Abstract Details
| Name: supravika Affiliation: intern Conference ID: ASI2015_788 Title : Development of planar fat sinusoidal tooth structure Authors and Co-Authors : A.Raghunathan Associate Engineer, Radio Astronomy Lab, RRI,Bangalore and N.Udaya Shankar Professor, Dept of A&A, RRI,Bangalore Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : 21cm line of neutral hydrogen is considered as an unique tool to detect signals from the Epoch of reionization (EoR). We describe in this paper, the design and development of a planar fat sinusoidal tooth structure which can used for the precise measurement of this signal.It is an all-sky feature visible at red shifted 21cm line and is predicted to be at most 20-30mK.Detecting such a weak signal in the presence of dominant Galactic and Extra-galactic background is challenging. Precise measurement of it requires detecting device such as an antenna to have frequency independent radiation pattern and return loss characteristics. Their frequency dependence results in undesired spectral features in the measured spectrum resembling EoR signal. Radiation pattern of the antenna like a simple half wave dipole can be made frequency independent by making its structure electrically small in dimension. However, high impedance mismatch produced as a result of this, produces a large ripple in its impedance characteristics due to i) its surface current not decaying linearly away from the feed point in a frequency dependent way and ii) an increase in the radiation reactance of the antenna. These two effects could be overcome by giving an appropriate profile to the structure of the antenna. Profile plays a major role in attenuating the surface current through efficient radiation of the surface signal. We have conducted extensive electromagnetic simulation and has shown that an antenna having sinusoidally profiled structure exhibits both frequency independent radiation and impedance characteristics. To achieve both these characteristics over a large bandwidth, dipoles are made generally very fat. However, with that arrangement, it is difficult to design the antenna which can respond to two orthogonal polarizations simultaneously. To achieve this specifically, along with frequency independent radiation and smooth impedance characteristics, over a large bandwidth, we have designed a planar fat sinusoidal tooth structure to operate in the frequency range 100 – 1000MHz.In this talk, we present the challenges faced in the design, methodology adopted in the process of fabrication and measurements of the radiation patterns. |