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A microstrip-fed broadband circularly polarised (CP) monopole antenna was studied. A broad impedance bandwidth and wide axial ratio bandwidth (AR-BW) could be achieved simultaneously. This antenna used a conventional monopole architecture, except for its deforming ground plane and asymmetricfeed approach. The asymmetric-feed was used to provide an orthogonal component distinct from its original linear polarisation. In addition, by embedding a slit and a stub on the ground plane, this antenna could generate CP wave radiation and achieve a broad impedance bandwidth. According to the measurement results, the impedance bandwidth was 6.56 GHz for a 10 dB return loss, which covered a range of 2.32-8.88 GHz. The AR-BW was 1.2 GHz for a 3 dB AR, which covered a range of 3.2-4.4 GHz.

We study the loading dynamics of an optical dipole trap and an optical lattice both experimentally and theoretically. A simple power dependence for the number of trapped atoms (N∝P3∕2) is revealed in both cases. We then study the parametric excitation of the trapped atoms. High order parametric resonance is observed close to but lower than 4ν in a CO2 laser optical lattice. The existence of the high harmonic and its shift toward lower frequency are attributed to the anharmonicity of the optical trapping potential. We investigate the discrepancy between experimentally measured optical lattice frequencies and the theoretical calculation for several published experiments and present corrected formula for trap frequency calculations. Using this corrected formula and accounting for the off-center lattice sites, we present a modified formula for calculating the optical lattice frequency and obtain better agreement between experimental measurement and theoretical calculation.

In this article, the S parameters of the prototype were measured using a vector network analyzer (Agilent E5071B).When the port 1 is excited and the port 2 is terminated to a 50-⍀ load, the measured and simulated S parameters of the prototype are shown in Figure 7. The measured impedance bandwidth, defined by Ϫ10 dB return loss, reaches 630 MHz (1860 -2490 MHz), which covers the UMTS band and 2.4-GHz WLAN band. Across the two bands, the isolations of the prototype are larger than 14 and 18 dB respectively. Because of the symmetric configuration, S 22 (S 12 ), which is not given in this article, is consistent with S 11 (S 21 ).When one of the two ports is excited and the other port is terminated to a 50-⍀ load, the radiation patterns of the proposed antenna are measured in an anechoic chamber. Figures 8 and 9 show the patterns of the two monopoles at 2.05 GHz, respectively. The measured patterns at 2.44 GHz, which have not been shown in this article, have similar characteristics with those at 2.05 GHz. One can find that the measured radiation patterns of monopole 1 and 2 cover complementary space regions, so the proposed diversity antenna can provide pattern diversity in a wireless communication system.In this article, the antenna efficiency is approximately calculated by ABSTRACT: A wideband coplanar waveguide (CPW)-fed two-arm spiral slot antenna without a balun circuit is presented in this article.Phase progressions at arm ports are realized through the coplanar waveguide excitations. A detailed characterization of all antenna components and parameters is provided along with guidelines and recom-mendations for broad bandwidth and small reflection. Variations of the impedance matching due to the turn numbers, the ground width separated between two neighboring turns and the slot width are tested and studied. The measured impedance bandwidth of a S 11 Յ 10 dB ranges from 1.63 to 8 GHz and covers most of the commercial wireless communication systems, such as DCS, PCS, IMT-2000, WLAN, Bluetooth, and HIPERLAN. ABSTRACT: The modified Yule-Walker scheme is employed to define arbitrary transmission scattering parameter of a multiple-level bandpass filter in the discrete-time domain. Equal-length microstrips including single-and double-section stubs are used to implement the multiplelevel band-pass filter. Experimental results are presented to illustrate the validity of this design method.

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