A low-power highly digitized receiver for 2.4-GHz-band GFSK applications

This paper describes the design and measurement results of a low-power highly digitized receiver for Gaussian frequency-shift keying modulated input signals at 2.4 GHz. The RF front-end has been based on a low-IF architecture and does not require any variable gain or filtering blocks. The full dynamic range of the low-IF signal is converted into the digital domain by a low-power high-resolution time-continuous SigmaDelta analog-to-digital converter (ADC). This leads to a linear receive chain without limiters. A fifth-order poly-phase loop filter is used in the complex SigmaDelta ADC. The digital block performs filtering and demodulation. Channel filtering is combined with matched filtering and the suppression of noise resulting from the SigmaDelta ADC. The high degree of digitization leads to design flexibility with respect to changing standards and scalability in future CMOS generations. The receiver has been realized in a standard 0.18-mum CMOS process and measures 3.5 mm2. The only external components are an antenna filter and a crystal. The power consumption is only 32 mW in the continuous mode, which is at least a factor of two lower than state-of-the-art CMOS receiver