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

Abstract

This paper presents the theory and design methodology of broadband RF-input continuous mode load modulated balanced power amplifier (CM-LMBA) by introducing the continuous mode output matching networks in the LMBA architecture. It is illustrated that the continuous mode 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 Watts saturated power. Power added efficiency (PAE) of 46.4-56.5% and 43.2-50.3% is achieved at 6 dB and 8 dB output power back-off throughout the designed band. When driven by a 100 MHz OFDM signal with 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 pre-distortion at 1.8 GHz and 2.1 GHz.

Mixture of Experts Approach for Piecewise Modeling and Linearization of RF Power Amplifiers

“…The observable data are the input and target vectors x and y, whereas it is unknown which expert generated each data point, formally expressed through the latent variable z. As discussed above, in order for the gate and expert parameters to be analytically solvable, the densities must belong to the family of the exponential densities, and additionally, instead of the likelihood function in (2), one should consider the joint density P (x, y) = P (y|x)P (x) [21], which reads…”

“…O VER the years, multiple power amplifier (PA) technologies have been developed with the goal of delivering enhanced power efficiency at different power back-off levels and over wide bandwidths [1]- [4]. Good examples are the Doherty PA (DPA) [5], [6] and the load modulated balanced (LMBA) PA [2], [7], which leverage the concept of load modulation that allows the power efficiency to be optimized dynamically at a specific power back-off, by tuning the load impedance. In order to further increase the power efficiency, digital predistortion (DPD) solutions are commonly deployed to compensate for the strong nonlinear distortion that originates inside the PAs whilst being operated with high efficiency [4], [8]- [11].…”

Millimeter-Wave Power Amplifier Integrated Circuits for High Dynamic Range Signals

“…Upon the invention of LMBA, there has been much follow-up research work on this topology and its derivatives. LMBA has been widely implemented in GaN technologies as hybrid modules or MMICs at RF frequencies [105]- [108] and in silicon for mm-Wave applications [109]. Additional LMBA variants include swapping Carrier and Control PAs for asymmetric Doherty-like PAs with linearity and deep PBO enhancement [110], [111].…”

Boosted Model Tree-Based Behavioral Modeling for Digital Predistortion of RF Power Amplifiers

“…13, which includes PC, signal generator, driver amplifier, PA, attenuator, and spectrum analyzer. The PA under test was an in-house designed broadband gallium nitride (GaN) load-modulated balanced PA operating at 2.1 GHz with 37-dBm output power and 42% drain efficiency [28]. The excitation input signals were five-carrier 100-MHz and ten-carrier 200-MHz orthogonal frequency-division multiplexing (OFDM) signals, both with 8-dB peak-to-average power ratio (PAPR).…”

“…Generally speaking, the reasons are twofold. The first factor is the widespread adoption of complex PA architectures, such as multiband/multimode and multistage Doherty [23]- [25] and load-modulated balanced amplifiers (LMBAs) [26]- [28]. While these techniques have greatly improved the energy efficiency of modern RF systems, these high-efficiency PAs are more difficult to model, because of the sophisticated interaction between their internal blocks.…”