Suppression of constant modulus interference in multimode transceivers using an adaptive nonlinear circuit

In multimode transceivers, the transmitter for one communication standard may induce a large interference in the receiver for another standard. Using linear techniques to suppress this interference requires a receiver with a very large dynamic range, leading to an excessive power consumption. A much more power efficient approach suppresses the interference using an adaptive Nonlinear Interference Suppressor (NIS). In previous works an ideal model was used to study the receiver performance afforded by the NIS. In this paper we present experimental results of a transceiver testbed that uses an implementation of the NIS, fabricated in 140 nm CMOS technology. Main imperfections that limit the NIS performance are identified and simple models are presented that explain the experimental results. Even with these imperfections, a substantial interference suppression is achieved.