Mode symmetry assessment of structurally non-uniform asymmetric coupled lines meandered for CMOS passive component design

This paper presents an accurate modeling of structurally non-uniform and asymmetric coupled lines meandered in RF CMOS integrated circuit, leading to the effective quantitative assessment of equivalent mode symmetry of even/odd mode that are often applied for designing microwave passive component. The four-port scattering parameter of the structurally asymmetric coupled CMOS lines was converted to the ABCD matrix, derived from a uniform pair of coupled lines. Thus the equivalent c-mode and pi-mode representation of the structurally asymmetric coupled CMOS lines was obtained. The proposed extraction procedure was applied to two design examples of highly structural asymmetry, loosely and closely coupled CMOS lines, confirming that the electrical mode symmetry property was properly maintained for both case studies. The even mode and odd mode propagation characteristics of the two case studies were validated theoretically and experimentally, showing excellent mode symmetry was achieved for the structurally asymmetric coupled CMOS lines.