A Terahertz Band-Pass Filter Based on Coplanar-Waveguide and Spoof Surface Plasmon Polaritons

A THz ultra-broadband band-pass filter based on coplanar-waveguide and spoof surface plasmon polaritons (SSPPs) is proposed, which can be operated from 0.65 THz to 2.02 THz with high efficiency and compact size. Additionally, the lower and upper cut-off frequencies of the proposed filter can be controlled independently by changing the corresponding parameters. The interdigital structure is used to filter the low frequency wave, meanwhile, the SSPPs is designed for producing the upper cut-off frequency. The operating principles are explained by dispersion curves and field distributions. The return loss and insertion loss of the proposed filter are higher than 11 dB and less than 2 dB in the passband, respectively. For validating the proposed band-pass filter design concept, a prototype of a filter operating at millimeter-wave frequency is fabricated and measured, and the measured results have a good agreement with the simulated ones.