THz narrow band-pass filter based on stopband modulation in corrugated parallel plate waveguides

We demonstrate stopband modulation in a corrugated parallel plate waveguide (PPWG) in terahertz (THz) frequency. Different from the traditional approaches to achieve narrow band-pass filter, a method based on the junction of two stopbands is provided. Two stopbands can come closer through adjustment of plate distance and controlling the grooves depth, which generate a narrowband transmission region. It is found that plate distance can control the interval of two stopbands. On optimization of plate distance, the filter can achieve a range of zero-sideband, high transmissivity (T=99.8%), narrow linewidth (5.8 GHz), and high-quality factor (Q approximate to 220). Furthermore, we also present the designs of tunable filter and modulate performance when liquid crystal (LC) is used as waveguide material. So, an excellent tunable filtering characteristic has been achieved. Finally, this work provides a new possibility for the designing of narrow band-pass filter devices.