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41 results on '"Dhar, Sagar K."'

9. High-Efficiency Class-iF−1 Power Amplifier With Enhanced Linearity

Author

Chu, Chenhao, Tamrakar, Vivek, Dhar, Sagar K., Sharma, Tushar, Mukherjee, Jayanta, and Zhu, Anding

Abstract

This article presents a new class of power amplifier (PA), designated as Class-iF−1, that utilizes input harmonics to achieve high efficiency with enhanced linearity performance beyond the conventional Class-F−1 PA. The amplitude-to-amplitude modulation (AM/AM) profile of the conventional Class-F−1 PA is mathematically modeled as a function of the input drive level, such that the occurrence of inflection points can be investigated. Theoretical derivation shows that the appropriate utilization of input nonlinearity poses a solution to rectify the double inflection characteristics of the conventional Class-F−1 PA, which, consequently, can be realized by proper manipulation of second harmonic source impedance ( $Z_{2S}$ ). The theoretical findings were validated with load—pull results at 2.3 GHz with a 2-mm gallium nitride (GaN) device, presenting enhanced linearizable output power and efficiency for the Class-iF−1 PA, with a broad second harmonic design space over the open-circuit region. As proof of concept, a Class-iF−1 PA was designed and fabricated, obtaining 40.1–40.8 dBm output power and 71.2%–77.3% drain efficiency (DE) performance at 3-dB gain compression level operating over 2.0–2.6-GHz frequency range. When tested with a 20-MHz 8.5-dB peak-to-average-power-ratio (PAPR) long-term evolution (LTE) signal, around 32.01-dBm average output power was attained at 2.3 GHz with an average DE of 34.59% and −56.05 dBc adjacent channel power ratios (ACPRs) after digital predistortion (DPD) correction.

Published
2023
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10. Broadband Sequential Load Modulated Balanced Amplifier With Extended Design Space Using Second Harmonic Manipulation

Author

Chu, Chenhao, Pang, Jingzhou, Darraji, Ramzi, Dhar, Sagar K., Sharma, Tushar, and Zhu, Anding

Abstract

This article presents the design methodology of a broadband radio frequency (RF)-input sequential load modulated balanced amplifier (SLMBA) with extended high-efficiency design space, by introducing the second-harmonic load manipulation over an enlarged range for the control amplifier (CA). The extension of CA load design space not only can provide the time-domain-varying drain current waveform inside the entire design continuum but also allows maintaining high efficiency at output power back-off (OBO) over an extended operation bandwidth. To validate the theory, a broadband SLMBA operating at 2.05–3.65 GHz was designed and fabricated using packaged gallium nitride (GaN) transistors. The implemented power amplifier (PA) attains a measured 45.2–46.8-dBm peak output power. Drain efficiency (DE) of 61.2%–79.7% at saturation and 50.5%–66.2% at 8-dB OBO is achieved throughout the designed bandwidth. When tested with a 100-MHz long-term evolution (LTE) signal with a peak-to-average-power ratio (PAPR) of 8 dB, the proposed SLMBA achieves 50.7%–63.5% average DE over 2.05–3.55 GHz and better than −45.1 dBc adjacent channel power ratio (ACPR) after digital predistortion (DPD).

Published
2023
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12. Waveform Engineered Sequential Load Modulated Balanced Amplifier With Continuous Class-F −1 and Class-J Operation.

Author

Chu, Chenhao, Sharma, Tushar, Dhar, Sagar K., Darraji, Ramzi, Wang, Xiaoyu, Pang, Jingzhou, and Zhu, Anding

Subjects
ENGINEERS, ENGINEERING, BANDWIDTHS, HARMONIC analysis (Mathematics)
Abstract

This article presents a novel waveform engineered sequential load modulated balanced amplifier (W-SLMBA) that uses a continuous Class-F−1 control amplifier (CA) to manipulate the impedance trajectory of the balanced amplifier (BA). It is demonstrated that the use of the continuous Class-F−1 CA can trigger a unique impedance load modulation mechanism by which the fundamental impedance of the BA is shaped by the varying second-harmonic load reactance of the CA. Theoretical derivations reveal that this special load modulation yields extended design space for the LMBA, in which high efficiency can be achieved over wide bandwidth and output power back-off (OPBO). A prototype operating from 1.80 to 2.75 GHz is designed following the proposed theory. The implemented LMBA achieves a measured drain efficiency (DE) of 60.2%–68.3% at saturation and 51.8%–69.0% at 8-dB OPBO. When tested with a 100-MHz long-term evolution (LTE) signal having peak-to-average power ratio (PAPR) of 8 dB, the proposed LMBA achieves 50.2%–59.1% average DE and better than −45.1-dBc adjacent channel power ratio (ACPR) across the target bandwidth after digital predistortion (DPD). [ABSTRACT FROM AUTHOR]

Published
2022
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