Marco Zahner

Direct Conversion of Free Space Millimeter Waves to Optical Domain by Plasmonic Modulator Antenna

A scheme for the direct conversion of millimeter and THz waves to optical signals is introduced. The compact device consists of a plasmonic phase modulator that is seamlessly cointegrated with an antenna. Neither high-speed electronics nor electronic amplification is required to drive the modulator. A built-in enhancement of the electric field by a factor of 35 000 enables the direct conversion of millimeter-wave signals to the optical domain. This high enhancement is obtained via a resonant antenna that is directly coupled to an optical field by means of a plasmonic modulator. The suggested concept provides a simple and cost-efficient alternative solution to conventional schemes where millimeter-wave signals are first converted to the electrical domain before being up-converted to the optical domain.

Personal radiofrequency electromagnetic field exposure measurements in Swiss adolescents

BACKGROUND Adolescents belong to the heaviest users of wireless communication devices, but little is known about their personal exposure to radiofrequency electromagnetic fields (RF-EMF). OBJECTIVES The aim of this paper is to describe personal RF-EMF exposure of Swiss adolescents and evaluate exposure relevant factors. Furthermore, personal measurements were used to estimate average contributions of various sources to the total absorbed RF-EMF dose of the brain and the whole body. METHODS Personal exposure was measured using a portable RF-EMF measurement device (ExpoM-RF) measuring 13 frequency bands ranging from 470 to 3600MHz. The participants carried the device for three consecutive days and kept a time-activity diary. In total, 90 adolescents aged 13 to 17years participated in the study conducted between May 2013 and April 2014. In addition, personal measurement values were combined with dose calculations for the use of wireless communication devices to quantify the contribution of various RF-EMF sources to the daily RF-EMF dose of adolescents. RESULTS Main contributors to the total personal RF-EMF measurements of 63.2μW/m2 (0.15V/m) were exposures from mobile phones (67.2%) and from mobile phone base stations (19.8%). WLAN at school and at home had little impact on the personal measurements (WLAN accounted for 3.5% of total personal measurements). According to the dose calculations, exposure from environmental sources (broadcast transmitters, mobile phone base stations, cordless phone base stations, WLAN access points, and mobile phones in the surroundings) contributed on average 6.0% to the brain dose and 9.0% to the whole-body dose. CONCLUSIONS RF-EMF exposure of adolescents is dominated by their own mobile phone use. Environmental sources such as mobile phone base stations play a minor role.

High-speed plasmonic modulator in a single metal layer

Ultrafast plasmonic modulation Plasmonics converts light into propagating electrical signals. This approach could allow us to shrink optical components to the nanometer scale, far below the hundreds of wavelengths typically set by conventional optics. Ayata et al. fabricated a plasmonic modulator from a single layer of gold using a substrate-independent process. They created a device with a footprint less than the cross-sectional area of a human hair and with modulation rates exceeding 100 GHz, which could provide a flexible platform for future ultrafast plasmonic technology. Science, this issue p. 630 A high-speed, small-footprint plasmonic modulator is fabricated from a single layer of gold. Plasmonics provides a possible route to overcome both the speed limitations of electronics and the critical dimensions of photonics. We present an all-plasmonic 116–gigabits per second electro-optical modulator in which all the elements—the vertical grating couplers, splitters, polarization rotators, and active section with phase shifters—are included in a single metal layer. The device can be realized on any smooth substrate surface and operates with low energy consumption. Our results show that plasmonics is indeed a viable path to an ultracompact, highest-speed, and low-cost technology that might find many applications in a wide range of fields of sensing and communications because it is compatible with and can be placed on a wide variety of materials.

Interference characterization and UWB channel measurements for wireless intensive care patient monitoring

The electromagnetic environment in a hospital is characterized by means of a measurement campaign. This serves as a basis for the evaluation of best-suited future technologies to be used for wireless patient monitoring, where highest quality of service is required for sensors recording vital data. Results show that the UWB band features equal dynamic ranges as the ISM band but allows operation at a significantly lower power level, which is crucial for Body Area Networks where low power consumption is highly required. Furthermore UWB channel measurements are done in order to specify main propagation paths for scenarios with a volunteer in a bed. Multi-path propagation with reflections at the ceiling and the bedside monitor could be identified as main propagation paths beside the Line-of-Sight link. The impact of these propagation paths on the system performance were evaluated in system simulations using a non-coherent UWB system.

Using impulse Radio UWB for medical monitoring sensor networks: a performance evaluation

A compact testbed for real-time UWB performance evaluation in terms of un-coded bit-error rate is presented. Both the transmitter and the receiver are realized in form of a small PCB. This testbed represents a very versatile tool for the evaluation of IR-UWB as physical layer for various wireless technologies. It operates in the frequency range from 3.1-5.0 GHz with a maximum data rate of 10 MBit/s. Several measurements involving the influence of the human body are performed in a laboratory room in order to get a realistic picture of the performance and reliability that can be expected using IR-UWB for body area networks. In this paper the focus is set on medical monitoring applications. A body area sensor network was emulated and showed good connectivity for all tested scenarios. At a data rate of 10 Mbit/s the measured bit-error rate was better than 10-5 for every node operating in the network.

Context-sensitive ecological momentary assessments; integrating real-time exposure measurements, data-analytics and health assessment using a smartphone application

INTRODUCTION Modern sensor technology makes it possible to collect vast amounts of environmental, behavioural and health data. These data are often linked to contextual information on for example exposure sources which is separately collected with considerable lag time, leading to complications in assessing transient and/or highly spatially variable environmental exposures. Context-Sensitive Ecological Momentary Assessments1 (CS-EMAs) could be used to address this. We present a case study using radiofrequency-electromagnetic fields (RF-EMF) exposure as an example for implementing CS-EMA in environmental research. METHODS Participants were asked to install a custom application on their own smartphone and to wear an RF-EMF exposimeter for 48h. Questionnaires were triggered by the application based on a continuous data stream from the exposimeter. Triggers were divided into four categories: relative and absolute exposure levels, phone calls, and control condition. After the two days of use participants filled in an evaluation questionnaire. RESULTS 74% of all CS-EMAs were completed, with an average time of 31s to complete a questionnaire once it was opened. Participants reported minimal influence on daily activities. There were no significant differences found between well-being and type of RF-EMF exposure. CONCLUSIONS We show that a CS-EMA based method could be used in environmental research. Using several examples involving environmental stressors, we discuss both current and future applications of this methodology in studying potential health effects of environmental factors.

Poster: A novel measurement system for environmental exposure monitoring

The realization of a prototype for a novel band-selective personal exposure assessment system is presented. The new system combines three features that are crucial for Non-Ionising-Radiation (NIR) monitoring, namely the measurement of power levels of selected near field sources, e.g. internal Wi-Fi module, field levels of far field sources and global position measurements. For this, it uses the features of a common smartphone by an additional software application and an external exposimeter module. The system can be either used for environmental monitoring of field levels or used in future epidemiological studies. Such an approach has the potential for huge NIR studies, featuring representative results with a higher measurement accuracy and an increased functionality compared to current systems.

Specification of the ADC interface for an interference robust UWB impulse radio

In this paper, the Analog to Digital Converter interface of a pulse based UWB system operating in the presence of strong interferer is specified. The minimum number of quantization bits is determined for interfering signals caused either by in-band or out-of-band service signals and for different front-end realizations. While for an undisturbed UWB communication link 4 quantization bits are sufficient, up to 14 bits are necessary for an UWB short range communication distance from 3–15 meters for a ‘worst-case’ interference scenario. Results show that a non-linear Analog to Digital Converter approach can significantly reduce the number of required bits from 14 to 8 bits. Fast Fourier Transformation processing methods have also been investigated in terms of processing load and influence on receiver sensitivity. We show that, with a moderate 32-points Fast Fourier Transformation resolution that enables simple serial processing, we can implement efficient interference notch filtering with negligible Bit Error Rate degradation of less than 0.5 dB at a Bit Error Rate of 10−3.

Exposure measurement platform for electromagnetic field monitoring and epidemiological research

Abstract Exposimetry of electromagnetic fields refers to a measurement technology aiming to quantify the immission or absorption of fields and/or energy in specific ranges of the electromagnetic spectrum. Portable, small and accurate measurement instruments were developed to provide tools for epidemiological research and environmental monitoring. The target measurement quantity was the average amount of RMS field strength that an average individual will experience in everyday environments. This quantity can be used to classify different groups of the population or to track changes in exposure conditions within defined regions or along specified tracks. Methods and tools for the assessment of the personal exposure to low-frequency magnetic fields (LF-MF), radio frequency electromagnetic fields (RF-EMF) and pulsed RF emissions from radar installations have been developed, characterized, and tested. The result is a measurement platform enabling a large variety of measurement procedures and study protocols.

Dealing with crosstalk in electromagnetic field measurements of portable devices: Correcting Crosstalk in EMF Measurements

Portable devices measuring radiofrequency electromagnetic fields (RF-EMF) are affected by crosstalk: signals originating in one frequency band that are unintentionally registered in another. If this is not corrected, total exposure to RF-EMF is biased, particularly affecting closely spaced frequency bands such as GSM 1800 downlink (1,805-1,880 MHz), DECT (1,880-1,900 MHz), and UMTS uplink (1,920-1,980 MHz). This study presents an approach to detect and correct crosstalk in RF-EMF measurements, taking into account the real-life setting in which crosstalk is intermittently present, depending on the exact frequency of the signal. Personal measurements from 115 volunteers from Zurich canton, Switzerland were analyzed. Crosstalk-affected observations were identified by correlation analysis, and replaced by the median value of the unaffected observations, measured during the same activity. DECT is frequently a victim of crosstalk, and an average of 43% of observations was corrected, resulting in an average exposure reduction of 38%. GSM 1800 downlink and UMTS uplink were less often corrected (6.9% and 8.9%), resulting in minor reductions in exposure (7.1% and 0.92%). The contribution of DECT to total RF-EMF exposure is typically already low (3.2%), but is further reduced after correction (3.0%). Crosstalk corrections reduced the total exposure by 1.0% on average. Some individuals had a larger reduction of up to 16%. The code developed to make the corrections is provided for free as an R function which is easily applied to any time series of EMF measurements. Bioelectromagnetics. 39:529-538, 2018.