Patent Application
20130027265
This invention relates to an antenna system for use in agricultural fields or other work areas.
Certain wireless systems (e.g., wireless soil sensor systems) used for agricultural fields may use radio frequency or microwave antennas mounted lower than an average crop height or crop canopy. One reason for mounting the antennas lower than the average crop height or crop canopy is to avoid damage from sprayers or other agricultural equipment that perform operations in the field. Because certain prior art antennas are mounted lower than the average crop height or crop canopy and are susceptible to attenuation from terrain, crops, and other vegetation, the propagation of wireless signals may be unreliable between one or more communication devices in the field and a central or remote location (e.g., farmer's office computer system). Thus, there is a need for an antenna system that increases the reliability of wireless signal propagation for agricultural fields and other work areas.
In one embodiment, an antenna system for use in an agricultural field or work area comprises a base having an upper side and a lower side opposite the upper side. A stake extends from the lower side. The stake is capable of mounting into the ground. A spring extends from the upper side of the base. A mast above the base is resiliently, movably mounted to the base by the spring. A lateral dielectric guard is mounted at or the near a top of the mast. An antenna is associated with the top of the mast, the antenna coupled to a transmission line that is secured to or by the mast.
The antenna system 11 comprises a base 14 having an upper side 13 and a lower side 15 opposite the upper side 13. A stake 10 extends from the lower side 15. The stake 10 is capable of mounting into ground. A spring 18 extends from or above the upper side 13 of the base 14. A mast 24 above the base 14 is movably mounted to the base 14 by the spring 18. A lateral dielectric guard 28 is mounted at or the near a top of the mast 24. An antenna 30 is associated with the top 29 of the mast 24. The antenna 30 is coupled to a transmission line 20 that is secured to the interior or exterior of the mast 24.
The base 14 may be generally rectangular, cylindrical or polyhedral, or shaped in other ways. A lower side 15 of the base 14 may form a stop that engages the ground when the stake 10 is placed into the ground by a maximum amount. A lower portion of the spring 18 may be cast, molded or otherwise secured to the base 14. The base 14 may be constructed from metal, an alloy, a plastic, a polymer, a composite material, a resin matrix with a filler, a fiber-filled plastic, or a fiber-filled polymer, for example. The fiber may comprise carbon fiber, fiber glass or another suitable filler.
In one configuration, the stake 10 comprises a blade 12 extending radially from a central vertical axis 19 of the stake 10, where the blade 12 is tapered radially inward toward a bottom of the stake 10. The bottom of the stake 10 may terminate in a point 16 or spear-shaped member. In another configuration, the stake 10 comprises a plurality blades 12 extending orthogonally and radially from a central vertical axis 19 of the stake 10, where the blades 12 are tapered radially inward toward a bottom (or point 16) of the stake 10.
The spring 18 may comprise a helical or coil spring 18 that is constructed of steel, spring steel, or another suitable alloy. In one embodiment, the spring 18 is selected to have a lateral resilience and vertical resilience, or a first equivalent spring constant, that supports the mass of the antenna mast 24, the dielectric guard (e.g., 28, 128 or 228), and the antenna (e.g., 30 or 130) when no external force is applied to the dielectric guard (28) or mast 24. In another embodiment, the spring 18 is selected to have a lateral resilience and vertical resilience, or a second equivalent spring constant, that supports the mass of the mast 24, the dielectric guard, and the antenna plus wind-loading of a certain maximum wind speed (e.g., 25 miles per hour (40.2 kilometers per hour)) or wind speed range (e.g., 25 miles per hour to 50 miles per hour (80.5 kilometers per hour)) to avoid permanent deformation of the spring 18, as opposed to elastic or resilient deformation. In another embodiment, the spring 18 is selected to have a lateral resilience and vertical resilience, or a third equivalent spring constant, that supports the mass of the antenna mast, dielectric guard and antenna plus ice-loading of a certain maximum thickness of ice (e.g., one-half inch (1.3 centimeters) to one inch of ice (2.54 centimeters)) on the mast and dielectric guard (e.g., 28, 128 or 228) to avoid permanent deformation of spring 18, as opposed to elastic or resilient deformation, where the antenna system (11, 111, or 211) is left in the field year round or during inclement weather.
In an alternate embodiment, the spring 18 is disposed above the upper side 13 to interconnect two longitudinal sections of an alternate mast.
In one configuration, mast 24 has a length or mast height 35 that is equal to or greater than the average crop height or the maximum crop height of a particular crop in the field. In another configuration, the mast 24 has a mast height 35 of approximately 5 to 7 feet (approximately 1.52 meters to 2.13 meters) for corn or maize, and a mast height 35 of approximately 2 to 4 feet (approximately 0.61 to 0.122 meters) for soybeans.
The mast 24 comprises a longitudinal member, a cylindrical member, a flexible member, a semi-rigid member, or a rod, for example. The mast 24 may be composed of a polymer, a plastic, a resin, a resin matrix with a filler, a fiber-filled polymer, a fiber-filled plastic, a fiber-filled resin, a composite material, and an elastomeric outer coating covering a semi-rigid metal inner cylindrical core or spring core. As illustrated, the transmission line 20 may comprise a coaxial cable that is fed through a lower opening 25 in the mast 24, through the hollow core (e.g., generally cylindrical hollow chamber), and the upper opening 27 in the mast 24 for electrical and mechanical connection to the antenna 30. The lower opening 25 and the upper opening 27 in the mast 24 communicate with the hollow core to retain and allow the transmission line 20 to be routed through the hollow core of the mast 24. The lower end of the transmission line 20 may terminate in a coaxial cable connector 22 for example. The transmission line 20 may be held captive by the central hollow core of the mast 24. Although the mast 24 has a hollow core as shown in
In one embodiment, the antenna 30 comprises a monopole antenna 30, with or without a ground plane. In an alternative embodiment, the antenna 30 may comprise a dipole element. In yet another alternative embodiment, the antenna 30 comprises a co-linear array of stacked monopole or dipole elements. In still another alternative embodiment, the antenna 30 comprises a yagi antenna or corner reflector antenna.
As illustrated, the dielectric guard 28 (e.g., lateral dielectric guard) comprises a generally conical member. Although the conical member has a larger radius or diameter of the conical member facing upward in
In one embodiment, in the rest mode 200 the spring 18 is oriented generally orthogonal to the upper side of the base 14, and the spring 18 has a lateral resilience and vertical resilience, or an equivalent spring constant, capable of supporting the mass of the mast 24, antenna 30, and dielectric guard 28 in a substantially vertical manner with respect to the ground. In the active mode 202, when the dielectric guard 28 or mast 24 is contacted by a vehicle or machine with greater than a threshold force, the spring lateral resilience and vertical resilience (of spring 18) is configured to allow the mast 24 to move resiliently with respect to the base 14, without permanent deformation of the spring 18.
In any active mode 202, the antenna system (11, 111 or 211) dissipates or dampens the mechanical energy from the contact of the vehicle or machine to return to the rest mode 200 (without material permanent deformation of the spring) where the mast 24, antenna (30 or 130), and dielectric guard (28, 128 or 228) in a substantially vertical manner with respect to the ground.
A transceiver, transmitter, receiver, sensor station, or other wireless station may be connected to the antenna 30 via the transmission line 20 and its connector 22. For example, the wireless station may comprise a cellular communications device, a satellite communications device, a two-way mobile radio, a paging receiver, a trunking radio, a code-division, multiple-access communications device, a time division-multiple, access-communications device, a transceiver in a mesh network, a point-to-point communications link, a point-to-multipoint communications system, a telemetry system, or a wireless local area network. The wireless station may be housed in a weatherproof, moisture-proof enclosure, salt-fog resistant, or hermetically sealed enclosure, such as a suitable National Electrical Manufacturers Association (NEMA) standards- compliant enclosure mounted at or near the base 14 of the antenna 30.
Any embodiments of the antenna system (11, 111, 211) disclosed in this document are well-suited for placement in an agricultural field where the boom of a sprayer or other agricultural equipment might strike the dielectric guard 28 or the mast 24. Accordingly, in an active mode 202 the antenna system (11, 111, 211) resiliently deflects downward when contacted by the boom or other agricultural equipment and then later returns to a rest mode 200 where the mast 24 is maintained in a generally vertical position with respect to the base 14 and the surface of the ground. The antenna system (11, 111, 211) is well-suited for placing the antenna (30 or 130) above the crop canopy or maximum crop height to avoid attenuation of the transmitted or received signal from the crop, among other things such as the surrounding terrain or other obstructions. The antenna system (11, 111, 211) facilitates reliable communications between one or more stations located in the field and a remote or central location of the grower, agronomist, or manager of the agricultural or other work operation.
Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
