| The objective of the proposed research is to present a new all-digital outphasing transmitter IC, a comprehensive explanation of its operation, and its performance characterization. The all-digital transmitter chip leverages flexible digital phase modulators (DPMs) to adaptively compensate for amplifier mismatches. As the DPM uses a digital input to directly modulate the RF phase of each path, the phase control becomes very simple and accurate for power amplifier (PA) gain/phase mismatch compensation. Furthermore, this digital phase modulation scheme also facilitates minimizing the distortion of an RF combiner. It is newly proposed that two distinct digital predistortion algorithms are required for perfect compensation for both PAs and a combiner. All phase calibration values can be adaptively calculated as a function of outphase angle and saved in digital look-up tables to predistort the phase inputs of two DPMs.;Various types of PAs and combiners are investigated to further enhance the performance of the outphasing transmitter. These features are implemented in a chip fabricated in a 0.18-microm CMOS process and evaluated with IEEE 802.16e baseband symbols. |
