A novel active load-pull system with multi-band capabilities

Gustafsson, Sebastian; Thorsell, Mattias; Fager, Christian

doi:10.1109/arftg.2013.6579056

Cited by 10 publications

(6 citation statements)

References 7 publications

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“…The performance of the VNA-WALP depends on the adopted algorithm to solve (3). In order to compare different candidate algorithms, let us consider, as reference metrics, the number of iterations and function evaluations (i.e., data download/upload and measurement) needed to reach a maximum error across frequency E ∞ within a user-prescribed tolerance.…”

Section: Walp Methods' Comparisonmentioning

confidence: 99%

“…These tones, under the reasonable assumption that the DUT displays periodicin-same-period-out (PISPO) behaviour [14], will fall on a predictable frequency grid with the same spacing as the original excitation signal a S1 . While the baseband as well as harmonic source and load terminations may have a significant impact on the device behavior [2], [3], this work will only consider load-pull for a certain BW around a given RF carrier. Overall, the frequency domain measurements will include both the input-excited tones and the spectral regrowth such as third or higher order intermodulation (IM) distortion products.…”

Section: Problem Statementmentioning

confidence: 99%

“…Finding the correct load injection signal a S2 (t) amounts to determining the unique solution (i.e., the zero of the error function) to (3). This is a classical problem in mathematics, with several numerical approaches reported in literature [15].…”

Section: Problem Statementmentioning

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: Walp Methods' Comparisonmentioning

confidence: 99%

Section: Problem Statementmentioning

confidence: 99%

See 1 more Smart Citation

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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“…For example, the antenna array characteristics can be identified from measurements of the array scattering parameters versus frequency. The PA model coefficients can be identified using active loadpull measurements [20], [21]. All identified coefficients can then be used in (13) to predict the output of the multi-antenna TX for kown input signals.…”

Section: Implementation Of the Simulation Techniquementioning

confidence: 99%

“…1) Active Load-Pull Measurements: In order to characterize dual-input PAs as in a multi-antenna TX, it is necessary to synchronously inject and measure signals both at the PA input and output at well-defined reference planes [20]. Hence, a mixed-mode active load-pull measurement setup [21] is used for the experimental extraction of the dual-input PA model coefficients. The active load-pull setup is calibrated using a short-open-load-through (SOLT) technique in a similar way as it is done with VNAs.…”

Section: B Pa Characterization and Modelingmentioning

confidence: 99%

Prediction of Nonlinear Distortion in Wideband Active Antenna Arrays

Hausmair

Gustafsson

Sánchez-Pérez

et al. 2017

IEEE Trans. Microwave Theory Techn.

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In this paper we propose a technique for comprehensive analysis of nonlinear and dynamic characteristics of multiantenna transmitters (TXs). The analysis technique is enabled by the development of a Volterra series-based dual-input model for power amplifiers (PAs), which is capable of taking into account the joint effects of PA nonlinearity, antenna crosstalk and mismatch for wideband modulated signals. By combining multiple instances of the PA model with linear dynamic antenna simulations we develop the analysis technique. The proposed method allows the prediction of the output signal of every antenna in an arbitrarily sized TX array, as well as the total far-field radiated wave of the TX for any input signal with low computational effort. A 2.12 GHz four-element TX demonstrator based on GaAs PAs is implemented to verify simulation results with measurements. The proposed technique is a powerful tool to study hardware characteristics, as for example the effects of antenna design and element spacing. It can be used in cases where experiments are not feasible, and thus aid the development of next generation wireless systems. Index Terms-Active antenna array, antenna crosstalk, mismatch, MIMO transmitter, power amplifier modeling I. INTRODUCTION Wireless communication systems face a steadily growing demand for higher data rates. However, the radio spectrum is a limited resource. Multiple-input multiple-output (MIMO) systems can be utilized to increase spectral efficiency [1]. For this reason, modern wireless telecommunication standards, such as LTE and Wi-Fi, include the use of multiple antennas. Largescale antenna systems, which comprise hundreds of antennas, have become a hot topic in the research community [2]. The use of several transmit paths in a transmitter (TX) increases system complexity and cost [3]. Therefore, integrated solutions, as have been used in, e.g., radar applications for many years, are preferred. Such integrated designs avoid costly components like bulky isolators between power amplifiers This research has been carried out in GigaHertz Centre in a joint project financed by the

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