Fast automatic gain control employing two compensation loop for high throughput MIMO-OFDM receivers

The performance of a receiver front-end limits the quality and range of the given communication link. An appropriate design based on well-defined system parameters and architecture can make a huge difference in the performance, cost and marketability of the entire system. In particular, there is a need for improved digital automatic gain control (AGC) for use in multi input multi output orthogonal frequency division multiplexing (MIMO-OFDM) systems with application to wireless local area networks (WLANs), targeted for the upcoming 802.11n standard based in H. Yu et al. (2004) and H. Yu et al. (2005). In this paper, we propose an efficient algorithm and implementation of the digital AGC for next generation WLANs. The proposed AGC algorithm has two feedback loops for gain control to improve convergence speed, and at the same time maintains the stability of the AGC circuit. Also, a complete set of parameters for practical implementation is obtained by various experiments with fixed point constraints and accuracy requirements.