RESEARCH ARTICLE Miniaturized on-body antenna for small and wearable brain microwave imaging systems Amir Arayeshnia 1 | Shervin Amiri 2 | Asghar Keshtkar 1 1 Faculty of Technical and Engineering, Imam Khomeini International University (IKIU), Qazvin, Iran 2 Department of Electrical Engineering and Information Technology, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran Correspondence Shervin Amiri, Department of Electrical Engineering and Information Technology, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran. Email: amiri@irost.ir Abstract A miniaturized inset-fed on-body meandered bowtie antenna designed for brain microwave imaging systems is presented in this article. The proposed on-body antenna can contribute to the realization of a wearable and portable brain microwave imaging system. The size of 18 × 18 mm 2 is achieved at a fre- quency range of 0.75 to 4 GHz by the simultaneous use of self-complementary structures and meandered lines. The frequency band is a trade-off between penetration depth and spatial resolution. The proposed antenna performance was studied at different positions on the human head voxel model in terms of several parameters such as reflection coefficient, near-field directivity, and fidelity factor. In addition, the antenna bandwidth was surveyed on several volunteers using a wearable measurement setup. It has been found that the averages of measured reflection coefficients in different scenarios are in good agreement with the corresponding simulation results, and the antenna shows stable performance under different practical situations. The proposed antenna takes advantage of a small footprint and body matching, which make it an eli- gible choice for compact, portable, and wearable head microwave imaging systems. KEYWORDS brain microwave imaging, head voxel model, miniaturized antenna, on-body antenna, wearable antenna 1 | INTRODUCTION Stroke is the second leading cause of death and the third cause of disability in the world. According to the World Health Organization (WHO) report, 15 million people suffer from stroke each year, of which about 5 million of them die and about 5 million of them become perma- nently disabled. 1 When a stroke occurs, special drugs must be used in less than 3 hours for complete recupera- tion. Conventional imaging devices such as magnetic res- onance imaging (MRI) and computed tomography (CT) are expensive, static, and usually inaccessible in minor hospitals and medical centers. Microwave imaging (MWI) provides a fast, cheap, and mobile solution and could replace or supplement conventional imaging methods. In MWI systems, an ultrashort time domain (wide- band frequency domain) pulse is transmitted to the object under imaging, and the scattered signals are col- lected for postprocessing purposes. Determining the sig- nal bandwidth is very important because the lower and upper limits determine the signal penetration in human tissues and the resolution of reconstructed images, respectively. Therefore, designing an array of wideband antennas that can transmit such broadband signals is necessary. Received: 4 September 2019 Revised: 14 December 2019 Accepted: 26 December 2019 DOI: 10.1002/mmce.22133 Int J RF Microw Comput Aided Eng. 2020;e22133. wileyonlinelibrary.com/journal/mmce © 2020 Wiley Periodicals, Inc. 1 of 15 https://doi.org/10.1002/mmce.22133