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Cancer affects a significant percentage of people, and early detection techniques are important for prompt and effective treatment. The use of microwave frequencies to achieve non-invasive and non-destructive cancer detections is currently under investigation by several research groups. In this frequency range, the dielectric properties of the biological tissue determine the interactions of the tissue with electromagnetic fields. Knowledge of the dielectric properties of both the normal and the malignant human tissues is therefore a fundamental starting point. A dielectric spectroscopy system, based on the use of a reflectometry setup, was used to perform an extensive experimental campaign on fresh surgical specimens. The measurement system allowed achieving a broadband dielectric characterisation of biological tissues up to 50 GHz, thus including millmetre-wave (mm-wave) frequencies. In the case of breast tissues, the results showed that the malignant and normal tissues exhibit significantly different complex dielectric permittivities of up to 50 GHz, due to their respective high and low water content. This permittivity difference is well detectable, and this paves the way to new screening methods based on mm-wave imaging systems.Introduction: Cancer is a leading cause of disease worldwide. Growing knowledge about this problem has significantly increased the success rate of medical treatments, particularly for breast cancer, which represents the most frequently diagnosed cancer among women [1]. This tendency is due to both improvements in the treatment approaches and to the widespread use of breast screening to permit early tumour detection. The best established methods for breast cancer detection are X-ray mammography (with the disadvantage of ionising radiation exposure) and ultra-sound. Magnetic resonance imaging can also be used to provide additional information, but it is not cost-effective as a screening technique. An interesting approach is based on imaging at microwave frequencies, which allows for non-invasive detection and accurate characterisation [2]. Microwave detection is based on the transmission of a microwave signal from an antenna; a fraction of the electromagnetic field is scattered by dielectric discontinuities of the biological tissues and can be collected by the antenna. Therefore, the contrast in the dielectric properties between normal and malignant tissues is fundamental for diagnostic applications of microwaves. Measurements of the dielectric properties of breast tissues in the radio and microwave frequency ranges have been previously reported [3]. In these studies, not all types of normal, benign and malignant tissues were included, and generally measurements have not extended above 3.2 GHz. A first wideband characterisation of human breast tissues characterising the dielectric properties of a large number of freshly excised tissue samples from breast reduction, biopsy, lumpectomy and mastectomy has been conducted covering the frequency range from 0.5 to 20 GHz [4].This Letter presents...

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The design and fabrication of a band-pass step impedance filter based on high and low dielectric constant sections has been realized on substrate integrated waveguide (SIW) technology. The overall process includes the design of the ideal band-pass prototype filter, where the implementation of the impedance inverters has been carried out by means of waveguide sections of lower permittivity. This can be practically achieved by implementing arrays of air holes along the waveguide. Several SIW structures with and without arrays of air holes have been simulated and fabricated in order to experimentally evaluate their relative permittivity. Additionally, the equivalent filter in SIW technology has been designed and optimized. Finally, a prototype of the designed filter has been fabricated and measured, showing a good agreement between measurements and simulations, which demonstrates the validity of the proposed design approach.

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