3,710 research outputs found
Reconciling Statistical Models with Practical Experience of Reverberation Chambers
No full textPresented are novel theoretical probability density functions (PDF) for the magnitude and phase of electromagnetic fields inside reverberation chambers (RC) operating in a dasiagood-but-imperfect regime. The derivation is based on considering two Gaussian random variables with mean values, variances and correlation between them that depart from the ideal assumptions. A multivariate approach using a complete joint Gaussian distribution of these variables is defined. Marginal distributions obtained by integration of this two-dimensional joint PDF are compared with theoretical PDFs for ideal situations, and significantly lower rejection rates are experienced for field data measured in real RCs. Additionally, these novel marginal PDFs are highly general since they are able to describe both ideal and non-ideal stirred fields
Modelling delay and noise in arbitrarily coupled RC trees.
No full textClosed-form equations for second-order transfer functions of general arbitrarily coupled resistance-capacitance (RC) trees with multiple drivers are reported. The models allow precise delay and noise calculations for systems of coupled interconnects with guaranteed stability and represent the minimum complexity associated with this class of circuits. Their accuracy is extensively compared against other relevant models and is found to be better or comparable to more expensive models. All results are derived from a theoretical approach, and their physical basis is examined. The simplicity, accuracy, and generality of the models make them suitable for use in early signal integrity analyses of complex systems and incremental physical optimization
Radiated Immunity Testing of a Device with an External Wire: Repeatibility of Reverberation Chamber Results and Correlation with Anechoic Chamber Results
No full textWe present the experimental radiated immunity results of an electronic device with an external wire obtained in reverberation and anechoic chambers. Repeatability and reproducibility of reverberation chamber measurements are investigated by repeating the test in three reverberation chambers with different characteristics. We show how the current state of the art allows a statistical control of RC measurement repeatability within an industrial installation, and that a statistical correlation with AC results frequency by frequency is possible in particular cases relevant to automotive application
A Compact 10-MHz RC Frequency Reference With a Versatile Temperature Compensation Scheme
No full textThis article presents the design and implementation of a compact CMOS RC frequency reference. It consists of a frequency-locked loop (FLL) that locks the period of a voltage-controlled oscillator (VCO) to the time an RC network takes to charge to a reference voltage. Conventionally, an RC time constant with a near-zero temperature coefficient (TC) is realized by using a trimmed network of resistors with different TCs. In this work, such a network is used to realize a temperature-dependent reference voltage whose TC cancels that of a single-resistor RC time constant. Compared with the conventional approach, which requires resistors with TCs of opposite polarity, the proposed approach can be implemented with resistors with TCs of similar polarity, and so it can be implemented in most CMOS processes. To compensate for RC spread, a trimmed capacitor is used to adjust the nominal frequency. Two prototype chips were made, one based on p- /n-polysilicon resistors and other based on silicided/p-diffusion resistors. Fabricated in a standard 180-nm CMOS technology, the polysilicon-based prototype has an active area of 0.01 mm2 and an absolute inaccuracy of ±2800 ppm from -45 °C to 125 °C with a fixed TC-trim and a one-point frequency trim. After one week of accelerated aging at 150 °C, however, significant drift (5000 ppm) was observed. The diffusion-based prototype exhibits greater inaccuracy (±14 400 ppm) but much less drift (600 ppm).Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
Using reverberation chambers for em measurements
No full textReverberation chambers (RC) are being used for several decades. The main advantage is the high field strength which can be generated, with only modest power. In the last few years the use of RCs became much popular, for testing multi-path propagation for communication links, or testing the coupling of complex fields into transmission lines, as well as testing coupling into objects, and measuring the shielding effectiveness of materials. The costs for setting up a conventional RC, with rotating mode stirrers, is low compared to the cost of anechoic chambers. Existing chambers are making use of a paddle wheel to change the resonant modes in the chamber. A transportable reverberation chamber with varying angles between wall, floor and ceiling and with vibrating walls has been used for testing of many systems. Inside this Vibrating Intrinsic Reverberation Chamber(VIRC) a diffuse, statistically uniform electromagnetic field is created without the use of a mechanical, rotating, mode stirrer. This chamber results in a better homogeneity and increased field strength compared to conventional mode stirred reverberation chambers. The use of flexible material to build the VIRC is making a test facility at even lower cost possible. Furthermore such a VIRC can be built around a test object,and the test object is not to be moved to an anechoic chamber. This can reduce test costs for complex systems. The basic principles of RC and VIRC are explained, and several applications shown
Using reverberation chambers for em measurements
No full textReverberation chambers (RC) are being used for several decades. The main advantage is the high field strength which can be generated, with only modest power. In the last few years the use of RCs became much popular, for testing multi-path propagation for communication links, or testing the coupling of complex fields into transmission lines, as well as testing coupling into objects, and measuring the shielding effectiveness of materials. The costs for setting up a conventional RC, with rotating mode stirrers, is low compared to the cost of anechoic chambers. Existing chambers are making use of a paddle wheel to change the resonant modes in the chamber. A transportable reverberation chamber with varying angles between wall, floor and ceiling and with vibrating walls has been used for testing of many systems. Inside this Vibrating Intrinsic Reverberation Chamber(VIRC) a diffuse, statistically uniform electromagnetic field is created without the use of a mechanical, rotating, mode stirrer. This chamber results in a better homogeneity and increased field strength compared to conventional mode stirred reverberation chambers. The use of flexible material to build the VIRC is making a test facility at even lower cost possible. Furthermore such a VIRC can be built around a test object,and the test object is not to be moved to an anechoic chamber. This can reduce test costs for complex systems. The basic principles of RC and VIRC are explained, and several applications shown
Radar cross-section estimation in reverberation chambers
No full textInternational audienceThis chapter is dedicated to recent advances in a rather unexplored range of applications. It deals with the ability of performing radar cross-section (RCS) measurements, using a reverberation chamber (RC). If feasible, it would allow broadband measurements in a simple Faraday cage at a much lower cost, absorbers being no longer required. However, using a RC for RCS measurement seems inadequate at a first glance. Adding an object under test in the chamber consists in introducing another scatterer, indistinguishable in a rich multipath environment offered by the RC. Chapter Contents: • 9.1 Definition of radar cross section and the radar equation • 9.2 Radar cross-section measurements • 9.3 Scattered cross section and antenna patterns in reverberation chambers • 9.4 Theory of radar cross-section pattern measurements in reverberation chambers • 9.4.1 Measurement setup • 9.4.2 Backscattered field in an empty RC • 9.4.3 Backscattered field from the target • 9.4.4 The backscattered coefficient • 9.4.5 RCS equation of the target • 9.4.6 Extraction of RCS • 9.5 Validation on simple targets • 9.5.1 Preliminary measurements in anechoic chamber • 9.5.2 Calibration in RC • 9.5.3 Measurement of the metal plate • 9.5.4 Measurement of a dihedral target • 9.5.5 The role of the stirrer • 9.5.5.1 Changing the stirrer position after empty RC measurement • 9.5.5.2 Multiple RCS measurements at several stirrer positions • 9.6 Discussion • References. © The Institution of Engineering and Technology 2021
Exploring Short Pulses in Reverberation Chambers
No full text12591264We present a detailed study of short versus long pulses in reverberation chambers (RC). Understanding their behaviour in RC should contribute to reliable EMC testing with pulsed signals. To this end, we analyse amplitude and shape of pulses averaged over stirrer positions as a function of chamber loading for different frequencies. While the amplitude essentially corresponds to theoretical expectations, there are unexpected features in the shape especially for short pulses
Hybrid numerical modelling of reverberation chambers
No full textThis paper describes recent advancements in hybrid numerical modelling of reverberation chambers (RCs). Motivation of modelling an RC is first described, and challenges in RC modelling are pointed out. Shortcomings and advantages of conventional numerical methods are discussed, and hybrid techniques are introduced to overcome disadvantages of different numerical methods while retaining their respective strengths. Benefits of hybrid methods are then illustrated using numerical examples, and future works are finally suggested
A pilot telephone intervention to increase uptake of breast cancer screening in socially deprived areas in Scotland (TELBRECS):study protocol for a randomised controlled trial
No full textBackground: Breast cancer accounts for almost 30% of all cancers and is the second leading cause of cancer deaths in women in Scotland. Screening is key to early detection. The Scottish Breast Screening Programme is a nationwide, free at point of delivery screening service, to which all women aged between 50 and 70 years are invited to attend every 3 years. Currently over three-quarters of invited women regularly attend screening. However, women from more deprived areas are much less likely to attend: for example in the 3 years from 2010-2012 only 63% of women in the most deprived area attended the East of Scotland Breast Screening programme versus 81% in the least deprived. Research has suggested that reminders (telephone or letter) and brief, personalised interventions addressing barriers to attendance may be helpful in increasing uptake in low-income women. Methods/Design. We will employ a brief telephone reminder and support intervention, whose purpose is to elicit and address any mistaken beliefs women have about breast screening, with the aim that the perceived benefits of screening come to outweigh any perceived barriers for individuals. We will test whether this intervention, plus a simple anticipated regret manipulation, will lead to an increase in the uptake of breast cancer screening amongst low-income women who have failed to attend a first appointment, in a randomised controlled trial with 600 women. Participants will be randomly allocated to one of four treatment arms i.e. 1) Letter reminder (i.e. Treatment as usual: CONTROL); 2) Telephone reminder (TEL), 3) Telephone reminder plus telephone support (TEL-SUPP) and 4) Telephone reminder plus support plus AR (TEL-SUPP-AR). The primary outcome will be attendance at breast screening within 3 months of the reminder letter. Discussion. If this simple telephone support intervention (with or without AR intervention) leads to a significant increase in breast screening attendance, this would represent a rare example of a theoretically-driven, relatively simple psychological intervention that could result in earlier detection of breast cancer amongst an under-served group of lower socio-economic women
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