Quantization Noise Minimization in ΣΔ-modulation based RF Transmitter Architectures

Artikel i vetenskaplig tidskrift, 2010

In this paper we describe an optimization method for minimization of quantization noise in ΣΔ-based RF transmitters. The aim of the method is to enable the use of reconstruction filters with wider passband, or alternatively, a lower switch-rate. The method uses a general representation of the ΣΔ-converters in combination with a differentiable approximation of the quantizer. Based on this, a Monte-Carlo based algorithm is developed around the damped Gauss-Newton iteration. As a result of the suggested algorithm, the residual quantization noise after reconstruction filtering is significantly decreased. Finally, simulations using a bandlimited signal with a Gaussian distribution are used to demonstrate the capabilities of the suggested algorithm when applied with the proposed ΣΔ-modulator representation. The resulting performance is compared to several cases of traditional integrator based ΣΔ-converters, demonstrating significant improvements in terms of reduced reconstruction normalized mean square error (NMSE). This implicates that the transmitter efficiency can be improved with minor changes in the modulator implementation.