Development of Novel 3-D Cube Antennas for Compact Wireless Sensor Nodes

Abstract

3-D antennas for narrow band, wireless sensor node applications are described herein. The antennas were designed on the surface of a cube which makes available the cube interior for sensor electronics placement. The layout of each antenna consists of a dipole fabricated on two sides of the cube and connected to a balanced-to-unbalanced line transition on the third side. The base of the cube serves as a ground plane for the microstrip feed line. The first cube antenna was designed for an operating frequency of 2.4 GHz and its 10 dB return loss bandwidth is 2%.of the proposed design is 0.55 and its measured gain is 1.69 dBi with 78% measured radiation efficiency. The second cube antenna is similar to the first one but it was loaded with high dielectric constant superstrates.of the second proposed antenna is 0.45, its measured gain is 1.25 dBi with 73% measured radiation efficiency and the bandwidth is 1.5%. The designs compare well with high efficiency, electrically small antennas that have been described in the open literature. A Wheeler Cap was used to measure the efficiency and the 3-antenna method was used for measuring the gain.Index Terms-3-D antennas, balanced, dipole antennas, electrically small antennas, Wheeler cap method, wireless sensor networks (WSNs).

A novel tunable origami accordion antenna

“…In addition, 3-D folding of antennas has been performed in [3], and the prototype was fabricated by printing metal on six planar sides, and then folded into the cubic structure. In [4], a 3-D dipole was designed for wireless sensor node applications. But both these two 3-D antennas can only work at folded state.…”

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“…Investigating available designs of UHF antennas in other applications reveals the use of several techniques, such as fractal [57], loop [58], metamaterial [59] and inverted F-shaped structures [60]. Additionally, folded structures are widely employed to reduce the size of the antennas especially in handset mobile devices [61]- [65]. However, despite achieving a compact size, the aforementioned antennas have narrow bandwidths, and omnidirectional radiation.…”

“…The first step in the design is to reduce the physical size using the methods explained in [64]- [65]. It is known that those methods cannot be applied directly to any arbitrarily structure as they might cause a significant degradation in the antenna's performance.…”

“…Moreover, the majority of the published three-dimensional antennas have omnidirectional radiation patterns [64], [65]. It is worth mentioning that in telecommunications; the directivity can be enhanced using a large ground near the main radiator [66].…”

“…In these configurations, the antenna design is conceptualized to be accommodated on a 3-D structure rather than folding it from certain positions. However, despite the miniaturization capabilities of existing 3-D antennas, they have narrow bandwidths [64]- [65]. This effect comes from the fact that reducing the size of an antenna with largest dimension of a, its Q-factor, which is inversely proportional to (ka) 3 (where k is the wave number), increases and thus, its impedance matching bandwidth reduces according to 1/Q [91].…”