Design of frequency independent profiled discone antenna for detecting spectral ripples from the epoch of recombination

Detection of distortions in the spectrum of cosmic microwave background radiation (CMBR) is the current challenging problem in the modern observational cosmology. It holds key to understand the evolution of early universe. These distortions are predicted to be 8-9 orders of magnitude weaker than CMBR temperature and hence require an antenna with smoothly varying radiation and impedance characteristics without any inflexions, for their detection. We describe in this paper the design of a sinusoidally profiled discone antenna having the frequency independent performance in the frequency range 2-4 GHz. The structure is electromagnetically modeled and optimized. The return loss of the prototype built is better than 15 dB and has non-uniformity at <; 1% level. The half power beam width has a max. variation of 10% across the operating band.