A Balanced-to-Doherty Mode Switchable Power Amplifier (4G/5G Wireless Platforms)

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Kenle Chen, Ph.D.
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US Patent Pending
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Balanced-to-Doherty Mode-Reconfigurable Power Amplifier with High Efficiency and Linearity Against Load Mismatch
IEEE Transactions on Microwave Theory and Techniques, vol. 68, no. 5, pp. 1717-1728, May 2020, doi: 10.1109/TMTT.2020.2979844

Key Points

  • A power amplifier that can switch operation between Doherty mode and balanced mode
  • Resolves antenna impedance mismatch faced by radio frequency (RF) PAs in 4G/5G and emerging communication systems
  • Can replace existing circuitry in PA/RF frontend products

Abstract

A researcher at the University of Central Florida has invented a power amplifier (PA) technology that can switch operation between Doherty mode and balanced mode to maintain high linearity and high efficiency against load mismatch. The low-cost UCF balanced-to-Doherty (B2D) mode-reconfigurable PA eliminates the need for a tuner or isolator/circulator. Thus, it is smaller than existing PAs and offers lower loss and reduced system complexity in wireless communication platforms. The invention applies to radio‐frequency modules on 5G systems with antenna arrays.

Essential modules in wireless platforms, power amplifiers boost wireless signals that are broadcast to target terminals via antennas. However, the antenna impedance can be frequently mismatched. The antenna mismatch not only degrades the PA performance but also leads to reliability and ruggedness issues. Causes of antenna impedance mismatch include 1) hand-gripping effects on mobile devices, 2) mutual coupling between antenna elements in a phased array, and 3) MIMO (multiple-in, multiple-out) data transfer operations. With MIMO, antenna mismatch is inevitable due to mutual coupling induced by multi-antenna cooperation.

The UCF invention provides a solution to these issues. Under moderate antenna mismatch, the PA operates at Doherty mode, ensuring high energy efficiency for wireless transmission. Under high antenna mismatch, the PA is reconfigurable to balanced mode for mismatch protection and performance recovery.

Technical Details

The UCF invention is a PA architecture that can switch between balanced mode (resistive loading) and Doherty mode (reactive loading). The amplifier circuit comprises two amplifiers coupled in quadrature phase through input and output 90‐degree quadrature hybrids. This technology applies to radio‐frequency modules on 4G/5G wireless platforms (for example, smartphones and base stations).

A switch placed at the isolation port of the output quadrature coupler allows the PA to alternatively connect to a pre-determined resistive load or a pre-determined pure reactive load—that is, short, open, or finite reactance. This technology supports FET-based (field-effect transistor), BJT-based (bipolar-junction-transistor), or any other types of power amplifiers. The switch can take the form of single-pole double-through (SP2T) circuitry or other possible circuit topologies implemented using solid-state technologies. Examples include CMOS (complementary metal-oxide-semiconductor), silicon-on-insulator (SOI), MEMS (micro-electro-mechanical systems), and GaAs pHEMT (gallium arsenide pseudomorphic high-electron-mobility transistor).

Partnering Opportunity

The research team is looking for partners to develop the technology further for commercialization.

Stage of Development

Prototype available.

Benefit

  • Eliminates the need for antenna tuners or isolators/circulators
  • Offers smaller size, lower loss and cost, and reduced system complexity

Market Application

  • Semiconductor companies