Digital signal processing and direct conversion for multichannel transmitters

A multichannel transmitter architecture is presented, combining an efficient transmultiplexer algorithm with direct conversion. Direct conversion is chosen for its simplicity and low cost, but it is necessary to compensate for the inherent amplitude and phase imbalances. These imbalances are shown to be frequency dependent in a multichannel environment, generating unacceptable levels of spurious sidebands and rendering current adaption techniques inappropriate. The paper proposes a compensation technique based on the multichannel transmitter architecture. It is computationally more efficient than the previous adaptive compensation techniques and simulations show that the undesired sideband can be controlled to meet ACI specifications