Sheau-Shong Bor

A WIDEBAND WIDE-STRIP DIPOLE ANTENNA FOR CIRCULARLY POLARIZED WAVE OPERATIONS

A thin dipole antenna is a well-known antenna with linearly polarized wave operation. In this work, a wide-strip dipole antenna is proposed for circularly polarized wave operations. To obtain circularly polarized (CP) wave operations, there are two conditions to be satisfled. One is that the antenna must have two degenerated orthogonal modes with difierent resonant frequencies. The other is that the phase difierence of two orthogonal modes is 90 degrees. To match the flrst condition, the slab width W is tuned to generate current distributions directed in two difierent directions. In addition, the second condition is matched by asymmetric feeding point by adjusting the overlapped square width C. The parametric study is completed by the Ansoft HFSS simulator. Simulated results reveal that the CP wave is mainly in∞uenced by the slab width W. The in∞uences of the parameters C and d on the performances of the proposed antenna are also investigated in this paper. Taking i8dB as reference, there are two working bands for this proposed antenna and the measured center frequencies are 0.66GHz and 2.04GHz, respectively, and the corresponding bandwidths are 0.27GHz (40%) and 1.78GHz (87%), respectively. In addition, the measured center frequencies and bandwidths of the axial ratio are 1.94GHz and 0.53GHz (27%), respectively.

High-sensitivity temperature-independent differential pressure sensor using fiber Bragg gratings.

By means of novel packaged-structure design, a temperature independent differential pressure sensor based on fiber Bragg gratings with high sensitivity is experimentally demonstrated. The differential pressure sensitivity of the sensor can reach to 821.87nm/MPa. This device can also be used for simultaneous measurement of temperature and differential pressure, which is suitable for applications involving measurement of liquid level, liquid density or specific gravity detection.

Miniaturized Dual-Band CPW-Fed Annular Slot Antenna Design With Arc-Shaped Tuning Stub

The design of a miniaturized dual-band CPW-fed annular slot antenna with arc-shaped tuning stub is proposed. The proposed feeding structure, which includes the arc-shaped tuning stub and a 50- transformer, is connected to the extremity of the CPW fed-line, achieving the dual-band input impedance matching. The return loss of the proposed design exhibits that two wide operating bands are over the bandwidths of 30.8% and 24.0%, respectively. By modifying the angle of the arc-shaped tuning stub, the first-higher order resonant mode can be shifted to the lower frequency band to combine with the fundamental mode of the annular slot, achieving the broadband operation with the bandwidth of 3048 MHz (78.4%). Moreover, the miniaturized design indicates an embedded strip is protruded from the ground plane into a slit, revealing the center frequencies of two resonant bands from 2752 to 1738 MHz (size reduction 60%) and 5022 to 3760 MHz (size reduction 44%), respectively. Two resonant bands of the prototype show the broadside radiation patterns with the maximum peak antenna gains of 3.8 dBi and 5.1 dBi, respectively.

Single-Feed Circularly Polarized Aperture-Coupled Stack Antenna With Dual-Mode Square Loop Radiator

The authors propose a compact single-feed stack antenna consisting of a square loop radiator with perturbation, an aperture-coupled structure, and a straight-strip feed line for circular polarization (CP) and unidirectional radiation applications. This perturbation applies both dual-mode and orthogonal-mode effects simultaneously in the square loop resonator to present bandwidth and CP characteristics. The stack antenna presents the desired axial ratio (AR) bands of 2.42 GHz with 3-dB bandwidth (BW) = 62 MHz (2.5%). The circular polarization is demonstrated with AR spectrum and orthogonal modes distributions. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns, and current distributions.

High-sensitivity simultaneous pressure and temperature sensor using a superstructure fiber grating

In this paper, we show that both pressure and temperature can be measured simultaneously by using a high-sensitivity fiber sensor. This sensor has a superstructure fiber grating (SFG) encapsulated in a polymer-half-filled metal cylinder, which has two openings on opposite sides of the wall of the polymer, to sense the pressure. The sensed pressure is transferred into axial extended-strain. The variation of pressures and temperatures will cause the variation of the center-wavelength and reflection of the SFG simultaneously due to the optical response of the SFG composed by the fiber Bragg grating (FBG) as well as long-period grating (LPG). Thus, the sensor can be used for measuring pressure and temperature simultaneously. It has a pressure sensitivity of 3 times 10-2 MPa-1, better than that using only a bare FBG. Temperature sensitivities in both 0.02 nm per degC and 0.16 dBm per degC have experimentally been obtained. This fiber sensor can be applied for boiler as well as for the underwater depth measurement

Electromagnetic backscattering from aircraft propeller blades

This paper gives a theoretical solution to the problem of determining the electromagnetic backscattering and Doppler spectrum of an aircraft propeller as presented to a radar operating in the 8-12 GHz band. At this band for all practical aircraft propeller the electromagnetic backscattering regime is in the optical region. The solution proceeds by modeling the aircraft propeller as a set of multiple skew-plated metal fan blades in the presence of a linearly polarized EM wave. Based on the quasi-stationary method combined with physical optics and physical theory of diffraction equivalent currents techniques are used to analyse the backscattering from aircraft propeller blades. Experimental results indicated that, in the far zone, the field can be considered as harmonic and expressions for the spectral components of the field are obtained. The observed waveforms are found to be in good agreement with theoretical results.

A platform for transcoding heterogeneous markup documents using ontology-based metadata

As new standards, markup languages, protocols, and client devices continue to emerge, the main problem of existing transcoding systems is the lack of intelligence to cope with the heterogeneous effects, including various transcoding policies, markup documents, device constraints, and server platforms. This study proposes a new approach, called hybrid transcoding, to combine the traditional transcoding technologies based on ontology-based metadata to improve these heterogeneous problems. Additionally, the heterogeneous markup document transcoding (HMDT) platform, based on the proposed hybrid transcoding and web services technologies, is also presented to serve as a transcoding service broker to facilitate interoperability between distributed heterogeneous transcoders. To demonstrate the feasibility of HMDT platform, an application scenario of hybrid transcoding is implemented to convert HTML forms into various client devices.

CPW-fed PIFAS with a Capacitively Coupling Slot for Dual Wide-Band Operations

CPW-fed planar inverted-F antennas (PIFAs) with small ground plane for dual-band performance are proposed. The lower band and upper band can be selected independently: PIFA is for the lower band, and capacitively coupling slot is for the upper band. Moreover, the frequency ratio of upper band to lower band can be obtained from 1 to 3.1. The proposed antenna with wider frequency ratio will enable antenna engineer to design dual-band antenna easily. The radiation patterns for the lower band are decided by the PIFA with the quarter-wavelength electric L-shaped monopole patterns, and those for the upper band are dominant over the coupling slot with the half-wavelength magnetic dipole patterns. Hence, both patterns in the dual-band are near omni-directional. An antenna example is given for WLAN dual-band applications. Simulated data are consistent with the measured ones. Measured impedance bandwidth for 2.4 GHz band is 1090 MHz (47.9%), and that for 5 GHz band is 1180 MHz (20.6%). Additionally, through a suitable adjustment in antenna parameters, a wider bandwidth of 1970 MHz (51.2%) can be obtained with center frequency at 3.845 GHz. The radiation patterns and gains are also studied and analyzed.

Spectral domain analysis of open cavities

Application of the incident /reflected wave boundary condition to the wave equation for a weakly irregular waveguide leads to a spectral domain analysis of the open cavity (Fig. 1) with a typical maximum -field spectrum shown in Fig. 2. Low Q value due to the diffraction loss and the consequent overlapping of neighboring modes are the two reasons for the broadening of resonant lines. The latter also lowers the spectral domain Q values relative to those based on the commonly employed time domain approach.

Antennas with Two Shorted Rectangular-ring Slots Coupled by Microstrip Line for the Opposite Sense CP in the Wide-Band Operations

The two shorted rectangular-ring slots antenna fed by a microstrip line is presented to achieve the novel characteristic of wide impedance bandwidth with the opposite sense circular polarizations (CP). If the two rectangular-ring slots are arranged to be shorted in the opposite direction, reversely circular polarization will be obtained in the different frequency band. A microstrip line is used to feed power and to couple to the two shorted rectangular-ring slots. Meanwhile, the impedance and axial-ratio (AR) matching are done by adjusting lines parameters. An antenna example is given to result in the lower and upper bands in the 1575 MHz and 1.8 GHz bands. The measured impedance bandwidth is 27.54% which covers the 1575 MHz and 1.8 GHz band. But the polarization for the lower and upper bands is right- and left-hand CP, respectively. The frequency ratio of opposite sense CP band can be lowered to 1.13 and then, give a good choice to design the low frequency ratio with opposite sense CP. The measured ARs center frequency and bandwidth for the lower band is 1.602 GHz and 2.81% respectively, and the minimum AR and antenna gain is 0.987 dB and 3.8 dBic for RHCP, respectively. Meanwhile, the ARs center frequency, bandwidth, antenna gain for the upper band are 1.820 GHz, 3.24%, and 2.43 dBic for LHCP, respectively. Radiation patterns in both bands are broadside radiations and similar to each other except the opposite sense CP characteristic.