Preliminary Study On The Characteristics Of HPM Beat Waves And Their Effects On Objects

According to existing theoretical and experimental researches, high power microwave (HPM) of low frequency has its merits in applications. However, larger radiation system is necessary for microwaves of lower frequencies to get enough far field gain. HPM beat wave, which behaves as high frequency wave modulated in amplitude by low frequency, can be radiated with antenna system of smaller size. And with proper nonlinear effects, it is possible to produce wave of low frequency related to beat frequency. As a result, HPM beat waves possess the advantages of low-frequency and high-frequency HPMs. In this thesis, some theoretical investigations on waveform and spectrum of some real HPMs and their beat waves, and the response HPM beat wave in linear and nonlinear coupling conditions as well as some experiments are carried out to obtain some insights into HPM beat waves and their effects on objects. The detailed research contents and results are listed below.Firstly, investigations are carried out on the characteristics of HPMs and their beat waves. HPMs actually do not work at a fixed frequency. Their phase shifts between pulses, and the waveforms are very complicated. If the frequency of each wave is fixed, the peak power of HPM beat wave is influenced by time synchronization and relative electric field strength. Time synchronization and phase differences must be precisely controlled when beat wave is emitted by an antenna array.Secondly, HPM beat wave coupling is mixed by linear and nonlinear processes which are investigated in this thesis. The electric field strength coupling into the cavity of HPM beat waves which are not cut off by the slot can be two orders of magnitude larger than that of single waves which are cut off by the slot. Quantitative results are got on the strength of low frequency waves produced in certain nonlinear processes.Finally, injection experiment is carried out on pre-amplifier circuits. Results reveal that, with the same pulse width and in similar frequency domain, the malfunction threshold power of beat wave is about 3 dB lower than that of a single wave. In beat wave case, the threshold is in Gaussian distribution and its variance is small. Due to the nonlinear effect of the pre-amplifier, a wave with beat frequency is generated when the beat wave is transmitted to the next circuit component. The further analysis of the general effects of the HPM beat wave reveals that, with equal peak power, the general effective power into the objects for HPM beat wave is about 10.9 dB and 50.9 dB higher than the wave with beat frequency in the considered two conditions separately.