Conventional breast cancer detection techniques including X-ray mammography, magnetic resonance imaging, and ultrasound scanning suffer from shortcomings such as excessive cost, harmful radiation, and inconveniences to the patients. These challenges motivated researchers to investigate alternative methods including the use of microwaves. This article focuses on reviewing the background of microwave techniques for breast tumour detection. In particular, this study reviews the recent advancements in active microwave imaging, namely microwave tomography and radar-based techniques. The main objective of this paper is to provide researchers and physicians with an overview of the principles, techniques, and fundamental challenges associated with microwave imaging for breast cancer detection. Furthermore, this study aims to shed light on the fact that until today, there are very few commercially available and cost-effective microwave-based systems for breast cancer imaging or detection. This conclusion is not intended to imply the inefficacy of microwaves for breast cancer detection, but rather to encourage a healthy debate on why a commercially available system has yet to be made available despite almost 30 years of intensive research.

We present the idea and design of a dual polarized metasurface for electromagnetic energy harvesting. A 4 × 4 super cell with alternating vias between adjacent cells was designed to allow for capturing the energy from various incident angles at an operating frequency of 2.4 GHz. The collected energy is then channeled to a feeding network that collects the AC power and feeds it to a rectification circuitry. The simulation results yielded a radiation to AC and an AC to DC conversion efficiencies of around 90% and 80%, respectively. As a proof of concept, an array consisting of 9 super cells was fabricated and measured. The experimental results show that the proposed energy harvester is capable of capturing up to 70% of the energy from a planewave having various polarizations and converting it to usable DC power.

In this letter, we propose metasurface absorbers for energy harvesting that work on the principles of destructive interference and phase cancellation. The metasurface is designed by arranging four L-shaped resonant unit cells in a fourfold symmetrical geometry leading to a cross configuration. At resonance frequency, such a geometrical configuration results in destructive interference of the electromagnetic waves emanating from diagonal elements. When used in a reflection mode as a metasurface absorber, the reciprocity theorem necessitates the flow of helicoidal resonant currents that vectorially cancel each other to make the overall metasurface nonradiative that, therefore, produces a null in the backscattering direction. A 90% absorption in simulation is achieved without explicit consideration for a free-space impedance matching or using dissipative substrate. The absorbed RF energy is harvested at 2.25 GHz to practically demonstrate the conversion efficiency of over 55% from microwave to dc.

This article presents a state-of-the-art 3-D-printed dielectric reflectarray antenna featuring one-shot deployability and wide-angle beam-scanning ability. The design is enabled by a series of a “kirigami”-inspired two-stage snapping-like element structure that can be retracted by 66% to save space. The prototype is fabricated with a stereolithography (SLA) 3-D printing method with the Formlabs Flexible 80A photopolymer. A bifocal phase distribution method is utilized to optimize the RF performance of the array, realized −30° to −10° and 10° to 30° beam-scanning ability. The outcome of this work demonstrated a high-performance dielectric reflectarray design with ease of fabrication for 5G and satellite communication applications.

A novel approach to designing rectenna systems by eliminating the use of a matching network between the antenna and the rectifier is presented. The proposed rectenna consists of a wide impedance bandwidth 8 octagon disks placed at two different layers laying on both sides of a single substrate and backed by a ground plane. A Schottky diode is placed at each layer right at the feeding location without matching network, forming an array of two rectennas. The rectified power is smoothed out using a low pass filter composed of two RF choke inductors for each rectenna. By virtue of the wide impedance bandwidth of the antenna, the measurement results of the rectenna yielded a 50% radiation to DC efficiency at the operating frequency of 2.1 GHz. The rectifiers were then connected in series or parallel to study the effect of the connection type on the rectified output power. Wideband load resistance response and configurable amount of output DC currents and voltages can be realized using certain DC power combining methods.

In this work, we propose a near-field microwave sensing modality that uses a single probe combined with a classification algorithm to help in detecting the presence of tumors in the human female breast. The concept employs a near-field resonant probe with an ultra-narrow frequency response. The resonant probe is highly sensitive to the changes in the electromagnetic properties of the breast tissues such that the presence of the tumor is gauged by determining the changes in the magnitude and phase response of the sensor’s reflection coefficient. A key feature of our proposed detection concept is the simultaneous sensing of tissue property changes to the two female breasts since the right and left healthy breasts are morphologically and materially identical. Once the probe response is recorded for both breasts, the Principle Component Analysis (PCA) method is employed to emphasize the difference in the probe responses. For validation of the concept, tumors embedded in a realistic breast phantoms were simulated. To provide additional confidence in the detection modality introduced here, experimental results of three different sizes of metallic spheres, mimicking tumors, inserted inside chicken and beef meat were detected using an electrically-small probe operating at 200 MHz. The results obtained from the numerical tests and experiments strongly suggest that the detection modality presented here might lead to an inexpensive and portable early and regular screening for breast tumor.