Abstract-An electronically reconfigurable transmitarray device at 12 GHz is presented in this work. This paper highlights the functioning of this kind of device and thoroughly examines the proposed reconfigurable transmitarray. The architecture is discussed along with the design and selection of all the constituting elements and the prototypes for all of them. In order to add reconfigurability to the transmitarray structure, 360° reflective phase shifters were designed, prototyped and validated for direct application. Eventually, a demonstrative prototype for an active transmitarray with phase shifters was assembled, and radiation pattern measurements were taken in an anechoic chamber to demonstrate the capabilities of this structure.

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This paper presents the design and fabrication of low loss, weight, and cost prototypes in groove gap waveguide technology at Ka-band, manufactured with a metallized 3-D printing technique. A wide analysis of loss mechanisms and printing imperfections has been conducted, as well as the effect of temperature on structural deformations. Metallized 3-D printed and CNC machined prototypes have been compared and characterized with simulations and measurements at a band from 28 to 30 GHz. The average measured losses for metallized plastic prototypes are 1.4 dB/m.

Abstract-A planar antenna is introduced that works as a portable system for X-band satellite communications. This antenna is low-profile and modular with dimensions of cm. It is composed of a square array of 144 printed circuit elements that cover a wide bandwidth (14.7%) for transmission and reception along with dual and interchangeable circular polarization. A radiation efficiency above 50% is achieved by a low-loss stripline feeding network. This printed antenna has a 3 dB beamwidth of 5 , a maximum gain of 26 dBi and an axial ratio under 1.9 dB over the entire frequency band. The complete design of the antenna is shown, and the measurements are compared with simulations to reveal very good agreement.

permittivity of 2.65) with its size 70 ϫ 57 mm 2 . Its dimension parameters are listed in Table I. RESULTS AND DISCUSSIONTo examine the performance in terms of impedance bandwidth, the return loss for the fabricated antenna was measured using an HP8510C network analyzer. The simulated and measured return losses of the antenna are shown in Figure 2. It can be seen that the investigated antenna can approach an impedance bandwidth from 2.0 to over 12 GHz for S 11 Յ Ϫ10 dB, and a notch centered at 5.76 GHz (about 260 MHz higher than that of the simulated one) is also observed. The difference between simulations and measurements is mainly due to the substrate errors (including its thickness and relative permittivity) and fabrication tolerances.The measured radiation patterns in the E-plane and H-plane at 3.0, 5.0, 7.0, 9.0, and 10.5 GHz are illustrated in Figure 3. Notice that the proposed antenna has almost bi-directional patterns, especially at lower frequencies, in the E-plane, and omni-directional patterns in the H-plane at the lower or higher frequencies. Meanwhile, the measured antenna gain, given in Figure 4, shows the antenna has a gain of about 3.8 -6.8 dBi across the UWB frequency band. A sharp notch, centered at 5.76 GHz, is also observed with the rejection level approximately 10 dB. CONCLUSIONA planar elliptical slot antenna has been investigated. The proposed antenna has a compact size of 70 ϫ 57 mm 2 because of employing FG-CPW structures. To co-exist with the WLAN systems, a V-shaped slot is introduced. The antenna offers UWB performance with frequency band-rejection characteristic and suitable radiation patterns, which is met for UWB applications.

Abstract-A uniform geometrical theory of diffraction (UTD) solution is developed for the canonical problem of the electromagnetic (EM) scattering by an electrically large circular cylinder with a uniform impedance boundary condition (IBC), when it is illuminated by an obliquely incident high frequency plane wave. A solution to this canonical problem is first constructed in terms of an exact formulation involving a radially propagating eigenfunction expansion. The latter is converted into a circumferentially propagating eigenfunction expansion suited for large cylinders, via the Watson transform, which is expressed as an integral that is subsequently evaluated asymptotically, for high frequencies, in a uniform manner. The resulting solution is then expressed in the desired UTD ray form. This solution is uniform in the sense that it has the important property that it remains continuous across the transition region on either side of the surface shadow boundary. Outside the shadow boundary transition region it recovers the purely ray optical incident and reflected ray fields on the deep lit side of the shadow boundary and to the modal surface diffracted ray fields on the deep shadow side. The scattered field is seen to have a cross-polarized component due to the coupling between the TE¡. and TM¡. waves (where z is the cylinder axis) resulting from the IBC. Such cross-polarization vanishes for normal incidence on the cylinder, and also in the deep lit region for oblique incidence where it properly reduces to the geometrical optics (GO) or ray optical solution. This UTD solution is shown to be very accurate by a numerical comparison with an exact reference solution.

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A circularly polarized slotted array antenna is presented. The array is fed by a circular waveguide propagating the TM01, to properly generate the required polarization. An omnidirectional azimuth radiation pattern is obtained, as well as a −10°/+30° elevation antenna coverage. Low losses are achieved because of the waveguide feed. The slot array is mechanized over the metallic wall of the circular waveguide. Furthermore, the antenna presents a solid and rigid mechanical structure, which guarantees an optimum and repetitive response in a manufacturing process. A prototype antenna has been designed and measured. Satisfactory results have been obtained. The slotted array takes part from a signal detection system centered in 36.85 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 638–642, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22207