Pulse compression radar reflectometry to measure electron density in plasma with parasitic reflections

Pulse compression radar reflectometry is used to obtain electron density profile in plasma with parasitic reflections in this article. The pulse compression radar relies on the relation between the temporal width of a pulse and the frequency bandwidth of this pulse: $Δt∝1∕Δf$⁠. So a set of sweep-frequency microwaves within a bandwidth $Δf$ can be introduced sequentially into the plasma to obtain the same information as the one obtained by a real pulse. By applying a Fourier transform to the data of reflectivity array in the frequency domain, the temporal response in the time domain is obtained. The limitation of the parasitic reflections on measurement can be eliminated from the temporal response by the method of time gate. This is a prominent advantage when this method is compared to the traditional reflectometry. For this method, an appropriate compromise between the spatial resolution and the electron density resolution is important. Experimental results show that the profile obtained from pulse compression radar reflectometry is similar to that from a double Langmuir probe.