A Broadband Low Conversion Loss Single-Ended Resistive Mixer with an Innovative Topology

To achieve better broadband performance and lower conversion loss (CL), a mixer using an innovative mixing unit is proposed in this letter, which contains two gallium arsenide (GaAs) pseudomorphic high electron mobility transistors (pHEMTs) and a coupled capacitor. Leveraging the analysis and the equivalent circuit of the proposed topology, the minimum local oscillator (LO) power ( $P_{\mathrm{LO},\mathrm{min}})$ and CL of the mixer are deduced and calculated. The analysis concluded that the ratio of the maximum time-varying impedance to the minimum time-varying impedance of the mixing unit maintains a substantial value across a wide frequency band, indicating enhanced broadband characteristics and reduced CL. In addition, based on the proposed topology and analysis, a single-ended mixer with a radio frequency (RF) range of 2–22 GHz and an intermediate frequency (IF) fixed at 100 MHz was implemented using the Sanan 0.15- $\mu$ m GaAs pHEMT process. With a 15-dBm LO power, the test results of this mixer reveal a 10-dB CL and 20-dB isolation within the operating frequency range of 2–22 GHz. The designed single-ended mixer monolithic microwave integrated circuit (MMIC) achieves a fractional bandwidth (FBW) of 166% and occupies a chip area of 0.7 $\times$ 1 mm $^{2}$ .