Design of Compact Microwave Multiplexer for RF Reflectometry Characterization of Silicon-Based Spin Qubits

In this paper, the design of a compact microwave multiplexer for RF reflectometry characterization of silicon-based spin qubits is discussed. A lumped element based four-way multiplexer was designed with operating frequencies 100 MHz, 120 MHz, 140 MHz, and 160 MHz, while having a very compact size of 23 mm x 24 mm. The multiplexer uses 112 lumped components and their values are optimized such that the required frequency response if achieved. The simulated input reflection, transmission, output reflection, and isolation coefficients are discussed.