Evaluation of Site Validation Methods for EMC Chamber from 18 GHz to 40 GHz

Different test sites are used for radiated emissions testing from 9 kHz to 40 GHz. The CISPR 16 and ANSI C63 standards mention the different site validation techniques for the test sites from 30 MHz to 18 GHz. They are based on the Normalized Site Attenuation test from 30 MHz to 1 GHz and Site VSWR test from 1 to 18 GHz. Due to the limitations of the conventional sVSWR test mentioned in the standards, an alternate method using Time Domain gating is proposed from 1 to 18 GHz. The Time Domain sVSWR method is a more robust and statistically consistent method and equivalent to the conventional sVSWR test. Although the different site validation techniques are laid out, there are no site validation methods mentioned from 18 to 40 GHz. This paper explores the site validation from 18 to 40 GHz using the Time domain sVSWR test and summarizes the test results in a 3m EMC chamber. It analyzes the various contribution factors for the measurement uncertainty budget and recommendations to reduce the sVSWR uncertainty factor. It also investigates the effect of gap in the absorber layout to the chamber validation results and the rationale for chamber validation from 18 to 40 GHz. In addition, an improved version of the CISPR 16 sVSWR test is presented and the results are compared to the time domain sVSWR method.