diode TVS, and design the transient protection circuit to discharge most of the energy of lightning electromagnetic pulse;

[0010] S4: Perform Fourier transform on the 8 / 20us lightning current and perform energy accumulation distribution. According to the characteristics of the lightning current, design a high-pass filter protection circuit to further suppress the low-frequency component of the residual voltage to obtain a lightning protection module;

[0011] S5: Simulate and experimentally verify the lightning protection module in step S4.

[0012] Preferably, in S1, the transmission channel includes a digital control circuit, a mixer, a local oscillator, a power amplifier, a filter, a standing wave protection, a PIN transceiver switch and an antenna, wherein the power amplifier is used as a sensitive device to conduct intrusion research on lightning electromagnetic pulses, and the filter can ensure the normal operation of the center frequency. The power amplifier and the filter are selected as sensitive devices to simplify the transmission channel of the communication system.

[0013] Preferably, in S2, the simulation design of the power amplifier includes the design and selection of an input impedance matching circuit, a DC bias circuit, an output impedance matching circuit and a transistor, wherein the DC bias circuit design is completed using the DC scanning circuit template in the ADS simulation software; the transistor uses the MRF300A produced by NXP; the stability analysis is to build an S parameter simulation circuit of the power amplifier in combination with the DC bias circuit, and then analyze the stability of the power amplifier. If there is an unstable area, a lossy component needs to be introduced to achieve circuit stability; the matching circuit design first uses the load-pull design Load-Pull module and the source-pull design Source-Pull module in ADS to obtain the optimal impedance matching value between the load end and the source end, and then uses the Smith chart to complete the design of the matching circuit;

[0014] The passband and stopband of the filter are designed according to the actual center frequency of the power amplifier. The center frequency of the power amplifier is 144MHz, and the filter cutoff frequencies are set to 118MHZ and 174MHz. The bandpass filter is designed using ADS simulation software.

[0015] Preferably, the specific steps of S3 are:

[0016] S31: GDT selection includes breakdown voltage U R and pulse discharge current I R Considering the fluctuation of the normal working voltage U and the accuracy of the breakdown voltage of the gas discharge tube, U R Greater than or equal to twice U, and the pulse discharge current only needs to be greater than the peak value of the lightning current;

[0017] S32: TVS selection parameters include clamping voltage, breakdown voltage, reverse working voltage and surge current capability. The breakdown voltage of TVS must be higher than the normal working voltage of the circuit. Clamping voltage refers to the maximum voltage at which TVS clamps the voltage within a safe range when a transient surge occurs. When selecting, the clamping voltage must be lower than the maximum voltage that the protected circuit can withstand. During transient voltage, the lower the clamping voltage, the better, and the more effective it can be in protecting the circuit. The reverse working voltage is the maximum continuous reverse voltage that TVS can withstand under normal working conditions, and the reverse working voltage should be slightly higher than the working voltage of the circuit. The surge current capability is the maximum transient impact current that TVS can withstand. The appropriate surge current specification should be selected based on the maximum transient current that the circuit may be subjected to.

[0018] S33: Transient protection circuit design: Use a GDT and multiple TVS to suppress the coupling voltage, and use the appropriate number to design the transient protection circuit.

[0019] Preferably, in S4, the high-pass filter protection circuit selects a 300Ω lightning channel wave impedance and a controlled current source in parallel to simulate the lightning discharge channel according to the lightning discharge theory, considers the return loss and insertion loss in the selection of the high-pass filter order, and comprehensively considers the selection of a suitable high-pass filter.

[0020] Preferably, in S5, the specific steps of simulation verification are:

[0021] Taking 2kA lightning current as the excitation source, a GDT and a decoupling resistor are used to test the attenuation trend of the residual voltage of 1 to 6 TVSs respectively. A lightning electromagnetic pulse is added to the power amplifier. According to the principle of the communication system transmission channel, the pulse needs to be reversed to the circuit. Then the designed protection module is placed in the circuit and put into ADS for S parameter verification.

[0022] Preferably, in S5, the specific steps of experimental verification are:

[0023] According to the simulation verification process, appropriate amplifiers and filters were selected to simulate and build the communication system transmission channel. The GPP-CWG-2010 combination wave test system was used to inject a 2kV lightning voltage. The DC power supply and network analyzer were used to measure the gain data before and after the lightning strike.

[0024] A lightning protection module for a transmission channel of a communication system comprises a transient protection circuit and a filter protection circuit. The transient protection circuit is composed of a GDT and six TVSs. A decoupling resistor is connected between the GDT and the TVS. The filter protection circuit is composed of a third-order high-pass filter.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The lightning protection module designed by the design method of the present invention is subjected to a lightning electromagnetic pulse intrusion test. The peak power in the simulation experiment is far less than the minimum value of the peak threshold power range that the power amplifier can tolerate. At the same time, before and after the lightning strike experiment, the data show that the gain of the amplifier at the center frequency is not compressed. In contrast, when the lightning strike is performed without adding a protection module and when only adding a transient protection module, obvious gain compression is observed at the center frequency. This indicates that the designed simplified communication system transmission channel and protection module will not be damaged under the impact of a lightning electromagnetic pulse, and can ensure that the communication system transmission channel is not interfered with, thereby effectively protecting the system's sensitive components. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the transmission channel principle of the communication system of the present invention.

[0028] Figure 2 It is a simplified design diagram of the transmission channel of the communication system of the present invention.

[0029] Figure 3 (a) is the lightning current spectrum diagram, and (b) is the lightning current accumulated energy distribution diagram.

[0030] Figure 4 It is a schematic diagram of the protection module of the present invention.

[0031] Figure 5 This is the schematic diagram of a third-order high-pass filter.

[0032] Figure 6 This is the schematic diagram of a fifth-order high-pass filter.

[0033] Figure 7 This is the schematic diagram of the seventh-order high-pass filter.

[0034] Figure 8The return loss and insertion loss graphs of three high-pass filters are shown below.

[0035] Fig. 9 Insertion loss diagram of a third-order high-pass filter.

[0036] Fig.10 This is a residual voltage attenuation variation trend diagram of multiple TVSs of the present invention.

[0037] Fig.11 It is a schematic diagram of the simulation verification module of the present invention.

[0038] Fig.12 Input signal and output signal diagram verified by simulation of the present invention.

[0039] Fig.13 This is a gain diagram of the power amplifier before and after the lightning strike verified by the simulation of the present invention. DETAILED DESCRIPTION

[0040] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0041] See also Figure 1-13 , the present invention provides the following technical solutions:

[0042] The design method of the lightning protection module of the transmission channel of the communication system includes the following steps:

[0043] S1: Understand the principles of the transmission channel of a typical communication system, and select sensitive devices to simplify the transmission channel; the transmission channel includes digital control circuit, mixer, local oscillator, power amplifier, filter, standing wave protection, PIN transceiver switch and antenna. The power amplifier is used as a sensitive device to study the intrusion of lightning electromagnetic pulses, and the filter can ensure the normal operation of the center frequency. The power amplifier and filter are selected as sensitive devices to simplify the transmission channel of the communication system.

[0044] The strong electromagnetic pulse received by the communication antenna may force the PIN diode to turn on, causing the over-pulse to flow into the standing wave protection circuit of the transmission channel. The standing wave protection circuit is generally not directly connected in series in the RF channel, and its response time is usually in microseconds. It cannot respond to strong electromagnetic pulses in time, so it cannot effectively prevent the propagation of strong electromagnetic pulses in the transmission channel. Therefore, it should not be used as a sensitive device. Subsequently, the over-pulse reaches the filter. The filter is usually composed of passive devices such as inductors and capacitors, and its damage threshold is relatively high. Therefore, it is not suitable as a sensitive device, but it has a greater impact on frequency.

[0045] The strong electromagnetic pulse reaches the power amplifier after passing through the filter. The power amplifier consists of a bias circuit, a matching network, and active amplification devices. The active amplification devices mainly include semiconductor devices such as bipolar junction transistors, field-effect transistors, and high electron mobility transistors. The damage power thresholds of these active semiconductor devices are relatively low and are easily affected by high temperature and high electric field.

[0046] Therefore, the power amplifier should be regarded as a sensitive device in the emission channel. Since the filter has a great influence on frequency components, a power amplifier with a gain of 20 dB and a filter are selected to simplify the simulation of the emission channel of the communication system affected by lightning strikes.

[0047] S2: Conduct simulation verification on the simplified emission channel; The simulation design of the power amplifier includes the design and selection of the input impedance matching circuit, the DC bias circuit, the output impedance matching circuit, and the transistor. The design of the DC bias circuit is completed using the DC sweep circuit template in the ADS simulation software; The transistor uses the MRF300A produced by NXP; The stability analysis is to build the S-parameter simulation circuit of the power amplifier in combination with the DC bias circuit, and then analyze the stability of the power amplifier. If there is an unstable region, a lossy component needs to be introduced to achieve circuit stability; The design of the matching circuit first uses the Load-Pull module and the Source-Pull module in ADS to obtain the optimal impedance matching values at the load end and the source end, and then uses the Smith chart to complete the design of the matching circuit;

[0048] The filter designs the passband and stopband according to the center frequency of the actual power amplifier. The center frequency of the power amplifier is 144 MHz. The cut-off frequencies of the filter are set to 118 MHz and 174 MHz, and the band-pass filter is designed using the ADS simulation software.

[0049] S3: Select the lightning protection devices gas discharge tube GDT and transient voltage suppressor TVS, and design a transient protection circuit to discharge most of the energy of the lightning electromagnetic pulse; The specific steps are as follows:

[0050] S31: The selection of GDT includes the breakdown voltage U R and the pulse discharge current I R . Considering issues such as the fluctuation of the normal operating voltage U and the accuracy of the breakdown voltage of the gas discharge tube, U R should be greater than or equal to twice of U, and the pulse discharge current only needs to be greater than the peak value of the lightning current;

[0051] S32: TVS selection parameters include clamping voltage, breakdown voltage, reverse working voltage and surge current capability. The breakdown voltage of TVS must be higher than the normal working voltage of the circuit. Clamping voltage refers to the maximum voltage at which TVS clamps the voltage within a safe range when a transient surge occurs. When selecting, the clamping voltage must be lower than the maximum voltage that the protected circuit can withstand. During transient voltage, the lower the clamping voltage, the better, and the more effective it can be in protecting the circuit. The reverse working voltage is the maximum continuous reverse voltage that TVS can withstand under normal working conditions, and the reverse working voltage should be slightly higher than the working voltage of the circuit. The surge current capability is the maximum transient impact current that TVS can withstand. The appropriate surge current specification should be selected based on the maximum transient current that the circuit may be subjected to.

[0052] S33: Transient protection circuit design: Use a GDT and multiple TVS to suppress the coupling voltage, and use the appropriate number to design the transient protection circuit.

[0053] For the design of transient protection circuit, since GDT has a long response time, this article adopts one GDT and uses multiple TVS in parallel to assist GDT to solve its shortcoming of slow response time, and also plays a certain role in discharging current; when the GDT with large current flow and the TVS with small current flow are directly connected in parallel, the transient suppression diode will be damaged under the action of over-pulse, and the advantage of GDT's large current flow cannot be brought into play. Therefore, when the two protection devices are used in combination, a decoupling resistor is required to cooperate between the two transient protection devices.

[0054] S4: Perform Fourier transform on the 8 / 20us lightning current and perform energy accumulation distribution. According to the characteristics of the lightning current, design a high-pass filter protection circuit to further suppress the low-frequency component of the residual voltage to obtain a lightning protection module. According to the lightning discharge theory, the high-pass filter protection circuit uses a 300Ω lightning channel wave impedance and a controlled current source in parallel to simulate the lightning discharge channel. The return loss and insertion loss are considered in the selection of the high-pass filter order, and a suitable high-pass filter is selected after comprehensive consideration.

[0055] S41: According to lightning discharge theory, a 300Ω lightning channel wave impedance and a controlled current source are selected in parallel to simulate the lightning discharge channel.

[0056] I(t)=KI 0 (e-αt-e-βt) (1)

[0057] Where I 0 is the peak value of lightning current, K is the pulse amplitude correction coefficient, α is the wavefront attenuation coefficient, β is the wavetail attenuation coefficient, and I(t) is the instantaneous peak value of lightning current; where α>0, β>0, and α>β; the Fourier transform of lightning current is used to obtain the hyperbolic spectrum function:

[0058]

[0059] S42: Take the absolute value of the spectrum function to obtain the amplitude spectrum function:

[0060]

[0061] S43: The energy distribution can be obtained from Pasval's theorem:

[0062]

[0063] S44: Filter protection circuit design: according to Figure 4 The spectrum diagram and cumulative energy distribution diagram show that the attenuation within 20kHz needs to be greater than 20dB, and the attenuation of the center frequency needs to be controlled within 1dB without affecting the transmission of normal signals. Therefore, a high-pass filter with a cut-off frequency of 1MHz is selected for filtering protection.

[0064] The filter protection designed in this paper first determines the normalized parameters of the filter. Referring to the "LC Filter Design and Production", the characteristic impedance of the normalized filter is 1Ω and the cut-off frequency is 1 / 2π. The filter to be designed calculates the values ​​of the capacitor and inductor in the filter according to the normalized filter using the following steps. Define an M value and a K value, as shown in equations (5) and (6). At this time, the capacitance and inductance values ​​of the filter protection circuit to be designed are determined by equations (7) and (8).

[0065]

[0066] Where F 1 is the cutoff frequency of the filter to be designed, F 0 is the cutoff frequency of the reference filter, R 1 is the characteristic impedance of the filter to be designed, R 0 is the characteristic impedance of the reference filter, L 0 and C 0 are the normalized inductance and capacitance values ​​respectively, L and C are the inductance and capacitance values ​​of the filter to be designed respectively.

[0067] According to the design data of the normalized high-pass filter, L 0 Take 1H and 0.5H, C 0 Take 0.5F, and list the third-order, fifth-order, and seventh-order high-pass filter models to compare the return loss and insertion loss. The filter schematics correspond to Figure 5 , Figure 6 and Figure 7 , where the insertion loss of each order filter calculated by the formula is Figure 8 , where the third-order insertion loss is Fig. 9 , it is observed that the insertion loss at 20kHz is much greater than 20dB, at 1MHz it is about 3dB, and at 144MHz it is less than 0.001dB. Figure 8 This shows that all three filters can meet the design requirements; however, in terms of return loss, Figure 8 The third-order high-pass filter has a smoother return loss curve, a larger return loss value, and better signal transmission characteristics. Therefore, the third-order high-pass filter is chosen as the filtering protection circuit.

[0068] S5: Simulate and experimentally verify the lightning protection module in step S4;

[0069] The specific steps of simulation verification are:

[0070] Taking 2kA lightning current as the excitation source, a GDT and a decoupling resistor are used to test the attenuation trend of the residual voltage of 1 to 6 TVSs respectively. A lightning electromagnetic pulse is added to the power amplifier. According to the principle of the communication system transmission channel, the pulse needs to be reversed to the circuit. Then the designed protection module is placed in the circuit and put into ADS for S parameter verification.

[0071] The damage power thresholds of some active amplifier devices and integrated circuits under continuous electromagnetic pulses are shown in Table 1:

[0072] Table 1 Damage threshold and damage power threshold of active amplifier devices

[0073]

[0074] From the data in the table, it can be seen that under the action of continuous electromagnetic pulses, the damage power threshold of common active amplifiers is usually between 20dBm and 40dBm. Under the action of strong electromagnetic pulses with extremely short duration, the damage power threshold can be appropriately increased to 50dBm. Through simulation analysis, it is found that the coupling magnitude of electromagnetic pulses can reach up to 90dBm. Comparing the two, if there is no protection circuit in the transmission channel of the communication system, the intruding strong electromagnetic pulse is likely to cause interference to the power amplifier. Under the continuous wave AC working state, the peak voltage of the final power amplifier can withstand 120V. The corresponding power is calculated by formula (9) to be 54.6dBm. In formula (9), V is the peak voltage and R is the input impedance value, which is calculated in mW.

[0075]

[0076] Using 2kA lightning current as the excitation source, a GDT and a decoupling resistor are used to test the attenuation trend of the residual voltage of 1 to 6 TVSs. Fig.10As shown in the figure, as the number of TVS in parallel increases, the residual voltage decreases, but the magnitude of the decrease also decreases. This is because as the number of TVS in parallel increases, the magnitude of the decrease in the equivalent resistance when it is turned on decreases, and as for the shunt current of each TVS, as the number of TVS in parallel increases, the shunt current of each TVS decreases.

[0077] In order to add lightning electromagnetic pulses to the power amplifier, according to the principle of the communication system transmission channel, the pulse needs to be reversed to the circuit, and then the designed protection module is placed in the circuit and put into ADS for S parameter verification. V1 is a normal signal, which is emitted by a frequency source with an impedance of 50 ohms and a power of 5dBm. X10 is a simplified transmission channel model, V2 is the output signal of the power amplifier, X1~6 are TVS, Y2 is GDT, and SRC1 is a 2kV lightning electromagnetic pulse. Fig.11 shown.

[0078] The above simulation circuit model is simulated and verified. Fig.12 are the input signal and output signal of the power amplifier from 7.8us to 8.2us respectively. The peak value of the output V2 will not exceed 7V. According to formula (9), the peak power will not exceed 30dBm, which is far less than the minimum value of the tolerable peak threshold power. Fig.13 This is the gain at the center frequency of the power amplifier when the protection module is added before and after the lightning strike. The gain at 144MHz before and after the lightning strike drops from 20.619dB to 20.544dB. There is no obvious gain compression, indicating that the power amplifier is working normally. The center frequency gains when no protection module is added and only the transient protection module is added are 15.623dB and 16.293dB respectively. Compared with the gain before the lightning strike, there is obvious compression, indicating that the power amplifier has been damaged.

[0079] The specific steps of experimental verification are:

[0080] According to the simulation verification process, appropriate amplifiers and filters were selected to simulate and build the communication system transmission channel. The GPP-CWG-2010 combination wave test system was used to inject a 2kV lightning voltage. The DC power supply and network analyzer were used to measure the gain data before and after the lightning strike.

[0081] The protection circuit of the communication system transmission channel is tested based on the electromagnetic pulse injection test system. The purpose is to compare the gain change of the amplifier before and after the lightning strike, observe whether there is obvious gain compression at the center frequency, and judge whether the protection circuit plays a role in protecting against strong electromagnetic pulses.

[0082] In order to study the protection performance of the protection circuit of the communication system transmission channel, according to the simulation verification, suitable power amplifiers and filters were selected to simulate and build the communication system transmission channel.

[0083] The GPP-CWG-2010 combined wave test system was used to inject a 2kV lightning voltage. The gain data before and after the lightning strike were measured using a DC power supply and a network analyzer. Some data between 118MHz and 172MHz are selected as shown in Table 2:

[0084] Table 2 Gain comparison before and after lightning strike

[0085]

[0086] According to the table, it is found that the gain at the center frequency is reduced compared with the simulation experiment. This is because there is a certain loss when the signal is transmitted. According to the Friis gain loss calculation formula, by measuring the transmission distance, the loss is 2dB to 3dB, which is basically consistent with the simulation data. By observing the data in Table 2, it can be concluded that the gain at 143MHz and 145MHz did not change before and after the lightning strike, and a gain compression of about 0.1dB appeared at nearby frequencies. The farther away from the center frequency, the more obvious the gain compression. This shows that the designed simplified communication system transmission channel and protection module will not be damaged under the impact of lightning electromagnetic pulses, which can ensure that the communication system transmission channel is not interfered with and plays a protective role.

[0087] The present invention also provides a lightning protection module for a transmission channel of a communication system, including a transient protection circuit and a filtering protection circuit. The transient protection circuit is composed of a GDT and six TVSs, a decoupling resistor is connected between the GDT and the TVS, and the filtering protection circuit is composed of a third-order high-pass filter.

[0088] In summary, the protection module designed using the design method of the present invention solves the hidden dangers that may be caused by lightning strikes in the transmission channel of the communication system, effectively protects the sensitive components therein, and enables the communication system to work normally after a lightning strike.

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lightning protection module design method for a communication system transmission channel, characterized in that: The following steps are involved: S1: Understand the transmission channel principle of typical communication systems and select sensitive devices to simplify the transmission channel; S2: Simulate and verify the simplified transmission channel; S3: Select the lightning protection devices gas discharge tube GDT and transient suppression diode TVS, and design the transient protection circuit to discharge most of the energy of lightning electromagnetic pulse; S4: Perform Fourier transform on the 8 / 20us lightning current and perform energy accumulation distribution. According to the characteristics of the lightning current, design a high-pass filter protection circuit to further suppress the low-frequency component of the residual voltage to obtain a lightning protection module; S5: Simulate and experimentally verify the lightning protection module in step S4.

2. The method for designing a lightning protection module for a transmission channel of a communication system according to claim 1, characterized in that: In S1, the transmission channel includes a digital control circuit, a mixer, a local oscillator, a power amplifier, a filter, a standing wave protection, a PIN transceiver switch and an antenna, wherein the power amplifier is used as a sensitive device to conduct intrusion research on lightning electromagnetic pulses, and the filter can ensure the normal operation of the center frequency. The power amplifier and the filter are selected as sensitive devices to simplify the transmission channel of the communication system.

3. The method for designing a lightning protection module for a transmission channel of a communication system according to claim 2, characterized in that: In S2, the simulation design of the power amplifier includes the design and selection of an input impedance matching circuit, a DC bias circuit, an output impedance matching circuit and a transistor, wherein the DC bias circuit design is completed using a DC scanning circuit template in the ADS simulation software; The transistor used is MRF300A produced by NXP; the stability analysis is to build the S parameter simulation circuit of the power amplifier in combination with the DC bias circuit, and then analyze the stability of the power amplifier. If there is an unstable area, it is necessary to introduce a lossy component to achieve circuit stability; the matching circuit design first uses the load-pull design Load-Pull module and the source-pull design Source-Pull module in ADS to obtain the optimal impedance matching value between the load end and the source end, and then uses the Smith chart to complete the design of the matching circuit; The passband and stopband of the filter are designed according to the actual center frequency of the power amplifier. The center frequency of the power amplifier is 144MHz, and the filter cutoff frequencies are set to 118MHZ and 174MHz. The bandpass filter is designed using ADS simulation software.

4. The method for designing a lightning protection module for a transmission channel of a communication system according to claim 1, characterized in that: The specific steps of S3 are: S31: GDT selection includes breakdown voltage U R and pulse discharge current I R Considering the fluctuation of normal working voltage U and the accuracy of breakdown voltage of gas discharge tube, U R Greater than or equal to twice U, and the pulse discharge current only needs to be greater than the peak value of the lightning current; S32: TVS selection parameters include clamping voltage, breakdown voltage, reverse working voltage and surge current capability. The breakdown voltage of TVS must be higher than the normal working voltage of the circuit. Clamping voltage refers to the maximum voltage at which TVS clamps the voltage within a safe range when a transient surge occurs. When selecting, the clamping voltage must be lower than the maximum voltage that the protected circuit can withstand. During transient voltage, the lower the clamping voltage, the better, and the more effective it can be in protecting the circuit. The reverse working voltage is the maximum continuous reverse voltage that TVS can withstand under normal working conditions, and the reverse working voltage should be slightly higher than the working voltage of the circuit. The surge current capability is the maximum transient impact current that TVS can withstand. The appropriate surge current specification should be selected based on the maximum transient current that the circuit may be subjected to. S33: Transient protection circuit design: Use a GDT and multiple TVS to suppress the coupling voltage, and use the appropriate number to design the transient protection circuit.

5. The method for designing a lightning protection module for a transmission channel of a communication system according to claim 1, characterized in that: In S4, the high-pass filter protection circuit uses a 300Ω lightning channel wave impedance and a controlled current source in parallel to simulate the lightning discharge channel according to the lightning discharge theory, and considers the return loss and insertion loss in the selection of the high-pass filter order, and comprehensively considers the selection of a suitable high-pass filter.

6. The method for designing a lightning protection module for a transmission channel of a communication system according to claim 1, characterized in that: In S5, the specific steps of simulation verification are: Taking 2kA lightning current as the excitation source, a GDT and a decoupling resistor are used to test the attenuation trend of the residual voltage of 1 to 6 TVSs respectively. A lightning electromagnetic pulse is added to the power amplifier. According to the principle of the communication system transmission channel, the pulse needs to be reversed to the circuit. Then the designed protection module is placed in the circuit and put into ADS for S parameter verification.

7. The method for designing a lightning protection module for a transmission channel of a communication system according to claim 1, characterized in that: In S5, the specific steps of experimental verification are: According to the simulation verification process, appropriate amplifiers and filters were selected to simulate and build the communication system transmission channel. The GPP-CWG-2010 combination wave test system was used to inject a 2kV lightning voltage. The DC power supply and network analyzer were used to measure the gain data before and after the lightning strike.

8. A lightning protection module for a transmission channel of a communication system designed according to the method of any one of claims 1 to 7, characterized in that: It comprises a transient protection circuit and a filtering protection circuit. The transient protection circuit is composed of a GDT and six TVSs. A decoupling resistor is connected between the GDT and the TVS. The filtering protection circuit is composed of a third-order high-pass filter.

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