Abstract
This paper describes an on-off ring oscillator-based multiband ultra-wideband transmitter for vital sign monitoring applications. A thorough analysis of the pulse generation is provided followed by a description of the oscillator, the mixer, and the AB-class power amplifier. Designed in a 0.18-mu m CMOS, the transmitter works in the UWB lower band of 3-5 GHz and consumes a low power of 7.8 mW at 50 MHz pulse repetition frequency, under 1.8-V power supply. The transmitter delivers a differential output swing of 0.64 V under 100-Omega load with the highest power efficiency of 37.6 pJ.