Reference Receiver Enhanced Digital Linearization of Wideband Direct-Conversion Receivers

Abstract

This paper proposes two digital receiver (RX) linearization and in-phase/quadrature (I/Q) correction solutions, where an additional reference RX (ref-RX) chain is adopted in order to obtain a more linear observation, in particular, of the strong incoming signals. This is accomplished with reduced RF gain in the ref-RX in order to avoid nonlinear distortion therein. In digital domain, the signal observed by the ref-RX is exploited in linearizing the main RX. This allows combining the sensitivity of the main RX and the linearity of the lower gain ref-RX. The proposed digital processing solutions for implementing the linearization are feedforward interference cancelation and nonlinearity inversion, which are both adapted blindly, without a priori information of the received signals or RX nonlinearity characteristics. The linearization solutions enable flexible suppression of nonlinear distortion stemming from both the RF and analog baseband components of different orders. Especially, wideband multicarrier RXs, where significant demands are set for the RX linearity and I/Q matching, are targeted. Using comprehensive RF measurements and realistic base-station scale components, an RX blocker tolerance improvement of 23 dB and a weak carrier signal-to-noise-and-distortion ratio gain of 19 dB are demonstrated with combined linearization and I/Q correction.