On-Line Calibration and Power Optimization of RF Systems Using a Built-In Detector

This paper develops a technique, using a built-in detector, for measuring the specifications of RF subsystems and fine-tuning them with a feedback control algorithm. At the same time, optimum power consumption points can be chosen from different biasing schemes. The detector has small area overhead with low frequency output. The sampled output waveform is analyzed using an FFT. The low frequency measurements are directly used to calculate the circuit specifications, without requiring learning steps. The technique was used to measure the performance parameters of a 940 MHz to 40 MHz down conversion mixer in a RF receiver front-end test chip, fabricated in a commercial 0.18 mum CMOS process. The tuning algorithm was implemented in the Labview environment, and tuning knobs on board were used for biasing and control optimization. Results show that the approach can provide accurate calibration of specifications and power for real RF chips.