Load-Modulated Balanced Amplifiers

Abstract

Researchers at the University of Central Florida have invented two kinds of load-modulated balanced amplifier architectures. The power amplifier (PA) is the most power-consuming module in any wireless platform, and it predominantly influences the system features, including power consumption, energy efficiency, temperature and bandwidth. With the UCF inventions, companies can achieve nearly unlimited bandwidth and high efficiency for amplifying high-dynamic-range 4G and 5G communication signals. They provide solutions for current and future energy-efficiency, multi-band, and multi-mode radio transmitters:

• Pseudo-Doherty Load-Modulated Balanced Amplifier (PD-LMBA)
• Reconfigurable Asymmetrical Load Modulation Balanced Amplifier (ALMBA)

Technical Details

• Invention Track Code: 11636, Pseudo-Doherty Load-Modulated Balanced Amplifier (PD-LMBA)—This invention offers a new architecture with a unique combination of control amplifier (carrier) and balanced amplifier (peaking) and a new phase-shifting method for achieving proper phase and amplitude controls. The PD-LMBA provides optimal load-modulation with maximized efficiency over extended power back-off range, resulting in unlimited operational bandwidth. This is a major benefit compared to conventional Doherty PAs and generic LMBAs without PD bias.
  
  As shown in Figure 1, the example PD-LMBA configuration can include a radio frequency (RF) input port, an RF output port, and a peaking amplifier circuit between the RF input and output ports. The peaking amplifier circuit is a balanced amplifier (BA) that includes a pair of power amplifiers and a carrier amplifier circuit operably coupled to the RF input port. The control amplifier is biased in Class-AB above the threshold of the transistor, and the BA is biased in Class-C below the transistors’ threshold. Transmission lines or equivalent circuits are added at the input of BA and CA for phase-delay control.

• Invention Track Code: 11637, Reconfigurable Asymmetrical Load Modulation Balanced Amplifier—This invention is an extension of the pseudo-Doherty load modulated balanced amplifier invention. The ALMBA uses two asymmetrical subamplifiers coupled quadratically and load-modulated by a control amplifier (CA), leading to optimized load modulation behaviors of all three amplifiers. With the proper setting of phase, amplitude, and turn-on sequence of three sub-amplifiers, a hybrid load modulation of the overall power amplifier (PA) is achievable. This leads to maximally enhanced efficiency over extended dynamic power range. Moreover, with the phase control method and a unique reconfigurable biasing scheme, the unlimited bandwidth of this load modulation amplifier can be maintained from regular LMBA.
  
  As shown in Figure 2, the example ALMBA configuration can include an RF input port, an RF output port, and a peaking amplifier circuit between the RF input and output ports. The peaking amplifier circuit is a balanced amplifier that comprises a pair of asymmetrical power amplifiers and a carrier amplifier circuit operably coupled to the RF input port. The pair of asymmetrical power amplifiers of the peaking amplifier circuit connect through quadrature couplers. The proper cooperation of the three amplifiers enables efficiency over the entire dynamic range and enhanced linearity.

Partnering Opportunity

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

Stage of Development

Prototypes available.

Benefit

Market Application

Publications

Pseudo-Doherty Load-Modulated Balanced Amplifier with Wide Bandwidth and Extended Power Back-Off Range, IEEE Transactions on Microwave Theory and Techniques, vol. 68, no. 7, pp. 3172-3183, July 2020, doi: 10.1109/TMTT.2020.2983925.

Asymmetrical Load Modulated Balanced Amplifier with Continuum of Modulation Ratio and Dual-Octave Bandwidth, IEEE Transactions on Microwave Theory and Techniques, vol. 69, no. 1, pp. 682-696, Jan. 2021, doi: 10.1109/TMTT.2020.3014616.