Patent Description:
The disclosure can be better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the disclosure. Furthermore, like reference numerals designate corresponding parts throughout the several views.

<FIG> depicts an antenna <NUM> according to an embodiment of the present disclosure. The antenna <NUM> comprises a coaxial cable <NUM> extending through a tube <NUM>. The tube <NUM> is a thin, conductive, cylindrical tube, formed from brass in the illustrated embodiment. (The tube <NUM> as illustrated is partially cut-away to show the coaxial cable <NUM> within the tube <NUM>. ) In one embodiment, the tube <NUM> has an outside diameter of. <NUM> inches (<NUM>) and is <NUM> millimeters long. The wall of the tube is between. <NUM> thick in one embodiment.

The tube <NUM> has a distal end <NUM> and a proximal end <NUM>. A center wire <NUM> of the coaxial cable <NUM> is electrically connected to the tube <NUM>. A shield <NUM> of the coaxial cable <NUM> terminates below distal end <NUM> of the tube <NUM> in the illustrated embodiment and is not electrically connected to any conductor at the distal end of the cable <NUM>. In one embodiment, the coaxial shield <NUM> terminates ¼ inches (<NUM>) below distal end <NUM> of the tube <NUM>. In one embodiment, the coaxial shield <NUM> terminates between <NUM> and <NUM> from the distal end <NUM> of the tube <NUM>. In one embodiment, a dielectric insulator (not shown) of the coaxial cable extends above the shield <NUM> of the coaxial cable <NUM> and terminates before the center wire <NUM> is connected to the tube <NUM>.

The coaxial cable <NUM> is substantially centered within the tube <NUM>. A centering spacer <NUM> keeps the coaxial cable <NUM> centered within the tube <NUM> for substantially the length of the tube <NUM>. At the distal end <NUM> of the tube, the center ware <NUM> is bent and electrically connected to the tube <NUM>. The centering spacer <NUM> is formed from an insulating material. In one embodiment, the centering spacer <NUM> is formed from polyurethane foam.

A first ferrite bead <NUM> and a second ferrite bead <NUM> are disposed on the cable <NUM> beneath the proximal end <NUM> of the tube <NUM>. The ferrite beads <NUM> and <NUM> extend around the shield <NUM> of the cable <NUM>. In one embodiment, the first ferrite bead <NUM> is spaced from the proximal end <NUM> of the tube <NUM> a distance of between <NUM> and <NUM>. In one embodiment, the second ferrite bead <NUM> is spaced from the first ferrite bead <NUM> a distance of between <NUM> and <NUM>. The spacing of the first and second ferrite beads <NUM> and <NUM> is designed to affect the resonant point of the antenna <NUM>. A connector <NUM> at the end of the cable <NUM> connects the antenna <NUM> into a system (not shown).

<FIG> depicts an antenna <NUM> according to an embodiment of the present disclosure. The antenna <NUM> comprises a mushroom-shaped housing <NUM> configured to be used in underground pits, such as a water meter pit. The housing <NUM> is formed from a nylon composite material in the illustrated embodiment. The housing <NUM> comprises a rounded top portion <NUM> unitarily formed with a threaded portion <NUM>. The threaded portion <NUM> is substantially cylindrical with continuous threads along an outer surface for receiving a threaded nut <NUM>. The rounded top portion <NUM> is circular when viewed from the top and extends outwardly from the threaded portion <NUM>. The threaded portion <NUM> may be fit within an opening (not shown) on a cover (not shown) of a water meter (not shown), for example, and the rounded top portion <NUM> is larger than the opening and the threaded portion and thus remains above the top of the cover and above ground when installed. The threaded nut <NUM> secures the antenna <NUM> to the cover. The antenna <NUM> can operate when installed in either metal or composite covers.

A coaxial cable <NUM> extends downwardly from a bottom of the housing <NUM> as shown. A first ferrite bead <NUM> and a second ferrite bead <NUM> are disposed on the cable <NUM> beneath the housing <NUM>. The ferrite beads <NUM> and <NUM> are substantially the same as the ferrite beads <NUM> and <NUM> discussed above with respect to <FIG>. The housing <NUM> houses the tube <NUM> discussed above, and the coaxial cable <NUM> is substantially the same as the coaxial cable <NUM> discussed above.

A waterproof connector <NUM> is disposed on the cable <NUM> beneath the second ferrite bead <NUM>. Additional cable length <NUM> extends on the other side of the connector <NUM>.

<FIG> is a partially cut-away view of a partial antenna assembly <NUM> according to the embodiment of the present disclosure discussed above with respect to <FIG>. In this partial assembly <NUM>, the centering spacer <NUM> has been installed on the coaxial cable <NUM>. A threaded flange <NUM> is disposed on the cable <NUM> between the distal end of the cable <NUM> and the first ferrite bead <NUM>. The threaded flange <NUM> comprises an opening (not shown) that receives the cable <NUM>. The threaded flange <NUM> is not rigidly affixed to the cable but can move upward and downward with respect to the cable <NUM>. The threaded flange <NUM> has exterior threads that mate with threads (not shown) interior to the housing <NUM> (<FIG>). As discussed further with respect to <FIG> below, the threaded flange <NUM> thus threadably mates with the bottom end of the housing <NUM>.

A stopper <NUM> is rigidly affixed to the cable <NUM> between the distal end of cable <NUM> and the threaded flange <NUM>. The stopper <NUM> prevents the threaded flange <NUM> from moving on the cable <NUM> when the threaded flange is threaded into the housing <NUM> (<FIG>). Although the threaded flange <NUM> is spaced apart from the stopper <NUM> in <FIG>, the threaded flange <NUM> rests against the stopper <NUM> when the threaded flange is screwed into the housing <NUM>.

A flexible seal <NUM> is compressed between the threaded flange <NUM> and the stopper and forms a water-resistant seal. In the illustrated embodiment, the seal <NUM> is an O-ring.

<FIG> is a partially cut-away view of a partial antenna assembly <NUM> according to the embodiment of the present disclosure discussed above with respect to <FIG>. In this partial assembly <NUM>, the conductive tube <NUM> has been added to the partial assembly <NUM> (<FIG>). The center wire <NUM> of the cable <NUM> has been bent over the tube <NUM> and electrically connected to the tube <NUM>. The centering spacer <NUM> fits within the tube <NUM> and serves to keep the cable <NUM> centered within the tube <NUM> for most of the length of the tube <NUM>. In this regard, for generally at least <NUM>% of the length of the tube, the cable <NUM> is centered within the tube before it is bent over to the tube wall. The centering spacer also serves to keep the tube <NUM>, which is very thin-walled, mechanically stable. The centering spacer <NUM> has an opening to receive the cable <NUM>. The outside diameter of the centering spacer <NUM> is slightly smaller than the inside diameter of the tube <NUM>.

Fig- <NUM> is a partially cut-away view of the antenna <NUM> of <FIG>. Importantly, the tube <NUM> extends above into the rounded top portion <NUM> a distance "d" as shown. This is important because the rounded top portion <NUM> is generally above ground when the antenna is in use, and the tube <NUM> generally needs to extend above ground in order for the antenna to transmit properly. In one embodiment, the distance "d" is between <NUM> (<NUM>) and <NUM> (<NUM>) inches.

The threaded flange <NUM> is engaged within the housing <NUM>. In this regard, external threads on the threaded flange <NUM> mate with internal threads (not shown) within the threaded portion <NUM> of the housing <NUM>.

<FIG> is a partially cut-away view of a partial antenna assembly <NUM> according to another embodiment of the present disclosure. This embodiment may be used above the ground. In this embodiment the inner workings of the antenna are substantially identical to the antennas discussed herein, but the housing is configured differently. In this partial assembly <NUM>, the centering spacer <NUM> has been installed on the coaxial cable <NUM>. A threaded flange <NUM> is disposed on the cable <NUM> between the distal end of the cable <NUM> and the first ferrite bead <NUM>. The threaded flange <NUM> comprises an opening (not shown) that receives the cable <NUM>. The threaded flange <NUM> is not rigidly affixed to the cable but can move upward and downward with respect to the cable <NUM>. The threaded flange <NUM> has exterior threads that mate with threads (not shown) interior to the housing, as further discussed below with respect to <FIG>.

A flexible seal <NUM> is compressed between the threaded flange <NUM> and the stopper <NUM> and forms a water-resistant seal. In the illustrated embodiment, the seal <NUM> is an O-ring. In some embodiments, a tear-shaped flexible seal <NUM> is used to maintain a spacing of the cable <NUM> within the threaded portion of the threaded flange <NUM>.

<FIG> is a partially cut-away view of an antenna <NUM> that may be used above the ground. A partial assembly of the antenna <NUM> was discussed above with respect to <FIG>. The threaded flange <NUM> is engaged within the housing <NUM>. In this regard, external threads on the threaded flange <NUM> mate with internal threads (not shown) within the housing <NUM>. In some embodiments, the threaded flange <NUM> mates with mounting hardware (not specifically shown) when attaching the antenna-for example, the antenna <NUM> shown in <FIG>-to a metal or composite cabinet or an 'L'-shaped metal bracket used for remote pole mounting.

<FIG> is a representation of the coaxial cable <NUM> of an antenna <NUM> as discussed herein with respect to <FIG>. The antenna is a half wave end fed configuration at the lowest operating frequency and at all harmonics, such as would commonly referred to as a "non-resonant end fed antenna. " The name derives from the fact that the feed line is actually part of the radiating element of the antenna after exiting the ferrite bead <NUM> (<FIG>). The coaxial cable <NUM> is represented in rough cross section by three lines in <FIG>: line <NUM> is the center conductor and lines 802A and 802B are the shield. Although coaxial cables are typically considered as having two conductors, at radio frequencies coax actually has three conductive surfaces: the center conductor <NUM>; the inside surface <NUM> of the shield (braid) 802A; and the outside surface <NUM> of the shield 802A. The center conductor <NUM> of the coaxial cable and the inside surface <NUM> of the shield comprises the feed line and carries the signal in the direction indicated by directional arrow <NUM> along its length to the load (common mode currents). When the RF signal reaches the end of the coax, the currents on the center conductor <NUM> and the inside surface <NUM> of the shield cancel each other and substantially no radiation is generated. The application of the conductive tube <NUM> (<FIG>) surrounding the cable <NUM> as discussed herein causes the RF energy to wrap around from the inside surface <NUM> of the shield and begin to flow on the outside surface <NUM> of the shield back toward the load, in the direction indicated by directional arrow <NUM>. This current flowing on the outside of the shield does not cancel and begins to radiate.

In order for a half wave end fed configuration to perform properly at the lowest operating frequency and at all harmonics, the RF current must not travel back to the transceiver (not shown). Therefore the radiating shield current must be prevented from continuing down the feed line, while allowing the internal feed currents to continue unaffected. The ferrite beads <NUM> and <NUM> (<FIG>) around the outer shield of the coaxial cable <NUM> limit the effect on the transceiver and the intended resonant point (resonant frequency) of the antenna. The limitations of the current create an end fed antenna.

The antenna broadband tuning is accomplished automatically by the addition of the tube <NUM> (<FIG>) placed over and around the end of the radiating element with the center coax conductor <NUM> attached to the distal end <NUM> of the tube as described and shown herein. The antenna does not require a ground plane or the necessity for retuning, unlike many other antennas, and is vertically polarized.

When the operating frequency varies, the antenna resonance is automatically changed due to the reaction of the inductive and capacitive reactance maintained between the two over a broad bandwidth. As frequency decreases below resonance and the antenna becomes inductive, this tuning network offsets this reactive shift, thereby stabilizing voltage standing wave ratio (VSWR). Once the frequency increases above resonance and becomes capacitive, the same tuning network offsets this reactive shift, continuing to stabilize VSWR.

Claim 1:
An ultra-wideband antenna (<NUM>) comprising:
a coaxial cable (<NUM>) extending through the center of a conductive tube (<NUM>), a distal end of a center conductor of the coaxial cable electrically connected to a distal end (<NUM>) of the conductive tube (<NUM>), a distal end of a shield (<NUM>) of the coaxial cable (<NUM>) not electrically connected to any conductor;
a first and a second ferrite bead (<NUM>,<NUM>) disposed on the coaxial cable (<NUM>) outwardly from a proximal end (<NUM>) of the conductive tube (<NUM>), outside of the conductive tube (<NUM>), the first and second ferrite bead (<NUM>,<NUM>) disposed serially on the coaxial cable (<NUM>), spaced apart from one another.