A Differential CMOS Active Mixer with Enhanced Conversion Gain for Portable Ground Penetrating Radar Receivers

Abstract

This paper presents the design, layout implementation, and performance evaluation of a differential CMOS active mixer intended for portable ground penetrating radar (GPR) receiver front-end applications. The proposed mixer employs a differential architecture
consisting of an RF transconductance stage and a local oscillator (LO) switching stage to achieve efficient frequency conversion from RF to IF while maintaining low noise and adequate linearity. The circuit schematic is designed and simulated, followed by physical layout implementation using Cadence Virtuoso, where careful layout techniques such as symmetry and device matching are applied to improve performance and minimize parasitic effects. The layout is verified using design rule check (DRC) and layout versus schematic
(LVS) procedures to ensure design correctness and fabrication compatibility. Simulation results show that the mixer achieves a maximum conversion gain (S21) of 15.48 dB at 2.4GHz. Noise analysis indicates a noise figure of approximately 5.31 dB at the same frequency, demonstrating good noise performance for radar receiver applications. Linearity characteristics obtained from harmonic balance analysis show an input-referred 1 dB compression point of −9.56 dBm, indicating acceptable large-signal handling capability. The combination of high conversion gain, moderate noise figure, and verified layout implementation confirms that the proposed CMOS mixer is suitable for integration in compact and energy-efficient GPR front-end systems.