A Novel Structure Optimizer Based on Heuristic Search for Delta-Sigma Modulator in Mobile Fronthaul
Dayong Tan, Yang Zou, Linsheng Zhong, Weiqi Lu, Jie Zhang, Xiaoxiao Dai, Qi Yang, Mengfan Cheng, Lei Deng, Deming Liu
Abstract
In this letter, a novel delta-sigma modulator structure design method based on the genetic algorithm is proposed. Compared to the widely adopted R.Schreier’s method, the proposed approach can significantly reduce the in-band quantization noise. Performance comparisons are carried out on 4th-order baseband delta-sigma modulators (DSMs) and 6th-order bandpass DSMs with center frequency at 2GHz. OSR of these delta-sigma modulators are set at 8. Numerical simulations, as well as experimental demonstrations, are conducted to show a 10-Gbaud intensity modulation direct detection transmission with the 64-QAM signal. Experimental results show that compared to R. Schreier’s method, the proposed GA method can improve the SNR by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 5$ </tex-math></inline-formula> dB and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 3$ </tex-math></inline-formula> dB for baseband DSM and bandpass DSM, respectively.