Digital and analog IM3 product compensation circuits for an RF receiver

摘要

Third-order intermodulation products (IM3) are attenuated in RF receivers by providing a typical main signal path and a parallel auxiliary signal path in which the IM3 products are accentuated, and the output from the main signal path is adaptively filtered to attenuate the IM3 products. In one embodiment, a multirate filter bank (MRFB) with asymmetric analysis and synthesis sections is used to detect and isolate the IM3 products. In another embodiment an analog nonlinear term generator is placed at the front of the auxiliary signal path. The analog nonlinear term generator takes advantage of the nonlinearities of a differential MOSFET circuit and a multiplier to extract the IM3 products in the RF input signal. The outputs of the main signal path and the auxiliary signal path are inputs to a complex least mean squares filter to attenuate the IM3 products in the resulting signal.