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Convergence rates of coupled electric field integral equation (EFIE) and thin dielectric sheet (TDS) surface integral equation is improved using a Calderon multiplicative preconditioner (CMP) for efficient analysis of densely discretised structures comprising perfect electric conductors and thin dielectric layers. When relative permittivity of the thin dielectric layer is not high, the integral operator for the TDS tends to have fast convergence rate than that of the EFIE because the TDS is derived from a volume EFIE that is well-posed. However, the integral operator for the EFIE is both unbounded and ill-posed when it is applied to densely discretised surfaces. Thus, the coupled EFIE and TDS integral equation have a slow convergence rate in an iterative solver. The proposed method shows fast convergence rate by application of the CMP to the EFIE-TDS. As a result, an iteration number in the iterative solver is reduced in the proposed method. [ABSTRACT FROM AUTHOR]

A novel wideband planar monopole antenna is proposed for wireless communication services and digital TV broadcasting signal reception in the ultra-high-frequency (UHF) band. The proposed antenna is a variation of the conventional planar triangular monopole. To obtain wideband characteristics and high gain, a notch is cut at the top side, and several steps are added to the oblique sides of a triangular patch. In addition, slopes are created at the front- and back-side ground planes, in order to further increase the bandwidth. Impedance matching has been optimised by adjusting the gap between the patch and the ground plane. The measured results show that the bandwidth is 2610 MHz in the range of 450-3060 MHz (148.72% bandwidth), which covers the entire UHF band. In the operating frequency range, the peak and the average peak gains in the Eplane were 2.73-6.09 and 4.62 dBi, respectively. [ABSTRACT FROM AUTHOR]

This study presents a novel wrist pulse detection system based on the variation of transmission coefficient (S21) of coupled resonators. Radiated signal from one resonator is modulated by the wrist pulse and transmitted to the other resonator. To improve sensitivity of the system, a radio-frequency (RF) interferometer concept is employed and its validity is mathematically analysed. Full-wave electromagnetic simulation is conducted with the wrist phantom model to predict the transmission coefficient between resonators. The peak level of the S21 is around -10 dB and the resonance frequency shifts to higher frequency as the distance between the resonator and wrist increases. A prototype of the system is fabricated and tested to show sensitivity enhancement around the 2.4 GHz industry-science-medical (ISM) band. Experimental results reveal that the wrist pulse signal measured by the RF interferometer system is in exact coincidence with the reference finger sensor. Also, the sensitivity is enhanced about 23 dB with the RF interferometer system based on the measurement results. [ABSTRACT FROM AUTHOR]

Pade-Chebyshev approximation of Clenshaw-Lord type with method of moments is proposed for wide-band analysis of an arbitrary-shaped perfect electric conductor structure. Moreover, various Chebyshev polynomials, such as first, third, and fourth kinds, are used to express the singular points in the graph to display the expected result for scattering characteristics. The proposed algorithm has a wide radius of convergence due to the use of Chebyshev polynomials and improves calculation speed because Clenshaw-Lord-type Pade approximation requires fewer sampling points than Maehly-type Pade approximation in the derivation of the rational function. The results of the proposed method agree very well with the exact solution and reveal its possibility of obtaining more accurate solution than the asymptotic waveform evaluation technique. [ABSTRACT FROM AUTHOR]

To supply a power distribution network with stable power in a high-speed mixed mode system, simultaneous switching noise caused at the multilayer PCB and package structures needs to be sufficiently suppressed. The uni-planar compact electromagnetic bandgap (UC-EBG) structure is well known as a promising solution to suppress the power noise and isolate noise-sensitive analog/RF circuits from a noisy digital circuit. However, a typical UC-EBG structure has several severe problems, such as a limitation in the stop band's lower cutoff frequency and signal quality degradation. To make up for the defects of a conventional EBG structure, a partially located EBG structure with decoupling capacitors is proposed in this paper as a means of both suppressing the power noise propagation and minimizing the effects of the perforated reference plane on the signal quality. The proposed structure is validated and investigated through simulation and measurement in both frequency and time domains. [ABSTRACT FROM AUTHOR]

This article presents a high-power and high-efficiency saturated Doherty amplifier using a GaN high electron mobility transistor for 3.5 GHz Worldwide Interoperability for Microwave Access application.The saturated Doherty amplifier is a Doherty amplifier based on class-F amplifiers, resulting in higher efficiency than a conventional Doherty amplifier. The distributed-type harmonic control circuit is located between a power transistor and an output matching circuit. From the measured results for a continuous wave of 3.5 GHz, the saturated Doherty amplifier attains a high P3dB of 45 dBm and a power gain of about 8.8 dB. Also, the proposed Doherty amplifier provides a high power-added-efficiency (PAE) of 37.7% and a drain efficiency of 42.7% at 6-dB back-off output power region from P3dB, which are 8.7% and 5.7% higher than those of the conventional Doherty amplifier. Compared to the single class-AB amplifier, we obtain 17.7% and 19.7% improvement of PAE and drain efficiency, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 570–573, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24977 [ABSTRACT FROM AUTHOR]

In this article, new type of planar inverted F antenna (PIFA) is presented. The radiating element of the antenna is folded to the backside of the substrate. Moreover, a substantial improvement in the bandwidth can be achieved by optimizing the locations of the two via holes that connect the radiating elements on top and bottom side of the substrate. Measured results show that more than 6.7% increase in the relative bandwidth around 2.6 GHz compare to the uniplanar topology, while maintaining nearly the same radiation patterns. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2413–2416, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24610 [ABSTRACT FROM AUTHOR]

Background. Artemisinin is of special biological interest because of its outstanding antimalarial activity. Recently, it was reported that artemisinin has antitumor activity. Its derivatives, artesunate, arteether, and artemeter, also have antitumor activity against melanoma, breast, ovarian, prostate, CNS, and renal cancer cell lines. Recently, monomer, dimer, and trimer derivatives were synthesized from deoxoartemisinin, and the dimers and the trimers were found to have much more potent antitumor activity than the monomers. Methods. We evaluated the antitumor activity of artemisinin and its various derivatives (dihydroartemisinin, dihydroartemisinin 12-benzoate, 12-(2′-hydroxyethyl) deoxoartemisinin, 12-(2′-ethylthio) deoxoartemisinin dimer, deoxoartemisinin trimer) in comparison with paclitaxel (Taxol), 5-fluorouracil (5-FU), cisplatin in vitro. Results. In this study, the deoxoartemisinin trimer had the most potent antitumor effect (IC50 = 6.0 μM), even better than paclitaxel (IC50 = 13.1 μM), on oral cancer cell line (YD-10B). In addition, it induced apoptosis through a caspase-3-dependent mechanism. Conclusion. The deoxoartemisinin trimer was found to have greater antitumor effect on tumor cells than other commonly used chemotherapeutic drugs, such as 5-FU, cisplatin, and paclitaxel. Furthermore, the ability of artemisinin and its derivatives to induce apoptosis highlights their potential as chemotherapeutic agents, for many anticancer drugs achieve their antitumor effects by inducing apoptosis in tumor cells. © 2006 Wiley Periodicals, Inc. Head Neck, 2007. [ABSTRACT FROM AUTHOR]

In this paper, an efficient time domain formulation is proposed for a low-frequency scattering by a complicated inhomogeneous dielectric scatterer. The formulation is based on the Born approximation and a sampling theorem. To extend the valid region of the proposed solution, the Rayleigh scattering formulation for a small dielectric object is used to modify the Born current inside the scatterer. In order to verify the obtained formulation, scatterings by several canonical objects such as a cubic box and a sphere are compared, which are calculated by the proposed formulation and the known exact or approximate solutions of a Mie series and the Rayleigh scattering. In addition, scattering by a human head is investigated at a very low-frequency band (< 100 Hz). For the simulation, two excitations are considered: plane wave incidence from outside the head and an artificial point source located inside the head. The head model is discretized by a 3 × 3 × 3 mm3 cubic box, which is comprised of eight types of tissue. These are blood, bone, fat, grey matter, white matter, muscle, skin and vitreous humor. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents the measurement of electromagnetic wave propagation in subway tunnels at f = 2.6425 GHz. The main goal of this work is to obtain more accurate knowledge of the propagation characteristics in straight and curved tunnels. Measurements have been conducted in four different types of tunnel courses: a straight tunnel, two curved tunnels (with 245-m and 500-m radius of curvature, respectively), and a tunnel that has both straight and curved sections. From the measured results, we analyze and compare the differences between the straight and curved tunnels, particularly with regard to path loss and the effect of path loss arising from different curvatures, and the characteristics of the combined tunnel (the straight and curved tunnel). The findings presented here should prove helpful in the estimation of link budget for satellite DMB service in tunnels and the determination of accurate propagation characteristics in tunnels. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 383–386, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21357 [ABSTRACT FROM AUTHOR]

In this paper, a variable-width meander-slot antenna fed by CPW is proposed for the use in miniaturized personal-communication devices. By optimizing the slot width of the antenna, we design a uniplanar antenna that is 8% to 12.3% of the size to a conventional rectangular microstrip patch antenna. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 188–191, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20940 [ABSTRACT FROM AUTHOR]

This paper presents a fully integrated low-phase-noise and high-efficiency VCO based on InGaP/GaAs HBT, which shows excellent power-efficiency performance, for 802.11a application. For improved phase-noise performance, an LC filtering technique is adapted. The measured phase noise is -87.8 dBc/Hz at 100-kHz offset frequency and -111.4 dBc/Hz at 1-MHz offset frequency. The phase-noise characteristic is shown to improve by 5 dB after employing the LC filter. The figure of merit (FOM), defined as a function of the phase noise and power efficiency of the fabricated VCO with LC filter, is -172.1 dBc/Hz, which is the best result among the 5-GHz low-phase-noise VCOs. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 123–126, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20564 [ABSTRACT FROM AUTHOR]

This paper presents the performance characteristics of an air-suspended high-Q MEM inductor that is characterized based on an open-short deembedding scheme and used for accurate and reliable evaluation of the parasitic effects experienced from feed lines as well as contact pads. The validity and effectiveness of the de-embedding method are proven with a fixed-length MEM transmission line along with various feed-line topologies. The measured inductances of the 20-μm elevated transmission line provide consistent data, as compared to the simpler open de-embedding method. For more realistic and complicated MEM inductors with 1.5 and 2.5 turns, the characterized inductance values agree very well with the calculated data, based on the Greenhouse algorithm. The measured and calculated inductances are within the 5% range. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 355–358, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20468 [ABSTRACT FROM AUTHOR]

This study attempted to evaluate whether oral lichen planus (OLP) has the potential to progress to oral squamous cell carcinoma (OSCC) by comparing the degree of genetic instability between clinically-curable OLP and lesions that progressed to OSCC. Fifteen cases of steroid-responsive OLP and two cases of lichenoid dysplasia (LD) that progressed to OSCC were used for this study. Chromosome in situ hybridization (CISH) was performed for chromosomes 9 and 17. The fraction of polysomic and monosomic cells for chromosome 9 increased in mucosal epithelium compared to those of lymphocytes in OLP. This difference was statistically significant (P=0.0017, 0.0054, respectively). Two LD patients showed 15.38% and 22.58% of P1 for chromosome 9. In OSCC that developed from LD. the fraction of monosomic cells for chromosome 9 increased by more than 70%. We concluded that LD should be treated as a high-risk premalignant lesion and strongly suggest that the monosomy of chromosome 9 may have a critical role in progress to malignancy from LD. [ABSTRACT FROM AUTHOR]

Two numerical techniques, the finite difference in time domain (FDTD) and the finite element method (FEM) in frequency domain, are employed to characterize microstrip hermetic transition geometries in an effort to investigate high-frequency effects. Measurements performed on these transitions compare favorably with theory. Two different types of transitions have been analyzed from 10 to 25 GHz and have been found to be limited in performance by higher return loss as frequency increases. It is shown that microstrip- through-CPW hermetic transitions in the shielded environment may suffer from parasitic waveguide modes which, however, can be eliminated with the use of vias at appropriate locations. The hermetic wall on top of the CPW section shows a relatively small (≤ 2 dB) effect on the original circuit performance. Similarly, the hermetic bead transition shows good performance at a lower frequency region while it degrades as frequency increases. This indicates the need for very careful characterization of transitions intended for use in microwave and millimeter-wave applications. [ABSTRACT FROM AUTHOR]

This letter presents a novel bio-radar system with phase-locked loop (PLL) for noncontact measurement of vital sign. As the leakage of the phase noise of local oscillator (LO) through antenna is dominant factor for the distances larger than about 30 cm, the performance of a bio-radar system can be improved with the PLL employment. The proposed bio-radar and PLL are implemented by using conventional commercial components, and the measured result shows that the bio-radar system performance is greatly improved with a PLL without any additional digital signal processing. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2074–2076, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25366 [ABSTRACT FROM AUTHOR]

This article investigates the high frequency characteristics of coplanar waveguide (CPW) lines fabricated with inkjet-printing technology on BT substrates. The optimal metallic thickness of a printed CPW line is approximately estimated to be 3 μm. When printed lines with higher electrical conductivity are realized through additional surface preparation steps, the findings of this study suggest that the RF performance level of these printed lines will be comparable to that of the copper clad laminate lines in the microwave frequency region. Finally, aspects of such improvements as well as applications of these types of printed lines are discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 780–782, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24987 [ABSTRACT FROM AUTHOR]

To build a stable power distribution network for high-speed digital systems, simultaneous switching noise (SSN) in multilayer PCBs and packages needs to be sufficiently suppressed. In this article, a novel triangular-type uniplanar compact electromagnetic band-gap with different bridges designed for power/ground planes is proposed for the ultra-broadband suppression of SSN. The SSN suppression performance of the proposed structure is validated both numerically and experimentally. A -30 dB suppression bandwidth for SSN is achieved starting at 800 MHz and extending to 15 GHz and beyond, that is, almost the entire noise band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1356–1358, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24322 [ABSTRACT FROM AUTHOR]

In this paper, a novel polishing method using magnetorheological (MR) fluid is presented in order to improve conductor-surface roughness and achieve high-frequency performance of the electroplated three-dimensional (3D) CPW, where the MR fluid is utilized to efficiently polish uneven and imperfect conductor surfaces resulting from the widely used MEMS process. For the purpose of comparison, two 50Ω CPW lines on glass substrate are fabricated in order to validate the performance of the proposed polishing scheme. From the measurement, the polished CPW lines using the MR fluid show much lower attenuation constants up to a maximum of 0.3–0.54 dB/cm than unpolished CPW lines, according to the geometries used. Thus, it is clear that the proposed MR fluid-based polishing scheme is very effective when used to smooth 3D high-frequency structures and can dramatically improve conductor-loss characteristics. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 405–407, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20318 [ABSTRACT FROM AUTHOR]

In this paper, the performance of a 10-μm-elevated low-loss and low-dispersion elevated coplanar waveguide (ECPW) is presented. It is shown that a wide range of characteristic impedances, encompassing the 40–100Ω range, is obtainable. A very low effective dielectric constant (close to 1) is predicted based on the 3D finite-difference time-domain (FDTD) method and confirmed by measurement. The overlapped configuration on standard silicon reveals the best performance, with a loss of about 0.2 dB/mm, which is much lower than that of a conventional CPW at 40 GHz. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 169–171, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11159 [ABSTRACT FROM AUTHOR]

In this Letter, a new Koch island microstrip patch antenna is proposed. The Koch patch is fractal shaped and characterized by space-filling and self-similarity properties. Due to the space-filling properties of fractal geometry, the proposed antennas are a smaller in size than conventional Euclidean-type ones. The characteristics of Koch patches are demonstrated by experimental results: when the fractal iteration factor is 2.5, then the patch is 45% smaller in size than a conventional square patch, thereby maintaining a radiation pattern comparable to that of a normal square patch. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 15–17, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10359 [ABSTRACT FROM AUTHOR]

In this Letter, a Koch slot loop in the ground plane has been utilized to obtain slow-wave characteristics, and its electrical performances are analyzed with the use of the ABCD matrix approach. The validity of this approach has been verified through experimental results, and this technique was then applied to microstrip patch antennas in order to obtain a small antenna size. The cross-sectional areas of this type of antenna are 47% to 65% smaller than those of conventional square patches. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 87–88, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10381 [ABSTRACT FROM AUTHOR]