Aperture Arrays for Radio Astronomy

Ultra-wideband capacitively coupled phased array antennas for low and mid frequency radio astronomy are presented. Two distinct and novel broadband techniques are employed for the candidate current sheet models. One of the arrays is designed to operate from 250 MHz to 1.3 GHz while the other functions from 50 MHz to 400 MHz. The radiating arrays comprise synthetic periodic aperture of fractal plates, each subdivided into a number of scaled down octagon rings. Both structures are dual-polarised and serve as low profile conformal arrays. A 16 x 16 mid-band finite array was constructed to demonstrate its wideband performance. The tightly coupled arrays are limited to bandwidths around 4: 1 (VSWR < 2) without using dielectric substrates. However, a 4 x 4 prototype of the low frequency antenna array validates the purpose of using a conductive resistive frequency-selective surfaces to extend the bandwidth towards higher frequencies. This feature leads to unique array properties, expanding the bandwidth to double. This paper also studies and analyses sensitivity and system noise contribution from such sub-arrays embedded in an infinite periodic array.