We present a new approach for designing dual-band miniaturized-element frequency selective surfaces (MEFSSs) with independent control of the frequencies of operation of each band. The proposed device is composed of two-dimensional periodic arrays of sub-wavelength inductive wire grids and capacitive patches separated by dielectric substrates. The structure is built upon an inductively-coupled MEFSS that uses capacitivelyloaded dielectric spacers as its main resonators. The two operating bands of this MEFSS correspond to the first and second resonant frequencies of its constituting resonators. By judiciously choosing the locations where the resonators are loaded and the load values, the frequencies of the first and second resonances can be controlled individually. This way, a dual-band MEFSS with independent frequency bands of operation can be obtained.Using the equivalent circuit model of this MEFSS, a synthesis procedure is developed that can be used to synthesize the dualband MEFSS from its system level performance indicators. A prototype of the proposed dual-band MEFSS with second-order bandpass response at each band is designed, fabricated, and experimentally characterized. The measurement results of this device show a stable frequency response with respect to the angle of incidence up to ±45 • for both TE and TM polarizations of incidence.
We present the design, simulation, and measurement results of a broadband, low-profile, multibeam antenna. The antenna uses multiple feed elements placed on the focal plane of a planar microwave lens to achieve high-gain, multibeam operation with a wide field of view. The lens is based on a recently reported design employing the constituting unit cells of appropriately designed miniaturized-element frequency selective surfaces (MEFSSs) as its spatial time-delay units. A new technique for modeling such lenses is also presented that greatly simplifies the full-wave electromagnetic simulation of MEFSS-based lenses. This technique is based on treating the pixels of the lens as effective media with the same effective permittivity and permeability and significantly reduces the difficulty of modeling and optimizing the proposed multibeam antenna with its relatively large aperture size in a full-wave electromagnetic simulation tool. Using this procedure, a prototype multibeam antenna operating in the 8-10 GHz range is designed. The prototype is fabricated and characterized using a multiprobe, spherical near field system. The measurement results are in good agreement with the simulation results obtained using the proposed simplified modeling technique. Measurements demonstrate consistent radiation characteristics over the antenna's entire operational band with multiple beams in a field of view of .Index Terms-Frequency selective surfaces, lens antennas, multibeam antennas. 1 In passive phased-arrays, variable phase shifters are integrated within the feed network to achieve beam steering.
0018-926X
We present a new approach to perform beam steering in reflecting type apertures such as reflectarray antennas. The proposed technique exploits macro-scale mechanical movements of parts of the structure to achieve two-dimensional microwave beam steering without using any solid-state devices or phase shifters integrated within the aperture of the antenna. The principles of operation of this microwave beam steering technique are demonstrated in an aperture occupied by ground-plane-backed, sub-wavelength capacitive patches with identical dimensions. We demonstrate that by tilting the ground plane underneath the entire patch array layer, a phase shift gradient can be created over the aperture of the reflectarray that determines the direction of the radiated beam. Changing the direction and slope of this phase shift gradient on the aperture allows for performing beam steering in two dimensions using only one control parameter (i.e., tilt vector of the ground plane). A proof-of-concept prototype of the structure operating at X-band is designed, fabricated, and experimentally characterized. Experiments demonstrate that small mechanical movements of the ground plane (in the order of 0.05λ0) can be used to steer the beam direction in the ±10° in two dimensions. It is also demonstrated that this beam scanning range can be greatly enhanced to ±30° by applying this concept to the same structure when its ground plane is segmented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.