Load Modulated Balanced Amplifier Research Articles

Design of Broadband Divisional Load-Modulated Balanced Amplifier With Extended Dynamic Power Range

Design of Broadband Divisional Load-Modulated Balanced Amplifier With Extended Dynamic Power Range

A Ka-Band Pseudo-Doherty Load-Modulated Balanced Amplifier With Gain Flatness Enhancement Technique

A <i>Ka</i>-Band Pseudo-Doherty Load-Modulated Balanced Amplifier With Gain Flatness Enhancement Technique

Inverted sequential load-modulated balanced amplifier for extending dynamic power range over wide bandwidth

This paper propose an inverted sequential load-modulated balanced amplifier (ISLMBA) for extending the dynamic power range of a power amplifier (PA) over a wide bandwidth. The proposed ISLMBA consists of a control amplifier (CA) and a balanced PA (BPA) pair. A composited impedance inverter is inserted between each BPA transistor and the output coupler. The composited impedance inverter is composed by the intrinsic elements and output matching network (OMN) of the BPA transistor. In this way, the intrinsic elements can be fully absorbed into the impedance inverter over a wide bandwidth. Meanwhile, the load modulation trajectories of the BPA transistors can be optimized over a wide bandwidth by tuning the characteristic impedance of the impedance inverter. The theoretical current, voltage and load-modulation profiles of the ISLMBA are comprehensively analyzed. It is illustrated that the proposed ISLMBA could maintain high efficiency at deep output back-off power level over a wide bandwidth. Moreover, this work designs and fabricates an ISLMBA operating over 1.3–2.55 GHz to verify the proposed PA architecture. The fabricated ISLMBA exhibits a saturation drain efficiency (DE) of 54.5%–73.8% and a saturation output power of 42.9–45.9 dBm. At the same time, the fabricated ISLMBA achieves a 10 dB back-off DE of 42.1%–63.9% over the frequency band of interest. When the fabricated ISLMBA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 10.2 dB at 2.0 GHz, the measured adjacent channel leakage ratios (after predistortion) are −47.7 and −48.8 dBc at the lower and upper bands, respectively.

Asymmetrical Sequential Load Modulated Balanced Amplifier With Composited Impedance Inverter and Reciprocal Mode for Broadband Applications

In this paper, the design of a broadband asymmetrical sequential load modulation balanced amplifier (ASLMBA) is presented. The composited impedance inverters, which contain the intrinsic elements and the output matching networks (OMNs) of the balanced power amplifier (BPA) transistors, are inserted before the output coupler of the BPA pair. In this way, optimal matching condition of the BPA transistors can be maintained over a wide bandwidth. In addition, to ensure an optimal load modulation trajectory of the control amplifier (CA) without over-saturation, a reciprocal mode is applied to the BPA pair by elaborately changing the turn-on sequence of the sub-amplifiers, which is affected by the composited impedance inverter and the OMN of the control amplifier. It is illustrated that the proposed ASLMBA can effectively maintain high efficiency over an extended dynamic range and a wide bandwidth. As a proof of concept, a broadband ASLMBA working over 1.35-2.55 GHz is designed and measured in this work. Experimental results show that the designed ASLMBA achieves a saturation output power of 43.2-45.1 dBm with a saturation gain of 6.5-10.5 dB and a saturation drain efficiency (DE) of 57.8-77.7%. Meanwhile, the 6 dB and 10 dB back-off DEs of the designed ASLMBA are 51.3-66.6% and 47.7-68.9%, respectively.

Ka-band stacked and pseudo-differential orthogonal load-modulated balanced power amplifier in 22 nm CMOS FDSOI

Abstract This paper presents an integrated power amplifier (PA) following the orthogonal load-modulated balanced amplifier (OLMBA) topology. The fixed-phase prototype in this paper is implemented with 22 nm complementary metal oxide semiconductor (CMOS) fully depleted silicon-on-insulator (FDSOI) process. The proposed PA operates at 26 GHz frequency range, where it achieves 19.5 dBm output power, 16.6 dB gain, 15.7% power added efficiency, and 18.3 dBm output 1-dB compression point ( $P_{\rm 1\,dB}$ ). The PA is also tested with high dynamic range modulated signals, and it achieves, respectively, 11.4 dBm and 4.9 dBm average output power (Pavg) with 100 MHz and 400 MHz 64-QAM third-generation partnership project/new radio frequency range 2 signals, and 14 dBm Pavg with 0.6 Gb/s (120 MHz) single carrier 64-QAM signal, measured at 26 GHz and using −28 dBc adjacent channel leakage ratio and −21.9 dB (8%) error vector magnitude as threshold values. The proposed OLMBA is also compared to a stand-alone quadrature-balanced PA. Modulated measurements show that the stand-alone quadrature-balanced PA has better linearity in deep back-off, but the OLMBA has better efficiency.

A GaN MMIC Load-Modulated Balanced Amplifier With Modified Output Coupler for Efficiency Enhancement Over a Larger Power Back-Off Range

This brief firstly presents a monolithically microwave integrated circuit (MMIC) load-modulated balanced amplifier (LMBA) developed in 0.15um GaN process. In this brief, the asymmetric output coupler is applied for further enhancing output power and output back-off (OBO) efficiency over a larger OBO range. This MMIC LMBA operating mode is dependent on a three-ways active load modulation process by modified the coupling coefficient of output coupler which can provide more design parameters and freedom. To validate the proposed LMBA at millimeter wave (mm-wave), a 24.7-25.7 GHz MMIC LMBA is demonstrated, fabricated and tested. Measurements show that this MMIC LMBA can deliver a 35.2-dBm saturated output power with a peak drain efficiency of 37.7%. At 6-dB/8-dB/10-dB OBO, 23.8-30 %, 24.2-27 % and 20-24% power added efficiencies (PAE) can be obtained, respectively. The measured S21 is 15-dB with a 1 0.4-dB gain variation. When driven by a 100MHz 64-QAM OFDM modulation signal with a PAPR of 9.2-dB, the measured ACPR is improved to -45.04 dBc with DPD. In this case, the PA achieves an average efficiency of 25.2% and a 26.2-dBm average output power.

Fully-Integrated Broadband GaAs MMIC Load Modulated Balanced Amplifier for Sub-6 GHz Applications

In this brief, a monolithically integrated broadband load modulated balanced amplifier (LMBA) chip without BA pre-matching network is proposed and designed. It is the first time that integrated LMBA operating at sub-6 GHz has been discussed about broadband performance. BA follows with only one inductor and output quadrature coupler, which can effectively reduce loss and improve efficiency. The load modulation behavior of BA is analyzed, indicating that it has an appropriate modulation trajectory. For verification, a LMBA chip was fabricated and measured in the 0.25-um GaAs pHEMT process. Continuous-wave measurements demonstrate a saturated output power of 30.2-31.8 dBm with drain efficiency (DE) of 34.3-59.2%, and 6-dB back-off DE of 27.7-40.4% in 4.2-5.2 GHz. Modulated signal measurements prove that the linearity of LMBA can be calibrated by digital predistortion.

Multiobjective Bayesian optimization for a 15‐dB back‐off high‐efficiency load modulated balanced amplifier design

AbstractIn this article, multiobjecive Bayesian optimization (MBO) with a non‐penalization strategy is proposed to design a 15‐dB back‐off high‐efficiency load modulated balanced amplifier (LMBA). Applying the proposed method, the output matching networks of the LMBA are optimized to achieve proper load modulation behaviors that providing good performance. To verify the proposed method, a 2.0‐GHz LMBA is designed and measured. Experimental results show that LMBA achieves an output power of 44.5 dBm with a gain higher than 6.6 dB at saturation. The measured drain efficiency (DE)/power‐added efficiency (PAE) are 67%/52% at saturation, 54%/43% at 9‐dB back‐off, and 52%/46% at 15‐dB back‐off, respectively. Tested with 20‐MHz signal with 10‐dB peak‐to‐average power ratio (PAPR) and a 256‐quadrature amplitude modulation (QAM) scheme, the LMBA achieves adjacent channel leakage ratio (ACLR) levels of −46.7/−47.5 dBc and an error vector magnitude (EVM) of 1.2% after digital predistortion.

Load-Modulated Balanced Amplifier Design for Handset Applications

In this letter, a load-modulated balanced amplifier (LMBA) design for handset applications is proposed. The proposed LMBA is demonstrated experimentally with GaAs-HBTs. A PAE of 40.7% and an NR ACLR of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 37.7 dBc at an average output power of 31.7 dBm are measured at 3.75 GHz under 5G NR 100 MHz, DFT-s-OFDM, QPSK operation. Moreover, the proposed LMBA maintains more than 32.9% efficiency with an NR ACLR of below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 37.7 dBc from 3.35 to 4.95 GHz, corresponding to 5G NR Band n77 and n79.

Design of a Load Modulated Balanced Amplifier with a Two-Stage Control Power Amplifier

While an ideal Doherty power amplifier has a linear response, the load modulated balanced amplifier (LMBA) has a compressive response under ideal conditions. This inherent nonlinear characteristic is due to the lower power contribution of the single auxiliary device as the balanced amplifier transistors approach compression. This article presents an LMBA with a two-stage control signal amplifier in place of the single auxiliary device. The idea is to preserve a high and constant gain across the high- and low-power regions by tuning the two-stage gain control signal to match the balanced amplifier gain. An optimal load trajectory can be found for a high-efficiency design by appropriately terminating the second harmonic while ensuring an optimal impedance match in all devices. At the same time, by setting an optimal output power from the auxiliary device, sufficient power is provided to linearize the response of the main power amplifier beyond the output back-off power boundary. As proof of concept, a prototype is designed and implemented. The experimental measurements demonstrate a drain efficiency of 59%–64% at maximum output power and 46%–52% at 7.5 dB output back-off power over the target frequency range of 3.3–3.8 GHz.

Divisional Load-Modulated Balanced Amplifier With Extended Dynamic Power Range

With the prevalence of complex modulated signals, it is of utmost significance to research the extension of the dynamic power range of radio frequency (RF) power amplifiers (PAs). This article proposes a divisional load-modulated balanced amplifier (DLMBA) for extending the high-efficiency power range. The proposed DLMBA is composed of a local modulated Doherty PA (DPA) and a class-C biased balanced PA (BPA) pair. The output signal of the local DPA is fed into the isolation port of the output coupler of the BPA pair, forming a global load modulation. The design parameters of the DLMBA are derived after a comprehensive analysis. It is illustrated that the dynamic power range of the DLMBA can be extended beyond 12 dB by combining a local DPA and a BPA pair. Meanwhile, each subamplifier of the DLMBA is presented with a modulated impedance over the whole dynamic power range, avoiding voltage oversaturation. As a validation, a DLMBA operating over 1.85–2.05 GHz is fabricated and measured in this article. The fabricated DLMBA delivers a maximum output power of more than 44.8 dBm, a saturation drain efficiency (DE) of more than 53%, and a 13 dB back-off DE of more than 44% in the interested frequency band. Meanwhile, when the DLMBA is excited by a 20-MHz wideband signal with a peak-to-average ratio of 10.2 dB, the measured adjacent channel leakage ratio reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 47.4 dBc after digital predistortion.

A review of Doherty power amplifier and load modulated balanced amplifier for 5G technology

SummaryIn this paper, functionality of the Doherty power amplifiers (DPAs) along with their design constraints such as DPA combining techniques are reviewed. This is because power amplifier (PA) is a key building block in the design of fifth generation (5G) communication systems. A significant trend is the DPA bandwidth enhancement technique, which is the subject of numerous papers in the literature. So, we will review some papers with different solutions to address DPA's bandwidth limitations. There are also different works in the literature that have focused on high‐efficiency PA structure designs, which are also discussed in this paper. An excellent option for effective power combining in broadband designs is using balanced amplifiers. We have discussed load modulated balanced amplifiers (LMBA) in this paper because designing an effective PA with a wide bandwidth is crucial. We also covered some papers that have proposed techniques based on the linearization method to bring the efficiency and linearity of DPAs to a fair level.

Load-Modulated Balanced Amplifier: From First Invention to Recent Development

The RF power amplifier (PA) is a unit in wireless transmitters that strengthens the signal to combat losses in transmission by converting dc electric power to the added RF output power. Over the past decades, with the rapid development of wireless communications, high-efficiency PA design has become one of the most popular topics in both academic research and industrial development as the PA consumes a high portion of the transmitter energy, and thus its power efficiency directly impacts the system performance. In addition, because the PA is the main source of distortion generated by the transmitter, linearity is another concern in PA design, particularly in wideband systems <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> .

Simulated Annealing Particle Swarm Optimization for a Dual-Input Broadband GaN Doherty Like Load-Modulated Balance Amplifier Design

In this brief, an automatic power amplifier (PA) design system based on simulated annealing particle swarm optimization (SA-PSO) algorithm is proposed to perform multi-objective optimization in designing broadband Doherty like load-modulated balanced amplifier (LMBA). Specifically, by combining the programming environment with commercial electronic design automation (EDA) software, the optimization process can be implemented automatically. Then, complex and rigorous impedance trajectory aligning at different power levels can be easily obtained using the proposed optimization algorithm, demonstrating the automatic PA design system’s superiority over the built-in optimizer in commercial EDA software for designing broadband Doherty like LMBA. A 2.5-3.5 GHz dual-input Doherty like LMBA is simulated and measured, showing a saturated output power of 45.4-48.2 dBm, a saturation drain efficiency of 60.7% - 69.7%, a 6 dB power back-off DE of 59.2% - 65.8%, and a 9 dB power back-off DE of 52.7% - 66.9%.

Mitigation of Load Mismatch Effects Using an Orthogonal Load Modulated Balanced Amplifier

This article presents an orthogonal load-modulated balanced amplifier designed to mitigate the effects of the load mismatch on the power-added efficiency and output power of the amplifier. This is achieved by electronically adjusting the ratio between the two input signals of the power amplifier (PA) (in phase and amplitude) and the reactive termination at the output nominally isolated port. The mode of operation of the PA is described using a theoretical analysis that highlights the role of the different tuning parameters and is confirmed by simulations using a simplified transistor model. The design and characterization under load mismatch of a prototype PA, working in the 1.6–3.2 GHz band are described and the experimental results compared to those of an analogous balanced PA, where it is shown that the orthogonal balanced amplifier is able to increase substantially the mismatch region on which a given target performance is achieved.

8‐12 GHz single‐input GaN load modulated balanced amplifier monolithic microwave integrated circuit

In this article, a broadband single-input GaN load modulated balanced amplifier (LMBA) with prematching networks is presented. The prematching networks of main PA are set up to reduce the difficulty of load modulation caused by high power control signal. The compact phase shifter and compression characteristic of the CS PA are used to monolithically integrate a single-input LMBA. The experimental results under continuous wave demonstrate a peak output power of 43.1–43.6 dBm, with drain efficiency (DE) of 49%–54% over the band of 8–12 GHz. Moreover, the DE is in the range of 30%–37% at the 6-dB power back-off region. By introducing a 16-quadrature amplitude modulation signal with 6-dB peak-to-average power ratio, the proposed single-input LMBA monolithic microwave integrated circuit achieves better than −28-dBc adjacent channel leakage ratio and higher than 32% average DE without digital predistortion at 9 and 11 GHz.

Reconfigurable DPD Based on ANNs for Wideband Load Modulated Balanced Amplifiers Under Dynamic Operation From 1.8 to 2.4 GHz

This article proposes a methodology to ensure linear amplification of a load modulated balanced amplifier (LMBA) while keeping the power efficiency as high as possible over a frequency band ranging from 1.8 to 2.4 GHz and where the transmitted signals can present different bandwidth (BW) configurations. The proposed reconfigurable linearization methodology consists of, in a first step, tuning some free parameters (with dependence on the signal BW and frequency of operation) of the LMBA to trade-off linearity and power efficiency. In a second step, two multipurpose adaptive digital predistortion (DPD) linearizers are considered, properly combined with crest factor reduction (CFR) techniques, to meet the required linearity specifications. Either a DPD based on artificial neural networks or a DPD based on polynomials can be selected taking into account the compromise between computational complexity and linearization performance. Experimental results will validate the proposed methodology to guarantee the linearity levels (ACPR <−45 dBc and EVM <1%) with high power efficiency in an LMBA under dynamic transmission, where both the signal BW (from 20 and up to 200-MHz instantaneous BW) and frequency of operation (in the range of 1.8–2.4 GHz) change.

Load Modulated Balanced Amplifier Design Method Based on Complex Impedance Trajectories

This paper presents a design methodology for a load modulated balanced amplifier (LMBA) focusing on AMPM distortion mitigation. By introducing second harmonic control as a degree of design freedom, a complex load trajectory can be selected to compensate for AMPM nonlinearities in the device without substantially affecting efficiency. A mathematical derivation is accompanied by a design procedure based on closed-form equations to fabricate an LMBA based solely on load-pull data. The theory is validated through the measured comparison of three different designs operating at 2.4 GHz in a pseudo-RF-input Doherty-like LMBA configuration, with class-J, -B, and -J* main PAs. The class-J prototype outperforms the other designs with 54% and 49% drain efficiency at peak output power and 6-dB back-off, respectively, and only 4 degrees of AM-PM across this power range. When driven with a 10-MHz, 8.6-dB PAPR LTE signal, 40.5% average efficiency is achieved with better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-40.5$</tex-math></inline-formula> dBc ACLR without digital predistortion.

Current-Injected Load-Modulated Outphasing Amplifier for Extended Power Range Operation

In this letter, the power range to be covered with maximized efficiency by a two-way outphasing power amplifier (PA) is significantly extended, thanks to a proposed architecture with the injection of an external signal. Using a reactively terminated quadrature hybrid coupler (QHC) as nonisolating combiner, the Chireix topology is transformed into a slight variation in the load-modulated balanced amplifier (LMBA) when the auxiliary branch is activated. This combined load-modulated (LM) strategy provides a nearly resistive loading of the individual outphasing PAs over a wide power range. An appropriate output network, approximating a class-E/F2 operation of the selected GaN-HEMT device under such loading condition, leads to remarkable drain efficiency figures at deep output power back off (OPBO). Values higher than 80%, 70%, and 60% have been measured at power levels 9.5, 13.3, and 15 dB below its peak (45.7 dBm), respectively. A 5-MHz Long Term Evolution (LTE) signal with a peak-to-average power ratio (PAPR) as high as 12.65 dB has been reproduced with an average efficiency above 62% and worst-case adjacent channel leakage ratio (ACLR) of −31 dBc.

Hybrid Load-Modulated Balanced Amplifier With High Linearity and Extended Dynamic Range

A novel hybrid load modulation (LM) architecture of power amplifier (PA) is presented in this letter, in which three amplifiers are combined through a quadrature coupler in properly defined phase offsets. Together with the well-aligned turning-on sequence, the PA can operate as a Doherty PA (DPA) and load modulated balanced amplifier (LMBA) at different power levels, whose overall behavior is similar to a three-way DPA. This unique hybrid LM mode effectively extends the dynamic power range of efficiency enhancement, which is further compatible with the high-linearity design. This concept is experimentally validated using a GaN-based prototype at 3.56 GHz. The CW measurement shows an efficient PA performance with 49%-63% of efficiency from P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Max</sub> to 9-dB back off. Under the modulated evaluation using a 20-MHz LTE signal, an adjacent channel leakage ratio of -37.5 dB is measured together with 45% average efficiency.