We describe a CubeSat constellation integrated with ultrawideband (UWB) multiple input and multiple output (MIMO) radars operating over the frequency range of 50–600 MHz for remote sensing of large ice sheets on the Earth, as well as distant planets and moons. It can be used for measurements of ice thickness and basal conditions of Antarctica and Greenland ice sheets, the mapping of lunar lava tubes, and sub-surface detection/characterization of volatiles on Mars. In this paper we provide a short discussion of the science requirements and conceptual design of a constellation of CubeSats with UWB MIMO radars for sounding ice and mapping of lava tubes.

This special issue addresses various jammers and their effect on different processing stages and overall Global Navigation Satellite System (GNSS) receiver performance, and presents countermeasures and solutions to combat interference.

This paper reviews Global Navigation Satellite Systems (GNSS) antennas and arrays for robust coverage in presence of interference signals with a focus on antenna design aspects. A number of small antenna designs are presented that cover multiple current and future GNSS frequency bands (1150-1610 MHz) with sizes as small as 1 in (25 mm) in diameter. Several arrays are presented with a size as small as 3.5 in (8.9 cm) in diameter and approximately 0.5 in (13 mm) thick as compared to commercially available apertures 14 in (35.6 cm) and 5.5 in (14.0 cm) in diameter. These small arrays are shown to satisfy the gain requirements of GNSS receivers while simultaneously offering four to six antenna elements for adaptive interference suppression.

Historically, antennas and microwave devices relied on isotropic media. This provided for limited degrees of freedom (one for dielectric and another for magnetic) in the design process. In contrast, anisotropic media introduce several more degrees of freedom (at least three more for dielectrics and three additional ones for magnetic) opening a new direction in designing radio-frequency (RF) communication devices and wireless systems. A focus of the paper is the introduction of anisotropic media parameters emulated using simple printed, but highly coupled, transmission lines (TRLs). The paper begins by introducing the equivalence between in-plane anisotropy and coupled TRLs to realize degenerate band edge (DBE) and magnetic photonic crystal (MPC) modes. This is followed by the design of miniature antenna elements via dispersion engineering, demonstrating their performance on small finite substrates. The second part of the paper is focused on concatenating DBE and MPC antenna elements to realize smaller size wideband arrays. Such arrays exploit the current sheet antenna (CSA) concept to achieve the coveted goal of small wideband metamaterial arrays. For example, by constructing an array of antenna elements ~ λ/10×λ/10 in size, highly conformal (very thin) apertures delivering 5 : 1 bandwidth are demonstrated while avoiding grating lobes. In contrast to transitional approaches, the proposed method exploits (rather than suppressing) the metallic ground plane inductance. Instead, the capacitance of the tightly coupled antenna elements is used to cancel the inductance over wide bandwidths. By further employing small size array elements, large bandwidths can be achieved using a smaller footprint.

This paper outlines the design and development of a low-cost, small-footprint wireless sensor capable of sampling and transmitting sensory data at frequencies more than 6000 Hz. This sensor has been designed and developed in-house using off the shelf components and open source software for container integrity monitoring. The paper presents details of the various refinements that have been carried out to improve the default performance of the sensory unit. Laboratory tests indicate that while the developed sensor has comparatively higher power consumption than other commercially available sensory units, its small form factor and low cost make it attractive enough for several applications. The paper then describes how these sensors can be used to realize a reliable, round-the-clock system for monitoring the stability and integrity of cargo containers.

A high-frequency asymptotic technique based on the Uniform Geometric Theory of Diffraction (UTD) is employed for building interior imaging. The analysis is implemented using a ray-tracing technique to account for multiple scattering interactions in a building, along with a set of heuristic diffraction coefficients for dielectric wedges and corners. Imaging of the synthetic aperture radar data is carried out by the conventional fast Fourier transform method to transform to the downrange domain, and combined with a coherent near-zone imaging function for cross-range. Comparisons with experimental data for a scaled-down building model are given to demonstrate the suitability and efficacy of our analysis for through-wall building imaging. The UTD ray mechanisms account for the dominant scattering features observed in the image.

The authors present generalized surface impedance conditions that improve medium characterization. One of the most common conditions that is often used to simulate a dielectric coating is the standard impedance boundary condition, and the improved boundary condition discussed can be viewed as a generalization of this, distinguished by the presence of higher-order derivatives of the field. By virtue of the derivatives, the conditions are less local in character, and the additional degrees of freedom can be used to better simulate the material properties of a surface. Following a review of the standard impedance condition, the new conditions are introduced. Several forms are presented, each with coefficients which are functions of the geometry and material properties of the surface. The applications of these to a variety of scattering problems are then discussed.>

The problem considered is that of a plane wave incident on a perfectly conducting half-plane with a thin dielectric coating on its upper face. The solution is accomplished by introducing a higher order boundary condition to simulate the effect of the dielectric, thereby allowing the structure to be treated as an infinitesimally thin half-plane. Two types of boundary conditions are developed, one applicable to a low-contrast dielectric and the other to a high-contrast one. The problem is then solved using a generalized version of the Maliuzhinets method in which certain additional constants are introduced to assure the correct behavior of the field at the edge. Although these constants play no role in the final solution, they are needed to cancel out inadmissible singularities in the solution of the homogeneous difference equation. The final solution is expressed in a uniform manner and some numerical results are presented.>

Previous uniform asymptotic evaluations of integrals have been restricted to cases where the integrand singularities are close to the saddle point(s). A method is presented here which allows such uniform evaluations with integrand singularities anywhere near the steepest descent path.