An 8–26 GHz Passive Mixer with Excellent Port Matching Utilizing Marchand Balun and Capacitor Compensation

Abstract

In this study, a broadband monolithic microwave integrated circuit (MMIC) double-balanced mixer designed for operation within the frequency range of 8–26 GHz is presented. The design is implemented using a 0.15 μm GaAs process. Traditional Marchand baluns, when applied to wideband mixers, face challenges in simultaneously achieving broad bandwidth and good port matching characteristics. To address this issue, we employ a spiral Marchand balun with a compensation capacitor. This innovative approach not only maintains the mixer's wide bandwidth but also enhances the matching between the local oscillator (LO) and radio frequency (RF) ports. Additionally, it significantly simplifies the complexity of designing the matching circuit. The optimization principle of the compensation capacitor is elaborated in detail within this paper. Experimental results demonstrate that, with an LO power of 14 dBm, the conversion loss remains below 8.5 dB, while the voltage standing wave ratio (VSWR) of the LO and IF ports is less than 2 and the VSWR of the RF port is below 2.4. In comparison with existing literature, our designed mixer exhibits a broader bandwidth and lower loss.