A compact high-performance circularly-polarized microstrip antenna for the global positioning system application is proposed. It comprises a fractal hi-impedance surface electromagnetic bandgap (EBG) structure printed on a high permittivity substrate. Measurements and simulation of return loss and axial ratio are in good agreement. It is shown that the proposed Global Positioning System antenna has good axial ratio performance in the upper half-plane, an improvement in gain and a significantly wider axial ratio bandwidth when compared to the same antenna without EBG

This Letter introduces a feasibility study of a scanning system for applications in biomedical bone imaging operating in the microwave range 0.5–4 GHz. Mechanical uncertainties and data acquisition time are minimised by using a fully automated scanner that controls two antipodal Vivaldi antennas. Accurate antenna positioning and synchronisation with data acquisition enables a rigorous proof‐of‐concept for the microwave imaging procedure of a multi‐layer phantom including skin, fat, muscle and bone tissues. The presence of a suitable coupling medium enables antenna miniaturisation and mitigates the impedance mismatch between antennas and phantom. The three‐dimensional image of tibia and fibula is successfully reconstructed by scanning the multi‐layer phantom due to the distinctive dielectric contrast between target and surrounding tissues. These results show the viability of a microwave bone imaging technology which is low cost, portable, non‐ionising, and does not require specially trained personnel. In fact, as no a‐priori characterisation of the antenna is required, the image formation procedure is very conveniently simplified.

A printed triangular monopole antenna with wideband circular polarization is presented. The wideband circular polarization is achieved by asymmetrical excitation of a triangular ground plane and planar triangular monopole. The combined radiation provides a wide axial-ratio bandwidth spanning from 1.42 to 2.7 GHz (62%). A parametric study of key geometric parameters is given for clear understanding of the radiation mechanism.

The aim of this work was to develop multimodal anthropomorphic breast phantoms suitable for evaluating the imaging performance of a recently-introduced Microwave Imaging (MWI) technique in comparison to the established diagnostic imaging modalities of Magnetic Resonance Imaging (MRI), Ultrasound (US), mammography and Computed Tomography (CT). MWI is an emerging technique with significant potential to supplement established imaging techniques to improve diagnostic confidence for breast cancer detection. To date, numerical simulations have been used to assess the different MWI scanning and image reconstruction algorithms in current use, while only a few clinical trials have been conducted. To bridge the gap between the numerical simulation environment and a more realistic diagnostic scenario, anthropomorphic phantoms which mimic breast tissues in terms of their heterogeneity, anatomy, morphology, and mechanical and dielectric characteristics, may be used. Key in this regard is achieving realism in the imaging appearance of the different healthy and pathologic tissue types for each of the modalities, taking into consideration the differing imaging and contrast mechanisms for each modality. Suitable phantoms can thus be used by radiologists to correlate image findings between the emerging MWI technique and the more familiar images generated by the conventional modalities. Two phantoms were developed in this study, representing difficult-to-image and easy-to-image patients: the former contained a complex boundary between the mammary fat and fibroglandular tissues, extracted from real patient MRI datasets, while the latter contained a simpler and less morphologically accurate interface. Both phantoms were otherwise identical, with tissue-mimicking materials (TMMs) developed to mimic skin, subcutaneous fat, fibroglandular tissue, tumor and pectoral muscle. The phantoms’ construction used non-toxic materials, and they were inexpensive and relatively easy to manufacture. Both phantoms were scanned using conventional modalities (MRI, US, mammography and CT) and a recently introduced MWI radar detection procedure called in-coherent Multiple Signal Classification (I-MUSIC). Clinically realistic artifact-free images of the anthropomorphic breast phantoms were obtained using the conventional imaging techniques as well as the emerging technique of MWI.

A novel technique to reconfigure the frequency range of a planar monopole antenna is presented. By adjusting the degree of spiral tightness, a shift of the well-matched operating frequency range is achieved. The proposed antenna is capable of covering the frequencies in the range from 2.9 to 15 GHz, depending on the degree of spiral tightness. The antenna yields a high-efficiency across the full operating bandwidth. Radiation patterns show good omni-directional features in all primary cuts and remain relatively stable with the change of antenna configuration, so that it is a remarkable candidate for indoor or mobile applications where a large frequency range and omnidirectional radiation are required.