A compact bandwidth controllable BPF using fish-like taijitu shaped resonators

The fish-like Taijitu pattern is a Chinese symbol for the concept of opposites existing in harmony. In this letter, a compact band-pass filter (BPF) using half fish-like taijitu shaped resonators is proposed. Compared to the square open loop resonator, the self-capacitance of the proposed resonator is increased, which is well suited for the design of narrow band BPFs. Furthermore, its bandwidth is easily controlled by rotating the taijitu pattern to obtain the required Q factor due to its skew-symmetric structure. Three prototypes of the BPFs working around 12GHz with different bandwidths are designed, fabricated and measured. The relative 3dB bandwidths of these filters are approximately 15.8%, 10.2% and 4.5% respectively. The simulated results and the measured results agree well with each other.