Intruder detection radar system and automatic nulling antenna array
First Claim
1. An intruder detection system for a secure area perimeter, comprising:
- a omni-directional transmitter antenna positioned substantially at the center of a secure area;
means coupled to the transmitter antenna for causing an electromagnetic continuous wave signal to radiate an annular ring surveillance zone surrounding the transmitter antenna and extending outwardly from the antenna beyond the secure area ring perimeter to an outside ring perimeter;
a plurality of receiving antennas circumferentially spaced around the secure area ring perimeter at known distances from one another for receiving a portion of a signal reflected by an intruder moving within the annular surveillance zone, and for simultaneously receiving a portion of the direct signal radiated from the transmitter antenna;
means coupled to the receiving antennas for comparing the reflected signal portion and the directly radiated signal portion received by the antennas and producing an output signal representative of the doppler cycles of phase difference between the reflective signal portion and the directly radiated signal portion;
means for receiving the phase difference output signals from one or more adjacent antennas and computing tracking data representative of the location, speed and direction of motion of an intruder within the surveillance zone, and including means for displaying intruder tracking data; and
means for transmitting the phase difference signals from the receiving antennas to the receiving and tracking means.
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Accused Products
Abstract
A bistatic VHF Doppler radar is utilized to detect and track one or more intruders crossing a large annular ring surveilance zone surrounding a central high security installation. A central omni-directional transmitter radiates the surveillance zone with a continuous wave (CW) signal. Predetermined ones of a plurality of receiver antennas circumferentially spaced around the surveillance zone receive a portion of the signal which is reflected by an intruder crossing the surveillance zone and a portion of the signal which is directly radiated from the transmitter antenna. The reflected signal portion may be received by antenna arrays each of which is controlled to form a null in its pattern toward the transmitter antenna to overcome direct signal overload. The direct signal portion may be received by stub antennas. Each antenna array and each stub antenna is connected to a separate channel of a dual channel receiver. An intruder moving across the surveillance zone causes signals representative of Doppler cycles of phase change to be generated. The outputs of the two separate channels are compared and their relative phase changes measured. A detected intruder causes an alarm signal at a central processing station and the Doppler information is processed to generate tracking data which is shown on a display device. An automatic null control circuit may also be utilized to accommodate multipath conditions and static clutter due to environmental factors.
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Citations
9 Claims
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1. An intruder detection system for a secure area perimeter, comprising:
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a omni-directional transmitter antenna positioned substantially at the center of a secure area; means coupled to the transmitter antenna for causing an electromagnetic continuous wave signal to radiate an annular ring surveillance zone surrounding the transmitter antenna and extending outwardly from the antenna beyond the secure area ring perimeter to an outside ring perimeter; a plurality of receiving antennas circumferentially spaced around the secure area ring perimeter at known distances from one another for receiving a portion of a signal reflected by an intruder moving within the annular surveillance zone, and for simultaneously receiving a portion of the direct signal radiated from the transmitter antenna; means coupled to the receiving antennas for comparing the reflected signal portion and the directly radiated signal portion received by the antennas and producing an output signal representative of the doppler cycles of phase difference between the reflective signal portion and the directly radiated signal portion; means for receiving the phase difference output signals from one or more adjacent antennas and computing tracking data representative of the location, speed and direction of motion of an intruder within the surveillance zone, and including means for displaying intruder tracking data; and means for transmitting the phase difference signals from the receiving antennas to the receiving and tracking means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification