Analysis and Design of Highly Efficient Wideband RF-Input Sequential Load Modulated Balanced Power Amplifier

Abstract

The analysis and design of an RF-input sequential load modulated balanced power amplifier (SLMBA) are presented in this paper. Unlike the existing LMBAs, in this new configuration, an over-driven class-B amplifier is used as the carrier amplifier while the balanced PA pair is biased in class-C mode to serve as the peaking amplifier. It is illustrated that the sequential operation greatly extends the high efficiency power range and enables the proposed SLMBA to achieve high backoff efficiency across a wide bandwidth. An RF-input SLMBA at 3.05-3.55 GHz band using commercial GaN transistors is designed and implemented to validate the proposed architecture. The fabricated SLMBA attains a measured 9.5-10.3 dB gain and 42.3-43.7 dBm saturated power. Drain efficiency of 50.9-64.9/46.8-60.7/43.2-51.4% is achieved at 6/8/10 dB output power back-off within the designed bandwidth. By changing the bias condition of the carrier device, higher than 49.1% drain efficiency can be obtained within 12.8 dB output power range at 3.3 GHz. When driven by a 40 MHz OFDM signal with 8 dB peak to average power ratio (PAPR), the proposed SLMBA achieves adjacent channel leakage ratio (ACLR) better than-25 dBc with an average efficiency of 63.2% without digital predistortion (DPD). When excited by a 10-carrier 200 MHz OFDM signal with 10 dB PAPR, the average efficiency can reach 48.2% and-43.9 dBc ACLR can be obtained after DPD.

Machine-Learning Assisted Optimisation of Free-Parameters of a Dual-Input Power Amplifier for Wideband Applications

“…Moreover, although the linearisation of LMBAs has been already addressed in the literature, e.g., [ 18 , 22 ], only modulated signals with moderate bandwidths (i.e., several tenths of MHz) have been considered. Nevertheless, in [ 23 ], the authors presented the design and linearisation of a LMBA considering several OFDM-based signals with bandwidths up to 200 MHz. With this last challenging bandwidth configuration of 200 MHz, however, the reported adjacent channel leakage ratio (ACLR) after DPD linearisation could not reach the threshold of −45 dBc, while no information on the error vector magnitude (EVM) to quantify the in-band distortion was provided.…”

Three-Stage Load Modulated Power Amplifier With Efficiency Enhancement at Power Back-Off

“…It has great potential in achieving both wide bandwidth and high efficiency performance [21]- [24]. By employing a coupler as the load modulation network, LMBA exhibits Doherty-like behavior to attain appreciably OBO ranging up to 12-dB, as reported in [25]- [27]. However, the existing LMBAs are still characterized by two peak efficiency points inside the available OBO.…”

Broadband RF-Input Continuous-Mode Load-Modulated Balanced Power Amplifier With Input Phase Adjustment

“…For example, the reported broadband LMBAs in [20]- [22] do not employ complete OMNs in the balanced PA. The reported RF-input LMBA in [23], sequential-LMBA (SLMBA) in [31] and phase controlled LMBA in [32] employ OMNs while the bandwidth performance and impact from the OMNs have not been analyzed in detail. In [33], the proposed Pseudo-Doherty LMBA (PD-LMBA) employs OMN for the carrier PA with similar system configuration to the SLMBA in [31] and achieves 57% fractional bandwidth with 10 dB OBO level, verified the feasibility of using OMNs in broadband LMBAlike architectures.…”

“…The reported RF-input LMBA in [23], sequential-LMBA (SLMBA) in [31] and phase controlled LMBA in [32] employ OMNs while the bandwidth performance and impact from the OMNs have not been analyzed in detail. In [33], the proposed Pseudo-Doherty LMBA (PD-LMBA) employs OMN for the carrier PA with similar system configuration to the SLMBA in [31] and achieves 57% fractional bandwidth with 10 dB OBO level, verified the feasibility of using OMNs in broadband LMBAlike architectures. The RF-input LMBA introduced in [23] has proven that Doherty-like operation can be achieved by the LMBA with RF-input structure.…”