the switched buffer multiplexer, this work achieves the phase noise of less than Ϫ121 dBc/Hz at 1 MHz offset and the frequency tuning range of 10% while consuming 52.2 mW from a 1.8-V supply.
ACKNOWLEDGMENTThe authors thank the Chip Implementation Center of the National Science Council, Taiwan, Republic of China, for supporting the TSMC CMOS process. This work was supported by Research Projects of the National Science Council, Taiwan, Republic of China, under Projects NSC 94 -2213-E-009 -051, and the National Chip Implementation Center. resonator loaded waveguide antenna with parasitic dielectric directors. However, in most cases the structures lack structural stability and are very large, and therefore, are not suitable to be used as compact antenna or as an array element. Recently, Abdel et al.
GAIN ENHANCEMENT OF[8] used a surface mounted short horn (SMSH) to enhance the gain of a microstrip patch antenna. They have made a horn from PVC sheet ( r ϭ 3.38) and mounted it on the patch structure. The inner surface of the horn is painted with the conductive silver epoxy.In this study, we presented how the gain of an aperture-coupled rectangular DRA can be enhanced by integrating with a SMSH. We also study the effects of the material required to support the SMSH on antenna performance. The proposed configuration, where the aperture coupled DRA acts as a feed to SMSH, is mechanical stable, very simple, and easy to fabricate. We achieved a gain of 8.5 dBi at 5.95 GHz, and an impedance bandwidth of 3.2% with this configuration. The design and optimization has been carried out on the Microwave Studio, commercial 3D-EM software from Computer Simulation Technology (CST) [9].
DESIGN OF SMSH FOR GAIN ENHANCEMENTOur aim was to enhance the gain of a standard rectangular DRA by integrating it with a quasi-planar SMSH as shown in Figure 1(a). First, a rectangular DRA, with a rectangular coupling slot in the ground, and excited by a 50-⍀ microstrip line feed, was designed as in [1] to operate around 6 GHz.The rectangular DRA parameters are: length ϭ 12.8 mm; width ϭ 7.3 mm; height ϭ 6.35 mm; dielectric constant ϭ 9.8; and loss tangent ϭ 0.002. Slot coupled feeding structure dimensions are: slot length ϭ 6.4 mm; slot width ϭ 1.24 mm; stub length ϭ 1.6 mm; microstrip width ϭ 1.16 mm; substrate dielectric constant ϭ 3.38; loss tangent ϭ 0.0022 and thickness (h f ) ϭ 0.508 mm. This antenna has a theoretical gain 6 dBi at the operating frequency of 6 GHz, and a 10-dB return loss bandwidth from 5.90 to 6.07 GHz. Then the design of the SMSH was considered. For that purpose, first the base dimensions of the SMSH were set following Abdel et al.[8] and the horn taper angle () was set to 45°. As we preferred to keep the height of the SMSH as small as possible, then we investigated the effect of horn height (H) on gain, over the frequency range of interest. The variation of gain with height for three different frequencies (5.95, 6.0, and 6.05 GHz) is shown in Figure 2(a). The gain increases with increasing height up to H Ϸ 9 mm ϭ 0.15 0...