The millimeter-wave (mmWave) antennas for smartphones are one of the key components to complete the transition to 5G mobile networks. Although research and development of mmWave 5G antennas for cellular handsets are currently at the center of a significant research effort in both academia and telecommunication industry, a systematic antenna design approved by wireless community has not been proposed yet. With this communication, we propose a novel, high gain, wide band and compact mmWave 5G antenna, namely clover antenna for cellular handsets. The presented antenna has clover like conductor profile whose parameters can be adjusted to obtain high gain or wide band. The designed antennas are simulated with a widely used full-wave analysis tool. Numerical results of the mmWave antenna are confirmed successfully by the experimental results in 24-28 GHz band. The antenna achieves measured peak gain of 7.8-9 dBi in the band. Besides, with a 16-element clover antenna array, the beam steering capability of the antenna is demonstrated. Beam steering between ±45° is achieved with low side lobe levels. Practical design considerations for the integration of the arrays in handset to obtain full-coverage in horizontal plane are investigated. The calculated spatial peak power density values of the proposed array on the outer surface of a head phantom are demonstrated for different scan angles.

An all-textile cavity-backed substrate integrated waveguide (SIW) antenna is proposed for military applications. The antenna matches standard military badge size. The aircraft-shape badge antenna that operates in X-band is designed for air force. SIW cavity and meandered slots that form the body and wing of the figure provide resonance at 8 GHz with 26% bandwidth. Symmetrical boresight patterns with very low sidelobes are observed. The measured gain and efficiency of the structure are 5.2 dBi and 79.2% at 8 GHz, respectively. This efficiency value is the highest among other SIW cavity textile-antennas. The antenna is investigated on conformal surfaces, as well. Bending of the antenna to follow body movements does not deteriorate performance of the textile antenna sensor. The peak specific absorption rate value over 10 g of tissue was 0.53 and 0.69 W/kg for 30 dBm input power for female and male breasts, which makes it suitable as an on-body antenna. The badge antenna is fabricated with standard textile fabrication techniques and its simulation performance is confirmed successfully by measurements. Usage of standard off-the-shelf parts for the assembly and fabrication with standard textile fabrication techniques enables simple and cost-effective mass production of the proposed badge antenna.

In this paper, a reconfigurable Multiple-Input Multiple-Output (MIMO) antenna array is presented for 5G portable devices. The proposed array consists of four radiating elements and an Electromagnetic Band Gap (EBG) structure. Planar monopole radiating elements are employed in the array with Coplanar Waveguide Ports (CWPs). Each CWP is grounded on one side to a reflecting L-shaped structure that has an effect of improving the antenna’s directivity. It is shown that by inductively connecting Minkowski fractal structure of $1^{st}$ order to the radiating element, the impedance matching is improved that results in enhancement in the array’s bandwidth performance. The EBG structure is used to provide the isolation between antenna elements in the MIMO array. The fractal structure is connected to the L-shaped reflector through four photosensitive light dependent resistor (LDR) switches. The effect of various LDR switching configurations on the performance of the antenna is investigated. The proposed array provides a novel performance in terms of S-parameters with enhancements in the radiation properties. Such enhancements

A conformal transverse slotted substrate integrated waveguide (SIW) metamaterial leaky-wave antenna sensor with uniform slots is investigated and analyzed for mmWave sensing applications. Firstly, its planar version is introduced. Then, its performance is compared with the curved SIW antenna. The metamaterial characteristics of the antennas are investigated. The transverse slots on the array forms a composite right/left-handed (CRLH) metamaterial structure that controls the radiation direction as the function of frequency. It behaves like a left handed metamaterial and radiates backward in the lower frequencies of the band (28-45GHz), whereas it behaves like a right handed metamaterial that scans forward direction at the higher frequencies (45-62GHz). Approximately 80° beam scanning is obtained in curved version with acceptable side lobe levels, whereas 110° beam steering is achieved with the planar version. Theoretical analysis and the simulation results are confirmed successfully by the experimental results in the 28-40 GHz band. Besides, a practical example of conformal SIW metamaterial antenna on military helmet made of a ballistic material is illustrated. The calculated spatial peak power density values of the proposed curved SIW metamaterial antenna on the outer surface of a head phantom are demonstrated.

This paper proposes a transmitter system based on direct antenna amplitude-shift keying modulation for point-to-point microwave link. The proposed system is formed from a conventional microstrip antenna and a novel reconfigurable metasurface layer (RMSL). The proposed RMSL has two states: OFF (or Logic-0) and ON (or Logic-1) where each switching scenario provides a certain gain level. This is achieved through controlling the proposed RMSL switching configuration to control the amplitude of the transmitted signal. Results show that such a system can modulate electromagnetic signals directly by varying the antenna’s gain from about 2 dBi for Logic-0 to 13.8 dBi for Logic-1. An analytical model-based ray-tracing technique is invoked to explain the operation of the proposed antenna system. To demonstrate the operation of the proposed system, both the antenna and the RMSL structures were fabricated, assembled and tested. Measurements show good agreement with the theoretical model and numerical simulations obtained using CST Microwave Studio software package. The overall system has dimensions of 25×25×7.3 cm3.

Popularity of millimeter wave circuits has increased recently. One of the main reasons for this increase is offering wide frequency band and high speed data transfer. Due to the manufacturing requirements, these circuits are covered with surface finishes. Although surface finish protects the exposed copper circuitry, these additive layers on copper foil affect the electrical properties of the conductor. Unlike previous papers in literature, this paper deals with the effects of surface finishing materials on millimeter wave antennas instead of transmission lines. With this aim, a differential dual exponentially tapered slot antenna (DETSA) that has almost constant gain, beamwidth and low reflection coefficient over the entire V-band is designed. A balun is designed for one port measurement of the differential antenna. Then, two widely used surface finish solutions, namely Electroless Nickel Immersion Gold (ENIG) and Immersion Silver (IAg), are applied on the copper profile of the differential integrated antenna combined with balun. The structures are simulated with a widely used full-wave analysis tool. The antenna without surface finish, with ENIG and IAg surface finishes are fabricated and measured. Peak gain of 8.7 -9 dBi is measured in the 57-64 GHz ISM band for the antenna without surface finish. Only 0.2 dB decrease in maximum gain is observed with 0.4 μ m silver. With ENIG surface finish, gain decrease is observed as 1 dB. ENIG has higher loss due to flow of current in nickel material having lower conductivity compared to copper. The measurement results are consistent with the numerical results.