A Narrow Band CMOS Active Dual-Mode Ring Resonator Bandstop Filter

A narrow band active dual-mode bandstop filter fabricated on complementary metal-oxide semiconductor (CMOS) 0.13 mu m process is proposed in this paper. In the design, a ring resonator is coupled to a main signal path through a quarter-wavelength length coupled line. Meandered complementary conducting strip transmission lines (CCS TLs) are used to form the ring resonator. The ring resonator is loaded with capacitors separated by quarter-wavelength to split the two degenerate modes, and compensated by two orthogonal crosscoupled pairs as well. This design achieves a small area of 0.0206 lambda(0) x 0.0206 lambda(0) and a narrow stopband of 0.10 GHz or 1.16% fractional bandwidth of 10 dB insertion loss (IL) level. A sharp response is demonstrated by simulation and shows an agreement with the measurement results.