In this paper we present an original way to simplify the architecture of a frequency synthesizer for the 3.1-10.6 GHz band. On the basis of measurement results, obtained by a produced CMOS prototype, the architecture performances are analyzed. As spur frequencies are inevitably generated, we propose to apply an interferences reduction method at the receiver. This solution allows meeting the MultiBand OFDM (Orthogonal Frequency Division Multiplexing) requirements, despite the imperfect spectrum of the generated frequencies and allows simplifying the synthesizer's structure, limiting the use of band-pass filters.

Direct-conversion architectures suffer from the mismatch between the in-phase (I) and the quadrature-phase (Q) branches, commonly called I/Q imbalance. Even low I/Q imbalances imply poor performance of orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose a new algorithm that uses both training and data symbols in a decision-directed fashion to jointly estimate the channel and compensate for high receiver I/Q imbalance. Simulation results show that our method can compensate for high I/Q imbalance values and also estimate a frequency selective channel.

This paper presents the impact of the high-frequency memory of a non-linear amplifier on a multi-carrier (OFDM) transmission and an original, yet very simple, method to compensate for it directly at the transmitter. Our method is efficient thanks to the usage of a long enough cyclic prefix, as in actual OFDM systems.