|
The detection and tracking of humans and vehicles on the battlefield using radar systems operating at microwave frequencies was first achieved almost 40 years ago. The subsequent generation of radars designed to detect personnel and vehicles on the battlefield has seen improvements due to increased signal processing capability. To date, most of the self-contained human detection radars have incorporated a co-located (monostatic) transmitter and receiver operated by humans. Approximately, three decades ago the bistatic radar was introduced and used for security at high value target sites. These bistatic "fence" radars employ a transmitter located at one end of a bistatic baseline and a receiver at the other end of the baseline. The receiver is tuned to the transmitter. Operation is simple; an intruder crosses the bistatic baseline and is detected after simple signal processing is performed on the bistatic signature produced by the intruder. The experiments demonstrate that passive bistatic radar can be used to detect humans and vehicles.
This paper describes "quick-look" experiments that have been conducted in the Atlanta, Georgia area to detect humans and vehicles using a passive radar configuration requiring no coordination between the receiver and transmitter. The illumination source (transmitter) is a High Definition Television (HDTV) broadcast transmitter located approximately 13.5 miles from the test area. The transmitter is broadcasting a 6 MHz wide digital signal with a pilot carrier on a frequency of 548.310 MHz. The continuous wave (CW) pilot carrier HDTV signal component is processed to extract the signature of the walking human or the signature of a vehicle. The experimental receiving system utilizes a commercial off-the-shelf (COTS) communications receiver. A set of multi-element back to back Yagi antennas are used to provide a reference signal and the signal from the area where the human subject is located. The walking human generates micro-Doppler that can be detected using micro-Doppler signal processing techniques. Vehicular targets can be detected without applying micro-Doppler processing due to a vehicle's larger radar cross section (RCS) and higher Doppler shift (higher velocity). The technical challenges that are addressed in the following sections include receiver stability, common signal cancellation, multipath environments, and geometries. The technique has also been tested inside of a building and it has been found that walking humans can be detected through walls and down long halls.
|
