Fundamental challenges for wideband antenna elements in focal-plane arrays

This paper discusses the main design challenges of wideband antenna elements which can be used in focal-plane arrays. A novel electrically-small wideband antenna is presented. It is based on a bow-tie antenna. The proposed antenna shows excellent input matching properties over a frequency band of more than one octave and nearly reaches the theoretical Chu-Harrington limit. It is shown that the centre element of a five-element feed array, operating at a centre frequency of 30 GHz, realizes an input matching bandwidth of 24.4 GHz