Enabling IoT interoperability through opportunistic smartphone-based mobile gateways

The theoretical limit for small antenna performance that was derived decades ago by Wheeler and Chu governs design tradeoffs for size, bandwidth, and efficiency. Theoretical guidelines have also been derived for other details of small antenna design such as permittivity, aspect ratio, and even the nature of the internal structure of the antenna. In this paper, we extract and analyze experimental performance data from a large body of published designs to establish several facts that have not previously been demonstrated: (1) The theoretical performance limit for size, bandwidth, and efficiency are validated by all available experimental evidence. (2) Although derived for electrically small antennas, the same theoretical limit is also generally a good design rule for antennas that are not electrically small. (3) The theoretical predictions for the performance due to design factors such as permittivity, aspect ratio, and the internal structure of the antenna are also supported by the experimental evidence. The designs that have the highest performance are those that involve the lowest permittivity, have an aspect ratio close to unity, and for which the fields fill the minimum size enclosing sphere with the greatest uniformity. This work thus validates the established theoretical design guidelines.

Experimental Validation of Performance Limits and Design Guidelines for Small Antennas

Composite technology, where a novel artificial material is fabricated by combining, for example, ceramic and polymer materials in an ordered manner or just by mixing, was earlier used widely for sonar, medical diagnostics, and NDT purposes. However, in recent decades, large numbers of ceramic–polymer composites have been introduced for telecommunication and microelectronic applications. For these purposes, composites of 0–3 connectivity (a three-dimensionally connected polymer phase is loaded with isolated ceramic particles) are the most attractive from the application point of view. Composites of 0–3 connectivity enable flexible forms and very different shapes with very inexpensive fabrication methods including simply mixing and molding. In this brief review, we gather together the research carried out within 0–3 ceramic–polymer composites for microwave substrates, also including embedded capacitor, inductor, or microwave-absorbing performances.

Polymer–Ceramic Composites of 0–3 Connectivity for Circuits in Electronics: A Review

A high impedance surface consisting of metallic square patches electrically connected through vias to the ground plane beneath them is made tunable. Tunability is achieved by connecting adjacent patches with varactor diodes thus altering the capacitance between the patches and hence the surface's resonance frequency. The varactor diodes are biased with the aid of a resistive grid. The grid is made resistive using surface mount resistors. Using an approximate equivalent circuit the effect of the varactor diode resistance is investigated for normal plane wave incidence. It is shown that at resonance, a small varactor resistance may lead to a significant absorption. The potential use of a waveguide simulator to characterize approximately the performance of the proposed metamaterial structure is investigated.

A Varactor-Tunable High Impedance Surface With a Resistive-Lumped-Element Biasing Grid

A novel printed crossed dipole with broad axial ratio (AR) bandwidth is proposed. The proposed dipole consists of two dipoles crossed through a 90°phase delay line, which produces one minimum AR point due to the sequentially rotated configuration and four parasitic loops, which generate one additional minimum AR point. By combining these two minimum AR points, the proposed dipole achieves a broadband circularly polarized (CP) performance. The proposed antenna has not only a broad 3 dB AR bandwidth of 28.6% (0.75 GHz, 2.25-3.0 GHz) with respect to the CP center frequency 2.625 GHz, but also a broad impedance bandwidth for a voltage standing wave ratio (VSWR) ≤2 of 38.2% (0.93 GHz, 1.97-2.9 GHz) centered at 2.435 GHz and a peak CP gain of 8.34 dBic. Its arrays of 1 t 2 and 2 t 2 arrangement yield 3 dB AR bandwidths of 50.7% (1.36 GHz, 2-3.36 GHz) with respect to the CP center frequency, 2.68 GHz, and 56.4% (1.53 GHz, 1.95-3.48 GHz) at the CP center frequency, 2.715 GHz, respectively. This paper deals with the designs and experimental results of the proposed crossed dipole with parasitic loop resonators and its arrays.

Broadband Circularly Polarized Crossed Dipole With Parasitic Loop Resonators and Its Arrays

Modern small satellites (MSS) are revolutionizing the space industry. They can drastically reduce the mission cost, and can make access to space more affordable. The relationship between a modern small satellite and a ldquoconventionalrdquo large satellite is similar to that between a modern compact laptop and a ldquoconventionalrdquo work-station computer. This paper gives an overview of antenna technologies for applications in modern small satellites. First, an introduction to modern small satellites and their structures is presented. This is followed by a description of technical challenges in the antenna designs for modern small satellites, and the interactions between the antenna and modern small satellites. Specific antennas developed for modern small-satellite applications are then explained and discussed. The future development and a conclusion are presented.

Antennas for Modern Small Satellites

The development of a circularly-polarized compact high-gain antenna to be used for the European Student Earth Orbiter small satellite mission is described. The antenna is realized stacking two coaxial shorted annular patches and placing the top one at half a wavelength from the lower one. At variance of other similar configurations proposed in the past, the one presented in this paper has several important features which can be extremely useful for application in the space environment. In particular, it can be easily fabricated employing suspended technology and its radiation characteristics are to some extent controllable by opportunely varying the geometry. In the following, a straightforward design procedure will be presented detailing the criteria to optimize top and bottom radiating elements. Both numerical and measured results will show that the proposed design satisfies the specifications and presents characteristics comparable to other larger and heavier solutions usually more difficult to design. Specifically, it will be shown that with this configuration it is possible to obtain gain values higher than 12 dB using ground plane of moderate size and that a further improvement up to 15dB can be obtained employing larger ground planes

A Compact High Gain Antenna for Small Satellite Applications

A transformation procedure directly computing the antenna far-field pattern from near-field samples acquired on a planar spiral is proposed in this paper. The convolution property of the radiation integral is exploited to efficiently perform the evaluation by taking advantages of the Fast Fourier Transform, without the need of any intermediate interpolation process. Validations on circular arrays of elementary dipoles are presented to show the effectiveness of the method.

/pdf/near-field-to-far-field-transformation-with-planar-spiral-1jmuso1fpr.pdf

Near-Field to Far-Field Transformation with Planar Spiral Scanning

A dual-band dual-linear polarization reflectarray configuration is developed for future 5G cellular applications. A single layer unit cell including two pairs of miniaturized fractal patches is designed to operate at two distinct frequencies within the Ka-band (27/32 GHz), in a dual-polarization mode. An in-depth analysis of the unit cell behavior is carried out, to demonstrate the total independence between the designed frequency bands and polarizations. The proposed configuration offers a very simply and thin structure, small unit cell sizes, and low losses, while leading to an independent optimization of the phase at each frequency and polarization. A dual-band/dual-polarized reflectarray prototype is designed and tested, thus demonstrating the unit cell flexibility to offer arbitrary beam directions/shapes at each frequency, for both polarizations.

/pdf/dual-band-dual-linear-polarization-reflectarray-for-mmwaves-83nbbnaa7l.pdf

Dual-Band Dual-Linear Polarization Reflectarray for mmWaves/5G Applications

A hybrid array configuration suitable for wideband millimeter-wave applications is presented in this work. The proposed structure is based on the use of circular waveguide elements electromagnetically coupled trough circular apertures to a stripline distribution network. The adopted excitation mechanism avoids the use of transition components generally reducing the overall antenna efficiency. Simulated and measured results on a Ka-band prototype are discussed to prove the wideband radiation behavior.

/pdf/hybrid-array-antenna-for-broadband-millimeter-wave-2vtd3hbckb.pdf

Giuseppe Di Massa

Papers

Antennas for Modern Small Satellites

A Compact High Gain Antenna for Small Satellite Applications

Near-Field to Far-Field Transformation with Planar Spiral Scanning

Dual-Band Dual-Linear Polarization Reflectarray for mmWaves/5G Applications

Hybrid array antenna for broadband millimeter-wave applications