A 0.25 µm CMOS I/Q-channel downconversion mixer with active coil for DCS-1800 applications

An I/Q-channel downconversion mixer for the DCS-1800 system has been integrated in a standard 0.25 µm CMOS process. The structure features an implicit single-ended to balanced conversion of the RF input-signal and permits DCS-1800 operation at very low LO levels. An active coil circuit prevents degradation of the conversion gain caused by low-frequency feedback mechanisms. At an LO of -9 dBm, a conversion gain of 24.8 dB, a noise figure of 21.5 dB and an IIP3 of 21 VdBm is achieved.