Design considerations for cognitive radio based CMOS TV white space transceivers

This paper discusses the design considerations for CMOS transceiver targeting for cognitive radio based TV white space applications. With the total frequency band ranging from 54 to 862 MHz, not only harmonic distortions in RF transceiver but also wideband LO generation in frequency synthesizer needs to be carefully addressed. We present that the dual-path direct-conversion architecture adopting on-chip harmonic rejecting scheme significantly lowers the harmonic emission problem in the transmitter and the harmonic mixing problem in the receiver. Also, the entire band is covered by a wideband LO generation block combined with a single LC-VCO synthesizer. For the energy detection for the spectrum sensing, the feedforward RF filtering scheme with the center frequency and bandwidth simultaneously tunable is presented.