Design and Simulation of a Compact Microstrip Diplexer for Medical Applications Using FR4 Substrate
Abstract
The paper describes the design and simulation of a small microstrip diplexer to be used in the medical wireless dual-bands (2 GHz, 3 GHz) using a low-cost FR4 substrate (εr = 4.7, h = 1.6 mm, tanδ = 0.015). The proposed diplexer utilizes a T-junction design that consists of two bandpass filters that are attached to a shared input port to allow a high level of signal separation at two separate frequency bands focused on 1.6 GHz and 2.34 GHz. This is designed on the theory of transmission line and optimized with full-wave electromagnetic simulation. The results obtained show that the impedance is good with the values of return loss of 19.84 dB and 17.62 dB correspondingly at the two operating bands. The insertion loss is kept at around 2.8 dB on both channels and a high isolation (more than 28 dB) is achieved, providing the channels with adequate separation. In spite of the intrinsic dielectric losses of the FR4 substrate, the diplexer has stable performance with narrow fractional bandwidths of around 2.5-2.6 %, and therefore it can be used in selective biomedical communication systems. The suggested design presents an effective trade-off between performance, size, and cost, and it has a high potential of being used as low-cost medical RF front-end.
