Envelope and phase delays correction in an EER radio architecture

Abstract

This article deals with synchronization in the Envelope Elimination and Restoration (EER) type of transmitter architecture. To illustrate the performances of such solution, we choose to apply this architecture to a 64 carriers 16QAM modulated OFDM. We first introduce the problematic of the realisation of a highly linear transmitter. We then present the Envelope Elimination and Restoration solution and draw attention to its major weakness: a high sensitivity to desynchronization between the phase and envelope signal paths. To address this issue, we propose an adaptive synchronization algorithm relying on a feedback loop, a Least Mean Square formulation and involving an interpolation step. It enables the correction of delay mismatches and tracking of possible variations. We demonstrate that the quality of the interpolator has a direct impact on Error Vector Magnitude (EVM) value and output spectrum. Implementation details are provided along with an analysis of the behaviour and performances of the method. We present Agilent-ADS and Matlab simulation results and then focus on the enhancement of the transmitter performances using the proposed algorithm.

Gain and delay mismatches cancellation in LINC and polar transmitters

“…The convergence time at 90% of the final value, t c , is also evaluated and for our test cases is under 150T s . These results are detailed in [5].…”

“…Moreover, the solution for delaying or advancing signals by fractional amounts relies on the use of interpolation filters which allow to adjust the delay without recomputing the coefficients of the filter [4]. We choose to implement a fifth order Lagrange interpolator using the Farrow structure, as we did in [5].…”

Adaptive gain and delay mismatch cancellation for LINC transmitter

“…The choice of this interpolator has to be studied further because it impacts directly the value of the interpolated signal EVM. For this reason, we choose to implement a fifth order Lagrange interpolator using the farrow structure [13].…”

Adaptive time mismatches identification and correction in polar transmitter architecture

“…The first one adaptively corrects the two delays induced by paths mismatches, while the second one only identifies these delays, but with a lower complexity. A preliminary version of the first algorithm was presented in [6]. The present version is more elaborated, detailed and enhanced in several aspects particularly concerning implementation issues and the analysis of performances.…”