| In view of the problem that the aviation antenna is in the strong electromagnetic pulse environment,it will be coupled to large energy,which may damage the antenna system or the electronic equipment.In view of the importance and vulnerability of the antenna system,this paper takes lightning strong electromagnetic pulse and nuclear electromagnetic pulse as the main background,and takes the antenna in the118～136MHz frequency band as the research object.Through the establishment test,the characteristics of antenna coupling strong electromagnetic pulse and the transient response characteristics of common surge devices are analyzed;Finally,the protection circuit design scheme of the antenna in the aviation communication frequency band is proposed,and the comprehensive protection performance is tested.The main conclusions are as follows:（1）The antenna is coupled with lightning electromagnetic pulse.When it is close to the excitation source,the antenna is in the energy storage field,and the coupled waveform is similar to the source waveform.With the increase of distance,the coupled waveform oscillates more and more obviously,the coupling frequency range is wider and the high-frequency components are richer.According to the calculation and analysis of the coupling energy of the antenna terminal,many devices will be damaged.（2）The antenna couples the nuclear electromagnetic pulse,and the coupled waveform is a typical damped oscillatory wave;when the antenna is parallel to the electric field,the coupling energy is the largest.When the impact electric field intensity is between 6kV/m～26kV/m,the coupling energy is between 10-4～10-3energy levels;The energy of antenna coupling is concentrated within 150MHz,of which 98%is concentrated within 100MHz.（3）The elliptic function approximation function filter circuit is selected,and the band-pass filter circuit in the frequency band of 118～136MHz is designed.It is composed of 13 order high pass circuit in series with 11 order low-pass circuit. The input and output impedance is 50Ω,and the in band attenuation is less than0.5dB.（4）The HEMP transient response of the protective device,the measured clamping voltage value of the TVS tube is generally smaller than the nominal clamping voltage value given by the manufacturer.When the impulse current reaches 250A or above,the 1.5KE400CA type TVS fails;The transient response clamping voltage is similar to the nominal maximum clamping voltage;The arc voltage of gas discharge changes little with the change of impulse current and is basically stable in a range.The greater the DC breakdown voltage of gas discharge tube,the greater the arc voltage will be.（5）For the antenna in the communication band of 118～136MHz,the two-stage reverse parallel connection of high-speed switch is applied to the circuit to reduce the distributed capacitance of the branch;Two kinds of comprehensive protection designs are proposed and made into real objects.The measured insertion loss of both is less than 3dB;According to the protection performance test,#2 protection module design meets the protection requirements.When the impulse current is 5kA,the average residual voltage is basically within 108V;PCI injection current is within 400A,#2 circuit can control residual current within 1A,meeting the test standard. |
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