Design of a Compact Lumped Element Based 4-Way Multiplexer for Cryogenic Applications

This paper presents the design of compact lumped element based 4-way multiplexer for very high frequency (VHF)-high band applications. The multiplexer is implemented as a star junction with a band pass filter arrangement in each output arm. Hence, no manifold sections are used in order to reduce the number of lumped elements to 40 for compactness and ease of fabrication. Commercially available surface mount devices (SMDs) were used to realize the multiplexer with center frequencies of 110 MHz, 130 MHz, 150 MHz, and 170 MHz. The insertion loss observed is from 3.5 dB to 5 dB across the bands at room temperature. The isolation is at least -15.4 dB between the output ports. For the first time, the performance of such a multiplexer using commercial SMDs at cryogenic temperatures for quantum reflectometry applications is presented.