Research Projects

This grant proposal addresses the urgent need for highly efficient and linear power amplifiers (PAs) in 5G/6G base stations. The 5G/6G wireless communications use complex, high-order modulation schemes such as QAM, and multi-carrier techniques like OFDM. These modulation schemes result in large variations in the envelope, resulting in the high peak-to-average power ratio (PAPR) modulated signals. Single-ended power amplifiers (PAs) are incapable of supporting high PAPR signals, as they can only give high efficiency at peak power. Whereas, at average power levels the efficiency of single-ended PA is poor. Therefore, 5G/6G base stations use dynamic load modulation power amplifiers such as Doherty PAs (DPAs). However, the bandwidth of DPA is limited due to its architecture consisting of a quarter-wave transformer. A sequential Load-modulated balanced amplifier (SLMBA) is a very recent addition to the dynamic load modulation PAs which has a wide bandwidth capability and flexibility to achieve efficiency peak at desired output back-off. Although dynamic load modulation PAs have efficiency peaks at saturation and OBO, they are typically matched for only fundamental frequencies which results in low efficiencies. In order to achieve high efficiency, the harmonic manipulation technique is popularly used. However, harmonic manipulation requires the design of a multi-harmonic matching network which increases the complexity of SLMBA. Moreover, nonlinearity exists in SLMBA due to its architecture which combines a carrier PA operating in Class B/AB and a peaking balanced amplifier operating in Class C. This results in intermodulation distortion (IMD), AM-AM, and AM-PM distortions, which degrade signal quality and cause spectral regrowth, making it difficult to meet stringent adjacent channel power ratio (ACPR) and linearity requirements of 5G/6G communications. This project proposes an innovative solution to these limitations by incorporating active harmonic injection in SLMBA. This approach aims to enhance efficiency and linearity by harnessing harmonics generated within the SLMBA’s carrier PA and peaking balanced PAs. By actively injecting harmonics in between the output of amplifier stages, the project seeks to improve the efficiency of SLMBA without the need for multi-harmonic matching networks. The project also seeks to improve the linearity of SLMBA by actively injecting harmonics from the output of one amplifier stage into the input of another, to pre-distort the signal at second harmonics, reducing nonlinearity and delivering a more linear output. This technique has the potential to cancel out unwanted distortions such as AM-AM and AM-PM distortions resulting in a more linear output signal. By enhancing SLMBA performance, the project addresses a crucial gap in the development of PAs that can meet the demanding efficiency and linearity standards of next-generation wireless systems.