Design of a C-band Coaxial Cavity Band Pass Filter

In this paper, a coaxial cavity band pass filter was presented with the volume of 28mm x 15mm x 13mm working at 4.88GHz and the 3dB bandwidth of 654.52MHz. The classical comb lines structure in the coaxial cavity filter was un-applicable for small size. The dressing-line structure was introduced in the coaxial cavity. By adding the capacitance circular plate on the cavity resonant column, the resonant frequency was increased with the volume of the cavity reduced greatly, and requirement of small-size was satisfied. The designed filter was fabricated and measurement was conducted. From measurement, the insertion loss at the center frequency is less than 0.7dB. The band rejection is greater than 49dB at 1-2GHz, and greater than 39dB at 8GHz-18GHz. These showed that the designed filter met the requirements.