Frequency up-conversion for the reflectionless propagation of a high-power microwave pulse in a self-generated plasma

In the study of the propagation of high power microwave pulse, one of the main concerns is how to minimize the energy loss of the pulse before reaching the destination. In the very high power region, one has to prevent the cutoff reflection caused by the excessive ionization in the background air. A frequency auto-conversion process which can lead to reflectionless propagation of powerful EM pulses in self-generated plasmas is studied. The theory shows that under the proper condition the carrier frequency ω of the pulse will indeed shift upward with the growth of plasma frequency ω-pe$/. Thus, the plasma during breakdown will always remain transparent to the pulse (i.e., ω > ω-pe$/). A chamber experiment to demonstrating the frequency auto-conversion during the pulse propagation through the self-generated plasma is then conducted in a chamber. The detected frequency shift is compared with the theoretical result calculated by using the measured electron density distribution along the propagation path of the pulse. Good agreement between the theory and the experiment results is obtained.