Globally, breast cancer is a major reason for female mortality. Due to the limitations of current clinical imaging, the researchers are encouraged to explore alternative and complementary tools to available techniques to detect the breast tumor in an earlier stage. This article outlines a new, portable, and low-cost microwave imaging (MWI) system using an iterative enhancing technique for breast imaging. A compact side slotted tapered slot antenna is designed for microwave imaging. The radiating fins of tapered slot antenna are modified by etching nine rectangular side slots. The irregular slots on the radiating fins enhance the electrical length as well as produce strong directive radiation due to the suppression of induced surface currents that radiate vertically at the outer edges of the radiating arms with end-fire direction. It has remarkable effects on efficiency and gain. With the addition of slots, the side-lobe levels are reduced, the gain of the main-lobe is increased and corrects the squint effects simultaneously, thus improving the characteristics of the radiation. For experimental validation, a heterogeneous breast phantom was developed that contains dielectric properties identical to real breast tissues with the inclusion of tumors. An alternative PC controlled and microcontroller-based mechanical MWI system is designed and developed to collect the antenna scattering signal. The radiated backscattered signals from the targeted area of the human body are analyzed to reveal the changes in dielectric properties in tissues. The dielectric constants of tumorous cells are higher than that of normal tissues due to their higher water content. The remarkable deviation of the scattered field is processed by using newly proposed Iteratively Corrected Delay and Sum (IC-DAS) algorithm and the reconstruction of the image of the phantom interior is done. The developed UWB (Ultra-Wideband) antenna based MWI has been able to perform the detection of tumorous cells in breast phantom that can pave the way to saving lives.

A novel, low cost, and comprehensive microwave imaging (MWI) system is presented for the detection of unwanted tumorous cells into the human breast. A compact metamaterials (MTM) artificial magnetic conductor (AMC) surface-inspired coplanar waveguide fed (CPW-fed) microstrip antenna is developed for MWI applications. The initial wideband CPW antenna is designed by the modified oval shape patch and half cycle copper stripe line ground. The antenna is incorporated with two layers uniplanar AMC structure which is composed of a $5\times 5$ array of square modified split ring resonator unit cells to obtain the desired antenna characteristics for the MWI applications like breast imaging. The metamaterial-based AMC structure improves the gain about 5 dB and produces stronger directive radiation characteristics. The enhancement of CPW performance proofs the effectiveness of the double layer MTM-AMC structure and its suitability for MWI. A microcontroller-based PC controlled alternative mechanical imaging system is designed to collect the scattering signal from the CPW-fed antenna. The changes of reflection and transmission coefficient with the variation of dielectric content into the breast phantom structure are analyzed. The remarkable deviation of scattered field is processed by image processing program using Matlab. By using these AMC inspired CPW-fed antenna based microwave imaging, the system can clearly detect the tumor inside the breast phantom.

This work proposes a compact metasurface (MS)-integrated wideband multiple-input multiple-output (MIMO) antenna for fifth generation (5G) sub-6 GHz wireless communication systems. The perceptible novelty of the proposed MIMO system is its wide operating bandwidth, high gain, lower interelement gap, and excellent isolation within the MIMO components. The radiating patch of the antenna is truncated diagonally with a partially ground plane, and a metasurface has been employed for enhancing the antenna performance. The suggested MS integrated single antenna prototype has a miniature dimension of 0.58λ × 0.58λ × 0.02λ. The simulated and measured findings demonstrate a wideband characteristic starting from 3.11 to 7.67 GHz including a high realized gain of 8 dBi. The four-element MIMO system has been designed by rendering each single antenna orthogonally to one another while retaining compact size and wideband properties between 3.2 and 7.6 GHz. The suggested MIMO prototype has been designed and fabricated on a low loss Rogers RT5880 substrate with a miniature dimension of 1.05λ × 1.05λ × 0.02λ and its performance is evaluated using a suggested 10 × 10 array of a square enclosed circular split ring resonators within the same substrate material. The inclusion of the proposed metasurface with a backplane significantly reduces antenna backward radiation and manipulates the electromagnetic field, thus improving the bandwidth, gain and isolation of MIMO components. The suggested 4-port MIMO antenna offers a high realized gain of 8.3 dBi compared to existing MIMO antennas with an excellent average total efficiency of 82% in the 5G sub-6 GHz spectrum and is in good accordance with measured results. Furthermore, the developed MIMO antenna exhibits outstanding diversity characteristics in respect of envelope correlation coefficient (ECC) less than 0.004, diversity gain (DG) close to 10 dB (> 9.98 dB) and high isolation between MIMO components (> 15.5 dB). Therefore, the proposed MS-inspired MIMO antenna substantiates its applicability for 5G sub-6 GHz communication networks.

A gap coupled hexagonal split ring resonator (GCHSRR) based metamaterial is presented in this paper for S-band and X-band microwave applications with absorptance. This gap coupled hexagonal split ring resonator is the amendment of the typical split-ring resonator (SRR). Three interconnected hexagonal split ring resonators are applied with a stripline to increase the electrical length and coupling effect of the GCHSRR. SRR has an impact on the extraction of effective parameters such as permittivity, permeability and refractive index. The dimension of the proposed GCHSRR unit cell is 10×10 mm2, which is printed on low-cost FR4 material. The transmission frequency of the proposed GCHSRR unit cell ranges from 3.42 GHz to 3.73 GHz and 11.27 GHz to 11.91 GHz, which makes the metamaterial applicable for S-band and X-band microwave applications. The GCHSRR unit cell has a double negative regime of 7.92 GHz to 9.78 GHz with an effective negative refractive index regime of 6.30 GHz to 10.22 GHz and 11.97 GHz to 12.61 GHz. The effective medium ratio is 8.4, which implies the novelty of the proposed design. Moreover, the GCHSRR has high absorption peaks of 99%, 98%, and 81% at 4.27 GHz, 5.42 GHz, and 12.40 GHz, respectively. An 18×20 GCHSRR array structure is also designed and studied. The effective parameters and the effective medium ratio with a high absorptance make the proposed GCHSRR based metamaterial suitable for practical microwave applications.

A miniaturized antenna employing a negative index metamaterial with modified split-ring resonator (SRR) and capacitance-loaded strip (CLS) unit cells is presented for Ultra wideband (UWB) microwave imaging applications. Four left-handed (LH) metamaterial (MTM) unit cells are located along one axis of the antenna as the radiating element. Each left-handed metamaterial unit cell combines a modified split-ring resonator (SRR) with a capacitance-loaded strip (CLS) to obtain a design architecture that simultaneously exhibits both negative permittivity and negative permeability, which ensures a stable negative refractive index to improve the antenna performance for microwave imaging. The antenna structure, with dimension of 16 × 21 × 1.6 mm³, is printed on a low dielectric FR4 material with a slotted ground plane and a microstrip feed. The measured reflection coefficient demonstrates that this antenna attains 114.5% bandwidth covering the frequency band of 3.4–12.5 GHz for a voltage standing wave ratio of less than 2 with a maximum gain of 5.16 dBi at 10.15 GHz. There is a stable harmony between the simulated and measured results that indicate improved nearly omni-directional radiation characteristics within the operational frequency band. The stable surface current distribution, negative refractive index characteristic, considerable gain and radiation properties make this proposed negative index metamaterial antenna optimal for UWB microwave imaging applications.