Microwave remote sensing systems detect and quantify the electromagnetic radiation arriving at a detector, this radiation being either emitted (passive sensors) or scatterered back (active sensors) from the objects. Three properties of the recorded electromagnetic signal are of particular interest: its intensity, its phase and its polarization. The specific quantification of each properties allows signal interpretation, as they depend on the roughness and dielectric characteristics of the surface (intensity and polarization) as well as of the range between target and sensor (phase). The detection of the microwaves is operated through two principal sensor elements: an antenna and a receiver. The antenna collects the incoming radiation and the receiver measures the collected electric signal. As active microwave systems produce their own electromagnetic radiation, they are equipped with two additional elements: a pulse generator and a transmitter. Usually, transmitter and receiver are situated on the same antenna. A simple detector system only detects the intensity of the signal and amplifies it. Coherent systems measure both the amplitude and the phase of the incident electromagnetic radiation. Microwave systems can be categorized in two different types: imaging and non-imaging sytems. Whereas for non-imaging systems each echoe (collected signal) provides a single measurement, imaging systems collect a sequence of echoes that generate a two dimensional image.
Explain what properties of microwave electromagnetic spectrum are recorded
Explain how the microwave signal is detected
Completed