Digital Suppression of Transmitter Leakage in FDD RF Transceivers: Aliasing Elimination and Model Selection

Abstract

The transmitter (TX) induced interference due to power amplifier (PA) nonlinearities poses severe desensitization problems to the receiver (RX) chain in frequency-division duplexing (FDD) transceivers. Due to nonlinear signal process involved, a high sampling rate is normally required in the existing digital suppression approaches, which can result in high cost and high power consumption in wideband systems. In this paper, a new digital suppression model is proposed to cancel the TX leakage at baseband with a low sampling rate. The cancellation model is based on the modified decomposed vector rotation (DVR) model. With the addition of cross-term products, the enhanced model is capable of eliminating the aliasing effect arising from the reduced sampling rate. Theoretical analysis of aliasing elimination is presented, and the algorithm is subsequently verified by both simulation and experiment results, confirming the effectiveness and feasibility of the proposed cancellation technique for TX leakage suppression. Compared to conventional solutions, the new approach uses much less hardware resource and consumes much lower power while achieving comparable performance.

Digital Suppression of Transmitter Leakage in FDD RF Transceivers With an Enhanced Low-Sampling Rate Behavioral Model

“…1, where the baseband input signalx(n) is fed into a sideband suppression block to produce the output spectral replicaṽ(n) that can be subtracted from the received signal to restore the fidelity of the received information. As described in [3], the digital signal processing of replica generation includes three parts: 1) frequency shift; 2) nonlinear modeling; 3) band-limited filtering. The frequency shift is carried out by multiplying e j∆ωn .…”

“…A direct consequence of the high sampling rate requirement is that the digital block of the behavioral model is required to work at a very high data rate, e.g., over giga-sample per second, that is not feasible in practice. To reduce the data processing rate, W. Cao et al in [3] proposed an alternative algorithm based on decomposed vector rotation (DVR) model [4] to perform the sideband suppression at a low processing rate. The idea was to use cross-term products to eliminate the aliasing distortion in replica generation.…”

“…After theoretical analysis of magnitude-and phase-related nonlinearity generations, this letter proposes an enhanced model for sideband suppression. Comparing with the model in [3], the new model can achieve a higher accuracy in generating the sideband replica with a lower residual inference and using a smaller number of coefficients.…”

Investigation and Suppression of RF Leakage Power in Front End Wireless Devices

“…H. Khatri et al,(2010) and A. Cicalini et al,(2006) proposed TX leakage filtering active cancellation techniques [9][10][11]. Lederer and Huemer (2011), Frotzscher and Fettweis (2008), and Kahrizi et al,(2008) discussed interference cancellation algorithms using adaptive based LMS and measured error to suppress noise through stopband of the frequency flat duplex [12][13].…”

Sampling Rate Reduction for Digital Predistortion of Broadband RF Power Amplifiers

“…A joint in-band/out-of-band DPD [20] used multiple signal chains to form a wideband signal, which does not necessarily reduce the overall power consumption. In [21], authors targeted at sideband replica modeling and proposed to add cross-terms into existing model expressions to partially compensate for aliasing distortion at a low sampling rate. A different work [22] employed a decomposed piecewise technique where each piecewise segment is filtered before used as basis functions.…”