Abstract:
A lightweight, nonmotorized radar antenna system specially adapted for use on a boat or ship includes a multiple section mount supporting a plurality of radiating elements to provide 360 degree coverage around a vertical structure, such as sailboat mast. The mount can have a variable inner diameter for installation on various sized structures.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lightweight, nonmotorized antenna system specially adapted for use on a boat or ship. 
     2. Description of Prior Art 
     Radar is widely used on both commercial and pleasure water craft of all sizes and motive means. Regardless of the type or size of the vessel, all marine radar sets are composed of the same basic building blocks, namely: the display, the data processing unit, the transceiver, and the antenna unit. One example of such a known marine radar set is shown in FIG. 1. In operation, the data processing unit 6 creates an electrical signal that is fed to the transceiver 8, and the transceiver 8 then feeds the signal through a coaxial cable 10 and a rotary joint 12 to the antenna 14. This signal is radiated from the antenna 14 in the form of an electromagnetic wave that propagates away from the antenna 14 until it encounters a solid object and is reflected. The antenna 14 then intercepts the reflected electromagnetic wave and converts it back into an electrical signal, which is fed back through the rotary joint 12 and the coaxial cable 10 to the transceiver 8. The transceiver 8 then communicates to the data processing unit 6 that the reflected signal has been received and the data processing unit 6 computes the distance and bearing of the solid object causing the reflection and produces information to be displayed on the display screen 16. Conventional marine radar antennas, such as antenna 14 in FIG. 1, are mounted on motorized mounts 18 that rotate the antenna in order to effectuate circular coverage. When such motorized mounts are employed, the resulting antenna/mount unit is substantially heavier than the antenna by itself. Nevertheless, these marine radar antennas must still be mounted as high as possible in order to maximize the range of the radar set. 
     Therefore, not only does the added weight of the motorized mount present a hazard and danger to the installer when the antenna unit is being mounted high upon a mast or support structure, but the extra weight of the motorized mount on its support structure can produce unnecessary, uncomfortable, and possibly even dangerous rolling motion upon the vessel. 
     Additionally, because motorized mounts are exposed to the elements, they are liable to rust and wear, especially when used in a high humidity environment as is encountered on the water. Such rust and wear inevitably result in requiring frequent preventive and corrective maintenance. 
     Finally, and significantly, when these motorized mounts are mounted to the mast of a sailboat, they are by necessity mounted either in front of, behind, or to the side of the mast. When positioned in this manner, the mast blocks radar coverage in a given segment of space. As shown in FIG. 2, mast 20 is mounted upon deck 22 of a vessel and motorized antenna 27 is mounted on horizontal member 23 in front of mast 20. Blind area 25 represents the segment of space that can not be scanned by motorized antenna 27. 
     OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
     It is, therefore, one object of the present invention to provide a radar antenna unit that does not require the use of a heavy motorized mount; thus saving weight and resulting in an easier, safer installation. Such weight savings will also result in less rolling of the vessel because a lighter weight will have been installed at the top of a long lever arm, that is, the mast or the antenna support structure. 
     It is a further object of the present invention to provide a radar antenna unit that does not require the use of a breakdown-prone and electrically noisy motorized mount, which typically employs a motor and a rotary joint. 
     It is a still further object of the present invention to provide a radar antenna unit that provides unobstructed 360 degree coverage around an obstruction such as a mast. 
     In accordance with one aspect of the present invention, there is provided a radar antenna unit that is lightweight, nonmotorized, simple, sealed and capable of providing unobstructed radar coverage around an obstruction. Lightweight, low profile antenna elements such as microstrip antennas are mounted around the perimeter of a multi-piece mount. This multi-piece mount is then mounted by a friction fit around an obstruction, such as a sailboat mast, thereby providing a radar antenna unit with 360 degree coverage around the obstruction without resort to the use of a motorized mount or a rotary joint. 
     Other features and advantages of the present invention will become apparent from the following description, which is to be read in conjunction with the accompanying drawings in which like reference numerals represent the same or similar elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a conventional marine radar system; 
     FIG. 2 is a perspective view showing obstructed radar coverage provided by a conventional radar antenna system; 
     FIG. 3 is a perspective view of a nonmotorized radar antenna system according to a first embodiment of the present invention; 
     FIG. 4 is a perspective view showing the unobstructed radar coverage provided by the first embodiment of the present invention shown in FIG. 3; 
     FIG. 5 is a partial cross-sectional view of the nonmotorized radar antenna system shown in FIG. 3 taken through section line A--A; 
     FIG. 6 is a plan view showing a nonmotorized radar antenna system in partial cross section according to a second embodiment of the present invention; 
     FIG. 7 is a plan view showing a nonmotorized radar antenna system in partial cross section according to a third embodiment of the present invention; 
     FIG. 8 is a plan view showing a nonmotorized radar antenna system in partial cross section according to a fourth embodiment of the present invention; 
     FIG. 9 is a plan view showing a nonmotorized radar antenna system in partial cross section according to a fifth embodiment of the present invention; and 
     FIG. 10 is a schematic of a radar system according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The general construction of a nonmotorized radar antenna system according to a first embodiment of the present invention is shown in FIG. 3, in which mast 20 is depicted rising above the surface of deck 22. Multi-piece mount 30, formed of a first mount section 30a coupled to a second mount section 30b, is mounted around mast 20. Multi-piece mount 30 is held to the mast by friction by clamping together sections 30a and 30b using fasteners 26a, 26b, 26c and 26d installed through fastener tabs 28a, 28a&#39;, 28b, 28b&#39;, 28c, 28c&#39;, 28d, and 28d&#39; or other similar means such as a latch arrangement. Radiating elements 24a, 24b, 24c, 24d, 24e, and 24f are mounted upon the exterior surface of multi-piece mount 30 using dielectric clips 80, 80&#39;, 81, 81&#39;, 82, 82&#39;, 83&#39;, 83&#39;, 84, 84&#39;, 85, and 85&#39;, or other suitable mounting means such as adhesive. Radiating elements 24d, 24e, and 24f are shown in FIG. 5. These radiating elements can comprise microstrip antennas, stripline antennas, slotted antennas, or other low profile, lightweight antennas. Coaxial cable, shown schematically in FIG. 10 but not shown in FIG. 3, or some other suitable waveguide is run either inside mast 20 or on its surface and connected to the electronic subsystems of the radar set. This cable, shown schematically in FIG. 10, serves to feed the radiating elements 24a, 24b, 24c, 24d, 24e, and 24f. 
     Referring now to FIG. 4, wherein the same reference numerals of FIG. 3 are applied to the same parts and therefore do not require detailed description, it is seen that since the radiating elements are mounted around mast 20, and since the radiating elements radiate radially outward, 360 degree radar coverage is provided by antenna system 50a regardless of the presence of mast 20. 
     In FIG. 5, wherein the same reference numerals of FIG. 3 are applied to the same parts, and therefore do not require detailed description, a partial sectional view of the first embodiment of the present invention is shown. 
     FIG. 6 shows a second embodiment of the present invention, in which the same reference numerals of FIG. 3 are applied to the same parts and therefore do not require detailed description. In this embodiment hinged mount 40 is formed of a first hinged mount section 40a and a second hinged mount section 40b. Hinged mount 40 is hinged on one side by hinge 26b, and is held closed on the opposite side by a suitable closure system, such as fasteners 26a and 26c securing mounting tabs 28a to 28a&#39; and 28c to 28c&#39;, respectively. Note, that fastener 26c and mounting tabs 28c and 28c&#39; are not seen in FIG. 6, because they are located below fastener 26a and mounting tabs 28a and 28a&#39;. Alternatively, hinged mount 40 could be held closed by latches or the like. When installed around a mast 20, and when held closed, as described above, hinged mount 40 is held to mast 20 by friction. 
     Still referring to FIG. 6, which is a plan view showing a nonmotorized antenna system in cross section according to the above-described second embodiment of the present invention, it is seen that because the radiating elements are mounted around mast 20 and radiate radially outward, 360 degree radar coverage is provided by antenna system 50b regardless of the presence of mast 20. 
     Multi-piece mount 30 of FIG. 3 or hinged mount 40 of FIG. 5 can be either custom designed for each application or can be designed to have a variable inner diameter to facilitate easy mounting on various sized obstructions, as shown in FIG. 7. In this embodiment of FIG. 7, variable support members 34a, 34b, 34c, and 34d are attached to arcuate members 32a and 32b. Variable support members 34a, 34b, 34c, and 34d can consist of springs, threaded studs, or the like and provide a means for pushing arcuate members 32a and 32b radially inward, thus varying the inner diameter of antenna system 50c. Arcuate support members 32a and 32b can be formed in shapes other than symmetrical arcs in order to facilitate mounting of antenna system 50c on obstructions with noncircular cross sections. 
     In the embodiment shown in FIG. 8, radiating elements 24a, 24b, 24c, 24d, 24e, and 24f are mounted flush with recessed mount 50d. Again, as in the other embodiments, the radiating elements 24a, 24b, 24c, 24d, 24e, and 24f are held in place by dielectric clips 80, 80&#39;, 81, 81&#39;, 82, 82&#39;, 83, 83&#39;, 84, 84&#39;, 85, and 85&#39;, or other suitable mounting means such as adhesive. Because the radiating elements are mounted around mast 20 and radiate radially outward, this embodiment also provides 360 degree radar coverage by antenna system 50d regardless of the presence of mast 20. Additionally, wind resistance is reduced and the chances of radiating elements 24a, 24b, 24c, 24d, 24e, and 24f getting snagged on a sail, not shown, when antenna system 50d is mountd upon a sailboat mast are also reduced. 
     In the embodiment shown in FIG. 9, radiating elements 24a, 24b, 24c, 24d, 24e, and 24f are mounted upon one-piece mount 50e, which is a unitary mount element with a central hole formed therein. This unitary mount element is fitted over an end of a vertical obstruction such as a sailboat mast and is held in place by friction between the interior of the central hole in the unitary mount element and the exterior of the obstruction. As with the other embodiments of this invention, this embodiment also provides 360 degree radar coverage around a mast or similar obstruction. 
     Operation of the various embodiments described above is identical. The radiating elements 24a, 24b, 24c, 24d, 24e, and 24f are fed an electrical signal through a coaxial cable 10 or other similar waveguide from transceiver 8, as shown in FIG. 10. Further, as depicted in FIG. 10, the inventive antenna system feeds a return signal back to the transceiver 8 through the coaxial cable 10. The feed network employed, such as a corporate feed network or a series feed network, will be a function of the array configuration chosen and the specific power distribution pattern required and need not be discussed here. Likewise the scanning algorithm employed, such as a monopulse algorithm or a sequential lobing algorithm, will also be a function of the array configuration chosen and the specific power distribution pattern required and need not be discussed here either. 
     There is provided, therefore, a radar antenna unit that does not require the use of a heavy motorized mount, thereby saving weight and resulting in an easier, safer installation. Such weight savings will also result in less rolling of the vessel, because a lighter weight will have been installed at the top of a long lever arm, that is, the mast or the antenna support structure. 
     The present invention additionally provides a radar antenna unit that does not require the use of a breakdown-prone and electrically noisy motorized mount. 
     Furthermore, the present invention provides a radar antenna unit that provides unobstructed 360 degree coverage around an obstruction, such as a mast. 
     Finally, it must be noted that although the present invention is described by reference to particular embodiments thereof, many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention, which is only limited by the appended claims. For example, the radiating elements could be microstrip antennas, stripline antennas, dipoles, slots or horns. Additionally, the number of radiating elements is not limited to the amount represented in the various embodiments. Therefore, the embodiments shown and described are only illustrative, not restrictive.