Image formation through walls using a distributed radar sensor network

Interest in methods for obtaining surveillance information through walls has been increasing for both domestic and military security applications. While our previous through wall sensor development activities have demonstrated acceptable imaging performance by synthesizing a large antenna aperture from a portable, collapsible antenna array, these operational constraints have driven AKELA to a concept of operation where images are created by a distributed array of individual sensors. Each sensor is a high range resolution radar that can be either fixed in place or carried by an individual. The sensors are connected with a wireless communication network that distributes timing and control information, receives data, determines sensor location, and fuses the data from each sensor to generate imaging and motion detection information. We have developed a frequency agile radar operating between 500 MHz and 2 GHz that is the sensor element in our networked concept. Its performance has been tested on a variety of wall materials. Results of these tests show that this new radar has the capability to detect the breathing response of a stationary individual through a reinforced concrete wall at a distance of 6.5 meters.