Broadband True-Time-Delay Microwave Lenses Based on Miniaturized Element Frequency Selective Surfaces

IEEE Trans. Antennas Propagat.

2014

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In this reprot, we introduce a new technique for designing miniaturized-element frequency selective surfaces (MEFSSs) with bandpass responses and no spurious transmission windows over extremely large bandwidths. The proposed, harmonic-suppressed MEFSSs consist of multiple metallic and dielectric layers. Each metallic layer is in the form of a two-dimensional arrangement of capacitive patches or an inductive wire grid with extremely sub-wavelength periods. Harmonicfree operation in these structures is achieved by using multiple, closely-spaced capacitive layers with overlapping unit cells to synthesize a single, effective capacitive layer with a larger capacitance value. This allows for reducing the unit cell size of a conventional MEFSS considerably and moving the natural resonant frequencies of its constituting elements to considerably higher frequencies. Consequently, the spurious transmission windows of such MEFSSs, which are caused by these higher-order harmonics, can be shifted to very high frequencies and an extremely broad frequency band free of any spurious transmission windows can be obtained. Using this technique, an MEFSS with a second-order bandpass response is designed to operate at 3.0 GHz with 20% fractional bandwidth and be free of spurious transmission bands up to 27.0 GHz. A prototype of this harmonic-free MEFSS is fabricated and experimentally characterized in the lab. Measurement results confirm harmonic-free operation of the proposed FSS for incidence angles in the ±60• range for both the TE and TM polarizations of incidence.

Section: Chapter 1 Introductionmentioning

confidence: 99%

Harmonic-Suppressed Miniaturized-Element Frequency Selective Surfaces With Higher Order Bandpass Responses

Abadi

IEEE Trans. Antennas Propagat.

2014

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“…More advanced multibeam lens antennas are obtained by using iterative design techniques to optimize the lens or using microwave lenses with multiple focal points [17]. Frequency selective surfaces (FSSs) have also been used to design microwave lenses [23]- [25]. In [24] and [25] miniaturized-element frequency selective surfaces (MEFSSs) were used to address the main shortcomings of conventional planar lenses (namely, the poor scanning performance).…”

Section: Introductionmentioning

confidence: 99%

Design of Wideband, FSS-Based MultiBeam Antennas Using the Effective Medium Approach

Abadi

IEEE Trans. Antennas Propagat.

2014

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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

“…In most lenses whether operating at optical wavelengths or microwave frequencies, chromatic aberration is an important issue that deteriorates overall performance of the system in which the lenses are used. In microwave lenses, when used as part of a wireless system (e.g., a high-gain antenna), these lenses tend to significantly distort the temporal characteristics of broadband pulses [1].…”

Section: Introductionmentioning

confidence: 99%

“…Many of these lenses tend to be narrow-band and dispersive and can introduce significant signal distortion even for narrowband modulated incident pulses. More recently, true-time-delay (TTD) planar microwave lenses [1] based on a class of bandpass frequency selective surfaces [4] have been demonstrated to be free of chromatic aberration. However, because of the bandpass nature of the time-delay units employed in such lenses, it is difficult to increase their bandwidths particularly at the lower edge of their operating band.…”

Section: Introductionmentioning

confidence: 99%

All-dielectric, true-time-delay, planar microwave lenses

2013 IEEE Antennas and Propagation Society International Symposium (APSURSI)

2013

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We present a new technique for designing planar microwave lenses with broadband, true-time-delay response types. The lenses examined in this work are planar structures with circular apertures populated with numerous spatial time-delay units (TDUs). Each TDU is the unit cell of an appropriately designed lowpass frequency selective surface (FSS) that provides a desired time delay over a wide frequency range. The lowpass FSSs used in this paper are all-dielectric type multi-layer structures that are composed of high-εr and low-εr dielectric substrates cascaded sequentially. An all-dielectric lens prototype with focal length to aperture diameter ratios (f /D) of 1.3 is designed, fabricated, and experimentally characterized. It is experimentally demonstrated that the fabricated lens can operate over a bandwidth of 40% without any chromatic aberrations. Moreover, the proposed lens demonstrates an excellent scanning performance with fields of views of ±60 • .