A Low Noise Image-Rejection Gilbert Mixer for Software Defined Radios

With the evolution in wireless communications there arose a need for reconfigurable radio architectures that meet the specifications of different standards. To implement such structures, cost-effective, high-performance silicon technologies must be available. This paper demonstrates a multi-standard image reject mixer using SiGe 8HP process that is well known for its high performance. In this paper, a down-conversion mixer is investigated, based on Gilbert Cell double-balanced topology. The mixer operates between 0.9-13.5 GHz and results affirm its feasibility for software-defined radio applications. The impedance matching section consists of varactors and spiral inductors to operate within a wideband. The analysis shows that the proposed mixer design has a high conversion gain of 22 dB with a noise figure of 2.5 dB and an image rejection ratio of 30.2 dB at 13.5GHz. The mixer operates at 1.2V and has moderate linearity performance with a third-order intercept point (IIP3) of -3.28 dBm and 1dB compression point (CP1) of -13 dBm.