A Novel Tunable LC Filter for Ultra High Frequency Applications

A novel LC filter is proposed in this paper. The proposed structure consists of a square spiral inductor with a tunable capacitor. The outer turn of the inductor is also a part of the capacitor. The capacitor is designed using floating technique to get high quality factor (570-690). The size of designed filter is 1.4×1.2 mm2. Tuning range of the filter is 35%. The maximum quality factor of the filter is 118. the insertion loss is about −1db and the return loss is equal to −27db and −25db in pass frequency of 5.8GHz-6.8GHz.