A wide modulation bandwidth bidirectional CMOS IQ modulator/demodulator for microwave and millimeter-wave gigabit applications

A wide modulation bandwidth bidirectional IQ modulator/demodulator using 0.18 μm CMOS process is presented in this paper. Two doubly balanced modified Gilbert-cell resistive mixers are employed in the circuit design to achieve both broad RF and baseband bandwidths. The proposed IQ modulator/demodulator demonstrates a RF bandwidth of from 25 to 52 GHz, and a modulation bandwidth of from dc to 14 GHz. Furthermore, the modulation or demodulation can be performed at the same input/output ports of the proposed circuit, and the complexity of the transceiver can be reduced. The bidirectional IQ modulator/demodulator has a potential for 10 gigabit bidirectional communication systems in microwave and millimeter-wave (MMW) band.