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In this paper, the finite-difference time-domain (FDTD) method is applied to calculate the resonant frequency of dielectric resonators (DR's) with curved surface. The contour-path integral FDTD (CFDTD) is modified to deal with the curved surface of the dielectric body while the traditional rectangular cells are maintained. Results are compared with theoretical values and staircase approximation, and show that the present method is more accurate than the staircase approximation. Index Terms - Dielectric resonator, FDTD.

In this paper, a novel broadband planar antenna based on the classic Yagi-Uda dipole array is presented. This 'quasi-Yagi' antenna achieves a measured 48% bandwidth for VSWR < 2, better than 12 dB front-to-back ratio, smaller than--15 dB cross polarization, 3-5 dB absolute gain and a nominal efficiency of 93% across the operating bandwidth. Finite-difference time-domain simulation is used for optimization of the antenna and the results agree very well with the measurement. Additionally, a gain-enhanced design is presented, where higher gain has been achieved at the cost of reduced bandwidth. These quasi-Yagi antennas are realized on a high dielectric constant substrate and are completely compatible with microstrip circuitry and solid-state devices. The antenna should find wide applications in wireless communication systems, power combining, phased arrays, and active arrays, as well as millimeter-wave imaging arrays. Index Terms--Broad-Band antennas, microstrip antennas, Yagi-Uda arrays.

In this paper, a novel broad-band planar antenna based on the classic Yagi-Uda dipole antenna is presented, and its usefulness as an array antenna is explored. This 'quasi-Yagi' antenna is realized on a high dielectric-constant substrate, and is completely compatible with microstrip circuitry and solid-state devices. This antenna achieves a measured 48% frequency bandwidth for voltage standing-wave ratio [is less than] 2, better than a 12-dB front-to-back ratio, smaller than -15 dB cross polarization, and 3-5-dBi absolute gain. Mutual coupling of the antenna in an array environment is investigated. Finally, three simple arrays are presented, demonstrating the usefulness of the antenna as an array element. This novel antenna should find wide application in wireless communication systems, power combining, phased arrays, and active arrays, as well as millimeter-wave imaging arrays. Index Terms--Planar antennas, quasi-Yagi antenna, spatial power combining.

A novel microstrip-to-waveguide transition utilizing a coplanar-strip Yagi-like antenna is presented. The compact and single-layered quasi-Yagi antenna fabricated on high dielectric-constant substrate has end-fire radiation patterns. This monolithic-microwave integrated-circuit (MMIC)-compatible antenna is inserted in the E-plane of the rectangular waveguide to launch the [TE.sub.10] dominant mode. With this new scheme of excitation, compact design and low-cost fabrication is achieved without requiring multilayered substrate or backshort hermetic sealing. This transition, in addition, achieves very broad bandwidth and relatively low insertion loss. The transition's broad-band characteristics are analyzed, and optimization guidelines for individual components of the transition are discussed in detail. A tolerance study proves that the transition is robust in mechanical alignment. The X-band transition with alumina substrate demonstrates 35% bandwidth with return loss better than -12- and -0.3-dB insertion loss at the center frequency. This transition should find wide applications due to its high compatibility with microwave-integrated-circuit/MMIC technology and very low fabrication cost. Index Terms--MMIC's, waveguide transitions, Yagi antennas.

A comparison between 51.84-Gb/s vestigial sideband 4-level pulse amplitude modulation (PAM4) and ON-OFF keying (OOK) signals at a transmission distance of 80 km is experimentally demonstrated for the first time. An electro-absorption modulated laser-based intensity-modulation and direct-detection 80-km transmission is achieved using both modulation formats without dispersion compensating fiber. The relative frequency between single sideband filter and signal is adjusted to find an optimized condition for both carrier to signal power ratio and sideband suppression ratio. The experimental results show that with linear equalization and without bandwidth limitation, the OOK signal has a 4-dB better sensitivity compared with PAM4 after 80-km standard single-mode fiber transmission. [ABSTRACT FROM PUBLISHER]