On-chip antennas present an excellent solution for higher integration levels with the lower number of off-chip components and lower cost, however, their efficiencies are much lower due to lossy Si substrates. In this paper, we present a novel combination of Artificial Magnetic Conductor (AMC) surface and a package which acts as a superstrate as well to enhance the on-chip antenna efficiency. Designed in standard 0.18 μm CMOS technology at 77GHz frequency band, the CPW-fed on-chip monopole antenna is a good candidate for automotive radar systems. Since the package of the chip acts a superstrate, it is not a mere protector of the chip but also provides functionality, qualifying this design as System-on-Package (SoP). The combination of the optimized AMC surface and superstrate package enhance the radiation efficiency of the antenna to 54.37% and the gain to 2.4dBi, achieving 22.1% efficiency enhancement and 9.1 dB gain enhancement as compared to the standalone on-chip antenna.

An optically transparent microwave absorber with broadband absorption based on frequency selective surface (FSS) have been proposed and fabricated using a simple, cost-effective, and controllable inkjet printing assisted patterning technique. The FSS and ground layers are made of silver nanowires (AgNWs) conductive networks with desired patterns. This new device exhibits broadband absorption performance with an optimized 90% absorption bandwidth over the frequency range of 9.1 to 12.2 GHz in X-band. Besides, due to the patterning of AgNWs FSS and ground layers, the optical transmittance of the fabricated absorber exceeds 83% at 550 nm wavelength, which is the highest among the transparent absorbers in literature. Based on the easy-processing, high performance, and excellent transparency, the proposed absorber shows great promise for various applications relating to transparent absorbers, such as photonic detectors, antennas and solar cells.

This paper presents a planar flexible transmitter antenna with quasi-isotropic radiation for the RF communication of marine animals tagging system. By adjusting the lengths of the two perpendicular monopoles, a 90° quadrature with each other is achieved and therefore this transmitter antenna can provide a near-isotropic radiation. And this transmitter system is simulated and fabricated on flexible polydimethylsiloxane (PDMS) substrate, which can be mounted on marine animal body surfaces. The simulated difference between the maximum and minimum radiation (gain deviation) is 4.75dB for planar condition and 6.2dB for bending condition at 2.4GHz.

RFID Tags, typically, require ultra-small antennas and at 900 MHz most of the designs end up being meandered line wire antennas. These may not be suitable because such antennas are heavily influenced by the object on which they are placed. An antenna with a ground plane, such as a microstrip antenna, is a more suitable candidate in that scenario, however, typically micrsotrip patch antennas are large in size. In this paper, we introduce a highly miniaturized microstrip antenna with multiple slots and a superstrate with high-permittivity material. The size of the microstrip antenna at 900MHz is reduced by 87.5% as compared to a conventional rectangular microstrip patch antenna at 900MHz. The gain of the miniaturized antenna is 0.36dBi, achieving 40% efficiency, which is decent enough for short to medium range RFID applications.

Billions of wireless sensing devices must be powered for Internet of Things (IoT) applications. Collecting energy from ambient RF spectrum to power sensor nodes is one of the possible solutions. In this work, we present an antenna for RF energy harvesting applications which operates at multiple bands and has been realized through additive manufacturing (combination of 3D and screen printing) on a package, thus optimizing the space and cost requirements. The antenna design utilizes the cantor fractal approach which enables it to operate at three frequencies (GSM900, GSM1800 and 3G at 2100MHz) simultaneously. Decent gain, triple-band performance, lower cost and compact size makes this antenna a promising candidate for ambient RF energy harvesting applications.

mm-Wave radars are widely used in the automotive industry, but the concept is rather new for wearable applications, such as detection of obstacles for visually impaired people. Beam-switching techniques for radar antennas, typically, are either complicated or bulky, whereas for wearable applications, simpler methods are desirable. In this paper, we present a high gain antenna array with a low profile and a simple beam-switching design. The concepts of parasitic antenna array and partially reflective surface have been combined to simultaneously achieve a narrow beam (higher gain) as well as beam-switching. Additive manufacturing (screen printing) has been utilized which ensures flexibility (essential for wearable applications) and a lower cost. A ±30° beam switching and 11-13 dB realized gain has been achieved, which is deemed suitable for the given application.

Semitransparent surfaces are used in antenna reflectors to obtain the required shape of the radiation pattern. The task of transparency optimization can be simplified with analytical formulae. In this paper, we investigate the scattering of a vector cylindrical wave by a semitransparent half-plane and axisymmetric reflector. The profile of the reflector can be concave, convex, or concavo-convex. We derive some asymptotic formulae for the radiation pattern of the scattering task. In this paper, we present the numerical results calculated through the asymptotic formulae. These results have also been verified through the method of moments.

A transparent, flexible antenna can be utilized on car windows, solar cells, and similar applications to make use of the existing space for communication. In this work, a flexible, transparent, and wideband mm-wave monopole antenna has been designed, fabricated and tested. The proposed antennas have been realized by inkjet printing of custom made silver nanowire (Ag NW) ink. The antenna shows ultra-wide bandwidth up to 26 GHz (from 18 GHz to 44 GHz), high radiation efficiency of 55% and a maximum gain of 1.45 dBi. In addition, more than 90% transparency has been obtained due to the high transparency of the Ag NW and the slot structure. The excellent performance enables the proposed antenna suitable for various applications.

We review machine learning and its applications in a wide range of electromagnetic problems, including radar, communication, imaging and sensing. We extensively discuss some recent progress in development and use of intelligent algorithms for antenna design, synthesis, and characterization. We also provide some perspectives for future research directions in this emerging field of study.