This article reviews the recent advancements in the utilization of over-the-air combining techniques to enhance the efficiency of phased-array transmitters for signals with a high peak-to-average-power ratio. A methodological comparison between three spatial over-the-air combining techniques - Doherty, outphasing, and quadrature combining - is proposed, along with analysis of their spatial properties, such as a beamwidth angle for a given error vector magnitude (EVM) value, directivity, out-of-band emission, and sensitivity to amplitude and phase mismatches between the different streams. The analysis suggests that the Doherty technique has the widest spatial angle range with EVM under -30 dB and the lowest sensitivity to mismatches, while quadrature combining exhibits the lowest adjacent channel power ratio (ACPR). Also, the Doherty technique enables the largest efficiency enhancement and allows to trade off efficiency enhancement for out-of-band emission. The different methods were tested over-the-air at 28 GHz with a four-element integrated phased array fabricated in 65 nm to validate the analysis.
|Number of pages||11|
|Journal||IEEE Transactions on Microwave Theory and Techniques|
|State||Published - 1 Jan 2022|
- 5G mobile communication
- Array signal processing
- Peak to average power ratio
- Phased arrays
- Transmitting antennas
- efficiency enhancement
- phased array transmitter
- sequential power amplifier (PA)
- transmitter efficiency.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Electrical and Electronic Engineering