A 270-GHz CMOS Triple-Push Ring Oscillator with a Coupled-Line Matching Network

A design procedure is proposed for triple-push ring oscillators, and an oscillator employing a coupled line-matching network is developed following the procedure. This stepwise procedure, which uses power-dependent Z-parameters of transistors, is applied to the design of each amplifier stage constituting a ring oscillator based on its steady-state oscillation condition. It is verified with both L-section and T-section topologies assumed for the load of the amplifier stages of a given triple-push ring oscillator, and the differences between the two topologies are compared. Based on the procedure, a 270 GHz triple-push ring oscillator that employs coupled lines for matching networks has been developed in a 65-nm complementary metal-oxide-semiconductor (CMOS) process. The circuit benefits from the advantages of coupled lines such as compact area and simplified layout. The fabricated oscillator exhibits a measured oscillation frequency of around 270 GHz and output power of -10.9 dBm, with phase noise of -96 dBc/Hz at 10 MHz offset.