Effect of ENIG Surface Finish to Insertion Loss on Reflective Type Phase Shifter

This paper presents a reflective-type phase shifter (RTPS) and the effect of an electroless nickel immersion gold (ENIG) surface finish on its insertion loss. The former is commonly used in transmit- and reflect-array designs for electrical beam steering. Its design is simple and robust, providing a high phase shift and low insertion loss. However, if proper attention is not paid to the surface finish applied on copper traces, higher-than-expected insertion losses can occur. This was demonstrated through simulations, which were compared with measurement results. Originally, there was a 2.9 dB difference in the insertion loss values between the simulation and measurement results for an S-band RTPS. After applying the ENIG layer to the simulations, the difference was reduced to 1.0 dB.