Measured Reflection Coefficient Research Articles

Smartphone-Based Blood Lipid Data Acquisition for Cardiovascular Disease Management in Internet of Medical Things

With the ubiquitous deployment of smartphones worldwide recently, biomedical diagnostic devices based on smartphones are potential to be widely used for smart health management on the Internet of Medical Things (IoMT) applications under point-of-care (PoC) settings. Therefore, this paper introduces one smartphone-based blood lipid data acquisition dongle to monitor blood lipid level, including total cholesterol (TC), triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C), using only a fingertip blood drop for cardiovascular disease management. During detection, a thin photochemical test strip that consists of LEDs and detectors is plugged into the compact dongle, where changed color intensities will indicate the lipid determinant concentration from the measured reflection coefficient of the chromogenic product. Such smartphone-based photochemical blood lipid data acquisition dongle was validated by comparing with a clinical analyzer, and reached a correlation coefficient over 0.903 and averaged coefficient of variation (CV)% of 4.575% for blood lipid measurement of 115 patients. The photochemical dongle is, therefore, promising for the future chronic disease management in the IoMT.

Polymer conductive fabric grid array antenna with pliable feature for wearable application

AbstractA flexible microstrip grid array antenna designed on polydimethylsiloxane (PDMS) substrate and copper conductive fabric as the patch and ground plane is presented. The proposed rectangular geometry designed at 15 GHz is made of 19 cells with 22 radiating elements. The proposed antenna achieves almost 40% wideband characteristics at −10 dB reflection coefficient from 11.10 GHz until 16.2 GHz with measured maximum gain of 14.0 dBi in normal state. Analysis on performance of antenna at bend state with various value of bend radius has been done. The measured reflection coefficient shows low sensitivity to bending effect where the antenna operates well at designed frequency which is at 15 GHz. Due to these criteria, it is a suitable candidate for wearable applications.

Miniaturized High-Order-Mode Dipole Antennas Based on Spoof Surface Plasmon Polaritons

A miniaturization method for antennas is developed based on spoof surface plasmon polaritons (SSPPs). With a large phase constant on the SSPPs transmission line, the guide wavelength can be dramatically reduced, with great potential on the miniaturization application of antennas. By introducing a miniaturization factor M , the relationship between M and the phase constant on the SSPPs dipole is studied, providing guidance to the design of miniaturized SSPPs dipoles. Then, SSPPs dipoles operating at 2.4 GHz are designed, including both the odd- and even-resonance dipoles. Simple feeding structures are developed for the odd- and even-resonance dipoles, respectively, and particularly for the even-resonance mode to realize a transition from 50 Ω to very large input impedance of the dipole. The miniaturized SSPPs dipoles operating at the 1st, 2nd, 3rd, and 4th modes are fabricated. The measured reflection coefficients and radiation patterns show good agreements with the simulated results. It can be concluded that the dipole lengths for these modes are reduced by 8%, 11%, 10%, and 13%, respectively, compared with the conventional printed dipoles on the same substrate.

Spiral resonator loaded S‐shaped folded dipole dual band UHF RFID tag antenna

AbstractA miniaturized UHF dual‐band passive RFID tag antenna operating in the 866‐869 and 950‐956 MHz bands is proposed. It consists of an S‐shaped Folded Dipole Antenna (FDA) resonating at 912 MHz, which is intermediary between the two required frequencies. To obtain dual‐band response perturbation method is employed. The electrical length of the FDA changes on loading a 2‐turn spiral resonator (2‐SR) to it. The 2‐SR splits the tag resonance at 912 MHz into two resonance frequencies (867 and 956 MHz). The proposed design is simulated using HFSS and then fabricated. Measured reflection coefficients at 867 and 956 MHz are −13.25 and −13.34 dB, respectively, exhibiting a 10 dB bandwidth of 11 MHz from 859 to 869 MHz and a 5 MHz 10 dB bandwidth from 953 to 957 MHz. Maximum read ranges of 5 m in 866‐869 MHz and 3.3 m in 950‐956 MHz band have been measured.

Optimization and Realization of Quadruple-Ridge Flared Horn With New Spline-Defined Profiles as a High-Efficiency Feed From 4.6 GHz to 24 GHz

In this communication, we present a new optimization and realization of a quadruple-ridge flared horn (QRFH) as a feed for reflector antennas of the square kilometer array (SKA) project. The QRFH has been numerically optimized by spline-defined profiles for both the ridges and the horn sidewall, with a conical cavity in the back short for maximum aperture efficiency. The final aperture efficiency better than (for horizontal polarization) or around (for vertical polarization) 78% over 4.6–8 GHz, 70% over 8–15 GHz, 65% over 15–20 GHz, and 60% over 20–24 GHz in the SKA offset-Gregorian dual-reflector antenna has been achieved. The realization of the horn has been carried out carefully by applying several new mechanical design solutions in order to guarantee accurate positioning of the ridges, the feed pins, and a good electrical contact. The measured reflection coefficients are mostly better than −10 dB and the predicted aperture efficiency based on the measured far-field patterns agrees well with the simulated result. System performance, such as the sensitivity and system noise temperature, is also estimated and presented.

Transparent dual‐band monopole antenna using a μ‐metal mesh on the rear glass of an automobile for frequency modulation/digital media broadcasting service receiving

AbstractA transparent dual‐band monopole (Inverted‐F) antenna using a micro‐metal mesh film (μ‐MMF) designed on the rear glass of an automobile (Hyundai K5) is presented. This design allows the optically transparent antenna to be installed in a wider space, thus overcoming the space limitation typically posed by roof‐mounted shark‐fin antennas. It can also reasonably solve the problem of low reception sensitivity and radiation interference from antennas operating in other service bands. The antenna is a combination of two simple monopoles operating in the frequency modulation (FM) (88–108 MHz) and the digital media broadcasting (DMB) (174–216 MHz) service bands. Measured reflection coefficients (S11) of the transparent antenna using μ‐MMF are under −6 dB (VSWR 3:1) in both the bands, and the radiation pattern shows directive patterns to the outward direction from the car; the average peak gains in the XY plane are 1.1 dB in the FM service band and 8.8 dB in the DMB service band.

Aerosol-Jet Printed Interconnects for 60-Gb/s CMOS Driver and Microring Modulator Transmitter Assembly

We developed an aerosol-jet printing technique to realize an optical transmitter assembly of a microring modulator and a high-speed CMOS driver in which the bonding wires are replaced by aerosol-jet printed silver interconnects. First, the technology is characterized by printing coplanar waveguides (CPWs) test structures on glass and epoxy in order to fully investigate the electro-magnetic behavior of the aerosol-jet printed interconnects. The printed CPWs on glass and epoxy showed a low attenuation of 0.57 and 0.76 dB/mm at 50 GHz, respectively. Then, the aerosol-jet printed interconnects were benchmarked with conventional bonding wires while separately interconnecting the ring modulator without the CMOS driver. The measured reflection coefficient ( $S_{11}$ ) of the aerosol-jet printed interconnects showed an increase in a resonance frequency of 20 GHz compared with Al bonding wires. Furthermore, the optical transmitter was successfully demonstrated at 60 Gb/s and the measured optical eye diagrams were clearly open even after 2 km of standard single-mode fiber. An extinction ratio of 4.63 dB was achieved while applying a drive voltage of 1 $\text{V}_{\mathrm{ pp}}$ .

A new error reduction technique for reflection coefficient measurements for use in quick laboratory tests

ABSTRACTReflection coefficient measurement is one of those fundamental methods for determining the performance of radar absorber materials, and reflections due to these measurements are originated from the discontinuities in the measurement system and they result in error. In this paper, a new technique for the calibration of the scalar reflection coefficient measurements in the frequency range of 3–18 GHz in a portable two-sectioned metallic chamber is being proposed for use in quick laboratory tests with reasonable error (redacted error). Calibration measurements are performed by two calibration standards in frequency domain and transformed to time domain for further calculation. Proposed technique exhibits a good agreement with the theoretical values for especially in compact chambers where plane-wave conditions are not fully satisfied, and it is not in need of any complex time gating process. Furthermore, it does not require considering the phase differences which occurs at the measurement plane, providing a cheap and faster solution, reducing time and complexity in characterization of radar absorber materials. This technique with the mentioned test set-up could supply scalar reflection coefficient measurements with overall 0.55 dB error level and useful for practical applications where high level of accuracy is not required.

Broadband and compact complex ratio measuring unit

AbstractThis study designs and analyzes Complex Ratio Measuring Unit (CRMU) and a Six‐port Reflectometer (SPR) at a center frequency of 2.4 GHz. CRMU is designed using a compact size and wideband 3 dB‐branch line coupler (BLC) and 3 dB‐Wilkinson power divider with enhanced series‐diamond stubs. The usage of these compact components leads to a compact size and improves the operating bandwidth. The idea of designing SPR is based on integrating a CRMU with 2 directional couplers along with isolator rather than a single BLC; to get a signal balance that enhances the quality of the reflection coefficient measurement. From the measurement result, it is found that the bandwidth of the CRMU and SPR is 1.7 GHz and the dimension of the CRMU is 60 × 45 mm. The proposed CRMU is fabricated using RT/duroid 5880 substrate with thickness of 0.38 mm. The dimension of the CRMU is 13 × 6.5 mm. The simulation and measurement results for both CRMU and SPR show good agreement.

Normal incidence sound transmission loss evaluation with a general upstream tube wave decomposition formula

This study presents a method for measuring the normal incidence sound transmission loss of acoustical materials used in classical piping systems from upstream surface complex reflection coefficient measurements only. Based on the standard transfer function method, the wave field of the upstream tube is further decomposed, and the relationship between the complex reflection coefficient and the twice-transmitted wave is deduced. Similar to the so-called upstream surface impedance (USI) method, two microphone locations and air cavities with several depths are required. As a validation of the proposed method, both symmetrical and non-symmetrical materials are investigated. The influence of the air cavity on the experiment result is also discussed. A comparison of the results between the proposed method and existing methods reveals a perfect agreement with the verified USI method.

Radiometric microwave field measurements of the complex dielectric constant of the water surface

The paper describes the new remote method of radiometric in situ measurements of the real and imaginary parts of the dielectric constant (permittivity) of the underlying sea surface, which is an important parameter for remote sensing of the Earth. The method does not require absolute calibration of a radiometer, but uses the black body with the underlying surface temperature, which simplifies the measurement and allows one to measure the effective reflection coefficient at specified polarizations. It is shown that, for a fixed value of the reflection coefficient in sensing to the nadir, R(θ = 0°) = const, the reflection coefficient at the horizontal polarization is almost independent of the of dielectric loss angle. The reflection coefficient at the vertical polarization is most sensitive to the loss angle in the vicinity of the Brewster angle Rv(θ = θBr). The paper presents the results of measurements of the sea surface reflection coefficient using the radiometer operating at frequency of 37.5 GHz. The reflection coefficients at vertical and horizontal polarizations are calculated taking into account the antenna pattern and the distribution of slopes of a weakly roughened sea surface. The paper presents the example of determining the real and imaginary parts of the permittivity based on experimentally measured values of reflection coefficients at incidence angles close to the nadir and the reflection coefficient Rv(θ = θBr) at the Brewster angle. The obtained experimental values correspond to the theory within the limits of diversity of existing models.

Effect of bevel angle on the reflection coefficient from open unflanged pipes.

Pipes terminating in bevel angled cuts are popular for automotive and motorcycle exhaust systems. This letter provides measured reflection coefficients and end impedances obtained from two-microphone experiments using unflanged open-ended pipes with bevel angles of 0°, 30°, and 60° for 0.03 < ka < 0.27, where k is the acoustic wave number and a is the pipe radius. The measurements at 0° match classical pipe reflection coefficient results within uncertainty. However, as the bevel angle increases to 60°, the magnitude of the reflection coefficient decreases by 2%, the end reactance increases by 130%, and the end resistance increases by 24%.

Effects of benthic biology on normal-incidence reflection coefficient measurements

Normal-incidence reflection coefficient measurements have been shown to be sensitive to sediment type based on the structure and amplitude of the returned signal. In contrast to other sediment classification methods such as coring, these measurements can be done quickly and easily over a large area. This type of sediment classification scheme can also be integrated into surveys by single- and multi-beam echo sounders. However, benthic biology can substantially change the normal-incident acoustic return possibly confounding the sediment classification methods while simultaneously providing a method of assessing benthic eco-systems. In this study, a collection of normal-incidence measurements taken in a variety of underwater environments will be analyzed for the effects of benthic biology. The areas surveyed include the Chesapeake Bay, the Arctic, the Western Mediterranean, and Gulf Coast. Each of the datasets will be considered for the presence of benthic biology and its affect on geo-acoustic properties. [Work supported by ONR, Ocean Acoustics.]

Octagonal Shaped Metamaterial Absorber Based Energy Harvester

In this study, a novel octagonal shaped metamaterial based broadband absorber is proposed for energy harvesting at WIMAX wireless communication band. The proposal has an absorption of 99.97 % at 5.5 GHz with a bandwidth of 1 GHz between 5 GHz and 6 GHz in Transverse Electric (TE) mode. Transverse Electric (TE), Transverse Magnetic (TM) and Transverse Electromagnetic (TEM) modes are studied numerically in this paper. In TM and TEM modes, proposed structure has absorption of nearly 96 % and 98 % respectively at 6 GHz. The proposed structure is polarization angle independent which is important for energy harvesting applications. Energy harvesting application is realized by using resistive loads on the design, simulations are parametrically studied on resistive loads and experimental study is realized for reflection coefficient measurement and compared with simulated results. Both experimental and simulated results are complying with each other. The proposed structure has different usage areas in stealth areas, detection and imaging. DOI: http://dx.doi.org/10.5755/j01.ms.24.3.18625

Assessing the stochastic error of acoustic scattering matrices using linear methods

To be able to compare the measured scattering matrices with model predictions, the quality of the measurements has to be known. Uncertainty analyses are invaluable to assess and improve the quality of measurement results in terms of accuracy and precision. Linear analyses are widespread, computationally fast and give information of the contribution of each error source to the overall measurement uncertainty; however, they cannot be applied in every situation. The purpose of this study is to determine if linear methods can be used to assess the quality of acoustic scattering matrices. The uncertainty in measured scattering matrices is assessed using a linear uncertainty analysis and the results are compared against Monte-Carlo simulations. It is shown that for plane waves, a linear uncertainty analysis, applied to the wave decomposition method, gives correct results when three conditions are satisfied. For higher order mode measurements, the number of conditions that have to be satisfied increases rapidly and the linear analysis becomes an unsuitable choice to determine the uncertainty on the scattering matrix coefficients. As the linear uncertainty analysis is most suitable for the plane wave range, an alternative linear method to assess the quality of the measurements is investigated. This method, based on matrix perturbation theory, gives qualitative information in the form of partial condition numbers and the implementation is straightforward. Using the alternative method, the measurements of higher order modes are analyzed and the observed difference in the measured reflection coefficients for different excitation conditions is explained by the disparity in modal amplitudes.

자동차 전면 글래스용 FM 대역 투명 모노폴 안테나

A transparent antenna designed on the front glass of an automobile operating in the FM broadcast band(88～108 MHz) is proposed. A transparent antenna designed on the front glass of the automobile to avoid space limitation is typically positioned as a roof-mounted shark-fin antenna. An antenna designed on the front glass can reasonably solve the problems of low reception sensitivity and radiated interference from antennas for other service bands. The front glass has a unique closed-line structure, and this structure causes the surface current to flow to the front glass’s surroundings; thus, the first resonance is caused before the broadcast band. Through the use of this closed-line structure, the surface current distribution is controlled, and an antenna for which the first resonance is operating in the frequency-modulated(FM) band can be designed. Moreover, the use of a micro-metal-mesh film that is a transparent electrode, suitable for designing a radio frequency device, enables the antenna to minimize visual perception through its transparency. The measured reflection coefficient(S11) of the antenna is less than −6 dB, and the average peak gain is −0.9 dB in the FM band. Experiments show that the transparent antenna on the front glass offers both the space and design freedom required to develop future automotive antennas.

Integration of Wireless Coil and Bluetooth Antenna for High Charging and Radiation Efficiencies

In this paper, a wireless charging coil integrated with a Bluetooth antenna is proposed. The equivalent circuit model is developed to analyze this multifunctional coil. The outermost turn of the coil is appropriately designed in order to improve the radiation efficiency of the antenna. In this way, the radiation frequency of the coil is determined by the length of the outermost coil. Meanwhile, the inductance of the coil is adjusted to achieve high charging efficiency. When the coil is taken as a Bluetooth antenna, the measured reflection coefficient has achieved a fractional bandwidth of 8.3%, covering a frequency range of 2.3–2.5 GHz, with $\vert {S} _{11}\vert dB. The measured radiation efficiency of the antenna is about 62% at 2.4 GHz. When the coil is applied, the system charging efficiency is about 61%. In particular, the entire circuit module is fabricated on the low-cost FR4 printed circuit board. It can be expected that both the radiation and charging efficiencies can further be improved by using low-loss substrate.

An Antenna Proximity Sensor for Mobile Terminals Using Reflection Coefficient.

This paper presents a new antenna proximity sensor for mobile terminals based on the measured reflection coefficient using a bidirectional coupler which is positioned between the main antenna and the front-end module. Using the coupled forward and reverse long-term evolution signals by the bidirectional coupler, the reflection coefficient looking into the antenna was calculated in the base-band processor. The measured reflection coefficients showed clear differences for both the types of objects, and the distances between the terminal and the objects. The proposed antenna proximity sensor showed a recognition distance that was approximately 5 mm longer than that of a conventional capacitive proximity sensor.

Correlation between Reflection Coefficient, Dielectric Properties and Brix Level of Malaysian Oranges at Microwave Frequencies

This paper presents sweetness degree (°Brix) prediction of the Malaysian oranges using microwave technique. Experimental measurement using monopole sensor and reflectometer was done in order to correlate the relationship between measured reflection coefficient, &lt;em&gt;S&lt;/em&gt;&lt;sub&gt;11&lt;/sub&gt; of the orange and its sweetness level. Up to fifty orange samples were freshly plucked from local grower’s farm and tested. The unique design of the monopole sensor’s holder is made of nylon. The experiment test bed was set up based on the standard dimension of monopole sensor available in the market. The operating frequency is focusing on 2.2 GHz as it shows significant sensitivity for determining Malaysian local oranges sweetness level.

A Simulation-Assisted Non-destructive Approach for Permittivity Measurement Using an Open-Ended Microwave Waveguide

A new convenient and non-destructive permittivity measurement method is presented. No physical cut of specimens is needed here for material characterisation. In the setup, the material under test is placed in the near-field region of a microwave open-ended waveguide. An electromagnetic model of the setup is built in the Computer Simulation Technology simulation software. Employing optimisation, the permittivity is obtained from the measured reflection coefficients hbox {S}_{11}. Using the same technique, the effect of the model size is investigated that could reduce the modelling effort for large structures. The efficiency of a traditional method (i.e., Newton) and an intelligent algorithm (i.e. particle swarm optimisation) for permittivity calculation is thoroughly studied and compared. The proposed methodology is validated by experimental data. It is demonstrated that the proposed method can provide more accurate permittivity results than the intrusive in-waveguide measurement. The proposed methodology can contribute to electromagnetic analysis, thickness measurement and non-destructive evaluation.