Design of a Fixed IF Down-Conversion Double-Balanced Mixer for UHF Band Applications

This paper presents a new SiGe HBT-based high dynamic range double-balanced down-conversion differential mixer. Operating within the 0.5 GHz to 1.8 GHz range, the suggested mixer is appropriate for a variety of applications, such as cellular base stations, satellite communication (SATCOM), and military radar. The down-conversion mixer is made up of a single-ended to a differential-balanced radiofrequency (RF) stage, a dual feedback linearization for the RF stage, a local oscillator (LO) balun, LO mixing cores, and a fixed intermediate frequency (IF)-tuned circuit connected between two outputs to serve as a load at 145 MHz. Compared to earlier research in the literature, the measured SSB noise figure is approximately 7 dB ± 0.4 dB, and the measured conversion gain is approximately 12 dB ± 1 dB for a full band of operation. The mixer achieves a good return loss of over 8 dB for an RF and LO port in the desired band and a measured return loss of over 18 dB at 145 MHz and IF frequency. Furthermore, the design achieved an RF-to-IF isolation of greater than 35 dB, LO feedthrough, and an LO leakage isolation of better than 50 dB. Lastly, the measured third-order intercept point was found to be +4.7 dBm, and the 1 dB compression point was approximately -8 dBm. These results demonstrate good linearity performance.