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Dual‐band stacked microstrip patch antennas are a popular choice for wireless and other vehicular communication applications. They are also being considered for use in feed arrays for reflector antennas. In this paper, novel center‐feeding schemes to achieve the desired dual‐band response will be presented. Also, novel side‐feeding schemes for a potential application in arrays have been investigated. L‐band frequencies were chosen to test the concept. For the stacked patch configuration, the primary objective was to get the antenna to resonate at two frequencies—1.575 GHz for the upper patch and 1.228 GHz for the lower patch—with a shared aperture and two independent excitations. Return‐loss, isolation, and pattern measurements for several antenna prototypes are presented. The measured results are compared with the simulation results from an FDTD code developed at UCLA. Extension of the concept for dual‐polarization and array configurations has been explored. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 467–475, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11092

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using stepped-impedance hairpin resonator with IDC of the DAML structure on GaAs substrate by surface micromachining. Figure 5 shows the simulation and measurement results of the filter with optimized dimensions. Inspecting the measurement results, the SIR band-pass filter shows a fractional bandwidth of 4.63 GHz at 56 GHz. A passband is from 54 to 58.63 GHz with a return loss better than 15 dB. The insertion loss in the passband is 3.37 dB. The stopband is greater than 31 dB within 37.03-45.51 GHz. Although there are some differences between the simulation and measurement data due to the processing tolerance, the experimental results show excellent agreement with the theoretical simulation results. CONCLUSIONIn this paper, a new slow-wave band-pass filter has been suggested and demonstrated successfully in 56-GHz range using the GaAs surface-micromachining technique. The filter has been synthesized and optimized from EM simulation. The band-pass filter has shown a sharp cut-off frequency response and low insertion loss. The measurement results of the band-pass filter agree well with simulation results. The DAML structure and the slow-wave bandpass filter can be used in the millimeter-wave range with active devices on the same substrate. ACKNOWLEDGMENTThis work was supported by Korea Science and Engineering Foundation (KOSEF) under the Engineering Research Center (ERC) program through the Millimeter-wave Innovation Technology (MINT) Research Center at Dongguk University (grant no. R11-1999-058-04003-0 INTRODUCTIONVarious ultra-wideband (UWB) antennas have been studied extensively, and the metal-plate monopole antennas of various shapes [1][2][3][4][5] are the simplest of the UWB antennas. Some updated ultrawideband designs have been developed. In [6], a planar invertedcone antenna with two circular holes was proposed, which provided a ratio impedance bandwidth of about 10:1. In [7], the proposed antenna has a "cobra" structure, which is designed based on the TEM horn travelling-wave antenna and is of VSWR Յ 2 frequency range from 800 MHz to 25 GHz. Another monopole antenna with a trapezoid metal plank is presented [8], whose ratio impedance bandwidth reaches 12:1. These antennas have an extremely wide impedance bandwidth; however, their structures are somewhat large. In this paper, we propose an ultra-wideband monopole antenna that consists of a leaf-shaped monopole with three holes and a ground plate covered by a dielectric layer of relative permittivity r ϭ 3.5 and thickness h ϭ 1.5 mm. This design not only achieves an extremely wide impedance bandwidth, but reduces the antenna size as well. The design of the proposed antenna and the effects of various parameters are presented. Figure 1 shows the geometry of the proposed antenna where a monopole element is mounted on a metallized dielectric substrate of area 80 ϫ 80 mm 2 . The radiating element is made of a 1-mm-thick brass sheet shaped as a leaf with a half-circle part of radius 29.2 mm and three holes of radii 10, 10, and 11 mm, respectively. The antenna is ...