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Microwave imaging based on the inverse scattering problem has attracted many interests in microwave community. To obtain a satisfactory imaging quality, in most cases, a scattering-free environment is desired. In this work, to provide such an environment, we experimentally demonstrate a compact microwave imager integrated with a board-integrated, multiport vector network analyzer and a miniaturized, cylindrical anechoic chamber dedicatedly designed for inverse scattering-based microwave imaging. Based on the principle of electrically induced transparency and the effective medium equivalence, an inhomogeneous, ultrathin, dual-angle absorbing surface was designed, simulated, and implemented, to simultaneously absorb incident and scattered fields. Experimental imaging verified its effectiveness. The proposed imager would help the promotion of practical imaging, showing the potential in on-side imaging. [ABSTRACT FROM AUTHOR]

Recently, microwave imaging based on randomized illuminations has demonstrated promising potentials. The key to realize such imaging is to implement an imager with a reconfigurable, randomized aperture. In this work, we discuss the theory and the guidelines for implementing such an imager and demonstrate an experimental prototype working in the 24-GHz ISM band. It is realized with a board-integrated, space-fed, 400-element phased array capable of realizing independent 1-bit phase modulations for each element. The fields transmitting through this aperture can be deterministically randomized by simply controlling direct current bias voltages. Assisted by optimized system calibration and standard $\ell _{1}$ -norm regularization, experimental imaging with a notably improved quality can be obtained. The proposed solution can be used in wide applications, especially suitable for the massive personal security screenings in common public, government, and military areas. [ABSTRACT FROM AUTHOR]

While achieving broadband angular selectivity for p-polarized wave has been well studied, it is still challenging for s-polarized wave. The reason is that at high frequencies such as terahertz spectrum, the permeability of materials has always approached unity. Here, we propose a solution to implement broadband angular selectivity for s-polarized incidences by combining an effective anisotropic diamagnetic medium and a staggered photonic structure. The diamagnetic medium is constructed with periodically arranged metallic rings, exhibiting negligible frequency dispersion in an ultra-wide terahertz band. By incorporating temperature-dependent dielectric into staggered structure, a thermally tunable broadband angular selectivity system is presented, with an adjustable selective angle ranging from 0° to 40°. Full-wave simulations verify the effectiveness of the proposed approach, breaking through the polarization limitation of the existing angular selectivity technology. The proposed approach is simple, robust, and scalable from microwave to terahertz frequencies. [ABSTRACT FROM AUTHOR]

Miniaturized Doppler radar sensor (DRS) for noncontact motion detection is a hot topic in the microwave community. Previously, small-scale physiological signals such as human respiration and heartbeat rates are the primary interest of study. In this paper, we propose a comprehensive approach that can be used to improve the demodulation linearity of microwave DRSs, such that detailed time-domain motion information ranging from micro-scale to large scale can be accurately reconstructed. Experiments show that based on a digital-IF receiver architecture, dynamic dc offset tracking, and the extended differentiate and cross-multiply arctangent algorithm, the displacement and velocity of both micrometer-scale vibration of a tuning fork and meter-scale human walking can be accurately recovered. Our work confirms that substantial time-domain motion information is carried by the signals backscattered from moving objects. Retrieval of such information using DRSs can be potentially used in a wide range of healthcare and biomedical applications, such as motion pattern recognition and bio-signal measurements. [ABSTRACT FROM AUTHOR]

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Subwavelength guiding of channel plasmon polaritons (CPPs) is realized by a properly structured metallic groove at frequencies far below the plasma frequency of metal. Compared with CPPs at visible frequencies, more versatile physical mechanisms can be introduced in these CPPs by surface patterning, so that they can exhibit superior features as visible CPPs, while eliminating the potential drawbacks of the latter. Such designer CPPs are explained physically with the effective-index method and verified experimentally in the microwave regime. [ABSTRACT FROM AUTHOR]

In the present letter, a design for active left-handed material collaborated with microwave varactors is proposed and experimentally realized. Both the results of simulation and experiment verify the tunable left-handed properties of the structure in microwave band. A controllable beam steering is then observed experimentally by a prism fabricated by such metamaterial. The simplicity of the active design and its tunable negative refraction indices make it useful for various applications. [ABSTRACT FROM AUTHOR]