The Need

In the era of 5G and beyond, wireless base station infrastructures require power amplifiers (PAs) that maintain high efficiency from backoff to peak power level. Conventional Doherty PAs, while popular, are inherently narrowband due to their reliance on a quarter-wave transmission line (TL). This limitation has led to numerous efforts to extend the bandwidth of Doherty PAs.

The Technology

Dr. Patrick Roblin, along with other researchers at The Ohio State University have developed a single-input hybrid Doherty power amplifier (HDω-PA). Unlike conventional Doherty PAs, the HDω-PA achieves wideband load modulation using the frequency dependence of the electrical length of the output combiner lines. A transmission line phase shifter provides the correct frequency-dependent input phase offset, ensuring wideband load modulation by the output combiner. The HDω-PA also includes a methodology for selecting the optimal input phase offset to reduce variation in saturation power versus frequency and minimize circuit size.

Commercial Applications

• Wireless Transmitter Systems: The HDω-PA can be used in wireless transmitter systems to enhance back-off power efficiency.
• 5G Base Stations: The technology can be adopted in 5G or beyond wireless base station infrastructures for high-efficiency power amplification.
• Broadband Applications: Due to its wideband capabilities, the HDω-PA can be used in various broadband applications requiring efficient power amplification.

Benefits/Advantages

• Enhanced Efficiency: The HDω-PA maintains high efficiency from backoff to peak power level.
• Wideband Capabilities: Unlike conventional Doherty PAs, the HDω-PA achieves wideband load modulation, extending its bandwidth.
• Optimized Performance: The technology includes a methodology for selecting the optimal input phase offset, reducing variation in saturation power versus frequency.
• Compact Design: The selection of optimal input phase offset also helps minimize circuit size.
• Improved Signal Quality: When excited by a 20-MHz long-term evolution (LTE) modulated signal with 6-dB peak-to-average-power ratio (PAPR), an average efficiency of 45%-59% and adjacent channel leakage ratio (ACLR) less than −50 dBc are achieved after digital predistortion (DPD).