A Passive Mixer for a Wideband TV Tuner

This brief presents the design of a direct conversion mixer for a wideband television tuner operating at 48-860 MHz. The mixer consists of a transconductance stage, a passive current switching stage, and a transimpedance amplifier stage. In the switching stage, by adopting an opposite phase auxiliary switching quad configured in parallel with the main switching quad, the unwanted harmonics at the output of the switching stage are suppressed, thereby preventing mixer linearity degradation at low input frequencies. The proposed mixer is implemented in a 0.13-μm CMOS technology, and measurements show more than a 19.5-dB voltage gain, 12-dB noise figure, and 8-dBm IIP3 over the entire operating band of 48-860 MHz while dissipating 4.5 mA from a 1.2-V supply.