Now showing 1 - 5 of 5
  • Publication
    Extend High Efficiency Range of Doherty Power Amplifier by Modifying Characteristic Impedance of Transmission Lines in Load Modulation Network
    A load modulation network with characteristic impedance-modified transmission lines (TLs) is presented in this paper to extend the efficiency range and bandwidth of the Doherty power amplifier (DPA). Characteristic impedance values for designing the proposed DPA with different high efficiency ranges are given and wideband performance can also be achieved. A DPA with 2.55-3.35 GHz bandwidth using commercial GaN transistors is designed and implemented to validate the proposed architecture. The fabricated DPA achieves a measured 9.2-10.4 dB gain and 44.3-45.4 dBm saturated power. 57.9-75.6% and 47.6-58.8 % drain efficiency is achieved at saturation and 8 dB output power back-off (OBO) within the designed bandwidth, respectively. When driven by a 5-carrier 100 MHz OFDM signal with 8 dB peak to average power ratio (PAPR), the proposed DPA achieves adjacent channel leakage ratio (ACLR) of better than -50 dBc after digital pre-distortion with average efficiency of 53.4%, 55.3% and 56.6% at 2.75, 2.95 and 3.15 GHz centre frequencies.
      377Scopus© Citations 11
  • Publication
    Broadband RF-Input Continuous-Mode Load-Modulated Balanced Power Amplifier With Input Phase Adjustment
    This article presents the theory and design methodology of broadband RF-input continuous-mode load-modulated balanced power amplifier (CM-LMBA) by introducing the CM output-matching networks in the LMBA architecture. It is illustrated that the CM impedance condition can be achieved by properly adjusting the phase difference between the different PA branches in the proposed CM-LMBA during the entire load modulation process. An RF-input CM-LMBA with 1.45-2.45-GHz bandwidth using commercial GaN transistors is designed and implemented to validate the proposed architecture. The fabricated CM-LMBA attains a measured 11.2-13.4-dB gain and around 40-W saturated power. Power-added efficiency (PAE) of 46.4%-56.5% and 43.2%-50.3% is achieved at 6- and 8-dB output power back-offs throughout the designed band. When driven by a 100-MHz OFDM signal with an 8-dB peak-to-average power ratio (PAPR), the proposed CM-LMBA achieves better than -46-dBc adjacent channel leakage ratio (ACLR) and higher than 45% average PAE after digital predistortion at 1.8 and 2.1 GHz.
      780Scopus© Citations 55
  • Publication
    28/38 GHz Dual-band Dual-polarized Highly Isolated Antenna for 5G Phased Array Applications
    This paper proposed a new dual-band dual-polarized array antenna operating at 28 GHz and 38 GHz for 5G communication applications. Three stacked patches are adopted to achieve the dual-band operation. The lower band from 27.48 to 28.50 GHz is achieved by using the lower large patch, which is couple-fed by the middle patch. While the upper band from 36.94 to 40.43 GHz is achieved by using the middle and upper patches. The two patches resonant at 38 and 40 GHz respectively and the two resonant modes coupled together, which greatly enhances the upper band. To increase the polarization isolation in the lower band, a shorting pin connecting the lower patch and ground is utilized. Taking advantages of the multi-layer technology, the position of the vertical feeding probe between the middle patch and lower patch is slightly shifted to ensure the good impedance matching in both lower band and upper band. For the antenna element, the simulated -12 dB bandwidths are 27.48-28.50 GHz and 36.94-40.43 GHz for the two bands, respectively. The in-band gains are over 6 dBi in the lower band, and over 4 dBi in the upper band. For the 2×2 antenna array, the isolations are better than 20 dB in both bands.
      1578Scopus© Citations 19
  • Publication
    Broadband High Efficiency Power Amplifiersfor RF Front-Ends of Wireless Transmitters
    (University College Dublin. School of Electrical and Electronic Engineering, 2022) ;
    This thesis explores Power Amplifier (PA) architectures for Radio Frequency (RF) front-ends of transmitters in Fifth Generation (5G) wireless communication systems. New PA operation classes and new efficiency enhanced architectures are presented with comprehensive analyses, well-designed state-of-art prototypes, and excellent experimental results. Firstly, a new class of PA, designated as Class-iF-1, is proposed, which utilizes input harmonics to achieve high efficiency with enhanced linearity performance beyond the conventional Class-F-1 PA. The Amplitude-to-Amplitude (AM/AM) profile of the conventional Class-F-1 PA is mathematically modeled as a function of input drive level. Theoretical derivation shows that the appropriate utilization of input nonlinearity poses a solution to rectify the double inflection characteristics of conventional Class-F-1 PA, which consequently, can be realized by proper manipulation of second harmonic source impedance. A broadened second harmonic design space over the open-circuit region is proposed. Secondly, a new solution for phase compensation in the Sequential Load Modulated Balanced Amplifier (SLMBA) architecture is presented. By using proper harmonic tuning in the control amplifier carrier branch, the load trajectory of the balanced amplifier can be made close to the real axis, which is beneficial to recovering peak output power and efficiency at both Output Power Back-Off (OPBO) and saturation of the SLMBA in wideband operation. Thirdly, a novel Waveform Engineered Sequential Load Modulated Balanced Amplifier (W-SLMBA) is proposed, which 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 SLMBA, wherein high efficiency can be achieved over a wide bandwidth and OPBO. Fourthly, the design methodology of a broadband RF-input SLMBA is introduced, with extended high efficiency design space, by introducing the second harmonic load manipulation over an enlarged range for the 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 OPBO over an extended operation bandwidth. Last but not least, the impact of input nonlinearity in SLMBA architecture is investigated. The Class-F-1 operation is selected as the solution for CA branch due to its advantage of high OPBO performance, efficiency flatness and immunity versus second harmonic source phase ¿G2S, which leads to the adoption of Class-B/J operation for BA. While Class-F-1 CA is immune to the second harmonic source variation, the safe design space for BA lands in the region where ¿G2S is over (-90¿, 90¿).
  • Publication
    Class-iF−1: Linearity Enhanced High Efficiency Power Amplifier
    This paper presents a new class of power amplifier (PA) - Class-iF- 1 - resolving the highly nonlinear double inflection characteristics in the conventional Class-F- 1 PA. It is illustrated that, by properly terminating the second harmonic source impedance Z 2S from conventional short-circuit to open-circuit, the double inflection nonlinear gain profile can be mitigated in the proposed Class-iF- 1 PA, wherein the same saturation output power is achieved with less gain compression without drain efficiency trade-off. The idea was validated with source/load-pull and a broadband prototype operating from 2.0 to 2.6 GHz was designed using a commercial 10-W Gallium Nitride (GaN) transistor. Under continuous wave (CW) signal test, the proposed Class-iF- 1 PA can achieve 40.1-40.8-dBm output power, 71.2%-77.3% drain efficiency (DE) and 67.4%-74.1 % power added efficiency (PAE) at 3-dB gain compression level over 2.0-2.6 GHz.
    Scopus© Citations 4  22