A novel tunable narrow bandstop filters with C-shaped slot notch structure

A novel low cost tunable bandstop filter with compact embedded C-shaped slot notch structure section is presented in this paper. The C-shaped slot is obtained by etch on the microstrip line which makes the notch filter in small size. The tunability is achieved by change the capacitance of varactors diodes which are equipped on the C-shaped slot section. The center frequency of the filter varies from 3.8 GHz to 4.3 GHz due to the equivalent capacitance changes. The maximum rejection depth can reach 37dB and the percent bandwidth of 10 dB stop-band is about 0.2%.