Chirp Spread Spectrum 시스템에 적합한 새로운 Automatic Gain Control 알고리즘

Abstract

In this thesis, we propose a novel automatic gain control (AGC) algorithm as a solution to improve the signal reception performance based on the IEEE 802.15.4a chirp spread spectrum (CSS) system. The CSS signals are composed of a number of full-chirps which are separated by the long guard time. A full-chirp is composed of two low-band sub-chirps and two high-band sub-chirps whose fading multipath channel characteristics are different. Due to the long guard time and the wideband properties of the CSS signal, it is not appropriate to make use of the conventional AGC algorithm which utilizes only one time window with fixed size in the integrator and regardless of the different bands. The proposed AGC algorithm is made up of two steps: the first step utilizes the short window integrator and the long window integrator alternatively, in order to avoid the dilemma between the adaptation time and the stability; the second step is based on two AGCs which are designed to be matched well with the low-band sub-chirp and the high-band sub-chirp separately for minimizing the quantization noise during the analog-to-digital conversion (ADC). Under our assumption, we calculate that the ratio of the signal power to the quantization noise power (SNR) can be improved by 4.08dB with the proposed AGC. The simulation results and the implementation result show that the power of the received signal is well controlled within our anticipated range by using the proposed AGC.