A. Lazaro

ANALYSIS OF VITAL SIGNS MONITORING USING AN IR-UWB RADAR

Ultra-wide Band (UWB) technology is a new, useful and safe technology in the fleld of wireless body networks. This paper focuses on the feasibility of estimating vital signs | speciflcally breathing rate and heartbeat frequency | from the spectrum of recorded waveforms, using an impulse-radio (IR) UWB radar. To this end, an analytical model is developed to perform and interpret the spectral analysis. Both the harmonics and the intermodulation between respiration and heart signals are addressed. Simulations have been performed to demonstrate how they afiect the detection of vital signs and also to analyze the in∞uence of the pulse waveform. A fllter to cancel out breathing harmonics is also proposed to improve heart rate detection. The results of the experiments are presented under difierent scenarios which demonstrate the accuracy of the proposed technique for determining respiration and heartbeat rates. It has been shown that an IR-UWB radar can meet the requirements of typical biomedical applications such as non-invasive heart and respiration rate monitoring.

New Power Factor Correction AC-DC Converter With Reduced Storage Capacitor Voltage

Most of single-stage power factor correction (PFC) ac-dc converters usually present a high voltage swing on the storage capacitor. That means, high size and cost of the storage capacitor is obtained. The Series Inductance Interval (SII) PFC converters allow reducing cost and size of the storage capacitor since the capacitor voltage is lower than the output voltage and, therefore, the voltage swing is significantly reduced. In this paper, the novel single-stage SII-B-2D PFC converter is presented. In addition, this topology provides input current harmonics under EN61000-3-2 Class D limits and advantageous component count

Radio Link Budgets for UHF RFID on Multipath Environments

Radio frequency identification (RFID) applications are growing rapidly, especially in the UHF frequency band, which is being used in inventory management. Passive UHF tags are preferred for this application. However, the read range is often overestimated using free space calculations. This paper presents a method to estimate the read range in multipath environments. Other effects with a direct impact on read range as the effect of materials on tag performance are also addressed. Using the proposed model and the ray trace method a RFID system simulator is presented.

Compact-Modeling Solutions For Nanoscale Double-Gate and Gate-All-Around MOSFETs

Compact-modeling principles and solutions for nanoscale double-gate and gate-all-around MOSFETs are explained. The main challenges of compact modeling for these devices are addressed, and different approaches for describing the electrostatics, the transport mechanisms, and the high-frequency behavior are explained. Several approximations used to derive analytical solutions of Poissons equation for doped and undoped devices are discussed, and the need for self-consistency with Schrodingers equation and with the current continuity equation resulting from the transport models is addressed. Several techniques to extend the compact modeling to the high-frequency regime and to study the RF performance, including noise, are presented and discussed

The fast response double buck DC-DC converter (FRDB): operation and output filter influence

The fast response double buck (FRDB) dc-dc converter was presented like a low output voltage dc-dc converter with fast transient response, in order to feed devices such as microprocessors and digital signal processors (DSPs). The topology of the FRDB is composed of two buck converters connected in parallel, each one of them with different features and aims, and controlled by means of the novel linear-non-linear (LnL) control. In this paper, the topology, the control strategy and the operation principle are shown. Finally, experimental results in different prototypes are presented to show both, the transient response and the recovery time when these prototypes are subjected to load current steps, and the influence of the output filter on these parameters.

Passive Wireless Temperature Sensor Based on Time-Coded UWB Chipless RFID Tags

In this paper, an RF identification sensor system is developed. It comprises passive sensors and an ultra-wideband (UWB) reader. The sensors are based on time-coded chipless tags. They consist of an UWB antenna connected to a delay line that is, in turn, loaded with a resistive temperature sensor. This sensor modulates the amplitude of the backscattered signals as a function of the temperature. The sensor tags are identified by changing the length of the delay line. In this paper, the operation principle and design of time-coded tags is presented and the integration of sensors in these tags is addressed. In addition, two measurement techniques are compared to implement the UWB reader. The first one is based on frequency sweeping and uses a vector network analyzer. The second one is based on a low-cost UWB radar. A full characterization of the sensor system is provided.

Chipless UWB RFID Tag Detection Using Continuous Wavelet Transform

The basic theory of operation of ultra wideband radio identification systems is explained in this letter. An experimental setup based on an ultrawideband radar working as a reader is proposed to measure time-coded tags. A method based on the Continuous Wavelet Transform is developed in order to overcome detection problems associated to a low signal-to-noise ratio at the receiver. Experimental results obtained with the ultrawideband radar and using an ultrawideband antenna connected to a delay line to emulate a tag are presented. A good improvement is achieved with this processing method.

Study of intermodulation in RF MEMS variable capacitors

This paper provides a rigorous study of the causes and physical origins of intermodulation distortion (IMD) in RF microelectromechanical systems (MEMS) capacitors, its analytical dependence on the MEMS device design parameters, and its effects in RF systems. It is shown that not only third-order products exist, but also fifth order and higher. The high-order terms are mainly originated by the nonlinear membrane displacement versus applied voltage and, in the case considered in this study, with an additional contribution from the nonlinear dependence of the reflection coefficient phase on the displacement. It is also shown that the displacement nonlinear behavior also contributes to the total mean position of the membrane. In order to study these effects in depth, an analytical frequency-dependent IMD model for RF MEMS based on a mobile membrane is proposed and particularized to the case of a MEMS varactor-a device for which IMD can be significant. The model is validated, up to the fifth order, theoretically (using harmonic balance) and empirically (the IMD of a MEMS varactor is measured). To this end, a two-tone IMD reflection measurement system for MEMS is proposed.

Wavelet-Based Breast Tumor Localization Technique Using a UWB Radar

This paper deals with the potential of ultra-wideband (UWB) microwave imaging for the detection and localization of breast cancer in its early stages. A method is proposed for locating tumors which is based on the signal time-of-∞ight backscattered by the tumor. Time-of-∞ight is detected using a wavelet transform algorithm. The feasibility of the method has been investigated by means of simulated results using Finite-Difierence Time-Domain (FDTD) and experimental results with a UWB radar and a phantom.

Frequency-Coded Chipless RFID Tag Based on Dual-Band Resonators

The integration of dual-band resonators in frequency-coded chipless RFID tags is proposed in this letter. It is demonstrated that 3N words can be coded in a tag when using N stub-loaded dual-band resonators. It is also shown that an operation bandwidth improvement is achieved in comparison to the use of conventional half-wavelength resonators. A theoretical analysis of the resonator is provided, and a four-resonator tag is designed, manufactured, and measured as a proof of concept. Two processing techniques are used to improve detection and increase the read range: calibration and time gating.