Robust DSP Type Squaring Loop with Adaptive Notch Filter Type Frequency Estimator and Adaptive BPF

Shigeki OBOTE
Yasuaki SUMI
Yoshio ITOH
Yutaka FUKUI

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E84-A    No.2    pp.441-448
Publication Date: 2001/02/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Noise Cancellation and Reduction Techniques)
Category: Narrow-Band Interference Cancellation
squaring loop,  coherent detection,  BPSK,  adaptive notch filter,  frequency estimator,  

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Recently, in the modem, the spread spectrum communication system and the software radio, Digital Signal Processor type Squaring Loop (DSP-squaring-loop) is employed in the demodulation of Binary Phase Shift Keying (BPSK) signal. The DSP-squaring-loop extracts the carrier signal that is used for the coherent detection. However, in case the Signal to Noise Ratio (SNR) is low, the DSP-Phase Locked Loop (DSP-PLL) can not pull in the frequency offset and the phase offset. In this paper, we propose a DSP-squaring-loop that is robust against noise and which uses the adaptive notch filter type frequency estimator and the adaptive Band Pass Filter (BPF). The proposed method can extract the carrier signal in the low SNR environment. The effectiveness of the proposed method is confirmed by the computer simulation results.