Evaluation of a reflection based dehydration sensing method for wristwatch integration

In this paper, a novel method to measure the amplitude and phase of two-tone third-order intermodulation products generated in a high-power amplifier is presented. The method is based on the sampled input and output signals of the amplifier. The presented measurement setup and the associated algorithms for the calculation of the amplitudes and phases are considerably faster and simpler than the current methods. By making use of the sampled input and output signals of the amplifier and the signal processing techniques, the need for a nonlinear reference, a tunable attenuator, and a phase shifter in the existing measurement setups is eliminated, which makes it simple and easy to use. Hence, this is a substantial simplification of the measurement setup compared to what has been reported earlier. The proposed measurement setup is also suitable for fast automated measurements, which is of interest for many applications that are both laboratory and production oriented. In addition, a method to increase the bandwidth of the measured signal is used to overcome the bandwidth limitation set by the Nyquist criteria for sampled systems. Measurements are done on two base-station high-power amplifiers and are found to be in agreement with theory and reference measurements.

We present a highly accurate measurement setup and related methods for the efficient characterization of inductive rotary position sensors. The test bench is designed to measure analog sine/cosine output signals of the device under test (DUT) under nominal conditions as well as deliberate misalignment, such as offset and tilt tolerances- enabling analysis of DUT performance w.r.t. the angle deviation, the harmonic decomposition, and tolerance sensitivities. The uncertainty of measurements with the proposed test bench setup is quantified with a repeatability study and an effort is made to determine the systematic deviation. By means of laser-guided positioning, the printed circuit board (PCB) of the DUT is automatically positioned relative to the rotary axis (runout ±5 μm) in airgap and radial direction (repeatability 5 μm, total deviation 30 μm). The setup is capable of high-speed measurements at a rotation speed of at least 2000 min−1. The proposed measurement setup is flexible to accommodate a wide range of rotary position sensors and enables fast (less than 3 s per tolerance scenario) and automated characterization of the DUT angle deviation with excellent accuracy better than 10′′ (0.003∘).

The methods reported for the measurement of distance and medium velocity using ultrasound are based on the principles of pulse radar, pulse Doppler radar, and continuous- wave radar. In this paper, the use of frequency-modulated sonic/ultrasonic radiations for such measurements has been proposed. The required measurement setup has been described, and the mathematical model needed for extraction of distance/medium velocity from the electrical output signal has been developed. The proposed measurement setup has been implemented for distance measurement with commonly used ICs.

A precise layer alignment is crucial to ensure performance repeatability of multilayer microstrip antennas. We introduce a novel lab-scale construction process for multilayer microstrip textile patch antennas that consists in combining an alignment method, based on laser-cut wood frames to perform accurate layer alignment, with a fast intralayer attachment method, based on thermally activated adhesive sheets. This lab-scale construction process is validated with an electromagnetically coupled microstrip rectangular patch textile antenna operating in the 2.45 GHz ISM band. It has been reproduced eight times to validate the proposed construction process. The differences between desired simulated versus measured average values of the resonant frequencies, impedance bandwidths, gains, and total efficiencies equal 6.25 MHz, 21.5 MHz, 0.6 dBi, and 4.45%, respectively. Moreover, the standard deviations of measured resonant frequencies, impedance bandwidths, gains, and total efficiencies equal 24.54 MHz, 14.02 MHz, 0.15 dBi, and 3.57%, respectively. These results confirm that the novel lab-scale construction process provides good performance repeatability of multilayer microstrip textile patch antennas.

The experiments of the open-ended coaxial sensor used in the liquid dielectric properties testing based on the transverse electromagnetic (TEM) model are presented. In this approach, the input admittance at the coaxial opening end is approximated as a polynomial of the complex wave number in the liquid under test (LUT) that terminates the sensor, which gives advantageous to de-embedding the unknown complex permittivity by iteratively solving an algebraic equation. To avoid the inconveniences in using a short circuit reference load, the saline solution with known complex dielectric constants given by the empirical dispersion equations is used as an alternative in the calibration. The performance of measurements on dilute saline water and a 900MHz phantom head tissue-equivalent liquid (TEL) are verified by comparisons with the reference data.

Implementation of the ultrasonic second harmonic generation has typically been restricted to simple setups such as through-transmission or Rayleigh surface waves. Recent research has evaluated the second harmonic waves generation in P- and SV- waves reflected from a stress-free surface to enable the single-sided interrogation of a specimen. This research considers the second harmonic generation in an aluminum specimen, which is analytically evaluated using an approach based on a perturbation method. Here, the model is chosen to mimic an experimental setup where the longitudinal wave is generated at oblique angle using a wedge transducer. Due to the mode conversion at the interface of the wedge and the specimen, it is necessary to evaluate longitudinal and shear waves, determining all second harmonic waves generated in the bulk and at the stress-free boundary. The theoretically developed model is then implemented in a commercial finite element code, COMSOL, using increasing fundamental wave amplitudes for different values of third order elastic constants. The results of this computational model verify the analytical approach and the proposed measurement setup, taking into account assumptions and approximations of the solution procedure. Furthermore, the computational model is used to draw important conclusions relevant to the experimental setup, including the need to avoid interaction with diffracted waves.

This study presents the radiation performance measurements of an antenna operating in a lossy medium with a complex dielectric constant. The proposed measurement setup provides antenna peak gains and radiation patterns under a tissue equivalent liquid environment for a biomedical application. The antenna gain is calculated by the modified Friis transmission formula for the lossy medium consideration. A liquid thermostat is implemented to maintain a constant temperature of the liquid to achieve precise measurements. Overall, this article deals with the designs, experimental results, and validation of the proposed measurement setup.

The capabilities of active load-pull are extended to be compatible with the characterization requirements of high-power base-station applications. The proposed measurement setup provides ultra-fast high-power device characterization for both CW, as well as, pulsed, duty-cycle controlled, operation. The realized system has the unique feature that it can handle realistic complex modulated signals like W-CDMA with absolute control of their reflection coefficients vs. frequency.

The rupture of the contact wire (CW) of a railway overhead contact line (OCL or catenary) is expected to be a rare event. However, when it occurs, and a pantograph transits under the already broken section of the CW, this can have catastrophic consequences for the pantograph which in turn can cause a further extension of the damaged portion on the OCL with a consequent disruption in the service and cause there to be a long time before the operating condition can be restored. Therefore, the prevention of such events through effective catenary monitoring is gaining significant attention. The purpose of this work is to investigate the feasibility of a monitoring system that can be installed at each end of an OCL section which is able to detect the occurrence of a broken CW event, sending an alert to the management traffic system, so as to stop the train traffic before the damaged catenary is reached by other trains. A nonlinear dynamic analysis is employed to model the OCL’s response following a simulated CW rupture and identify a set of variables that can be measured at the line’s extremities related to the occurrence of breakage in the CW. Several locations of the rupture of a CW section along the line are simulated to investigate the influence on the time pattern of the measured variables and consequently on the extraction of a signature. Finally, a proposed measurement setup is presented, combining accelerometers and displacement transducers, instead of the direct measurement of the axial load of the OCL conductors.

The use of a vertically oriented rod antenna is requested by several standards for the measurement of radiated emissions below 30 MHz both from civil and military equipment. In all the cases, the measurements are performed with the antenna at short electrical distances from the equipment under test. The measurement results depend on the geometrical and electrical parameters of the setup in a not negligible and complex way. For this reason, during the years technical committees have tried to define a setup with boundary conditions able to provide the same measurement results whenever repeated. To that end, different bonding solutions for the counterpoise of the rod antenna have been proposed, obtaining different advantages and drawbacks. In this framework, in this article the authors describe the results of numerical and experimental analysis activities performed on the spatial distribution of the electric field under measurement in the proposed measurement setup. The activities have been done in order to define the optimal operative conditions that allow to obtain measurement results providing a faithful representation of the disturbance field generated by the equipment under test in undisturbed conditions, i.e., the field under measurement. Experimental activities have been performed with an innovative rod antenna with an integrated receiver that can also be operated in a completely isolated mode by using an optical fiber interconnection for its remote control.

Specific Absorption Rate is a measure of the rate at which electromagnetic energy is absorbed by a living dielectric object while exposed to microwave radiation. Specific Absorption Rate estimation in different standard human phantoms is commonly performed to safeguard human health from possible hazards of cell phone radiation. Plants and flowers that possess reasonably high dielectric properties are also continuously exposed to electromagnetic radiation from wireless communication antennas installed on towers and high rise buildings. Hence, considerably high electromagnetic energy absorption rate is expected among different plants and flowers too; and consequent investigations on possible biological effects should also be carried out. With this background, this work aims at dielectric properties characterization of hibiscus flowers and estimating Specific Absorption Rate for a typical hibiscus flower structure at 2.45 GHz ISM band. Linearly polarized plane wave irradiation has been impinged as per global electromagnetic regulatory guidelines prescribed by International Commission on Non¬Ionizing Radiation Protection. Estimated maximum local point, 1g averaged and whole body averaged Specific Absorption Rate data have been reported and observed to be of significant level.

A novel, low-cost and compact microwave sensor based on Electromagnetic Bandgap Structure (EBG) has been proposed to detect and sense the change in the reflection coefficient of a compact Koch fractal patch antenna for different dielectric constant liquids at 2.45 GHz ISM Band. The proposed design of a sensor is composed of a 2 × 2 array of square unit cells as an EBG plane, and a Koch modified fractal antenna designed on a specialized polymer-based Rogers 5880 substrate. A trench is etched out from the substrate in between the 2 × 2 unit cells of EBG plane to act as a microfluidic channel for deposition of the liquids. A variation in the reflection phase of an EBG plane is observed when these etched out microfluidic channels are filled with liquids of different permittivities using a patch antenna placed on it at a height of $0.082\lambda_{0}$ . To verify this concept, three liquids of different dielectric properties (butan-1-ol, ethanol, and methanol) are filled in the microfluidic channels of EBG plane. A significant change in the reflection coefficient of a patch antenna is observed with good quality factor and sensitivity. Our demonstrated EBG-based sensor remarkably decrease the cost and the size of a sensing platform without compromising sensitivity and provides a route to realize highly efficient and affordable sensor for dielectric characterization in liquids and detection of contaminants in daily edible items.

In this paper, electronically steerable microstrip and leaky wave antennas using tunable ferroelectric material are proposed. These antennas are lightweight, low volume, low profile, and conformal. They have low fabrication costs and are easily mass produced. They are thin and do not perturb the aerodynamics of a host automobile or aircraft. Linear, circular, and dual polarization are achieved with simple changes in feed position. Beam steering is accomplished by varying the relative phase between radiating elements. In planar array, both horizontal and vertical beam can be combined to provide full scanning capabilities. Tunable ceramic phase shifters are used in these antennas. In microstrip antennas, they are deposited as thin films on the feed lines whereas in the leaky wave antennas they have been used as a traveling waveguide with a ground plane on one side and metallic periodic grating on the opposite side. The dielectric properties of the ferroelectric material are changed by a bias voltage applied to the waveguide which in turn controls the leaky wave direction of the antenna. A simple experiment is presented which shows a good agreement with the theoretical prediction.

Polymer matrix composites with lightweight, low dielectric constant (ε) and dielectric loss tangent (tan δ), high‐temperature resistance, and excellent mechanical properties are urgently needed in the fields of aviation, aerospace, transportation, and wireless communication services. In this work, 3D woven spacer Kevlar/polyimide composites (3DKPC) with excellent dielectric properties and robust mechanical properties were designed and obtained by combining 3D weaving technology and thermal imidization process. Results show that the volume density of the prepared composites is as low as 0.24 g·cm −3 , but its compressive strength can be up to 6.24 MPa. The dielectric constant and loss tangent of 3DKPC at room temperature are extremely low, with the value of ~1.32 and 6.9 × 10 −3 , respectively. Moreover, the compressive strength retention rate is more than 96% and the dielectric constant can be consistently lower than 1.36 when the temperature increases from 25 to 300°C, demonstrating the outstanding mechanical and dielectric stability of 3DKPC. In addition, as an application example of resulting composites, a microstrip antenna with 3DKPC as the substrate material was designed, followed by the simulation of its electromagnetic properties via High Frequency Structural Simulator. The results display that the gain of the microstrip antenna is 6.2 dB, which is superior to those of many other reported microstrip antennas, indicating that the 3DKPC proposed here has great application potential in aerospace, wireless communication, and other fields.

Microstrip Antennas (MSAs) have several advantages, including that they are light weight and small volume and that they can be made conformal to the host surface. In addition, MSAs are manufactured using printed circuit technology, so that mass production can be achieved at a low cost. In comparison to traditional antenna elements, however, the electrical performance of the basic microstrip antenna suffers from a number of serious drawbacks, e.g. narrow bandwidth; high feed network losses, poor cross polarization, and low power handling capacity. The major disadvantage of the microstrip-patch antenna is its inherently narrow impedance bandwidth of only a couple of percent. Intensive research is going on to develop bandwidth-enhancement techniques by keeping its size as small as possible. Accordingly, increasing the bandwidth of the MSA has been a primary goal of research in the field. We present here a compact two-layer electromagnetically coupled patch antenna with an impedance bandwidth of 35%. The radiation efficiency is obtained 90% in the operating band. The designed antenna is right-hand circularly polarized and operates in the 2.4 GHz ISM-band frequency The proposed structure has been initially optimized using IE3D software followed by experimental verification on Agilent Vector Network Analyzer, E5062A.