Information extraction from sensor nodes using air-borne radar and back-scatter modulation

Radar imaging is a powerful tool in remote sensing due to its ability to image vast areas with high resolution. However, the ability to sense a particular parameter depends on the extent to which the parameter affects the reflected microwave radiation. In this respect, multi-functional sensor nodes offer an immense potential to sense environmental parameters which cannot be directly sensed by radar imaging techniques. With this motivation, we develop techniques to collect information at an air-borne radar from a large group of sensor nodes. Back-scatter modulation is used on the sensors. The techniques utilize synthetic aperture radar (SAR) processing to resolve responses from multiple sensors and to simultaneously obtain a geographic map of the sensor locations. Sensor and clutter returns are separated by utilizing the ability of the sensors to modulate the radar return. The sensor modulation is structured such that sensor and clutter returns can be separated in the spatial frequency domain