Measurement of the antenna impedance mismatch through the time domain mode of the vector network analyzers: An experimental procedure

In this paper we show a procedure to measure the impedance mismatch of antennas by exploiting the Time Domain (TD) option available in usual VNAs. The procedure can be applied even in the presence of reflecting obstacles in the measurement scenario surrounding the antenna under test (AUT). It is shown that effective application of the procedure requires to fulfill a reduced number of constraints basically involving the distance of the AUT from the nearest obstacle, the response resolution to be set through the TD option of the VNA, and the length of the gating aperture to be applied to the received signal. The proposed measurement procedure is in principle applicable to any antenna. However, it is very easy and advantageous for antennas having short responses in the time domain, such as horn antennas, where the method can likely be applied to frequencies less than 500 MHz. Comparison between the results obtained from measurements performed inside an anechoic chamber (that is, in the absence of reflecting obstacles around the AUT), outside the anechoic chamber, and even inside a reverberation chamber, demonstrate the effectiveness of the proposed measurement procedure.