Antenna-coupled microbolometers for passive millimeter-wave imaging

Antenna-coupled microbolometers have demonstrated an adequate sensitivity for mm-wave detection. The detector operating principle is based on a lithographic antenna, which is terminated by a matched resistive bolometer. The incident RF power is dissipated in the bolometer element, and the resulting temperature rise is measured with low noise electronics. In this paper, we summarize the recent development in microbolometer technology for millimetrewave imaging. The aim is to develop a 20 element linear array of detectors with an optical NEP< 10 . 10(-12)/root Hz at room temperature. In order to reach good performance, excellent thermal isolation of the bolometer element is required. This can be achieved either by silicon micromachining techniques or by the use of low thermal conductivity substrate materials. For good optical performance, a careful design of the coupling structures is required. The lithographic antenna candidates best suited for array applications is discussed. Also the requirements for integrated quasioptical elements are presented.