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A wideband radio-frequency (RF) power detection system is presented. The detection technique uses NMOS devices operating in the triode regime to generate an average current proportional to RF input power; this current is converted to voltage and amplified using a piecewise linear logarithmic approximation. Optimization of the NMOS devices is discussed, and a method of gain control is proposed for compensation of temperature and process variation. The power detector occupies an active area of 0.36 mm2 in a 0.18 mum CMOS process and consumes 10.8 mW from the power supply. Error between the output and a linear-in-dB best-fit curve is plusmn2.4 dB for a 20 dB input range, when measured at discrete frequencies. The output response is frequency independent, varying by less than 1.8 dB for a fixed input power as frequency is swept across the UWB spectrum.
Date of Publication: Feb. 2009