Now showing 1 - 7 of 7
  • Publication
    Power Adaptive Digital Predistortion for Wideband RF Power Amplifiers With Dynamic Power Transmission
    (IEEE, 2015-10-05) ; ;
    To reduce power consumption of wireless transmitters, the transmission power level of RF power amplifiers (PAs) may dynamically change according to real-time data traffic. This leads that the existing digital predistortion (DPD) techniques cannot be directly employed because they are mainly suitable for eliminating distortion induced by the PAs operated at a relatively stable condition, e.g., at a constant average power level. To resolve this problem, a power adaptive DPD is proposed in this paper. By accurately modeling the behavior change pattern of the PA with the input power adjustments and embedding it into the DPD model, the proposed DPD system is able to adjust its coefficients to adapt to the behavior variation of the PA induced by the power adjustments without real-time recalibration. A low-complexity online coefficients updating method is also proposed to track the behavior change of the PA caused by other factors, such as bias shifting or temperature variation, during real-time operation. Measurements with a high power LDMOS Doherty PA have been used to validate the proposed approach. Results show that the proposed DPD and its coefficients updating approach can produce excellent performance with very low complexity compared to the conventional approaches.
      323Scopus© Citations 35
  • Publication
    Digital Compensation for Transmitter Leakage in Non-Contiguous Carrier Aggregation Applications With FPGA Implementation
    In this paper, a generalized dual-basis envelope-dependent sideband (GDES) distortion model structure is proposed to compensate the distortion induced by transmitter leakage in concurrent multi-band transceivers with non-contiguous carrier aggregation. This model has a generalized structure that is constructed via first generating a nonlinear basis function that maps the inputs to the target frequency band where the distortion is to be cancelled, and then multiplying with a second basis function that generates envelope-dependent nonlinearities. By combining these two bases, the model keeps in a relatively compact form that can be flexibly implemented in digital circuits such as field programmable gate array (FPGA). Experimental results demonstrated that excellent suppression performance can be achieved with very low implementation complexity by employing the proposed model.
      495Scopus© Citations 14
  • Publication
    Highly Efficient Broadband Continuous Inverse Class-F Power Amplifier Design Using Modified Elliptic Low-Pass Filtering Matching Network
    This paper proposes a design approach for a broadband and high-efficiency continuous inverse Class-F (CCF−1) power amplifier (PA) based on a modified elliptic low-pass filtering (LPF) matching network (MN). From theoretical and practical perspectives, the importance of a swift impedance transition from the higher end of the fundamental frequency band to the lower end of the second harmonic band is discussed, when designing a broadband single-mode PA. After being compared with widely used Chebyshev LPF MNs, a modified elliptic LPF MN, which provides a sharp roll-off, is utilized to provide the required rapid transition. A step-by-step design procedure of the proposed modified elliptic LPF MN is presented. Experimental results show that a high-efficiency CCF−1 PA is realized from 1.35 to 2.5 GHz (fractional bandwidth = 60%) with measured drain efficiency of 68%–82% and output power of 41.1–42.5 dBm. When stimulated by a 20-MHz LTE signal with an average output power of approximately 34.5 dBm, the proposed PA, combined with digital pre-distortion, achieved adjacent channel leakage ratios (ACLRs) below −45 dBc, with average efficiency (AE) ranging from 37% to 45.8%. Similar performance is measured when the proposed PA is driven by a dual-band dual-mode modulated signal with a 100-MHz instantaneous bandwidth at a center frequency of 2.14 GHz.
      780Scopus© Citations 89
  • Publication
    A Broadband High-Efficiency Doherty Power Amplifier with Integrated Compensating Reactance
    This paper presents a high-efficiency gallium nitride Doherty power amplifier (DPA) using an integrated compensating reactance (CR) for broadband operation. With an additional quarter-wavelength transmission line integrated in the peaking amplifier output, a CR is generated to compensate the load impedance of the carrier amplifier in the low-power region and thus enhance the back-off efficiency over a wide frequency range without affecting the Doherty load modulation at saturation. For this purpose, a peaking output matching network (OMN) is employed to convert the output impedance of the peaking device into quasi-short circuit when it is off and achieve proper impedance matching when it is on. A two-point matching technique using the transmission (ABCD) matrix is employed to design such desired OMN. Measurement results show that the DPA has a 6-dB back-off efficiency of 50%-55% and a saturated efficiency of 57%-71% over the frequency band of 1.7-2.8 GHz (49% fractional bandwidth). When driven by a 20-MHz long term evolution modulated signal at 6.5-dB back-off power, the DPA can achieve an average efficiency of more than 50% with high linearity after linearization over the design frequency band.
      545Scopus© Citations 94
  • Publication
    Output-Controllable Partial Inverse Digital Predistortion for RF Power Amplifiers
    In this paper, an output-controllable digital predistortion (DPD) technique is proposed to partially inverse the nonlinear behavior of RF power amplifiers (PAs). Compared to the existing DPD, the proposed method changes the goal that the PA output must be exactly the same as the original input to a new one that the PA output can be arbitrarily controlled according to user's demand. The proposed approach largely expands the capability of DPD and thus provides more flexibility for system designers to effectively use DPD to manipulate the PA output in order to handle more application scenarios and objectively conduct further system optimization. Various application cases have been tested. The experimental results demonstrate that the proposed approach has great potential in future wireless communication system design.
      284Scopus© Citations 10
  • Publication
    Power Adaptive Decomposed Vector Rotation Based Digital Predistortion for RF Power Amplifiers in Dynamic Power Transmission
    (IEEE, 2017-01-18) ;
    In this paper, a power adaptive digital predistortion (DPD) model is proposed to linearize RF power amplifiers (PAs) operated in dynamic power transmissions. By employing the decomposed vector rotation (DVR) based nonlinear weighting technique to adjust the DPD coefficients dynamically, the distortion induced by the dynamic power operation can be effectively compensated. Experimental test results with a high power Gallium Nitride (GaN) Doherty PA confirm that higher linearization performance can be achieved by employing this model, compared to that using the existing approaches.
      327Scopus© Citations 6
  • Publication
    Simplified online coefficients updating for digital predistortion of wideband/multi-band RF power amplifiers
    (IEEE, 2015-12-09) ; ;
    In this paper, a simplified online coefficients updating technique is proposed to realize real-time timing of digital predistortion (DPD) for RF power amplifiers (PAs), particularly focusing on wideband and concurrent multi-band scenarios. It is achieved by equally weighting the memory terms in conventional DPD models that leads to a significant reduction of numerical calculation complexity in the coefficients updating process and thus saves time and power during real system operation. To validate the proposed method, both wideband LTE- A (100 MHz) and concurrent dual-band (20 MHz + 20 MHz) cases have been tested. Experimental results show that the proposed method can achieve excellent performance with significant reduction of system complexity compared to the conventional approaches.
      278Scopus© Citations 2