Performance limits and design techniques for Watt-level power amplification at millimeter-wave (mm-wave) frequencies using silicon germanium (SiGe) HBT Class-E power amplifiers (PAs) is presented in this paper. A Class-E power modulator architecture is proposed for demonstrating high-speed data transmission using ASK modulation at mm-wave frequencies. Several of these 1-b power modulators are power combined to realize a Watt-level digital PA with several levels of output amplitude at mm-wave frequencies. A dynamic load modulation concept is proposed to mitigate the effect of load pulling in the digital PA at power back-off. A tunable transmission line architecture with variable characteristic impedance is proposed to realize this dynamic load modulation network and enable efficiency enhancement at power back-off levels in the Watt-level digital PA. Watt-level power generation at mm-waves was demonstrated in a eight-way combined digital PA with dynamic load modulation, fabricated in a 0.13-   $\mu \text{m}$    SiGe BiCMOS process with    $\approx $   29 dBm (0.8 W) measured output power at 46 GHz, 18.4% peak power-added-efficiency, and 60% of the peak efficiency at 6-dB power back-off.
['Kunal Datta', 'Hossein Hashemi']
Watt-Level mm-Wave Power Amplification With Dynamic Load Modulation in a SiGe HBT Digital Power Amplifier