Radar chirp waveform selection and circuit optimization using ACPR load-pull measurements

Martin, Josh; Moldovan, Matthew; Baylis, Charles; Marks, Robert J.; Cohen, Lawrence S.; Graaf, Jean de

doi:10.1109/wamicon.2012.6208465

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…This made it impossible to analyze changes, in the signal during operation caused by widely understood memory effects at the stage of amplifier design. Moreover, optimization of amplifiers' parameters (e.g., ACPR) generally was based on the appropriate selection of load impedance, during load-pull measurements, in order to determine its value for which the optimized parameters reach a satisfactory range [15,[32][33][34]. This approach is unenforceable in case of An appropriate use of the Envelope simulation [31] together with the large-signal electro-thermal model allows for simulating and modeling of amplifier's transmittance changes.…”

Section: Measurement Setup and Amplifier Modellingmentioning

confidence: 99%

A GaN HEMT Amplifier Design for Phased Array Radars and 5G New Radios

2020

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Power amplifiers applied in modern active electronically scanned array (AESA) radars and 5G radios should have similar features, especially in terms of phase distortion, which dramatically affects the spectral regrowth and, moreover, they are difficult to be compensated by predistortion algorithms. This paper presents a GaN-based power amplifier design with a reduced level of transmittance distortions, varying in time, without significantly worsening other key features such as output power, efficiency and gain. The test amplifier with GaN-on-Si high electron mobility transistors (HEMT) NPT2018 from MACOM provides more than 17 W of output power at the 62% PAE over a 1.0 GHz to 1.1 GHz frequency range. By applying a proposed design approach, it was possible to decrease phase changes on test pulses from 0.5° to 0.2° and amplitude variation from 0.8 dB to 0.2 dB during the pulse width of 40 µs and 40% duty cycle.

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Section: Measurement Setup and Amplifier Modellingmentioning

confidence: 99%

A GaN HEMT Amplifier Design for Phased Array Radars and 5G New Radios

2020

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“…In general, power amplifier design involves the tradeoff between different metrics, i.e., gain, noise, output power, nonlinear distortion and efficiency. Unfortunately, these metrics are optimal at different transistor load impedance values, which has been empirically observed using load pull techniques in both AB [25]- [27] and Doherty design [28], [29]. Hence, the power amplifier designer must choose the load impedance at transistor levels compromising between these metrics.…”

Section: A Power Amplifier Designmentioning

confidence: 99%

“…Therefore, AB amplifier architecture may be considered when out-of-band emissions and load impedance mismatches may occur. The minimization of the out-of-band error or any other metric can be done using load pull techniques [27]. These techniques can also provide, in the form of contours, the sensitivity to load impedance variations.…”

Section: B Sensitivitymentioning

confidence: 99%

Output Impedance Mismatch Effects on the Linearity Performance of Digitally Predistorted Power Amplifiers

Zenteno

Isaksson

Händel

2015

IEEE Trans. Microwave Theory Techn.

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This paper analyzes the effects of load impedance mismatch in power amplifiers which linearity has been enhanced using various digital predistortion (DPD) algorithms. Two different power amplifier architectures are considered: a class AB and a Doherty amplifier and three model structures for the DPD model are compared: memoryless polynomial (MLP), general memory polynomial (GMP) and Kautz-Volterra functions (KV). This paper provides a sensitivity analysis of the linearized amplifiers under load mismatch conditions and reports the performance when dynamic parameter identification for the DPD is used to compensate for the changes in the load impedance. In general,power amplifiers linearity is sensitive to load impedance mismatch. Linearity may degrade as much as 10 dB (in normalized mean square error) according to the magnitude and the phase of the reflection coefficient provided by the load impedance. However, depending on the amplifier design, the sensitivity toload impedance mismatch varies. While the Doherty amplifier studied show significant linearity degradations in the in-band and out-of-band distortions, the out-of-band distortions of the studied class AB were less sensitive to the load impedance mismatch. In adaptive DPD schemes, the performance obtained in the MLP model does not benefit from the updating scheme and the performance achieved is similar to a static case, where no updates are made. This stresses the memory requirements in the predistorter. When employing the GMP and the KV models in an adaptive DPD scheme, they tackle to a larger extent the linearity degradations due to load impedance mismatch.

QC 20150123

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“…In a 2011 paper, we demonstrated the use of a steepest‐ascent algorithm for a single‐objective impedance optimisation, optimising for maximum output power [24]. We also demonstrated the dependence of PAE and ACPR on the amplifier load impedance for radar chirp waveforms [25]. We recently described an indirect search algorithm capable of finding a Pareto optimum impedance through two peak searches [1].…”

Section: Introductionmentioning

confidence: 99%

Direct algorithm for the Pareto load‐pull optimisation of power‐added efficiency and adjacent‐channel power ratio

Fellows¹,

Baylis²,

Martin

et al. 2014

IET Radar, Sonar & Navigation

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Adaptive radar systems will be required to operate in different frequency bands with spectrum requirements that will likely change both in time and with geographic region. A new algorithm is presented that allows direct optimisation of an amplifier's load reflection coefficient to find a Pareto optimum between the power-added efficiency (PAE) and adjacentchannel power ratio. Comparisons of simulation and measurement results are presented. The new algorithm's results compare well with traditionally acquired data and show consistency between the optimum values for PAE that are obtained from different starting points. Measurement comparison is performed with the previous optimisation algorithm reported by the authors, and results show that up to a 50% reduction in the number of measured experimental queries can be obtained. This translates into a significant time savings in reconfiguring a radar transmitter power amplifier.

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Radar chirp waveform selection and circuit optimization using ACPR load-pull measurements

Cited by 10 publications

References 7 publications

A GaN HEMT Amplifier Design for Phased Array Radars and 5G New Radios

A GaN HEMT Amplifier Design for Phased Array Radars and 5G New Radios

Output Impedance Mismatch Effects on the Linearity Performance of Digitally Predistorted Power Amplifiers

Direct algorithm for the Pareto load‐pull optimisation of power‐added efficiency and adjacent‐channel power ratio

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