A 5.2 GHz Linearized SiGe Quadrature Modulator Using Current Feedback from Output Buffer

A linearized SiGe up-mixer using current feedback from output buffer is described. The up-mixer consists of a conventional Gilbert cell mixer, an output buffer and a current feedback circuit. According to the output envelope current of the output buffer, the bias current of the mixer is controlled by this feedback circuit. As a result, the proposed up-mixer can realize linearized performance. The simulated P
1dB
improvements of the proposed up-mixer and the quadrature modulator (QMOD) including this up-mixer are 3.3dB and 1.6dB compared with the conventional types, respectively. The fabricated 5.2 GHz SiGe QMOD achieves the P
1dB
of -13.9dBm.