Antenna and Sensor System for Sharply Defined Active Sensing Zones
A sensor system having a sharply defined zone of active sensing comprising a compound antenna system comprising an antenna structure disposed in relation to a shield structure and spaced from the shield structure, the shield structure having an open aperture in front of the antenna structure in the direction of a lobe of sensitivity of the antenna structure. In various embodiments, the shield structure may be layered on the inside between the antenna and the shield structure with an RF absorbing material. The aperture may be formed in part by adjustable panels and the antenna spacing from the aperture may be adjustable by adjusting an antenna mounting position within the shield. The compound antenna system may be coupled to a receiver having a threshold response based on the compound antenna system response characteristic.
1 . A compound antenna system having a sharply defined coverage zone, comprising:
an antenna structure having a feed point for coupling signals to and from said compound antenna system; and
a shield structure;
said shield structure disposed or extending forward from said antenna structure toward said coverage zone; said shield structure having an open aperture between said antenna structure and said coverage zone; said open aperture configured for allowing direct line of sight radio frequency communication between said antenna structure and objects within said coverage zone;
said shield structure configured for providing radio frequency attenuation and/or blocking for signals from or to objects outside of said coverage zone;
wherein an edge of said shield structure is aligned between said antenna structure and an edge of said coverage zone.
2 . The compound antenna system of claim 1 , further including an RF absorbing material disposed between said shield structure and said antenna structure for attenuating signals from or to objects outside of said coverage zone.
3 . The compound antenna system of claim 1 , wherein the antenna structure has a directionality greater than a dipole.
4 . The compound antenna system of claim 3 , further including a tapered horn reflector coupled to said antenna structure to enhance a directionality of said antenna structure.
5 . The compound antenna system as recited in claim 1 , wherein said antenna structure is capable of receiving ultra-wideband signals.
6 . The compound antenna system as recited in claim 1 , wherein said antenna structure comprises a Vivaldi antenna structure.
7 . The compound antenna system as recited in claim 1 , wherein said open aperture is formed at least in part by at least one adjustable panel.
8 . The compound antenna system as recited in claim 1 , wherein said antenna spacing from said open aperture is adjustable by varying an antenna mounting distance from said open aperture within said shield structure.
9 . The compound antenna system as recited in claim 1 , wherein said open aperture is spaced at least one wavelength from an antenna phase center of said antenna structure.
10 . The compound antenna system as recited in claim 1 , wherein said open aperture is at least two wavelengths in a length dimension.
11 . The compound antenna system as recited in claim 1 , wherein said open aperture defines a perimeter shape of said coverage zone.
12 . The compound antenna system as recited in claim 1 , wherein said antenna structure is configured for communicating linearly polarized or circularly polarized signals.
13 . The compound antenna system in accordance with claim 1 , further including
a receiver system coupled to said compound antenna system, said receiver system configured for receiving a received signal from a transmitter within said coverage zone of said compound antenna system and for processing said signal based on a received amplitude of said received signal exceeding a predetermined threshold.
14 . The compound antenna system as recited in claim 13 , wherein said predetermined threshold is adjustable.
15 . The compound antenna system as recited in claim 14 , wherein said adjustable threshold is set based on a maximum response within said active zone.
16 . The compound antenna system as recited in claim 14 , wherein said adjustable threshold is separately adjusted for at least one transmitter based on an identification of said transmitter.
17 . The compound antenna system as recited in claim 14 , wherein the threshold is based on a maximum signal amplitude slope as a function of a path through said active zone.
18 . A method of producing a sharply defined coverage zone for an antenna structure, comprising:
directing said antenna structure toward said coverage zone;
producing a compound antenna system by:
positioning a shield structure, at least in part, forward from said antenna structure toward said coverage zone;
providing an open aperture through said shield structure, said open aperture allowing direct line of sight radio frequency communication between said antenna structure and objects within said coverage zone;
configuring said shield structure to provide radio frequency attenuation and/or blocking for signals form or to objects outside of said coverage zone; and
aligning an edge of said shield structure between said antenna structure and an edge of said coverage zone for enhancing a response slope of said compound antenna structure.
19 . The method in accordance with claim 18 , further including a step of:
positioning RF absorbing material between said shield structure and said antenna structure for attenuating signals from or to objects outside of said coverage zone.
20 . The method in accordance with claim 18 , further including a step of:
adding a directive element to said antenna structure to enhance the directionality of said antenna structure.
21 . The method in accordance with claim 18 , wherein said antenna structure is capable of receiving ultra-wideband signals.
22 . The method in accordance with claim 18 , further including a step of:
adjusting said open aperture by adjusting a panel forming said open aperture.
23 . The method in accordance with claim 18 , further including a step of:
spacing said open aperture at least one wavelength from an antenna phase center of said antenna structure.
24 . The method in accordance with claim 18 , further including a step of:
forming said open aperture at least two wavelengths in a length dimension.
25 . The method in accordance with claim 18 , further including a step of:
forming said open aperture to define a perimeter shape of said coverage zone.
26 . The method in accordance with claim 18 , further including a step of:
receiving a signal from a transmitter within said coverage zone of said compound antenna system and for processing said signal based on a received amplitude of said received signal exceeding a predetermined threshold.
27 . The method in accordance with claim 26 , further including a step of:
adjusting said threshold.
28 . The method in accordance with claim 26 , further including a step of:
adjusting said threshold based on a maximum response within said active zone.
29 . The method in accordance with claim 26 , further including steps of:
determining an identification of a transmitter;
accessing a memory for a historical property associated with said transmitter; and
adjusting said threshold in accordance with said historical property.
30 . The method in accordance with claim 26 , further including steps of:
determining a maximum signal amplitude slope as a function of a path through said active zone; and
adjusting said threshold in accordance with said maximum signal amplitude slope.