Abstract
This article presents a quasi-load insensitive (QLI) Doherty power amplifier (DPA). The proposed theory makes the amplifier load insensitive in terms of output power, while its efficiency is slightly degraded for complex loads. The load insensitiveness is achieved by dynamically changing the supply voltages ( <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex>${V_{DD}}$</tex> </formula> ) and the input power splitting for both the carrier and peaking transistors. The optimal, load-dependent, <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex>${V_{DD}}$</tex> </formula> values are theoretically derived from back-off (BO) and full power conditions using load line theory. The optimal input excitation signals for the carrier and peaking devices are also derived for these variable <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex>${V_{DD}}$</tex> </formula> conditions. A 3.6-GHz QLI DPA was designed, and a complete system, composed of the DPA output stage, a two-channel medium power driver, an adaptive input driving stage, and a load sensing system, was implemented. The laboratory measurements have been performed for loads distributed inside a 2.0 maximum voltage standing wave ratio (VSWR) circle and show an output power variation between 43.8 and 42.6 dBm and a BO efficiency between 50% and 35%. Under modulated signal excitation, for the worst case loads, the peak output power capability of the DPA is improved from 41.7 to 43.1 dBm, and the average efficiency is increased from 32.6% to 43%.
Highlights
P OWER amplifiers (PAs) are used for various applications, and their performance has a considerable impact on the overall system operation
A technique capable of improving the performance of a two-way symmetrical Doherty power amplifier (DPA) operating for nonoptimal loads was presented
The experimental validation was performed on a 3.6-GHz symmetrical DPA with a maximum nominal output power of 43.5 dBm and 5.1 dB of OBO with a drain efficiency above 50%
Summary
P OWER amplifiers (PAs) are used for various applications, and their performance has a considerable impact on the overall system operation. Driving signals of digital Doherty PAs can be designed to use some power of the peaking amplifier to correct the carrier load, but this will degrade the BO efficiency of the PA and can only compensate for variations toward lower loads. By properly controlling the drain voltages of the devices, we achieve reduced load sensitivity In this expanded version, we go one step further, showing that this correction technique is only effective if the radio frequency (RF) input signals of the carrier and peaking devices are load-dependent. We go one step further, showing that this correction technique is only effective if the radio frequency (RF) input signals of the carrier and peaking devices are load-dependent These optimal input signals are derived, presented, and implemented using an analog adaptive input driving stage.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IEEE Transactions on Microwave Theory and Techniques
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
