Matching for Concurrent Harmonic Sensing in an M-Phase Mixer-First Receiver

This brief proposes the use of passive mixer-first receiver topology to sense signals at higher LO harmonics. The advantages of such a receiver include sensing of multiple bands concurrently and reduced tuning range requirements in the frequency synthesizer. The single and joint harmonic matching performance of a zero-IF M-phase mixer-first receiver is analyzed. It is shown that minimum possible return loss for joint matching occurs when the geometric mean of input impedances at the highest and lowest sensing bands equals the antenna impedance. The noise figure (NF) when sensing higher order LO harmonics is shown to result in only modest degradation, with the loss becoming even less with increasing number of LO phases. As an example, a 12-phase harmonic-sensing mixer first receiver is simulated and its performance at first, third, and fifth harmonics is evaluated in terms of input matching and NF.