Development of flexible antenna for breast cancer application

Abstract

Breast cancer is the most diagnosed cancer among women all over the world after skin cancer. Meanwhile, microwave imaging has been a prominent detection technique for biomedical diagnosis in recent years and it has become very popular and widely accepted by the researchers and physicians for breast cancer detection (BCD) at an early stage. However, the microwave imaging is struggling with the spatial resolution that can be solved by an imaging technique based on the antenna with a wide operating bandwidth at the higher frequency range. In this thesis, a flexible Elliptical Ring Slotted Planar Monopole Antenna (ERSPMA) with a wide – 10 dB bandwidth of 7 GHz has been proposed for a breast cancer imaging application. This printable monopole antenna, after being design on flexible Polyimide substrate, operates from 7 GHz to 14 GHz which covers the entire X-band frequencies. The proposed antenna has achieved an average flat gain of 4 dBi with an average radiation efficiency of 92% for the entire – 10 dB bandwidth. Therefore, the – 20 dB bandwidth of the antenna covers the entire X-band (8 GHz – 12 GHz) with an average flat gain of 4 dBi and average radiation efficiency of 95%. Therefore, the minimum return loss of the antenna is as low as -58 dB. To justify the design stability, the proposed antenna has been realized on the other two different substrates, Paper and PET. With an average gain of around 4 dBi, the ERSPMA on Paper and PET substrates have achieved an average radiation efficiency of 92.5% and 85.5% respectively for the entire – 10 dB bandwidth of 7 GHz. Therefore, the average radiation efficiency of 97% and 90.5% have achieved with Paper and PET substrates respectively for the X-band frequencies. The average VSWR value for the proposed antenna has achieved around 1.5 and 1.1 for the whole –10 dB bandwidth and X-band frequencies respectively with a minimum value of 1 for all three substrates, which justifies a greater impedance matching between the radiator and the transmitter of the proposed antenna. The quasi-omnidirectional radiation pattern of the antenna offers the freedom of placing the antenna both at the front and back position on the body surface. Therefore, the average Specific Absorption Rate (SAR) of the proposed antenna is below than 0.5 W/kg for 1-gram mass that is within the specified standard by the FCC (≤1.6 W/Kg for 1-gram mass) for the public at microwave frequencies. For flexibility, the bending performance of the antenna has been presented for four different directions. The optimized antenna-prototype has a bandwidth of 5.4 GHz (8.6 – 14 GHz) with a minimum VSWR of 1. Due to the compact area of 13×13 mm2, an average gain of 4.4 dBi and a peak gain of 6.33 dBi, the fabricated antenna is a suitable candidate for biomedical applications in X-band frequencies by utilizing a low-cost manufacturing process. Moreover, the optimized antenna-prototype of the proposed ERSPMA shows good performances with the in-Vivo test.