Resonant notch filters based on rectangular waveguide extensions

Notch filters based on resonant reflection of the incident guided wave of a single-mode rectangular guide designed for frequencies of 28 and 70 GHz are numerically and experimentally studied. As shown by experiments, the 28 GHz two-sectioned resonant notch filter provides the attenuation of -60 dB at the central frequency f=28 GHz, more than -30 dB attenuation within the frequency band δf=60 MHz and attenuation-free band up to 36 GHz. For the 70 GHz notch filter, the measured maximum attenuation is -60 dB at the operating frequency. The notch bandwidth at the level of -55 dB is 100 MHz. These characteristics allow use of the notch filters for protection of HF receivers of high sensitivity, for spectral measurements and other related purposes.