A 5GHz-band SiGe-MMIC quadrature modulator using a circular polyphase filter for 1Gbps transmission

A 5GHz-band SiGe-MMIC direct conversion quadrature modulator using a circular polyphase filter for high data rate is described. High I/Q vector accuracy is achieved using a circular polyphase filter with a completely symmetric layout as a 90 degrees LO power divider. By combining high cut-off frequency baseband amplifiers and broad-band unit mixers, a fabricated quadrature modulator shows the EVM of 3.3% rms at 5.5 GHz using 64-QAM OFDM signals with the channel bandwidth of 204 MHz, which corresponds to the data rate of 1.161 Gbps.