A CMOS low loss/high linearity passive mixer for 2.45 GHz low power applications

Abstract

-A fully integrated passive mixer suitable for 2.45 GHz low consumption and low cost applications is proposed and demonstrated in a 90 nm CMOS technology. An original operating principle is adopted which is based on the use of a local oscillator square signal exhibiting a duty cycle less than 1/4. By using such a LO driving, the mixer operates as a sampler and can theoretically achieve a voltage conversion gain of 0 dB. This mixer has been integrated in a complete monolithic receiver. According to simulations, measurements demonstrate improvements of 5 dB on gain and 3 dB on noise figure without any linearity degradation and any additional cost, when compared to a common LO driving of 1/2 duty cycle.

A K-band BiCMOS low duty-cycle resistive mixer

“…Test-bench used for mixer characterization contribution can be estimated to −2.1 dB. This result is very close to the −1.9 dB predicted by the theory [4].…”

“…This technique cancels out the crosstalk that is observed in IQ receivers featuring a 50% dutycycle LO signal and increases the overall receiver's gain by at least 3 dB [2] [3]. Additionnally, when used in a voltage-driven configuration, the resistive mixer operates as a sampler and the conversion losses are almost entirely cancelled theoretically [4]. However, the circuits involved in the generation of a low duty-cycle LO driving signal are frequency-limited and cannot be pushed beyond few GHz [5], which greatly limits the number of applications targeted by such architecture.…”