Effects of tuner IQ imbalance on multicarrier-modulation systems

After giving a short description of the underlying principles of orthogonal frequency division multiplexing (OFDM) as a representative of a multicarrier modulation (MCM) system, this paper sets the main emphasis on investigating the effects of IQ imbalance caused by the analog signal processing in the tuner. A mathematical description of the resulting distortions is given. Special attention is paid to the description in the frequency domain. This is the prevailing level of digital signal processing in OFDM receivers to extract useful information from the received signal. An OFDM 64 QAM (quadrature amplitude modulation) transmission chain according to the European DVB-T (terrestrial digital video broadcasting) standard has been simulated in order to evaluate the impact of the tuner imperfections on the constellation diagram and the bit-error rate (BER). In the framework of the DVB-T system possible strategies to equalize these imperfections are briefly suggested.