A fully digital multimode polar transmitter employing 17b RF DAC in 3G mode

A direct quadrature voltage modulator has been disclosed and current mode upconversion mixer with linearity boosting technique as preferred concepts for WCDMA transmitters (TX), enabling a solution for TX noise reduction at some duplex distances. Two problems remain unsolved: how to remove the TX SAW at the other duplexer distances, and how to support still highly desirable 2G and 2.5G modes, required for full coverage, without increasing power consumption and system complexity. A multimode solution was addressed but 2G and 2.5G far-off noise performance was not disclosed and in 3G high band an external local oscillator signal was still used. Further multimode work has been presented, where required far off noise performance has been achieved but at the expense of the large chip area due to dedicated 2G/3G signal paths and still a high power consumption. The single-chain TX (all modes reuse the same signal path) has been focus in the work, where other advantages of a digital concept have been demonstrated, but the TX SAW filter in 3G mode cannot be omitted due to higher-than-allowed far-off noise and remaining repetition spectrum. A further single-chain TX solution based on the analog polar modulator has been disclosed, demonstrating reuse of the signal path for 2G/3G systems in an analog polar transmitter concept, but TX noise in the RX band has not been disclosed. Recently, a fully digital polar modulator for 2G and 2.5G modes has been published with a low chip area and low power consumption, but still with unsolved far-off noise for the co-existence of cellular application with navigation and connectivity.