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A simple method of depositing titanium dioxide (TiO2) nanoparticles onto graphene oxide (GO) as a catalytic support was devised for photocatalytic degradation of methylene blue (MB). Thiol groups were utilized as linkers to secure the TiO2 nanoparticles. The resultant GO-supported TiO2 (GO-TiO2) sample was characterized by transmission electron microscopy (TEM), near-edge X-ray absorption fine structure (NEXAFS), and X-ray photoelectron spectroscopy (XPS) measurements, revealing that the anatase TiO2 nanoparticles had effectively anchored to the GO surface. In the photodegradation of MB, GO-TiO2 exhibited remarkably enhanced photocatalytic efficiency compared with thiolated GO and pure TiO2 nanoparticles. Moreover, after five-cycle photodegradation experiment, no obvious deactivation was observed. The overall results showed that thiolated GO provides a good support substrate and, thereby, enhances the photodegradation effectiveness of the composite photocatalyst. [ABSTRACT FROM AUTHOR]

A broadband and high gain tapered slot antenna (TSA) by utilizing a broadband microstrip- (MS-) to-coplanar stripline (CPS) balun has been developed for millimeter-wave imaging systems and sensors. This antenna exhibits ultrawideband performance for frequency ranges from 70 to over 110 GHz with the high antenna gain, low sidelobe levels, and narrow beamwidth. The validity of this antenna as imaging arrays is also demonstrated by analyzing mutual couplings and 4-element linear array. This antenna can be applied to mm-wave phased array, imaging array for plasma diagnostics applications. [ABSTRACT FROM AUTHOR]

A band-rejection type RF switch, which has very high off-state isolation, low on-state insertion loss, and adjustable bandwidth, is proposed using a dual-mode ring resonator and two PIN diodes. To enable sharp band stop and dual-mode transmission, the ring resonator is directly fed using nonorthogonal feeding. Two PIN diodes are mounted in shunt after a quarter-wavelength transmission line from each feeding point, to turn the switch on and off and to reduce the size of the ring resonator. To estimate the practicable transmission characteristics of the proposed switch in relation to the angle of feeding and the wire-bonded PIN diodes, a lossy transmission-line equivalent circuit model is proposed, and even–odd mode analysis is carried out. The calculated frequency response shows good agreement with the measurement. The fabricated switch exhibits off-state isolation of 43.08 dB, and on-state insertion loss of 0.74 dB, within the range of 2.298–2.401 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:947–950, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25080 [ABSTRACT FROM AUTHOR]

A spectral inverse technique, applying the moment-method procedure with a series expansion for the induced field in each enlarged cell, is suggested to reconstruct permittivity profiles of inhomogeneous dielectric objects. In particular, averaging the reconstructed permittivity distribution over each cell with a weighting function becomes an effective tool to regularize the error arising from a Gaussian random noise of the scattered field. [ABSTRACT FROM AUTHOR]

For the size reduction and sharp attenuation of the low-pass filter in lower RF frequency range, a semilumped elliptic-function low-pass filter was proposed using microstrip meander line, chip capacitor, and radial stubs. To estimate more accurate inductance of microstrip meander line, it was modeled in an inhomogeneous dielectric environment, and then the calculated inductance was compared with the conventional case. To provide an additional attenuation pole in stop-band, radial stubs were added to the proposed structure. The 3-order low-pass filter has a cutoff frequency of 1GHz and dimension of 14.6 × 16.3 mm2 on the substrate with a relative dielectric constant of 3.38. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1777–1779, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22545 [ABSTRACT FROM AUTHOR]

Compact semilumped bandstop resonators are simply designed using parallel-coupled microstrip line and lumped capacitors. The lumped capacitors loaded in between coupled lines increase the odd mode electrical length, and the frequency of transmission zero can be controlled by the lumped capacitors. For the accurate estimation of the transmission zero frequency, the four-port impedance parameter is derived using the even/odd mode analysis in an inhomogeneous dielectric medium. Two types of the bandstop resonators are proposed using the coupled line with the length of λg/8 (@2 GHz), and the calculated and measured results of transmission zero frequency are compared in 1–3 GHz ranges. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 367–369, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22135 [ABSTRACT FROM AUTHOR]

A design of an ultra-wideband transition from a stripline (SL) to a conductor-backed coplanar waveguide (CBCPW) is presented. The proposed transition provides smooth field transformation between adjacent transmission lines. The transition in a back-to-back configuration is measured to have <1.5 dB insertion loss and >10 dB return loss up to 25 GHz. The proposed transition can be easily integrated with SL-based circuits for various applications. [ABSTRACT FROM AUTHOR]