Research On Key Technologies Of Ultrawideband RCS Measurement System

Since the emergence and later advancement of Ultra-Wide Band(UWB) technology, it has been applied to many areas. One of them is UWB time domain measurement technique. in which the narrow pulses in time domain can be selected by a time window, thus keeping signals from target while discarding ones from the background. In frequency domain, the narrow pulse is ultra broadband, so only one measurement can get the target scattering characteristics of UWB. This measurement mode may not require an anechoic chamber, the measurement is simple and convenient operation, you can save a lot of testing time.Firstly, time domain signal characteristics of RCS testing system are introduced, select the Time Window according to the characteristics of the signal, can filter out coupled interference signal between the two antennas and signal reflect from the wall, and find the target in time domain, then we can get target’s frequency domain scattering characteristics by Fourier transform. And using the object that known RCS as a calibration, we can get ultra wideband RCS of the target under test.Because we will use the ultra-wideband signal, so that the system requires UWB antenna as transmitting/receiving antennas. For the antenna, we have requirements not only in frequency domain, but also in time domain.For the pulse, the quality of reproduction is very important. UWB horn antenna do well in this aspect. So in this paper we design ultra-wideband TEM double-ridged horn antenna loaded with dielectric lens and ultra-wideband dual polarized TEM quad ridge horn antenna loaded with dielectric lens. Spinal curve of the antenna is steepest decline line(Cycloid). The dielectric lens in E and H plane are hyperbolic, so that pattern E and H has some improvement.Finally, we use the system do the measurement experiment of metal balls. Through the experiment results, we know that the measurement value is compared with the theoretical value around 2.5GHz~18GHz. And through the measurement of the background environment, found that at low frequencies, there is a larger interference, lead to inaccurate measurement results. Through the scattering of receiving signal spectrum analysis, in 18GHz~20GHz, the received signal energy decline sharply, probably because of pulse itself or the LNA. So the measurement bandwidth of the system is 2.5GHz~18GHz.