Body effect influence on 0.18µm CMOS ring oscillator performance for IR-UWB pulse generator applications

A three-stage ring oscillator in 0.18µm CMOS technology for IR-UWB applications is analyzed in this paper. The influence of the ring oscillator transistors body effect on its frequency is investigated. New methods that can be used to increase and control the ring oscillator frequency are proposed. Connecting the MOS transistors body terminals to suitable bias voltage (Vdd in case of the PMOS transistors, and ground in case of the NMOS transistors) using the same type of MOS transistors, the ring oscillator frequency can be tuned in appropriate frequency range by adjusting the auxiliary transistors gate control voltage. As the ring oscillator is a part of an IR-UWB (Impulse Radio - Ultra Wideband) pulse generator and its oscillating frequency determines the central frequency of the pulse spectrum, the ability of the frequency adjustment is very desirable advantage as it provides directly the spectrum fitting within the FCC mask.