Transmission line and Lange coupler implementations in CMOS

This paper presents the design, characteristics, and measured results of various passive structures needed in the realisation of millimetre wave radio front ends in CMOS. Transmission lines are inherently scalable in length and, thus, different inductance values can be realised easily using short circuited lines. Three different coplanar waveguide structures were characterised and the benefits and drawbacks are discussed. In addition, we present the design of a Lange coupler for 90-degree division and combination of millimetre-wave signals in nanoscale CMOS. This structure can be used in the realisation of image rejecting or direct conversion millimetre-wave radio front ends in CMOS.