Advances in Microwave Near-Field Imaging: Prototypes, Systems, and Applications

Abstract

Microwave imaging is a science which evolves from detecting techniques to evaluate hidden or embedded objects in a structure or media using electromagnetic (EM) waves in the microwave range (i.e., from 300 MHz to 300 GHz). Microwave imaging is often associated with radar detection such as target detection and tracking, weather pattern recognition, and underground surveillance which are far-field applications. In recent years, due to microwave's characteristic that allows penetration into optically opaque media, short-range applications including medical imaging, nondestructive testing and quality evaluation, through-the-wall imaging, and security screening have been utilized. Microwave near-field imaging occurs when detecting the profile of an object within the short-range: when the distance apart from the sensor to the object is from less than one wavelength to several wavelengths --This is coarse definition because the size of the antenna and the object is often comparable to the range between them.A near-field microwave imaging system attempts to reveal the presence of an object and/or an electrical property distribution by measuring the scattered field from many positions surrounding the object. Typically many sensors are placed near the object and either a quantitative or a qualitative algorithm is applied to the collected data. Over the past few decades, both the hardware and software components of a near-field microwave imaging system technology have attracted interest throughout the world. Due to limitations of hardware technology (unavailability of data acquisition apparatus), experimental microwave imaging is very challenging for the pioneers. Examples can be found are the canine kidney imaging experiment carried by Jacobi and Larsen in the 1970s [1]-[3], and active microwave imaging for horse kidney by Jofre and Bolomey [4]. In 1990s, researchers started being able to use microwave signal higher than 1 GHz in real imaging systems. One example is by Bolomey and Pichot, who developed a practical system [5] and designed a planar microwave camera, both operating at This paper has been accepted by IEEE Microwave Magazine and published on a future issue.2.45 GHz [6]. However, Probably due to the hardware cost, most of the studies (operating at a few GHz) were still focused on software only. The feasibility of using microwave approaches to image different types of objects have been tested and verified by simulations in a variety of applications. Further, work has been conducted on improving both quantitative and qualitative algorithms to improve simulated reconstruction results. Nowadays, benefitting from the hardware progress and reduction of their cost, researchers are eager to pursue real experimental validations instead of simulations, and, more unique prototypes and commercial systems have been built for various applications. These prototypes and systems are a result of years of dedicated work and it is important to review the advancements in developed prototype systems. The article will provide an overv...

A Simulation-Based Methodology of Developing 3D Printed Anthropomorphic Phantoms for Microwave Imaging Systems

“…Microwave technology offers a low-cost, mobile, and non-ionizing diagnostic alternative modality for applications such as cerebrovascular disease monitoring or tumor detection. Several studies have shown that, in the microwave frequency range, a significant difference in dielectric properties exists between normal and pathological tissues [ 1 , 2 , 3 , 4 ]. Consequently, several research teams are working on this topic around the world and some imaging systems dedicated to these applications are emerging [ 5 , 6 , 7 , 8 , 9 ].…”

Complementary Split-Ring Resonator With Improved Dielectric Spatial Resolution

“…A substantial contrast in dielectric properties has been established between normal and malignant breast tissue over a broad frequency range from 0.5 to 50 GHz [14]. Based on this dielectric contrast, several microwave imaging systems [15] and algorithms [16] for breast cancer detection have been developed which resulted in multiple clinical prototypes [17].…”

Ring‐shaped antenna array for multistatic microwave breast imaging systems

“…Within the last 20 years, microwave imaging has attracted significant interest in medical applications, and a number of research groups around the world are now working on developing efficient microwave imaging systems. [1][2][3] In general, a microwave imaging system is comprised of hardware and software components. The hardware collects microwave scattering data from the object under test.…”