Calibration of the loop probe for the near-field measurement

This article reports an SDR (software-defined radio) operating as a receiver for nearfield measurement, aiming at EMC pre-compliance tests. The SDR replaces professional-grade RF instrumentation with benefits, with lower costs. Its software application is based on open-source GNU-Radio, which grants a higher versatility to the signal processing and visualization, requiring a single laptop to analyze the data and control the whole system, in real time. Reported tests used two commercial PCB magnetic field probes, and a proof-of-concept near-field imaging is performed in an L-shaped transmission line at 1100 MHz.

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“…• Use of a TEM structure whose fields can be either analytically described or found after numerical simulations [20].…”

Section: Probes and Characterizationmentioning

confidence: 99%

Near-Field Measurement System Based on a Software Defined Radio

Perotoni¹,

Silva²,

Silva³

et al. 2022

PIER Letters

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“…Though with different sizes, both loops showed similar sensitivities, and the ideally-null response for the E-excitation is found to be approximately 40 dB below the expected H-excitation, in spite of the unshielded probe designs. Other methods are employed for the calibration, such as analytical formulas describing field amplitudes around TEM lines [16], which can be used to extract the absolute field levels. Another interesting method involves the use of an exciting loop whose current is sampled by a series resistor and using it as input to Ampère law, therefore computing the magnetic field at the probe position [6].…”

Section: Near-field Probes and Their Calibrationmentioning

confidence: 99%

Pre-Compliance Near-Field Tests Based on Oscilloscopes

Perotoni,

Silva,

Almeida

et al. 2022

PIER M

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This paper covers the use of oscilloscopes in near-field, pre-compliance radiating tests. Using commercial low-cost planar magnetic probes, a procedure is presented to use the time-domain waveforms to address emitted radiation patterns. In spite of its lower sensitivity in relation to spectrum analyzers, a comparison between the two instruments is presented, with the inferior response of the oscilloscope compensated by means of off-the-shelf broadband amplifiers. Complete system calibration is described and performed, relating the voltage measurements in a transmission-line structure to field amplitudes provided by a full-wave simulation. Two different typical devices are tested using the procedure here developed: a direct current motor, driven by a square wave, and a microprocessor board. Results show the potential use of the almost omnipresent instrument in sophisticated field evaluations, enabling its use in situations where spectrum analyzers are not available.

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“…Moreover, since the EMF influence can be different depending on the position, a multipoint analysis achieved by moving/translating the probe was proposed [10]. Benefiting from the case of the analyzed planar emitter coil fed by a constant frequency and the spatially symmetrical micro-construction (2.5 mm radius) of the measuring head described in our paper, its influence on the measured field was practically negligible.…”

Section: Introductionmentioning

confidence: 99%

“…Measuring the electromagnetic field in order to reduce the electromagnetic influences (EMIs) requires avoiding the disturbance of the measuring probe in the measured EM field. Because this goal cannot be assumed for any probe, the solution proposed in [10] was to calibrate the measuring probe by placing it in a well-defined reference field.…”

Section: Introductionmentioning

confidence: 99%

Implementation of an Accurate Measurement Method for the Spatial Distribution of the Electromagnetic Field in a WPT System

2023

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In an inductive wireless power transfer (WPT) system, the transferred power depends on the coupling between the transmitter coil and the receiver coil and, consequently, on their spatial positioning with respect to each other. Since this positioning needs to be as flexible as possible, one can design various construction shapes for the coils, in terms of both winding geometry and core geometry. The system efficiency for different positionings and configurations can be assessed if the structure and distribution of the electromagnetic field (EMF) in the space close to the system are determined. In this context, this paper proposes an investigation method based on measuring the intensity of the electromagnetic field generated by the emitting coil in the WPT space in terms of both modulus and direction. The measurements needed to be performed at a sufficient number of points, so that the entire field was determined. The EMF value was estimated by linear spatial interpolation between the measured points. Moreover, this paper presents the method and the results of investigations carried out only in the presence of the emitting coil. Calibration or correction solutions were also proposed to obtain sufficient accuracy, and the viability of the method was therefore demonstrated.

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Calibration of the loop probe for the near-field measurement

Cited by 3 publications

References 15 publications

Near-Field Measurement System Based on a Software Defined Radio

Near-Field Measurement System Based on a Software Defined Radio

Pre-Compliance Near-Field Tests Based on Oscilloscopes

Implementation of an Accurate Measurement Method for the Spatial Distribution of the Electromagnetic Field in a WPT System

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