A wideband digital predistortion for highly linear and efficient GaN HEMT Doherty power amplifier

Abstract

In this article, we propose the wideband digital predistortion (WDPD) for a highly linear and efficient GaN HEMT Doherty power amplifier (DPA). The WDPD is composed of the memory less DPD and the memory system, which compensates for the memory effects to achieve a highly linear wideband performance. The 11th-memoryless polynomial characterizes the behavioral model of the DPA. The AM/AM and AM/PM lookup tables and the coefficients of the memory system are determined by the Recursive Least Square algorithm. For a 2-FA WCDMA signal with 10 MHz carrier spacing at 2.14 GHz, the adjacent channel leakage ratio at 610 MHz offset are improved over À50 dBc without the efficiency degradation at an output power of 36 dBm.

Advanced design of a double Doherty power amplifier with a flat efficiency range

“…The DDPA delivers three efficiency-peaking points by the double Doherty operation, and the the measured results are summarized in Table l We have employed the memory DPD technique to satisfy the linearity specification. The 11 t h -memoryless polynomial characterizes the behavioral model of the DDP A and the entries in the AM/AM and AM/PM lookup tables (LUTs) and the coefficients of the memory system are determined by the recursive least square (RLS) algorithm via MATLAB [9]. Fig.…”

“…Doherty power amplifiers COPAs) have been widely investigated and developed as the prime candidate for high efficiency at a large back-off power (BOP) [1 ]- [9]. Recently, modulated signals in the modem communication systems have a high peak-to-average power ratio (P APR) of over 9 dB.…”

Doherty power amplifier with cascaded peaking cells

“…However, the PAs operated at a large BOP has a serious problem such as poor efficiency. Therefore, several techniques such as switchingmode PAs, envelope elimination and restoration, and Doherty PAs (DPA) have been investigated to boost the efficiency [1][2][3][4][5][6][7][8][9][10][11][12]. Among these techniques, the DPAs are regarded as the promising solution due to high efficiency at a BOP without an additional circuitry [5][6][7].…”

“…Figure 6 represents the power spectrum densities (PSDs) before and after the digital distortion (DPD) linearization at an output power of 37 dBm. The nonlinearity of the proposed DPA is characterized by the split augmented Hammerstein model, and the predistored signal is generated by the direct learning architecture [11,12]. From the DPD linearization, the ACLR improvement of 17.7 dB and 12.8 dB are achieved at þ2.5 and þ5 MHz offsets, respectively, without efficiency degradation.…”

“…Also, CBCPWs have the advantage of mechanical strength, heat sinking ability, and lower characteristic impedance than conventional coplanar waveguide in designing microwave-integrated circuits (MICs). These and several other advantages make CBCPWs ideally suited for MIC as well as monolithic MIC (MMIC) applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”