A PA-noise cancellation technique for next generation highly integrated RF front-ends

The evolution of efficiency in RF power amplifiers has been very gradual. Even today, they dissipate a lot of energy as heat which reduces the efficiency and increases the noise level. This PA noise is generally attenuated down to the thermal noise floor of the receiver by using highly selective duplexers. High selectivity necessarily carries high insertion loss and hence the PA output power requirement further increases. In the next generation of radios, efforts are underway to substantially reduce duplexer size and selectivity specifications. This will lead to a significant increase in the PA noise falling into the receive band. This work looks at a new technique to mitigate this receive-band noise by means of a mixed signal architecture using analog and digital components. We demonstrate that the cancellation of this noise can be accomplished by the receiver, and SNR gains can be demonstrated using commercial RFICs.