Design and Analysis of Non-Uniformly Spaced Dipole Array Antenna

Dipole antenna array is designed at operating frequency of 450MHz using FR4 substrate. Uniform circularly polarized (UCP) and non-uniform circularly polarized (NUCP) dipole arrays are designed. NUCP array is achieved by placing antenna elements at unequal distance from the reference element. Low side lobe level is necessary to reduce interference with other frequencies in the band which is achieved in case of NUCP array compared UCP array. The simulation is carried out using EM flow solver HFSS. The simulation results indicate that there is a reduction in the side lobe level for the 1×7 NUCP array as compared to UCP array. To enhance the gain of the dipole array dielectric lens is used as the secondary radiator which also acts as a radome to protect the array. The maximum gain achieved is 1.59dB with lens. Return loss less than -15dB is achieved in all cases. Axial ratio less than 3dB achieved for circular polarized arrays. The designed NUCP array with lens can be used in SAR (synthetic aperture radar) applications.

A Non-Dispersive X-ray Fluorescence Unit for the Analysis of Biological Tissue Sections

An X-ray fluorescence analysis unit has been designed and built especially for the measurement of certain mineral elements in individual biological tissue sections. Such a section may contain in the neighborhood of 10-10 grams of an element of interest, in a concentration in the range of 1-100 p.p.m.The unit consists of a special high-power X-ray tube with a builtin interchangeable secondary radiator, which irradiates the speciman with the characteristic lines of the radiator element) and a proportional counter and pulse-height analyzer system, which provides analysis of the X-ray spectrum emitted by the specimen. Because the emitted spectrum is greatly simplified by the use of an appropriate radiator element, a diffracting crystal can be omitted, permitting a great increase in absolute sensitivity.The system is feasible only because of two peculiarities of our biological specimens: they are so thin that matrix effects are negligible, and they consist essentially of a few mineral elements in a light matrix.Design considerations, calibration procedures, procedures for the analysis of the observed proportional counter pulse-height spectra and results to date will be discussed.

The direct production of characteristic Röntgen radiations by cathode particles

It is now well known that many elements can be stimulated to produce characteristic X-rays. So far, the only successful method of obtaining the characteristic rays has been to place the element in the path of a beam of X-rays, whereupon it becomes a secondary radiator; and, if the exciting X-rays have the necessary penetrating power, the characteristic rays will make their appearance. Some years ago a remarkable paper by Kaye appeared, in which he showed that if an element, say, copper, were made the anticathode in an X-ray bulb, it could become a source of intense radiation characteristic of copper.