Extraction of Inphase and Quadrature Components from Oversampled Bandpass Signals Using Multistage Decimator with BPFs and Its Performance Evaluation

Takashi SEKIGUCHI  Tetsuo KIRIMOTO  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E77-A   No.9   pp.1457-1465
Publication Date: 1994/09/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section of Papers Selected from the 8th Digital Signal Processing Symposium)
Category: Multirate Signal Processing
Keyword: 
digital filters,  analog to digital converters,  oversampling,  quadrature detection,  signal to noise ratio,  Hilbert transformers,  

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Summary: 
We present a method of extracting the digital inphase (I) and quadrature (Q) components from oversampled bandpass signals using narrow-band bandpass Hilbert transformers. Down-conversion of the digitized IF signals to baseband and reduction of the quantization noise are accomplished by the multistage decimator with the complex coefficient bandpass digital filters (BPFs), which construct the bandpass Hilbert transformers. Most of the complex coefficient BPFs in the multistage decimator can be replaced with the lowpass filters (LPFs) under some conditions, which reduces computational burden. We evaluate the signal to quantization noise ratio of the I and Q components for the sinusoidal input by computer simulation. Simulation results show that the equivalent amplitude resolution of the I and Q components can be increased by 3 bits in comparison with non-oversampling case.