Multimode detector and I/Q imbalance compensator in a software defined radio

Selected components of a software defined radio (SDR) supporting UMTS (UTRA FDD) and WLAN (IEEE 802.11a) are presented in this paper. The novelty of the approach discussed here is the idea of unifying an I/Q imbalance compensation module and a multimode detector based on the frequency domain equalization principle. Both functionalities are designed and implemented based on the FFT operation and make the RAKE receiver obsolete. Two I/Q imbalance compensation methods allowing the re-use of hardware components, hard decision based (HD) and preamble based (Pre) algorithms, are analyzed and a comparison of their performance and resource demands is drawn. Theoretical results of the study are valid for a whole range of SDR systems, not only for the one investigated in this paper.