Receiver Design for Passive Millimeter Wave (PMMW) Imaging

Passive Millimeter Wave (PMMW) sensors are used for remote sensing and security applications. They rely on radiometric receivers to sense very small power differences. The performance of radiometric receivers should be characterized in different ways than communications and radar receivers. In communications we typically think in terms of carrier-to-noise ratio (CNR) or signal-to-noise ratio (SNR) relating a generated signal to noise floor. In a PMMW system, the signal sources are random white ‘noise’ resulting from black body radiation from objects in a scene. The power emitted by an object is proportional to its temperature on a Kelvin scale (relative to absolute zero) and contrast is achieved in a PMMW image by spatial correlation of temperature differences within the scene.