Miniaturized on‐body antenna for small and wearable brain microwave imaging systems

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 mm2 is achieved at a frequency 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 eligible choice for compact, portable, and wearable head microwave imaging systems.

Improving the Probability of Stroke Detection inside the Human Head Using Wideband Polarimetric Synthetic Aperture Radar Imaging

“…A method to effectively improve the reflection coefficient, as well as radiation characteristics of the antenna, is to immerse antennas in a coupling liquid which acts as an impedance-transformer medium between the radiator and the tissue. However, placing the antennas in the coupling liquid makes it impractical/hard to implement a transportable device [3,8,15].…”

“…Since the antenna and its array configuration play a major role in the success of imaging systems, several types of antennas and arrays for EM head imaging have been proposed in the literature alongside previously mentioned imaging systems [8,[13][14][15]. Realizing features such as compactness, low profile, body-matched, and directive patterns in such systems is challenging due to antenna size and frequency band limitations [4,16].…”

Enhanced head phantom for wearable microwave tomography devices evaluation

“…22 Therefore, the reflection coefficient can be used as a measure to investigate the performance of the proposed phantom. In this regard, an on-body antenna (a printed meandered bowtie shown in Figure 5) 23 with an operational spectrum of 0.5-4.5 GHz and footprint of 18 Â 18 mm 2 was chosen to study its characteristic on the numerical model and fabricated phantom. The effect of human head layers on the antenna radiation gain is described by the author in Reference 23.…”

“…The results indicate that the bandwidth of the antenna performance is almost equal to 0.75-4 GHz reported in the reference by a series of measurements on a group of volunteers. 23 The electromagnetic wave propagations through the numerical head model at 1-4 GHz and different scenarios are illustrated in Figure 10. As shown, some of the radiated power is propagated through the skin-skull channel and not penetrated to the intracranial tissues, which emphasizes the importance of these two tissues in the head model and performance of MWT instruments.…”