RF transparent method and apparatus for antenna radiation through a metal utility pit lid

Abstract

A meter transmission unit (MTU) is attached to the underside of a metal pit lid covering an in-ground electrical utility pit. The metal pit lid has a mounting hole with a diameter D that is much smaller than the effective wavelength λeff of the wireless RF communication signals transmitted by the MTU. An RF transparent cap with a spiral shaped slot with a slot length of at least half an effective wavelength allows the wireless RF communication signals to be transmitted through the small mounting hole.

Description

Attorney Docket No. 34704.2539 (940-0191 -AT WO)RF TRANSPARENT METHOD AND APPARATUS FOR ANTENNA RADIATION THROUGH A METAL UTILITY PIT LIDFIELD

[0001] The present disclosure relates to a lid or manhole cover for a utility enclosure. More particularly, the present invention related to an RF (radio frequency) transparent a lid or manhole cover for a utility enclosure.BACKGROUND

[0002] In-ground utility pits are used in several industries — e.g., electrical, cable, water or gas — to house wire and cable connections, communication and monitoring equipment and system control devices. They are used by electrical utilities for power distribution and supply, by the water and gas industries for meter and billing purposes, by the telecommunications industry to route cable television and Internet, and in the construction industry for pulling, splicing and accessing cable and wires, and also for housing system equipment. An in-ground utility pit may also sometimes be called an underground utility pit, junction box, electrical handhole, underground enclosure, or splice box. In-ground utility pits come in various shapes and sizes, but generally feature a removable metal lid or door to protect the contents of the pit.

[0003] The water, gas and electrical utilities use Meter Transmission Units (MTU) housed within in-ground utility pits to electronically collect data from utility meters (e.g., water, gas or electricity meters). The data is then transmitted wirelessly to a central facility for system control and billing purposes. Distributing MTU in in-ground utility pits allows for automated meter reading without the need for utility company personnel to make onsite visits.

[0004] Ground-level, through-the-lid radio communications from MTUs housed in in-ground utility pits has been a significant challenge in the utility industries. The MTU is positioned below a metal pit lid to protect the MTU from damage. However, since the lid is made of metal, radio frequency (RF) radiation cannot pass through it. The conventionalsolution is to provide a low-profile disc antenna which is mounted on the lid's surface. The antenna's feeding cable of the disc antenna is routed through a small mounting hole in the metal lid. The small mounting hole is typically a standard feature of metal pit lids designed for Automatic Metering Infrastructure (AMI) applications. This conventional solution of using a low-profile disc antenna on the metal pit lid is subject to damage from road traffic, high costs, and the complexity of the design and installation process.SUMMARY

[0005] Various embodiments of the present disclosure can overcome the aforementioned disadvantages and other drawbacks associated with conventional low-profile disc antennas mounted on metal pit lids, and offer new advantages as well. The various embodiments eliminate the need for an external antenna above the lid. Instead, a halfwavelength folded plastic ring, referred to herein as an "RF transparent cap" is positioned within the small mounting hole of the metal utility pit lid. Typically, the top of the cap is aligned flush with the lid's surface to minimize the possibility of damage due to road traffic.

[0006] According to various embodiments of the present disclosure there is provided an RF transparent cap apparatus for transmitting a wireless RF communication signal through a hole of diameter D in a metal plate. Various embodiments of the apparatus are drawn to an RF transparent cap that includes a first end and a second end, the first end being positioned adjacent to a source of the wireless RF communication signal.

[0007] Various embodiments of the apparatus also include a folded structural component configured as part of the RF transparent cap, the folded structural component includes a first end, a second end and a shaped side. The first end of the folded structural component is separated from the second end by the shaped side. A conductive layer configured as part of the RF transparent cap covers the shaped side.

[0008] The first end of the folded structural component extends into the hole in the metal plate, and the RF transparent cap transmits the wireless RF communication signal of wavelength As through the hole in the metal plate, and the RF transparent cap is characterized by a slot length.. The wavelength As of the RF communication signal is greater in length than the diameter D of the hole in the metal plate.

[0009] In some forms, a conductive connector component in electrical contact with the conductive layer makes electrical contact with the metal plate, and the folded structural component is made from a non-conductive material.

[0010] In some forms, the hole is a mounting hole and the metal plate is a metal pit lid, and the signal wavelength As is over twice as large as the diameter D of the hole in the metal pit lid.

[0011] In some forms, the shaped side is a spiral shaped side, and the folded structural component is a spiral structural component. The conductive layer covering the spiral shaped side of the spiral structural component forms a spiral shaped slot with a slot length measured along the centerline of the spiral shaped slot.

[0012] In some forms, the non-conductive material has a dielectric constant, and the slot length is at least equal to one-half of the effective wavelength Aeff of the wireless RF communication signal passing through the non-conductive material.

[0013] In some forms, the effective wavelength Aeff in mm equals 300 / (F x (er)1 Z2) where the F is a frequency in GHz of the wireless RF communication signal and the er is the dielectric constant of the non-conductive material.

[0014] In some forms, the metal plate includes a top surface and a bottom surface, and the hole passes through the metal plate from the top surface to the bottom surface. In some forms, the conductive layer has a thickness of at least at least 0.5 mils but no greater than 0.125 inch.

[0015] In some forms, the metal plate is a metal pit lid configured to cover an in-ground utility pit, and the hole is a mounting hole in the metal pit lid.

[0016] In some forms, a meter transmission unit is removably attached to the bottom surface of the metal pit lid. The meter transmission unit transmits the wireless RF communication signal through the metal pit lid via the RF transparent cap.

[0017] Various embodiments are drawn to a meter transmission unit apparatus configured to transmit a wireless RF communication signal through a hole of diameter D in a metal pit lid. The apparatus includes an antenna configured to transmit the wireless RF communication signal, an RF transparent cap that has a first end and a second end. The first end of the RF transparent cap is positioned adjacent the antenna. The apparatus also includes a folded structural component configured that has a first end, asecond end and a shaped side. The first end is separated from the second end by the shaped side. A conductive layer of the RF transparent cap covers the shaped side. The first end of the folded structural component extends into the hole in the metal plate, and the RF communication signal has a signal wavelength As greater in length than the diameter D of the hole in the metal plate. The RF transparent cap transmits the wireless RF communication signal through the hole in the metal plate, and the RF transparent cap is characterized by a slot length.BRIEF DESCRIPTION OF THE DRAWINGS

[0001] Various aspects and advantageous features of the present disclosure will become more apparent to those of ordinary skill when described below in the Detailed Descriptions reference to the accompanying drawings wherein:

[0002] FIG. 1A depicts a cut away side view of an RF transparent cap mounted on a Meter Transmission Unit (MTU) which is attached to a metal pit lid according to various embodiments disclosed herein.

[0003] FIG. 1B depicts a cutaway oblique view of a Meter Transmission Unit (MTU) attached to a metal pit lid according to various embodiments disclosed herein.

[0004] FIG. 2A depicts a top view of a first type of metal pit lid with an RF transparent cap according to various embodiments disclosed herein.

[0005] FIG. 2B depicts an oblique view of a second type of a metal pit lid with an RF transparent cap according to various embodiments disclosed herein.

[0006] FIG. 3A depicts an oblique view of the RF transparent cap according to various embodiments disclosed herein.

[0007] FIG. 3B depicts a top view of the RF transparent cap of FIG. 3A according to various embodiments disclosed herein.

[0008] FIG. 3C depicts a top view of the conductivity component according to various embodiments disclosed herein.

[0009] FIG. 4 depicts top views of three folded slots for various implementations of an RF transparent cap according to various embodiments disclosed herein.DETAILED DESCRIPTIONS

[0010] FIG. 1A depicts a cut away side view of an RF transparent cap 101 mounted on a Meter Transmission Unit (MTU) 150 which is attached to a metal pit lid 199 according to various embodiments disclosed herein. FIG. 1B depicts a cutaway oblique view of a Meter Transmission Unit (MTU) attached to a metal pit lid according to various embodiments disclosed herein.

[0011] The various embodiments include a metal skirt 103 that fits into a mounting hole (sometimes a threaded mounting hole), an RF transparent cap 101, and an MTU 150 with an antenna 151 mounted below the lid. Some implementations have the RF transparent cap 101 fitted inside a metal skirt 103. The metal skirt 103 ensures good electrical contact with the metal pit lid 199. The MTU 150 may contain a printed circuit board (PCB) antenna, an external antennas or other types of antennas. The antenna 151 radiates RF signals through the RF transparent cap 101 into the air above the metal pit lid 199. The RF transparent cap 101 is able to transmit antenna radiation of a wavelength longer than the diameter of the mounting hole through the metal pit lid 199, thus enabling effective radio communication between the MTU 150 inside an in-ground utility pit with a DCU (Data Collection Unit) outside the pit.

[0012] The ends of RF transparent cap 101 are typically positioned to span as much of the distance as possible between the antenna 151 and the rim of the bottom of the mounting hole. In some implementations, the ends of RF transparent cap 101 are no greater than 10% the length of the greatest wavelength transm itted by the MTU 150 away from the antenna 151 and the rim of the mounting hole. In various other implementations, the distances from the ends of RF transparent cap 101 to antenna 151 and the mounting hole rim are no greater than 2%, or are no greater than 5%, or are no greater than 15%, or are no greater than 20%, or are no greater than 25%, the length of the greatest wavelength transmitted by the MTU 150. The metal skirt 103 is preferably no greater than 20% the length of the greatest wavelength transmitted by the MTU 150. It should be noted, however, that the various brands of metal pit lids 199 vary greatly in thickness. Different heights of RF transparent caps 101 and metal skirt 103 may be implemented in order to accommodate the varying widths of different brands of metal pit lids 199.

[0013] The various embodiments utilize the principle of shielding, where a metal enclosure becomes substantially RF-transparent when it contains a half-wavelength opening. A challenge arises because the mounting hole in a utility pit lid is typically much smaller than the wavelength of low-frequency RF signals, such as those at 450MHz. To overcome this, the small mounting hole can be transformed into a longer opening by forming a circular slot, a spiral shaped slot, or a folded slot of another shape having sufficient length. The folded shaped slot may be constructed using the same metal as its boundary, or may be constructed using another metal that is a good conductor (e.g., copper).

[0014] The metal pit lid 199 is generally made from cast iron in order to have sufficient strength to hold up vehicles passing over it. In some implementations the metal pit lid 199 may be made from stainless steel, iron or another type of metal. The metal pit lid 199 is typically made of metal that is from 0.25 to 1.0 inches thick with structural fins to reinforce the surface. The metal pit lid 199 structure is typically two to three inches thick, and has a mounting hole. The mounting hole in metal pit lid 199 is typically 1.75 + / - 0.2 inches in diameter. In some implementations the metal pit lid 199 and the mounting hole may be larger or smaller than these typical dimensions, e.g., a mounting hole no greater than 2.5 inches, no greater than 3.0 inches, no greater than 4.0 inches.

[0015] In some implementations the MTU 150 may have a threaded mounting tube that screws into female threads on the inside of threaded mounting hole of metal pit lid 199. For a 1.75 inch mounting hole the interior hollow portion of threaded mounting tube is approximately 1.5 inch in diameter. The antenna 151 broadcasts RF communication signals 153a from MTU 150 into the threaded mounting tube. The RF communication signals 153a from an MTU 150 are typically broadcast at UHF frequencies — e.g., 450 MHz. Since the wavelength of UHF is much larger than the inside diameter of the threaded mounting tube (e.g., 1.5 inch), transmitting the RF communication signals 153a through the threaded mounting tube results in a great deal of attenuation to the point of almost completely blocking the signal. In some implementations the RF communication signals 153a may be as low as 250 MHz to as high as 3 GHz.

[0016] FIG. 2A depicts a top view of a first type of metal pit lid 199 with an RF transparent cap 101 according to various embodiments disclosed herein. FIG. 2B depictsan oblique view of a second type of a metal pit lid 299 with an RF transparent cap according to various embodiments disclosed herein. In some metal pit lids 299 the mounting hole is located off-center as shown in FIG. 2B.

[0017] FIG. 3A is an oblique view of the RF transparent cap 101 according to various embodiments disclosed herein. FIG. 3B is a top view of the RF transparent cap of FIG.3A according to various embodiments disclosed herein. The present inventors recognized that, although the RF communication signals 153a (of FIG. 1A) at UHF frequencies won’t properly transmit through a round 1.5 inch diameter opening (e.g., the inside diameter of the metal skirt 103 positioned within the mounting hole) it will transmit through a slot that has a slot length of one-half wavelength (A / 2).

[0018] A UHF frequency of 450 MHz has a wavelength of 0.67m (26.4 inches), which is much larger than the 1.5 inch diameter opening of mounting hole. To overcome this, the present inventors used a spiral shaped slot rather than a slot with a rectangular crosssection or another folded shaped slot. It should be noted that the slot can be other shapes aside from spirals. The RF transparent cap 101 depicted in FIGS. 3A-B has a spiral slot bounded by the conductive layer 107. The spiral slot designed to make the RF transparent cap 101 substantially transparent to a signal with a wavelength which is over twice the diameter of the spiral. The spiral centerline 101a shown in FIG. 3B indicates the length of the slot. The spiral centerline 101 a is longer than the diameter of the spiral. The spiral slot of FIGS. 3A-B has a length of approximately one-half the effective wavelength Aeff of the RF signal that the RF transparent cap 101 is designed to optimally transmit — that is, allow to pass through it. The length of a folded slot is defined by the length of its centerline as shown with the spiral slot of FIGS. 3A-B.

[0019] The RF transparent cap 101 can be implemented using a shaped non-conductive material as the spiral shaped folded structural component 105 — such as plastic having the desired dielectric constant — to form a folded ring at least one-half wavelength long (i.e. , A / 2). The dielectric constant srof the non-conductive material is chosen such that the electric length of the folded of the RF transparent cap 101 is at least half the effective wavelength Aeff of RF communication signals 153a from MTU 150 as they are passing through the dielectric material in RF transparent cap 101. The effective wavelength Aeff is the wavelength the signal has as is passes through the non-conductivematerial in the RF transparent cap 101. The relationship between the dielectric constant Er and the effective wavelength Aeff in mm (millimeters) is: Aeff = 300 / (F x (£r)1 / 2) where F is the transmitted frequency in GHz (gigahertz). The dielectric constant of the material used in RF transparent cap 101 affects the necessary slot length to pass a signal of a given frequency.

[0020] A 450 MHz UHF frequency with a wavelength of 26.4 inches requires a half wave-length slot of 13.2 inches in length if the slot is open space (air with a dielectric constant of 1). Putting a dielectric material with a dielectric constant of 8 in the slot reduces the necessary slot length to 4.6 inches for a 450 MHz signal. If the diameter of the RF transparent cap of FIG. 3A is 1.5 inches, the length of spiral centerline 101a is approximately 4.6 inches — somewhat shorter than the 13.2 inch half wavelength of 450 MHz. Alternatively, a 13.2 inch slot length may be achieved by using a longer, concentric spiral, with more spirals — or other shapes of folded slots — as shown in FIG. 4.

[0021] The non-conductive structural material of spiral shaped folded structural component 105 is covered by a thin coat of a conductive material, e.g., metal, to form a conductive layer 107. The spiral shaped folded side coated by the conductive material may be continuous, going all the way around the non-conductive spiral shaped folded structural component 105, as can be seen in FIGS. 3A-B. The conductive layer 107 is typically at least 0.5 mils thick (i.e., 0.5 thousanth of an inch), and typically not greater than 0.125 inch thick. Copper tape (sometimes called copper clad tape) is a material suitable for use as the conductive layer 107. The shaded areas of the RF transparent cap 101 depicted in FIG. 3A are the thin layer the conductive material (e.g., copper tape) formed to be the conductive layer 107 that covers the non-conductive spiral shaped folded structural component 105 which is formed from the non-conductive material such as plastic. The conductive layer 107 may go all the way around the non-conductive spiral shaped folded structural component 105, but is not present on the top or bottom of the RF transparent cap 101. The uncovered top and bottom of the RF transparent cap 101 may be called a first end and a second end, and the portion coated by the conductive material may be called the spiral shaped sides.

[0022] In various embodiments the conductive layer 107 is electrically connected to the metal of the metal pit lid 199. This may be done using a conductive connectorcomponent 111 , as shown in FIG. 3C. The conductive connector component 111 — which is typically made of metal — is shaped to cover the end of RF transparent cap 101 adjacent to the slot — that is, the portion of RF transparent cap 101 through which no RF signals are transmitted. In other embodiments, the conductive connector component 111 may take the form of other shapes. The conductive connector component 111 is in electrical contact with conductive layer 107 and is configured make electrical contact with the metal pit lid 199. All or part of the conductive connector component 111 from point 111-1 to point 111-2 (indicated by the arrows on FIG. 3C) may be in electrical contact with conductive layer 107. In some implementations the conductive connector component 111 may be soldered to the conductive layer 107. The flat portion towards the end 111-3 of conductive connector component 111 may be electrically connected with the metal pit lid 199. This may be achieved by fastening the conductive connector component 111 to the metal pit lid 199 with screws or bolts, by welding or brazing them together, by running a metal wire from the conductive connector component 111 to the metal pit lid 199, by affixing a metal clamp — electrically connected to the conductive connector component 111 — to the metal pit lid 199, or other ways of making an electrical connection known to those of skill in the art.

[0023] Other materials may be used to implement the RF transparent cap 101. For example, the transparent cap 101 may alternatively be implemented using a non-conductive material such as plastic, glass, rubber, neoprene and / or using a conductive material such as aluminum, steel or other like types of conductive or non-conductive materials known to those of ordinary skill in the art.

[0024] Turning again to FIG. 1A, a non-conducting top cover 109 may be provided above the RF transparent cap 101 for structural support, and to protect the cap 101 from the elements. The non-conducting top cover 109 holds the the RF transparent cap 101 in place. The non-conducting top cover 109 preferably does not extend above the top surface of metal pit lid 199, and is typically fairly thin — e.g., no greater thickness than 0.65 inch thick. It should be noted, however, that the various brands of metal pit lids 199 vary somewhat in thickness. Different heights of RF transparent caps 101 may be implemented in order to accommodate the varying widths of different brands of metal pit lids 199.

[0025] One end of the RF transparent cap 101 is positioned adjacent the antenna 151 of MTU 150, as shown in FIG. 1A. The other end of RF transparent cap 101 preferably reaches upward to be adjacent the upper rim of the mounting hole in order to maximize the strength of the RF communication signals 153b emanating upward from the street level — e.g., reaches up to just beneath the non-conducting top cover 109.

[0026] FIG. 4 depicts top views of three folded slots for various implementations of an RF transparent cap according to various embodiments disclosed herein. The RF transparent cap 101’s spiral slot 261 of FIG. 4 has more spirals and a longer spiral slot length than those of the RF transparent cap 101 shown in FIG. 3A. The additional spirals and longer slot results in an RF transparent cap 101 that is transparent to lower frequencies with longer wavelengths than the frequencies passed through RF transparent cap of FIGS. 3A-B according to various embodiments disclosed herein. Numerous other slot shapes and slot lengths can be used to implement the various embodiments and accommodate the requirements of other frequencies and other applications — e.g. slot shape 263 and 265 of FIG. 4 — and other slot shapes known to those of ordinary skill in the art.

[0027] An RF transparent cap 101 with a slot shape of 261-265 is arranged similar to the disclosure of RF transparent cap 101 described above in conjunction with FIGS. 1A-3C. RF transparent caps 101 are implemented using a shaped non-conductive material such as plastic covered by a thin coat of a conductive material such as copper tape. The conductive layer goes all the way around the non-conductive structure. Other materials may be used to implement the RF transparent cap 101 aside from plastic for the nonconducting structural portion and the copper clad tape for the conductive portion, as are known to those of ordinary skill in the art.

[0028] One of ordinary skill will appreciate that the exact dimensions and materials are not critical to the disclosure and all suitable variations should be deemed to be within the scope of the disclosure if deemed suitable for carrying out the objects of the disclosure.

[0029] One of ordinary skill in the art will also readily appreciate that it is well within the ability of the ordinarily skilled artisan to modify one or more of the constituent parts for carrying out the various embodiments of the disclosure. Once armed with the presentspecification, routine experimentation is all that is needed to determine adjustments and modifications that will carry out the present disclosure.

[0030] The phrase “substantially RF-transparent” is used herein in the disclosure of the various embodiments. “Substantially RF-transparent” is defined to mean that the signal is attenuated by no more than 6.0 dB. The word “slot” is used herein in the disclosure of the various embodiments. A “slot” is a space through which something can pass. A slot may be filled with air, or may be filled with a material through which something can pass. A slot may be filled with a dielectric material through which an RF signal can pass. The phrase “spiral shaped” is used herein in the disclosure of the various embodiments. A “spiral shaped” item has at least a portion that is circular, spiral shaped or rounded through at least 270 degrees.

[0031] The phrase “metal pit lid” is used herein in the disclosure of the various embodiments. A “metal pit lid” is a cover akin to a manhole cover that is typically placed over an in-ground utility pit — e.g. a cover for an in-ground utility pit used by an electrical, cable, water or gas utility company. The phrase “configured make electrical contact with” is used herein in the disclosure of the various embodiments. An apparatus that is “configured make electrical contact with” another item is defined to have some mechanism designed to achieve electrical connection with the other item. For example, the apparatus may have bolt holes that align with holes on a metal portion of the other item, allowing the two items to be bolted together; or the apparatus may have a copper wire attached to a metal clamp designed to be clamped to a metal portion of the other item.

[0032] The above embodiments are for illustrative purposes and are not intended to limit the scope of the disclosure or the adaptation of the features described herein. Those skilled in the art will also appreciate that various adaptations and modifications of the above-described preferred embodiments can be configured without departing from the scope and spirit of the disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.

Claims

CLAIMSWhat is claimed is:

1. An apparatus for transmitting a wireless RF communication signal through a hole of diameter D in a metal plate, the apparatus comprising:an RF transparent cap comprising a first end and a second end, the first end being positioned adjacent a source of the wireless RF communication signal;a folded structural component configured as part of the RF transparent cap, the folded structural component including a first end, a second end and a shaped side, wherein the first end is separated from the second end by the shaped side; anda conductive layer configured as part of the RF transparent cap, the conductive layer covering the shaped side;wherein the first end of the folded structural component extends into the hole in the metal plate;wherein the RF communication signal has a signal wavelength As greater in length than the diameter D of the hole in the metal plate; andwherein the RF transparent cap transmits the wireless RF communication signal through the hole in the metal plate, and the RF transparent cap is characterized by a slot length.

2. The apparatus of claim 1 , further comprising:a conductive connector component in electrical contact with the conductive layer, wherein the conductive connector component is configured make electrical contact with the metal plate;wherein the folded structural component is made from a non-conductive material.

3. The apparatus of claims 1 or 2, wherein the hole is a mounting hole and the metal plate is a metal pit lid; andwherein the signal wavelength As is over twice as large as the diameter D of the hole in the metal pit lid.

4. The apparatus as in any one of claims 1 through 3, wherein the shaped side is a spiral shaped side, and the folded structural component is a spiral structural component, the conductive layer covering the spiral shaped side of the spiral structural component forms a spiral shaped slot; andwherein the slot length of the spiral shaped slot is measured along a centerline of the spiral shaped slot.

5. The apparatus as in any one of claims 1 through 4, wherein the non-conductive material has a dielectric constant; andwherein the slot length is at least equal to one-half of an effective wavelength Aeff of the wireless RF communication signal passing through the non-conductive material.

6. The apparatus of claim 5, wherein the effective wavelength Aeffin mm equals 300 / (F x (£r)1 / 2) where the F is a frequency in GHz of the wireless RF communication signal and the £ris the dielectric constant of the non-conductive material.

7. The apparatus as in any one of claims 1 through 6, wherein the metal plate includes a top surface and a bottom surface, and the hole passes through the metal plate from the top surface to the bottom surface.

8. The apparatus as in any one of claims 1 through 7, wherein the conductive layer has a thickness of at least at least 0.5 mils but no greater than 0.125 inch.

9. The apparatus as in any one of claims 1 through 8, wherein the metal plate is a metal pit lid configured to cover an in-ground utility pit, and the hole is a mounting hole in the metal pit lid.

10. The apparatus of claim 9, wherein a meter transmission unit is removably attached to the bottom surface of the metal pit lid; andwherein the meter transmission unit transmits the wireless RF communication signal through the metal pit lid via the RF transparent cap.

11. A meter transmission unit apparatus configured to transmit a wireless RF communication signal through a hole of diameter D in a metal pit lid, the apparatus comprising:an antenna configured to transmit the wireless RF communication signal;an RF transparent cap comprising a first end and a second end, the first end being positioned adjacent the antenna;a folded structural component configured as part of the RF transparent cap, the folded structural component including a first end, a second end and a shaped side, wherein the first end is separated from the second end by the shaped side; anda conductive layer configured as part of the RF transparent cap, the conductive layer covering the shaped side;wherein the first end of the folded structural component extends into the hole in the metal pit lid; andwherein the RF communication signal has a signal wavelength As greater in length than the diameter D of the hole in the pit lid; andwherein the RF transparent cap transmits the wireless RF communication signal through the hole in the pit lid, and the RF transparent cap is characterized by a slot length.

12. The apparatus of claim 11 , further comprising:a conductive connector component in electrical contact with the conductive layer, wherein the conductive connector component is configured make electrical contact with the pit lid;wherein the folded structural component is made from a non-conductive material; andwherein the antenna is a printed circuit board antenna.

13. The apparatus of claims 11 or 12, wherein the hole is a mounting hole and the pit lid is a metal pit lid; andwherein the signal wavelength As is over twice as large as the diameter D of the hole in the metal pit lid.

14. The apparatus as in any one of claims 11 through 13, wherein the shaped side is a spiral shaped side, and the folded structural component is a spiral structural component, the conductive layer covering the spiral shaped side of the spiral structural component forms a spiral shaped slot; andwherein the slot length of the spiral shaped slot is measured along a centerline of the spiral shaped slot.

15. The apparatus as in any one of claims 11 through 14, wherein the non-conductive material has a dielectric constant; andwherein the slot length is at least equal to one-half of an effective wavelength Aeff of the wireless RF communication signal passing through the non-conductive material.

16. The apparatus of claim 15, wherein the effective wavelength Aeffin mm equals 3001 (F x (£r)1 / 2) where the F is a frequency in GHz of the wireless RF communication signal and the sris the dielectric constant of the non-conductive material.

17. The apparatus as in any one of claims 11 through 16, wherein the pit lid includes a top surface and a bottom surface, and the hole passes through the pit lid from the top surface to the bottom surface; andwherein the conductive layer has a thickness of at least at least 0.5 mils but no greater than 0.125 inch.

18. The apparatus as in any one of claims 11 through 17, wherein the metal pit lid configured to cover an in-ground utility pit, and the hole is a mounting hole in the metal pit lid.

19. The apparatus as in any one of claims 11 through 18, wherein the meter transmission unit apparatus is removably attached to the bottom surface of the metal pit lid.

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