Arokiaswami Alphones
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Publication Bragg reflection filter by periodic photoexcitation of a semiconductor waveguide(1999-10-20) Alphones, A.; CENTRE FOR WIRELESS COMMUNICATIONSThe propagation characteristics of periodically photo-induced plasma grating on a semiconductor slab waveguide have been analyzed by the coupled-mode theory, and the Bragg reflection characteristics of millimeter waves have been investigated. By periodic optical illumination, the photoinduced plasma grating structure is modeled as a permittivity-modulated waveguide, and is systematically analyzed. The variation of phase and attenuation constants at the first Bragg resonance is numerically evaluated. The results can be used for optically controlled filters and switches in the millimeter-wave band.Publication Periodically photoinduced Bragg reflection filter(1999) Alphones, A.; CENTRE FOR WIRELESS COMMUNICATIONSBy periodic optical illumination, the photoinduced plasma grating structure is modeled as permittivity modulated waveguide and is systematically analyzed by coupled mode theory. The variation of phase and attenuation constants at the first Bragg resonance is numerically evaluated. The results could be used for optically controlled filters and switches at millimeter wave band. © 1999 IEEE.Publication Optical control on millimeter wave radiation in a semiconductor backed periodic structure(1998) Alphones, Arokiaswami; CENTRE FOR WIRELESS COMMUNICATIONSThe leaky wave radiation characteristics of a corrugated dielectric waveguide backed by a partially plasma occupied semiconductor slab and its optically-controlled behavior were analyzed by a singular perturbation technique based on multiple space scales. By optical illumination, the plasma-induced semiconductor was capable of controlling the radiation characteristics of a leaky wave. With the increase in optically-induced plasma density, leakage constant and radiation efficiency improved.Publication Frequency-dependent behavior of optically illuminated HEMT(2001-07-20) Yajian, H.; Alphones, A.; CENTRE FOR WIRELESS COMMUNICATIONSAn analysis of the ac characteristics of an AlGaAs / GaAs HEMT under illumination with modulated light has been carried out for a small-signal condition. A new model for the photovoltage calculation is outlined. The effect of the signal frequency on the photoconductive current is evaluated; the results show that the photoconductive current is very small, and can be neglected in the calculation. The frequency dependence of the photovoltage along with the 2-DEG charge density, drain-source current and transconductance of the device have been studied analytically for an HEMI structure. © 2001 John Wiley & Sons. Inc.Publication Leaky wave radiation of millimetre waves by photoinduced plasma grating in a semiconductor slab(1999) Alphones, A.; Tsutsumi, M.; CENTRE FOR WIRELESS COMMUNICATIONSThe paper reports investigations on leaky wave radiation of millimetre waves from a periodically photoinduced semiconductor slab waveguide. The photoinduced plasma grating structure is modelled as a permittivity modulated layer by considering the average permittivity as of a uniform plasma occupied thin layer and is systematically analyzed using a singular perturbation procedure based on multiple space scales up to second order. The radiation efficiency of a leaky wave is derived and the results are outlined as a function of optically induced plasma density. Experiments have been carried out at 40 GHz by illuminating the grounded silicon slab using the slide of a periodic slit pattern through a xenon arc lamp. The dependence of periodicity on the radiation pattern is also reported.Publication Periodically slotted microstrip ring resonator(2000-11-05) Alphones, A.; Yee, W.K.; CENTRE FOR WIRELESS COMMUNICATIONSThis paper investigates the periodically slotted microstrip slow-wave ring resonator. This novel structure has an improved quality factor compared to the conventional ring resonator. It also reduces the overall dimensions thus making its application attractive in wireless communications and other areas.Publication Microwave envelope solitons in YIG film under oblique magnetisation(2001-12) Subbiah, S.; Alphones, A.; CENTRE FOR WIRELESS COMMUNICATIONSA detailed study of the output pulse profiles and envelope soliton characteristics are studied in a YIG film under oblique magnetisation for different input pulse widths, operating frequencies and ferrimagnetic resonance line widths. Dispersion characteristics and nonlinear characteristics of the YIG film are predicted by the first order multiple scale method. The analysis of the soliton in the YIG film is carried out using a split step Fourier method for arbitrary orientation of magnetisation. The conditions for the bright and dark soliton are established using the Lighthill criterion. A switchable bright to dark soliton is theoretically predicted by varying the angle of DC magnetisation. Pulse compression is also estimated for different magnetisation angles.Publication Leaky wave radiation in a corrugated ferrite slab under arbitrary orientation of magnetization(2000) Shanthi, S.; Alphones, A.; CENTRE FOR WIRELESS COMMUNICATIONSThe leaky wave phenomena of the corrugated ferrite slab was analyzed using the perturbation method with multiple scales. A shift of 3° was observed in the main beam of the radiation pattern when the orientation of the DC bias field is changed from 0 to 30°.Publication Edge coupled microstrip resonators with periodical slot loading(1999) Alphones, Arokiaswami; Goswami, Nandini; CENTRE FOR WIRELESS COMMUNICATIONSPeriodically capacitive loaded half wavelength microstrip resonator and edge coupled microstrip resonator have been studied. This novel structure with the slow wave effect has higher quality factor compared to conventional single/coupled microstrip resonator. The variation of resonant frequency and the quality factor with the number of slots have been examined.Publication Analysis of periodically corrugated gyrotropic waveguide(1999-05-20) Alphones, A.; CENTRE FOR WIRELESS COMMUNICATIONSA periodically corrugated structure on a thin-film gyrotropic waveguide is analyzed by the singular perturbation technique based on multiple space scales. The radiation efficiency and phase difference between forward and backward propagation constants are numerically evaluated as a function of the off-diagonal element in the dielectric tensor of the medium and the thickness of film. The results are quantitatively discussed.