Patent Application
20070247380
The present invention relates generally to the field of automatic meter reading (AMR) and, more particularly, to antennas and assemblies for use in an AMR system.
AMR devices must be able to communicate in various unfriendly environments. For example, AMR devices for water meters must be able to communicate in the RF unfriendly environment of the iron water pit. Typically, this is accomplished by placing an antenna on top of the water pit lid, with the connection to the meter going through a hole in the lid. This allows a large antenna area, but the antenna often protrudes dangerously high above the lid, and requires a field-installed connection between the antenna and the water meter.
Another typical installation has the antenna protruding through a hole in the pit lid. This has the advantages of a low profile above the lid, and the connection from the antenna to the water meter can be made at the factory. The main drawback is that the entire antenna must be small enough to fit through a small hole in the lid, and cannot have much elevation above the lid.
In view of the foregoing, there is a need for systems and methods that overcome such deficiencies.
The following summary provides an overview of various aspects of the invention. It is not intended to provide an exhaustive description of all of the important aspects of the invention, nor to define the scope of the invention. Rather, this summary is intended to serve as an introduction to the detailed description and figures that follow.
The present invention is directed to an antenna that is used in an AMR module and comprises a pin and disk radiator. The antenna may be a top loaded short monopole antenna, for example. Additionally, the antenna may be used in a module for a water meter. The pin and disk radiator may be stamped from a single sheet of material.
An example antenna is provided that protrudes through the lid, but has the performance of an above the lid antenna. The antenna works well in an iron water pit, mounted through the pit lid, as well as in plastic pit lids and remote mounted boxes, for example.
Additional features and advantages of the invention will be made apparent from the following detailed description of illustrative embodiments that proceeds with reference to the accompanying drawings.
The foregoing summary, as well as the following detailed description of preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings exemplary constructions of the invention; however, the invention is not limited to the specific methods and instrumentalities disclosed. In the drawings:
The present invention is directed to an antenna that can be used in an AMR module for a water meter, for example. The antenna may be used in an iron water pit, mounted through the pit lid, as well as in plastic pit lids and remote mounted boxes, for example.
According to an example, the antenna includes a solid pin 17 that is connected to an antenna disk radiator 15. Desirably, the pin 17 goes through the opening 16, but does not project beyond the back surface of the radiator 15. The pin 17 may be attached to the radiator 15 using any appropriate means, such as a tin/lead solder or a mechanically pressed connection, for example. The disk radiator 15 may comprise 0.025″ brass sheet, C2600 alloy ¼-½ hard, for example, and may have a diameter of about 0.900″. The pin 17 may have a diameter of 0.0785 inches, for example, and an opening 16 in the radiator 15 for the pin 17 may be made using a #47 drill, for example. The length of the pin 17 may be about 1.02 inches, for example. Other materials could be used to construct pin 17 and disk radiator 15 provided they are electrically conductive. Additionally, other sizes could be used to accommodate different RF frequencies and different mechanical packages.
The antenna may be a water module antenna for example, and may be used with Elster Electricity's REX™ metering system or other types of metering systems. The mounting configuration desirably allows the disk to protrude slightly above the level of the pit lid to provide a good radiation pattern. Additionally, the antenna desirably can be covered by an internal shield, for example, so that the entire assembly can be potted without degrading the performance of the antenna.
Because the antenna desirably contains its own ground plane and does not rely on the pit lid, it performs equally as well in a plastic lid (either mounted through a hole, or internally to the plastic lid, for example) or as a stand-alone product. Acting as a stand-alone product allows the module to be repackaged to mount to a wall or a meter itself without changing any of the internal hardware.
The antenna 10 may be connected to the printed circuit board 22 via a soldered through-hole connection. Additionally, the antenna 10 may have a shoulder, or similarly functioning structure, on the bottom of the pin to hold the antenna in the proper orientation during the solder operation. The printed circuit board 22 may be connected to the plastic housing 25 using integrated plastic standoffs. The plastic housing 25 is desirably used as a mechanical mounting point for the printed circuit board 22 and antenna 10, as well as for environmental protection.
In an example, the iron pit lid 33 has a 1⅞″ hole that can either be cast when the lid is manufactured, or drilled as a retrofit of a standard lid. The beveled retaining nut 35 mechanically attaches the assembly 20 to the iron pit lid 33, and places the disk 15 in the desired location. The beveled retaining nut 35 protrudes minimally above the iron lid 33, and desirably has a shallow bevel around the perimeter to minimize tripping hazards when placed in a location subject to foot traffic.
The plastic lid 43 desirably comprises an electrically non-conductive material that minimally affects the transmission of radio frequency waves. This allows the disk 15 to be placed below the surface of the plastic lid 43 without adverse effects on the RF communications. The plastic lid 43 may be manufactured with a hollow area that is surrounded by a lip that acts as an internal shelf. This shelf allows AMR devices to be mechanically attached to the inside of the plastic lid 43. The retaining nut 45 may be used to mechanically attach the assembly 20 to this shelf.
The material may be 0.025″ brass sheet, alloy 26, ½ hard, for example. Other electrically conductive materials could be used, provided they could be stamped into this form. The length of the pin 55 may be about 1.02 inches, for example. The pin 55 may have a connector 57 at the end opposite the disk 50 for a mechanical and electrical connection to a printed circuit board, for example. Desirably, the stamped antenna shown in
The pin 55, 65 is desirably formed such that the shape at the circuit board attachment end yields a square or almost square (aspect ratio close to 1) portion that serves as a peg or pin (e.g., element 57 in
Moreover, the connector 57, 67 desirably has a shoulder (e.g., element 69 in
Consequently, the antenna may be self-fixturing, and desirably supports itself upright or perpendicular to the circuit board in any desired orientation during the soldering operation, and the soldered joint is both mechanically and electrically very substantial.
While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom.
