2.4/5.7-GHz dual-band dual-conversion architecture with correlated LO signal generators

A 2.4/5.7-GHz dual-band dual-conversion downconverter is demonstrated using 0.35-mum SiGe heterojunction bipolar transistor (HBT) technology. This downconverter employs a complex dual-conversion system and a complex filter to reject the first and second image signals, respectively. The LO 1 frequency is 2.5 times the LO 2 frequency and is generated by a divide-by-two divider, a frequency doubler and a single-sideband up-converter. As a result, the correlated LO signals maintain excellent image-rejection performance of the dual-conversion system while only one LO input is needed. The downconverter achieves a 40/39-dB image-rejection ratio of the first image and a 44/46-dB image-rejection ratio of the second image for 2.4/5.7-GHz modes, respectively.