A Floating Octave Bandwidth Cone-Disk Antenna for Detection of Cosmic Dawn

The critical component of radio astronomy radiometers built to detect redshifted 21 cm signals from Cosmic Dawn is the antenna element. We describe design and performance an octave bandwidth cone-disk this signal in band 40–90 MHz. predicted be wideband spectral feature orders magnitude weaker than sky ground brightness. Thus, engineering challenge at low frequencies, which able provide, with high fidelity, faint cosmological signal, along foreground sky, receiver. characteristics must not compromise detection by imprinting any confusing features on celestial radiation, emission, or receiver noise. Innovation present operating electrically smaller half-wave highest frequency operation surface a sufficiently large water body. homogeneous permittivity medium beneath small results achromatic beam pattern, radiation efficiency, minimum unwanted features. was optimized WIPL-D FEKO. A prototype constructed deployed lake validate its field measurements.