A Novel Modulated Rapid Load Pull System with Digital Pre-Distortion Capabilities

Alsahali, Sattam; Gecan, Dragan; Alt, Alexander; Wang, Guofeng; Anera, Syed M. H. Syed; Chen, Peng; Woodington, S.; Sheikh, Aamir; Tasker, P.J.; Lees, Jonathan

doi:10.1109/arftg.2019.8739220

Cited by 6 publications

(8 citation statements)

References 6 publications

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“…The overall goal of WALP is to find the correct signal a S2 to inject on the load side, such that the required Γ T (f ) is synthesized. In the classic WALP implementation, the computation is typically performed in an iterative fashion, starting from a 50-Ω environment when the load source is turned off, and using successive time-domain waveform acquisitions to guide convergence to the target [1]- [4], [12]. In particular, at a given iteration, the injection signal a S2 (t) is computed as the inverse Fourier transform of B 2 (f ) • Γ T (f ), where B 2 (f ) represents the frequency spectrum of the measured b 2 (t).…”

Section: Problem Statementmentioning

confidence: 99%

“…It is important to highlight that this approach does not make use of any cross-frequency phase reference, as the arbitrary and unknown phase shift of the local oscillator (LO) signal is eliminated when calculating the ratio of synchronous acquisitions. Moreover, standard VNA HW can be used, eliminating the need for the broadband demodulators used in vector signal analyzers [2], [4] to cover the BW of interest.…”

Section: Measurement Setupmentioning

confidence: 99%

“…It also allows to replicate the active load-modulation conditions often realized in application-like scenarios, such as in complex PA architectures [5], [6], as well as providing complete datasets for PA modeling [7]. Several commercial solutions for WALP are available [2], [4], which make use of time-domain waveform demodulation capabilities exploiting broadband acquisition hardware (HW) [1]- [4].…”

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confidence: 99%

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Wideband Active Load–Pull by Device Output Match Compensation Using a Vector Network Analyzer

Angelotti

Gibiino

Nielsen

et al. 2021

IEEE Trans. Microwave Theory Techn.

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This work investigates wideband active load-pull (WALP) on microwave electron devices with a standard vector network analyzer (VNA), solely using calibrated frequencydomain relative measurements. Differently from the methods requiring full time-domain waveform acquisition capabilities, this approach removes any instantaneous bandwidth (BW) requirement, allowing to target modulated signals with arbitrarily large BWs. A VNA-based measurement setup is presented, and a novel mathematical framework is developed in order to enable the synthesis of an arbitrary wideband load profile using suitable numerical algorithms. A linear pre-compensation of the LS output match of the device, here implemented by different methods, is shown to significantly improve the speed and the stability of the basic secants' iterative method used to reach the target. Performance results, investigating the convergence properties of the approach and the effects of the setup dynamic range, are reported for a Gallium Nitride (GaN) high-electronmobility-transistor (HEMT) for up to 120-MHz output BW in the sub-6 GHz range.Index Terms-Active load-pull, modulated signals, power amplifiers, vector network analyzer, device characterization. I. INTRODUCTIONT HE ever-growing demand for high data rates in modern mobile communication standards, e.g., 5G, requires the operation of power amplifiers (PA) in radio frequency (RF) transmitters across extremely wide bandwidths (BWs), i.e., tens or hundreds of MHz. In this respect, novel characterization techniques are required to evaluate the behaviour of electron devices used in PA circuits under operating conditions that closely approximate typical telecom applications. Wideband active load-pull (WALP) has been proposed as a promising technique to characterize microwave transistors and to optimize PA performance using excitations that mimic typical communication standards [1]-[4]. The method allows to set, for a given device-under-test (DUT), a user-prescribed load reflection coefficient profile across a wide modulation BW at fundamental and harmonic frequencies. The approach, at the cost of increased complexity, overcomes the main disadvantages of traditional passive load-pull. WALP can provide full coverage of the Smith Chart compensating for insertion loss, and can extend the narrow relative BW due to delay

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Section: Problem Statementmentioning

confidence: 99%

Section: Measurement Setupmentioning

confidence: 99%

mentioning

confidence: 99%

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Wideband Active Load–Pull by Device Output Match Compensation Using a Vector Network Analyzer

Angelotti

Gibiino

Nielsen

et al. 2021

IEEE Trans. Microwave Theory Techn.

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“…Afterwards, the quadrature error which is caused by imperfections in the load pull injection hardware should be fixed through nulling the local oscillator and its image. Finally, a load pull-loop calibration step is performed with a modulated signal, which covers the full load-pull modulated bandwidth, as discussed in [6,7].…”

Section: Fig 2 Measurement System Configurationmentioning

confidence: 99%

“…As both ET characterisation and load‐pull systems use PXI chassis‐based modules, it is possible to combine all the PXI‐based hardware in one PXI chassis, resulting in a compact, yet very robust and flexible measurement system [7]. The chassis controller hosts both the ET and RLP software, as shown in Figs.…”

Section: Measurement System Descriptionmentioning

confidence: 99%

Modulated rapid load pull system for the emulation of envelope tracking power amplifiers

Alsahali

Gecan²,

Alt

et al. 2020

Electron. lett.

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This Letter presents a novel characterisation system that is able to fully emulate a complete envelope tracking power amplifier (ET-PA) environment, with modulated impedance synthesis and dynamic supply voltage generation while using industry-standard modulated signals and digital pre-distortion. The system is used to characterise a 10 W GaN device and provide impedance control over the signal and distortion bandwidths, in response to a 10 MHz long-term evolution signal. A National Instruments PXI-based measurement system is utilised to apply tracking signals to a bespoke supply modulator and successfully improve the average power added efficiency by ∼18 percentage points. Three different shaping functions are implemented, and their efficiency and linearity performance evaluated. In addition, digital pre-distortion (DPD) is used to linearise the PA while operating with the three different tracking trajectories. Experimental results demonstrate that when applying shaping functions, a trade-off needs to be made between efficiency and linearity. Even though a constant gain shaping function provides lower efficiency, it achieves good raw linearity performance without DPD, which is a good option if local linearisation is not available. This novel system is a useful tool in the design of ET-PAs, to more completely investigate the performance of the device.

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VNA-Based Testbed for Accurate Linearizability Testing of Power Amplifiers Under Modulated Signals

Messaoudi

Ayed

Teyssier

et al. 2022

2022 99th ARFTG Microwave Measurement Conference (ARFTG)

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A Novel Modulated Rapid Load Pull System with Digital Pre-Distortion Capabilities

Cited by 6 publications

References 6 publications

Wideband Active Load–Pull by Device Output Match Compensation Using a Vector Network Analyzer

Wideband Active Load–Pull by Device Output Match Compensation Using a Vector Network Analyzer

Modulated rapid load pull system for the emulation of envelope tracking power amplifiers

VNA-Based Testbed for Accurate Linearizability Testing of Power Amplifiers Under Modulated Signals

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