CMOS Ku/K band distributed oscillators using cascade of CPW coupled n-FETs gain cells with record performance of phase noise and Ka-band third harmonic generation technique

Abstract

A novel distributed oscillator (DO) is reported with cascade of inductive coplanar waveguide (CPW) coupled two common-source n-FETs, the novel gain-cell of DO. Two common-source n-FETs are connected with each other through a coplanar waveguide only, acting as an on-chip inductor. The design uses 3 stages of n-FETs cascade gain cell, with a bias of 1.4V. This oscillator called OSC-1 operates at K-band frequency 18.40G~z with 10.75dbm power level and the phase noise is a record in an industry standard 0.18pim CMOS technology of -126.857dBc/Hz at 1MHz offset from the carrier. A design modification is reported called OSC-1A and with body biasing of n-FETs from -1.5V to 0.6V, the frequency tuning of this 19.47 GHz D-VCO is 1.16 (18.89 - 20.05) GHz with uniform phase noise performances. With supply voltage variation, the OSC-1A frequency of 19.47 GHZ at 1.8V is tunable up to 18.57 GHz at a bias of 0.9V i.e. 900MHz. With different width of n-FETs, this design can be reused for other frequencies like Ku band frequency of 17.74 GHz with 5.07dBm or K-band frequency of 19.81GHz with 2.41dBm at 1.8V operation. A novel design is proposed for third harmonic generation in DO topology with five stages called OSC-TH, 3rd harmonic frequency of 29.27 GHz in Kaband with -0.3dBm power level is reported, whereas the fundamental is of -12.828dBm at 9.756G~z and 2nd harmonics of -17.289dBm.