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 μm 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 cross-coupled pairs as well. This design achieves a small area of 0.0206 λ0 × 0.0206 λ0 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.