Multimode software defined radio receiver using direct conversion and low-IF principle: Implementation and evaluation

In recent years, software defined radio has attracted attention as radio with features that can be freely changed by software. The authors have previously proposed a concept for a receiver that converts the entire bandwidth of a desired system to digital signals and selects the signals of the desired channel in the digital stage. In addition, they have applied this concept to propose a basic configuration of a software defined radio using the direct conversion and low intermediate frequency (low-IF) principle. In this paper, the authors investigated a specific implementation of the previously proposed wideband analog stage using the direct conversion and low-IF principle and digital stage having an image rejection function and evaluated this implementation through experiments using the 1.5- and 1.9-GHz bands. The results showed that a 10-MHz wideband was implemented for the bandwidth and that at least 25 dB was obtained for the image rejection ratio by using the direct conversion principle and at least 61 dB was obtained by using the low-IF principle. In addition, the authors performed the evaluation using the entire receiver and confirmed that the implementation was error free for multiple modulation modes. (C) 2003 Wiley Periodicals, Inc.