Near-field Scan Research Articles

EMI Prediction of Slew-Rate Controlled I/O Buffers by Full-Wave and Circuit Co-Simulation

In this paper, a modeling and co-simulation methodology is proposed to predict the radiated electromagnetic interference (EMI) from on-chip switching I/O buffers. The output waveforms of I/O buffers are simulated including the on-chip I/O buffer circuit and the RC extracted on-chip interconnect netlist, package, and printed circuit board (PCB). In order to accurately estimate the EMI, a full-wave 3D simulation is performed including the measurement environment. The simulation results are compared with near-field electromagnetic scan results and farfield measurements from an anechoic chamber, and the sources of emission peaks were analyzed. For accurate far-field EMI simulation, PCB power trace models considering IC switching current paths and external power cable models must be considered for accurate EMI prediction. With the proposed EMI simulation model and flow, the electromagnetic compatibility can be tested even before the IC is

An Empirical Approach to Develop Near-Field Limit for Radiated-Emission Compliance Check

Based on measurements from a near-field scanner and far-field measurements obtained in a semi-anechoic chamber, a statistical relationship is established between a magnetic field in the near field and an electric field in the far field. The relationship makes it possible to transform a radiated-emission regulatory limit from the far-field to the near-field zone. The transformed near-field limit can allow efficient prediction of radiated-emission compliance for high-speed printed circuit boards. The presented results demonstrate the feasibility of the proposed method for a quick radiated-emission precompliance check without heavy equipment investment.

Quantitative Study of Two Experimental Demonstrations of a Carpet Cloak

An all-dielectric carpet cloak, formulated using the optical transformation technique, is presented here. The carpet cloak was fabricated by implementing a dielectric disk matrix (DDM) with varying periods. To demonstrate that it is functional for multiple angles of incidence, the cloak is measured in a near-field scanner. The performance of this cloak is then quantitatively compared to that of a carpet cloak composed of a nanoparticle-loaded polyurethane foam using a novel technique that can be applied to evaluate the performance of other devices.

Automated Near-Field Scanning Algorithm for the EMC Analysis of Electronic Devices

This paper presents an automated procedure to determine the electric or magnetic near-field profile of electronic systems and devices in a given plane. It combines sequential sampling to determine the optimal coordinates of near-field scan points at arbitrary coordinates in the scanning plane. The effectiveness of the approach is illustrated by applying it to both a simulated and a measured printed circuit board example.

Planar Near-Field Measurement of Digital Phased Arrays Using Near-Field Scan Plane Reconstruction

A phased array with a transmit/receive (T/R) digital beamforming (DBF) network was designed and fabricated by CEA Technologies Pty Ltd., Canberra, Australia, under the joint Australia/USA AUSPAR Program. The array was characterized through a series of antenna measurements that utilized a compact range and planar near-field scanning facility at the U.S. Naval Research Laboratory. The near-field measurements acquired element-level near-field responses that were received by the array of digital receivers present at each element in the array. This paper discusses a processing technique - referred to as near-field scan plane reconstruction - to generate any desired beam from the element-level data. The results are compared to compact range measurements of beams formed using real-time processing showing good agreement.

Electromagnetic Analysis Enhancement Based on Near-Field Scan

Electromagnetic emissions leak confidential data of cryptographic devices. By exploiting such emissions, electromagnetic analysis (EMA) is performed with EM probes to extract secret information from these devices. Owing to the locality of EM emissions, namely, secret information may leak from multiple locations around cryptographic devices, it is difficult to determine the exact location before conducting an EMA. In this paper, signal variance of EM emissions during encryption is proposed to identify the information leakage of unprotected and protected cryptographic modules. We prove that signal variance is an equivalent metric to Difference of Means (DoM). Thus, by computing the higher signal variances based on near-field scan, the data-dependent EM emissions are disclosed, namely, the leakage locations are found. In addition, a small and low-cost probe is made to verify the proposed EMA on application-specific integrated circuit (ASIC) implementations. The experiment on AES PPRM1 implementation indicates that misjudgments of leakage are reduced, and the accuracy is improved 48.6% compared with existing methods. Moreover, the experiment of EMA against AES WDDL implementation shows that signal variance is also effective in exposing the leakage locations in the presence of countermeasures. The performance of EMA is enhanced.

Prediction of Radiated Emissions Using Near-Field Measurements

A procedure is developed to predict electromagnetic interference from electronic products using near-field scan data. Measured near-field data are used to define equivalent electric and magnetic current sources characterizing the electromagnetic emissions from an electronic circuit. Reconciliation of the equivalent sources is performed to allow the sources to be accurately applied within full-wave numerical modeling tools like finite-difference time domain (FDTD). Results show that the radiated fields must typically be represented by both electric and magnetic current sources if scattering and multiple-reflections from nearby objects are to be taken into account. The accuracy of the approach is demonstrated by predicting the fields generated by a microstrip trace within and outside of a slotted enclosure, and by predicting the fields generated by the microstrip trace close to a long wire. Values predicted from near-field scan data match those from full-wave simulations or measurements within 6 dB.

Construction and Measurement of a 31.3–45 GHz Optimized Spline-profile Horn with Corrugations

A corrugated spline-profile horn has been designed to meet the stringent specifications and constraints of a receiver for Band 1 (31.3–45 GHz) of the Atacama Large Millimeter Array (ALMA). Given the physical restrictions of the receiver, the horn will be located behind a focusing lens placed 191 mm over its aperture. After this first focusing stage, the horn must have a reflection coefficient less than −20 dB and the cross-polarization not exceeding the −30 dB level in the entire frequency range. The side-lobes should be less than −25 dB at all frequencies and its half power beamwidth must be approximately 24° at 31.3 GHz and 16° at 45 GHz. The horn has been constructed using the split-block technique and characterized in a near-field scanner setup. The results show an excellent performance complying with all the requirements.

Simultaneous near field imaging of electric and magnetic field in photonic crystal nanocavities

The insertion of a metal-coated tip on the surface of a photonic crystal microcavity is used for simultaneous near field imaging of electric and magnetic fields in photonic crystal nanocavities, via the radiative emission of embedded semiconductor quantum dots (QD). The photoluminescence intensity map directly gives the electric field distribution, to which the electric dipole of the QD is coupled. The magnetic field generates, via Faraday's law, a circular current in the apex of the metallized probe that can be schematized as a ring. The resulting magnetic perturbation of the photonic modes induces a blue shift, which can be used to map the magnetic field, within a single near-field scan.

A Noninvasive Microwave Sensor and Signal Processing Technique for Continuous Monitoring of Vital Signs

The use of the noninvasive microwave method for measuring changes in lung water content has been previously reported and validated in animal experiments. The approach is based on measuring the transmission coefficient across the thorax and correlating results with changes in lung water content. In this letter, we extend this technique to the monitoring of multiple vital signs including heart rate and breathing as well as the changes of lung water content from a single transmission coefficient measurement. Using a short-time Fourier transform-based digital signal processing method, it is shown that these vital signs can be accurately detected and extracted from a single microwave transmission coefficient measurement. Experimental measurements were made on a thorax phantom model, and the obtained data confirmed the validity and accuracy of the proposed approach. The radiation bio-safety aspects of this approach were evaluated using a DASY4 near-field scanner, often used for certifying cell phones. Obtained results for a 30-mW input power show that the specific absorption rate (SAR) values are about one third of the FCC safety standard at the operating frequency of 915 MHz. The microwave applicator design together with the experimental procedure and the extracted vital signs results are presented, and avenues for future clinical implementation are discussed.

Analysis and design for VMS EMC based on MPC555

In order to ensure the vehicle management system (VMS) satisfy the RE and CE standards which are required by national regulations, the EMC design method is necessary to be integrated into the controller PCB design flow. Through filtering for signal line and decoupling for power system on VMS based on MPC555, the properties of VMS’ EMC are improved. With spectrum analyzer and EMSCAN near-field scanner, the feasibility of Antiinterference measures is verified. The VMS passed the CE test level 5 and the RE test level 4 in CISPR25: 2002.

Relation between transmission and energy stored in random media with gain

Received 16 January 2010; revised manuscript received 5 July 2010; published 13 September 2010 In this work, we investigate a possibility of using the ratio between optical transmission, T, and energy stored inside the system, E, as a quantitative measure of the enhanced mesoscopic corrections to diffusive transport of light through a random medium with gain. We obtain an expression for T / E as a function of amplification strength in the diffusive approximation and show that it does not a have tendency to diverge when the threshold for random lasing is approached, as both T and E do. Furthermore, we find that a change in T / E signifies a change in the electric field distribution inside the random medium. In the localization regime, we also investigate the correlations between transmission and energy stored in the medium with and without amplification. Our results suggest that T / E is a promising parameter which can help characterize the nature of wave transport in random medium with gain. In this work, we investigate the properties of the ratio between transmission T and the energy inside a random me- dium E, with the goal of formulating a criterion of AL which would be applicable in the presence of gain. Both parameters should be experimentally accessible in planar systems, e.g., perforated dielectric films, in which the spatial field distribu- tion inside the medium can be obtained via near-field scan- ning optical microscopy. In Sec. II, to motivate our choice of the parameter in the form T / E, we consider random medium in regime of diffu- sive transport. First we note that when taken separately, both transmission and the energy inside the system E exhibit an expected tendency to increase with an increase in the gain strength and to diverge when threshold for random lasing is approached no saturation mechanism is assumed. However, when taken in a form of a ratio, the divergence is eliminated and the tendency to increase is greatly reduced. Second, we show that in passive systems the ratio can be related to the spatially dependent diffusion constant Dz. The latter con- cept has been recently invoked 17,18 in the self-consistent theory of AL to extend the applicability of diffusion approxi- mation into the localized regime. The connection between T / E and Dz demonstrates that the former can, indeed, be used as a quantitative measure of the contribution of local- ization interference phenomena in transport through disor- dered systems. In Sec. II D, we obtain an expression for T / E from the solution of the diffusion equation in a random medium us- ing the slab geometry with gain. This establishes a baseline—a decrease in the parameter T / E below the diffu- sion prediction obtained in this section can be used to quan- tify the extent to which the gain promotes the localization effects. In order to further assess the usefulness of T / E as a local- ization criterion, in Sec. III we also consider random medium in the localized regime where we investigate the correlations between the transmission and stored energy in the same dis- order configuration. We show that the ratio strongly depends on the spatial location of localization center. This introduces an additional geometrical source of fluctuation which is not present in the transmission coefficient alone. Interestingly,

Packaging of Dual-Mode Wireless Communication Module Using RF/Optoelectronic Devices With Shared Functional Components

This paper reports the design, fabrication, and testing of a compact radio-frequency (RF)/ free space optical (FSO) dual mode wireless communication system. A modified split dual-director quasi-Yagi antenna is integrated with optical transmitter and receiver by sharing layout structural components. Bare die vertical-cavity surface-emitting laser (VCSEL) and P-i-N photodiode (PIN) are placed on antenna director pads and wire bonded to printed circuit board (PCB)-mounted laser driver and transimpedance amplifier (TIA) circuits. Detailed analysis of coupling between RF channel and associated electrical connections for the FSO channel is presented using commercial simulation tools to predict its impact on link degradation. Although crosstalk appears between RF and optical channels, the prototyped system demonstrated dual-mode high-rate communication capability with measured 2.5 Gb/s data rate in FSO link. Variations in RF subsystem features due to coupling from the FSO subsystem is estimated through radiation pattern measurement using near-field scanner.

Cube probe structures for integrated near-field scanner module

Two new miniature near-field 'cube probe' structures for EMC/EMI measurements are proposed. Their performances are compared to those of the classical H-field loop probe in two orthogonal planes. The single cube probe effectively replaces three conventional orthogonally oriented loops. An array of cube probes is also proposed to form a near-field scan module dedicated to the characterisation of integrated circuit radiated emissions.

A comparison of hydrophone near-field scans and optical techniques for characterising high frequency sonar transducers

Two potential methods of fully characterising the response of high frequency sonar transducers and arrays operating in the frequency range 100 kHz to 500 kHz are compared. In the first approach two-dimensional planar scans, with a spatial resolution of better than half a wavelength, are performed in the acoustic near-field using a small probe hydrophone. The measured two-dimensional data are propagated numerically using a Fourier Transform method to predict the far-field response. Alternatively the data can be back-propagated to re-construct the pressure distribution at the source, a powerful diagnostic technique which can identify defects in transducers and array elements. The second approach uses a scanning laser vibrometer to measure the velocity of the transducer surface; with the resulting velocity data also being used to predict the far-field response by numerical propagation. The two approaches are compared for a number of devices. Comparison of the propagated hydrophone near-field scan data with direct measurements at these ranges shows very good agreement, indicating the usefulness of the method for deriving far-field transducer responses from near-field measurements in laboratory tanks. The potential limitations introduced to the optical approach by the acousto-optic effect are discussed.

Estimation of High-Frequency Currents From Near-Field Scan Measurements

High-frequency currents on the pins of integrated circuits (ICs) and on printed circuit board (PCB) traces are needed to predict and analyze electromagnetic interference in high-speed devices. These currents can, however, be difficult to measure when traces are buried within the PCB or chip-package, especially when several current-carrying traces are in close proximity. Techniques for estimating high-frequency currents from near-field scan data are proposed in this paper. These techniques are applied to find currents on the pins of an IC, on traces buried beneath other traces in a PCB, and on traces over a slot in the ground plane. Methods of dealing with the ill-posed nature of the current-estimation problem are discussed, as are applications to electrically large structures. A study of the sensitivity of the technique to errors in the measured fields, errors in the circuit geometry, and errors in the estimated dielectric constant of the PCB or chip package show that, for reasonable errors in these parameters, currents can be estimated to within an average of 20% (1.6 dB) or less of their correct values.

Characterisation of electromagnetic susceptibility of integrated circuits using near-field scan

A susceptibility characterisation test for integrated circuits using a miniature magnetic near-field probe is described. The method is efficient up to a frequency of 6 GHz and maps immunity to radiated fields.

Calibration and Compensation of Near-Field Scan Measurements

A procedure for the calibration and compensation of near-field scanning is described and demonstrated. Ultimately, the objective is to quantify the individual field components associated with electromagnetic interference (EMI) from high speed circuitry and devices. Specific examples of these methods are shown. The effects of compensation are small but noticeable when the uncompensated output signal from near field scanning is already a very good representation of the field being measured. In other cases, the improvement provided by compensation can be significant when the uncompensated output signal bears little resemblance to the underlying field.

Near-Field Scanner for the Detection of Passive Intermodulation Sources in Base Station Antennas

Passive intermodulation (PIM) distortion is a challenging problem in the design and manufacturing of base station antennas. Small nonlinearities, typically in junctions, may cause a distortion signal that interferes with the receiver even with a level of -155 dBc in a GSM900 system. The PIM level specification of an outdoor base station antenna is difficult to achieve and the sources of PIM generation are laborious to track down. In this paper, a near-field measurement method is presented to localize and investigate passive intermodulation sources in antennas and open transmission lines. The principle of the PIM near-field measurement is otherwise the same as in a common reactive near-field measurement, but instead of measuring the signal at the input frequency, the signal amplitude and phase at the PIM frequency of interest are acquired. The constructed measurement system is capable of measuring PIM signal levels down to -110 dBm with 2/spl times/43 dBm transmit power in the GSM900 frequency band. As demonstration measurements, PIM sources in a two-element base station antenna and in a microstrip line are localized.

Sensitivity measurements of a passive intermodulation near-field scanner

A passive intermodulation (PIM) near-field XY scanner for the GSM900 frequency band has been constructed to localize distortion sources in antennas and in other open structures. The equipment should be able to measure distortion levels down to -115 dBm with an input power of 2/spl times/20 W, since the noise floor of a GSM900 base station is typically around -110 dBm. The sensitivity is limited either by thermal noise or by residual intermodulation distortion, depending on the probe coupling. Various causes of residual intermodulation distortion in the passive intermodulation near-field measurement are considered and evaluated. Sensitivity measurements of the scanner have been carried out on two test devices. Sensitivities of -112 dBm and -110 dBm have been achieved with an electric and a magnetic field probe, respectively.