The Need

With the rapid growth in modern communication, transmitter systems must use a wider fraction of the spectrum, to support the continuously increasing data rate. In addition, signals with large peak-to-average power ratio (PAPR) are used in communication systems to increase the spectral efficiency. This has led to an increase in demand for multi-band and broadband power amplifiers (PA) for signals with large PAPR. The conventional Doherty power amplifier faces significant challenges to achieve high average efficiency. Recent novel developments have imrpvoed the average efficiency substantially.

The Technology

Dr. Patrick Roblin, along with other researchers at The Ohio State University, has developed a new dual-input microwave power amplifier (PA) with high-efficiency. This PA exploits the continuum of modes between the Doherty and Chireix PA mode of operation to achieve 40% fractional bandwidth while relying on the physical linear dispersion of the transmission lines of the lossless output combiner. A constant output is achieved at peak power over the entire bandwidth. The output backoff varies from 6 dB in the Doherty mode to 8 dB in the Chireix mode. Dr. Roblin's team has created a demonstrator circuit for a frequency operating range varying from 4 to 6 GHz.

In this band, the PA achieves on average 45% drain efficiency at peak power and 40% drain efficiency in backoff. The PA actually operates well over a wider range of frequencies from 1 to 8 GHz. The dual-input PA operates in mixed-mode and thus requires variable input power drives and an outphasing angle. A four input implementation is also presented to allow the final sliding mode PA stage to operate in the high efficiency mixed mode while using constant power levels at the four inputs. This new PA provides a high efficiency for an exceptionally large fractional bandwidth.

Commercial Applications

• Telecommunications
• Electronic Warfare
• Transmissions
• Electronics manufacturers
• Technology Industries

Benefits/Advantages

• Establishes design of matching networks
• Improves drain efficiency
• Operational in multiple frequency bands