PIM characterization at satellite level: An ISRO experience

It is very essential to perform Passive Inter Modulation (PIM) measurement in multi-band communication satellites to avoid unwanted interference. Since source of PIM product can be any metallic or ferromagnetic objects, etc. it is very important to precisely identify the source of PEVI i.e from external environment or satellite transponder chain. For this reason, before conducting any PEVI measurement at satellite level in any anechoic chamber it is usual practice to measure the inherent PIM level of the chamber at measured frequencies. In this paper, procedure for PEVI characterization at satellite level is discussed. Also, one case study is discussed when, PIM product was observed in one satellite, the sequence of operations that were carried out to precisely identify the source of PEVI and corrective action that was taken to suppress them.