Volume 75, Issue 3-4

A novel printed and compact profile monopole antenna with hybrid reconfigurability structure for switching the resonant frequency and direction of maximum radiations is proposed in this research work. A novel mathematical model for the architecture of Reconfigurable Patch Antenna (RPA), considering input impedance, bandwidth, antenna gain, antenna efficiency and resonant frequency is proposed. For the desired functionality, antenna is incorporated with three switches in such a way that Switch 1 and Switch 2 direct the radiation beam patterns towards different directions while Switch 3 controls the frequency reconfigurability. When Switch 3 is ON, the designed antenna operates at 26.4 GHz covering the 24.2–26.5 GHz band. When Switch 3 is OFF, it operates at 28 GHZ, covering the 27.4–29.8 GHz band. The antenna is proposed to operate at the 5G mobile communication band having a center frequency at 27.6 GHz with a reflection coefficient of −21.5 dB. A 3D design tool HFSS has been used for the simulation purposes.

In this article, the design of a radiation beam-reconfigurable antenna using the reflector pins is presented. The reflector pins make a short or open connection with the ground, via switches and Plated Through Hole (PTH), which helps in controlling radiation characteristics of the proposed antenna. This design contains a simple 3D printed Cylindrical Dielectric Resonator Antenna that is located at the center of the substrate. The beam-sweeping of the antenna is attained by operating switches in different combinations of ON and OFF states. The reconfigurable CDRA operates at 4.5 GHz and covers all azimuth angles in four steps with a maximum measured gain of 6.6 dBi. This beam-switching antenna is very advantageous because of its trait of eliminating fade zones and beamforming.

A Triple-band Multiple-Input-Multiple-Output (MIMO) antenna for 5G mobile terminal applications is proposed in this paper. The design comprises four-port/two resonators, each having two concentric circular slot ring radiators etched on a ground plane of size 50 mm ×${\times}$ 50 mm. The antenna is fed by perpendicularly arranged 50 Ω microstrip line feeds on the top layer. Decoupling techniques were used to suppress mutual coupling between the two resonators. The perpendicular arrangement of the feed lines and port reduces mutual coupling between the two ports and increases isolation. The antenna operates in multiple bands: 3.35–3.69 GHz, 24–28 GHz, and 37–40 GHz frequency range with central frequencies at 3.5 GHz, 26 GHz, and 38 GHz, respectively allocated for 5G. The antenna provides a gain of 2.7–7.8 dB and a radiation efficiency of 0.49–0.85 in the operating bands. Diversity performance is studied in terms of the Envelop Correlation Coefficient (ECC), Diversity Gain (DG), and Total Active Reflection Coefficient (TARC) were found to be less than 0.01, greater than 9.99 dB, and less than −10 dB respectively. The proposed antenna offers good S-parameters, voltage standing wave ratio (VSWR), TARC, radiation pattern, high gain, and low ECC. The antenna was fabricated and tested. The measured results and simulated results are in good agreement. It possesses sufficient potential for 5G mobile terminal and smart wearable applications.

In this paper a coplanar waveguide feed (CPW) monopole antenna backed with artificial magnetic conductor (AMC) structure for efficient radiation has been presented for off-body wearable applications. A split ring resonator (SRR) having thiner and longer lines to produce higher inductance and six splits with smaller gaps for high capacitance have been placed underneath CPW fed monopole to achieve resonance mode at a lower frequency. Higher values of inductance and capacitance produce resonant modes at relatively lower frequencies resulting in highly miniaturized antenna. The desired −10dB S 11 bandwidth has been optimized firstly, by tuning/optimizing flow of surface currents with the help of several slots/slits and later by realizing AMC reflector with the help of full ground backed foam. The proposed antenna covers 2.45 GHz industrial, scientific and medical (ISM) band body area network (BAN) application and posses good front to back ratio (FBR) and thereby low and acceptable values of specific absorption rate (SAR). The proposed antenna has been designed and simulated using Ansys high frequency structured simulator and tested using vector network analyzer and anechoic chamber. The simulated and measured results well agree with each other.

This paper presents electrical equivalent circuit modelling of various fractal-based UWB antennas. Three different designs have been discussed here as case studies, whose characteristics are diversified in nature. Even the implemented fractal geometries are also unique in nature for these antenna problems. An easy circuit model for each antenna structure is proposed which deciphers the insight device physics of the structure. Without applying much more complicated mathematical jugglery, the models have been presented here. Finally, a comparison of FEM simulated data and the result obtained from circuit modelling is concluded, which establishes the validity of the proposed models.

In this article, broadband gain enhancement of an ultra-wide band (UWB) antenna is achieved by using 4 × 4 array of a wideband negative refractive index (NRI) metamaterial as a reflector layer. A novel shaped metamaterial sized 14.8 × 14.8 mm 2 with double negative (DNG) characteristics in three frequency regions has been fabricated on a flexible FR4 with 0.25 mm thickness. The proposed metamaterial gives a continuous NRI bandwidth of 10 GHz (2–12 GHz). The effective parameters of the unit cell cover S, C, X, and Ku-band independently and show DNG region of 6.1 GHz at C (4–8 GHz) and X band (8.8–10.5 GHz, 11.2–11.6 GHz). The unit cell structure is also found to be feed insensitive. The unit cell has small volume of 54.76 mm 3 along with flexible nature which makes it suitable for wearable applications. For a 4 × 4 array the metamaterial still exhibits DNG characteristics. To understand the physical behavior of the unit cell, the circuit analysis along with the study of magnetic and electric field distribution at three resonance frequencies (2.2, 8.2 and 14.2 GHz) is done. Both simulation and measured results indicate that the gain and bandwidth of metamaterial antenna are enhanced by 2 dB and 0.8 GHz.

In this paper, an Archimedean spiral antenna-based biosensor has been proposed for the early detection of breast tumor. By monitoring the variation of S 11 over 1–3.5 GHz frequency range, the proposed scheme can identify the tumor location, as well as distinguish the types of tumor (benign or malignant) based on shapes and dielectric properties contrast. To validate the concept, full wave simulation using CST microwave suite are performed along with VNA based experimental measurements on breast phantoms and tumors, prepared by easily available materials like glass, petroleum jelly, mixture of water and wheat flour. The demonstrated device is able to detect the tumor of less than 1 mm in radius and positioned anywhere in 5 × 5 × 5 cm of breast fat. The proposed method is easy to use, low cost, safe, comfortable, non-invasive and non- ionizing in nature.

In this paper, a methodical approach for the in-situ monitoring of the mechanical wear of electrical conductors is presented. The state of life can be assessed by means of the characteristic attenuation of an applied high-frequency alternating current. The advantages of this approach include its non-destructive nature and the applicability to installed and otherwise inaccessible conductors.