High gain, wide-angle QCTO-enabled modified Luneburg lens antenna with broadband anti-reflective layer.

The gradient-index (GRIN) Luneburg lens antenna offers significant benefits, e.g. high aperture efficiency, low-power, minimal cost, wide beam scanning angle and broad bandwidth, over phased array antennas and reflector antennas. However, the spherical shape of the Luneburg lens geometry complicates the integration of standard planar feed sources and poses significant implementation challenge. To eliminate the feed mismatch problem, the quasi-conformal transformation optics (QCTO) method can be adopted to modify the lens' spherical feed surface into a planar one. However, Luneburg lenses designed with QCTO method are limited to poor performance due to the presence of the reflections and beam broadening arising from the quasi-conformal mapping. In this paper, we present a new method of implementing QCTO-enabled modified Luneburg lens antenna by designing a broadband anti-reflective layer along with the modified lens's planar excitation surface. The proposed anti-reflector layer is inherently broadband in nature, has a continuously tapered inhomogeneous dielectric permittivity profile along its thickness, and ensures broadband impedance matching. To show the new QCTO modified Luneburg lens antenna, an example lens antenna was designed at Ka-band (26-40 GHz) and fabricated using fused deposition modeling (FDM) based additive manufacturing technique. Electromagnetic performance of the lens antenna was experimentally demonstrated.

Encapsulated follicular variant papillary thyroid carcinoma: problems in histological diagnosis.

Thyroid neoplasms are the commonest endocrine neoplasms and account for the most number of thyroidectomies done. Encapsulated thyroid lesions are being encountered more commonly in thyroidectomy specimens in recent time. The present study was undertaken to analyse the incidence of thyroid malignancies with a changing pattern and to discuss the difficulties encountered in histopathological interpretation of encapsulated neoplastic lesions of follicular cell origin. It is a retrospective study done in the department of pathology, NRS Medical College, Kolkata. Data of all the thyroidectomy specimens examined over last four years (August 2006 to July 2010) were retrieved and slides were reviewed. All slides of thyroid lesion received in the department of pathology, NRS Medical College for review were also included in this study. Frequency distribution study was done with the sample analysed. Follicular variant of papillary carcinoma was the commonest type of thyroid malignancy, on review, with the encapsulated sub-variant exceeding the diffuse type. This variant is a diagnostic challenge because it has to be differentiated from other encapsulated follicular thyroid lesions, especially follicular adenoma. The data analysis, results and problems in the diagnostic protocols are discussed in this study along with review of literature. Reclassification of thyroid tumour may be warranted in future with this background.