Trans-grade communication network
Methods and apparatus that provide grade-level RF transceivers for use in trans-grade wireless communication networks. The methods involve incorporating slot antennas into grade-level opening covers, such as manhole covers, to provide built-in antennas for transceivers that may be connected by transmission lines. The grade-level transceivers use coupling mechanisms to connect transceivers to the slot antennas by way of transmission feed lines. Multi-slot grade-level transceivers use switching mechanisms to switch between multiple slot antennas. Certain embodiments may also include adaptable RF circuitry. Trans-grade wireless communication networks use these grade-level transceivers to communicate between below-ground and above-ground portions of the network, which may be used in underground utility systems such as combined sewer systems.
1. A manhole cover with built-in RF antenna and feed,
wherein said built-in RF antenna comprises a slot through said manhole cover, and
wherein said built-in RF antenna feed comprises a transmission line connector having first and second conductors connected to first and second sides of said slot, respectively.
2. The manhole cover of claim 1 , wherein said slot is filled with a low dielectric constant material.
3. The manhole cover of claim 1 , wherein said transmission line connector is a coaxial connector disposed within the vertical space defined by said slot.
4. A method of incorporating an RF antenna into a grade-level opening cover, comprising:
creating a slot in the grade-level opening cover to radiate at a predetermined radio frequency;
connecting one line of a transmission line to a first side of said slot; and
connecting another line of said transmission line to a second side of said slot.
5. The method of claim 4 , further comprising:
providing a transmission line connector;
connecting said transmission line connector adjacent said slot; and
connecting said transmission line to said slot through said transmission line connector.
6. A grade-level cover RF transceiver, comprising:
a grade-level cover having a first slot therethrough, said slot sized and shaped to radiate at a predetermined radio frequency;
a first cable having first and second conductors connected to first and second sides of said slot, respectively; and
an RF transceiver connected to said first cable.
7. A grade-level cover RF transceiver, comprising:
a grade-level cover having a first slot therethrough, said slot sized and shaped to radiate at a predetermined radio frequency;
a first cable having first and second conductors connected to first and second sides of said slot, respectively;
an RF transceiver connected to said first cable;
a second slot through said grade-level cover said second slot having the same size and shape as said first slot;
a second cable having first and second conductors connected to first and second sides of said second slot, respectively; and
an RF switch connected to said first and second cables and controlled by said RF transceiver for switching between said slots.
8. The grade-level cover RF transceiver of claim 7 , wherein said RF switch includes an impedance matching network.
9. The grade-level cover RF transceiver of claim 8 , wherein said impedance matching network comprises a two-stage impedance tuner.
10. The grade-level cover RF transceiver of claim 8 , wherein said first and second slots are rectangular and said second slot is substantially orthogonally positioned with respect to said first slot.
11. The grade-level cover RF transceiver of claim 10 , wherein said grade-level cover comprises a manhole cover.
12. The grade-level cover RF transceiver of claim 10 , wherein said grade-level cover comprises a storm drain grate.
13. The grade-level cover RF transceiver of claim 7 , further comprising a microcontroller configured to use said RF switch to establish the best RF link with an above-ground node.
14. A trans-grade communication network, comprising:
a below-grade communication device;
an above-grade communication device; and
a grade-level cover incorporating first and second antennas and associated feeds for RF communications between said below-grade communication device and said above-grade communications device, said first and second antennas having slots of the same size and shape; and
an RF transceiver connected to said first and second antennas and configured for antenna selection.
15. The trans-grade communication network of claim 14 , wherein said below-grade communication device comprises an environmental sensor.
16. The trans-grade communication network of claim 14 , further comprising an impedance matching network for adjusting the impedance of said first antenna.
17. The trans-grade communication network of claim 14 , wherein said first and second antennas each comprise a slot through said grade-level cover.
18. The trans-grade communication network of claim 14 , further comprising an RF switch connected to said first and second antennas.
19. The trans-grade communication network of claim 14 , further comprising a microcontroller configured to use said RF switch to establish the best RF link with an above-ground node.
20. A method of incorporating an RF antenna into a grade-level opening cover, comprising:
creating a slot in the grade-level opening cover to radiate at a predetermined radio frequency;
connecting one line of a transmission line to a first side of said slot; and
connecting another line of said transmission line to a second side of said slot;
wherein said slot has sidewalls and end walls defining a vertical space extending through and below said cover, said method further comprising:
mounting a coaxial connector on the underside of said cover with an inner conductor and outer conductor of said coaxial connector positioned within said vertical space;
mechanically supporting said coaxial connector within said vertical space with a metallic coupler mechanically and electrically connected to said outer conductor and to the first side of said slot; and
electrically connecting said inner conductor to the second side of said slot.
21. A grade-level cover RF transceiver, comprising:
a grade-level cover having a first rectangular slot therethrough, said slot sized and shaped to radiate at a predetermined radio frequency;
a first cable having first and second conductors connected to first and second sides of said slot, respectively;
an RF transceiver connected to said first cable;
a second rectangular slot through said grade-level cover, substantially orthogonal to said first slot, and sized and shaped to radiate at a predetermined radio frequency;
a second cable having first and second conductors connected to first and second sides of said second slot, respectively; and
an RF switch connected to said first and second cables and controlled by said RF transceiver for switching between said slots, said RF switch including an impedance matching network having a two-stage impedance tuner.
22. The grade-level cover RF transceiver of claim 21 , further comprising a microcontroller configured to use said RF switch to establish the best RF link with an above-ground node.