0.4-5.2GHz broad-band SiGe-MMIC direct conversion quadrature mixer (Q-MIX) has been developed for multi-band multi-mode cognitive radio receivers by using 0.35□m SiGeBiCMOS process. To realize broad-band characteristic, a static frequency divider with two-stags emitter follower is used as 90 degree power divider for LO and broad-band doubly balanced mixers are used as I/Q unit mixers. The 90 degree power divider enable to achieve multioctave operation for LO which covers whole band of 0.4-5.2GHz. Broad-band unit mixers also enable to achieves wide RF band (0.4-5.2GHz) and wide base band (up to 500MHz.) The fabricated Q-MIX performs EVM of less than 3% over the whole RF frequency range of 0.4-5.2GHz and shows the dynamic range of more than 40dB for 0.4GHz UHF application (16QAM/OFDM), 0.8GHz/2GHz W-CDMA (QPSK) and 5.2GHz IEEE 802.11a W-LAN (64QAM/OFDM) receptions.