Lightning detection sensor

Abstract

To provide a lightning detection sensor that can eliminate the need for a grounding cable.SOLUTION: A lightning detection sensor comprises a sensing element 102 that detects radio-frequency (RF) signals relating to lightning activity, a circuit 106 that receives the detected RF signals from the sensing element and amplifies the RF signals for output to a digital signal processing device, and a reference element 104 coupled to the circuit. The reference element is connected to an antenna ground 110 that is isolated from a power ground 112, the antenna ground is isolated from the power ground using a DC-DC converter 114, and the reference element and the antenna ground are not connected to an external ground plane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION This application relates generally to systems and apparatus for lightning detection, including antennas for use in lightning detection sensors. [Background technology]

[0002] The signal generated by lightning is broadband (e.g., 0 Hz to 1 GHz), with most of the power in the low-frequency band. Because the signal is very strong at low frequencies, the antennas used in lightning detection sensors typically do not need to be very efficient. In general, current lightning detection sensor technology frequently uses monopole field-varying antennas, where the voltage output is proportional to the electric field with exponential decay.

[0003] However, this type of antenna requires a strong ground plane and the installation of a separate ground cable. In certain geographic areas (e.g., remote or developing areas with poor electrical infrastructure), it can be difficult to find a strong ground plane and install a ground cable. Furthermore, ground cables are susceptible to corrosion, breakage, and other deterioration over time, which can cause the lightning detection sensor to become inoperable. Continuously monitoring the integrity of the sensor and ground cable and periodically repairing or replacing the ground cable is typically difficult and expensive. Summary of the Invention

[0004] Therefore, there is a need for an improved antenna design for lightning detection sensors that overcomes the above-mentioned challenges by eliminating the need for a separate ground cable. Antenna embodiments described herein utilize a center-fed dipole design, which offers the advantage of eliminating the need for a ground cable connected to the lightning detection sensor and extending to the ground plane, thereby improving the efficiency and costs associated with installing and maintaining sensors, particularly in locations where power lines are not well established (or enforced) or in areas that rely on generators to power the sensor. Furthermore, antenna design embodiments described herein advantageously minimize the risk of water bridging and corrosion by providing a sensor body made of a water-resistant plastic material (e.g., a thermoplastic such as polycarbonate or polyvinyl chloride (PVC)) in combination with an asymmetric electrode design (one electrode located on the exterior surface of the sensor body and the other electrode housed or embedded within the sensor body).

[0005] In one aspect, the invention features a lightning detection sensor including a detection element for detecting radio frequency (RF) signals associated with lightning activity, a circuit for receiving the detected RF signals from the detection element and amplifying the RF signals for output to a digital signal processor, and a reference element connected to the circuit, the reference element being connected to an antenna ground that is isolated from a power supply ground, and the reference element and the antenna ground not being connected to an external ground plane.

[0006] In some embodiments, the sensing element and the reference element are made of a conductive metal, hi some embodiments, the conductive metal is an aluminum alloy. In some embodiments, the lightning detection sensor comprises a sensor body housing one or more of the sensing element, the circuitry, and the reference element. In some embodiments, the sensor body is made of a plastic material. In some embodiments, the plastic material is polycarbonate or polyvinyl chloride (PVC). In some embodiments, the sensor body is cylindrical. In some embodiments, the circuitry is embedded in the sensor body. In some embodiments, at least a portion of the sensing element is disposed on an outer surface of the sensor body, and at least a portion of the reference element is embedded in the sensor body. In some embodiments, at least a portion of the sensing element is embedded in the sensor body, and at least a portion of the reference element is disposed on the outer surface of the sensor body. In some embodiments, the antenna ground is connected to a ground element disposed inside the sensor body.

[0007] In some embodiments, the gain of the circuit is constant and calibrated. In some embodiments, the antenna ground is isolated from the power supply ground using a DC-DC converter. In some embodiments, the circuit comprises an inverting charge amplifier that amplifies the RF signal. In some embodiments, the inverting charge amplifier is a fully differential amplifier.

[0008] In some embodiments, the sensor is attached to a mount that secures the sensor to a physical structure. In some embodiments, the circuitry is connected to a remote network via a network port connected to the circuitry.

[0009] Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. The above-described advantages of the present invention, together with further advantages, may be better understood by reference to the following description taken in conjunction with the accompanying drawings, in which the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram of an antenna circuit design according to one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram of another antenna circuit design according to one embodiment of the present invention. [Figure 3] FIG. 3 is a diagram of a lightning detection sensor according to one embodiment of the present invention. [Figure 4A] FIG. 4A is an exploded view of another lightning detection sensor according to one embodiment of the present invention. [Figure 4B] FIG. 4B is an assembly diagram of the lightning detection sensor of FIG. 4A. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 is a diagram of an antenna circuit design 100 according to one embodiment of the present invention. As shown in FIG. 1, the antenna circuit design 100 includes a center-fed dipole design with a sensing element 102, a reference element 104, an amplifier 106, a capacitor 108, an antenna ground 110, a power ground 112, a DC-DC converter 114, a power supply 116, and a signal output 118. The sensing element 102 comprises a device (e.g., a whip antenna, an electrode, or a similar device) that detects RF signals resulting from atmospheric lightning activity, such as cloud-to-ground (CG) strokes and intra-cloud (IC) pulses. The sensing element 102 transfers the detected RF signals to the amplifier 106 and capacitor 108 pair via an optional 100 ohm resistor. In some embodiments, the amplifier 106 is an inverting charge amplifier, although it should be understood that other types, models, and / or configurations of amplifiers are possible. The amplifier 106 is connected to the reference element 104, which in some embodiments is a whip antenna, an electrode, or a similar device. In some embodiments, such as the embodiment shown in FIG. 1, the reference element 104 is connected to the antenna ground 110 and the DC-DC converter 114. As can be appreciated, the antenna includes the reference element 104 because the electric field changes need to be measured relative to a reference. A typical monopole design uses an external ground connection. The current antenna circuit design 100 does not have an external ground connection, so the reference element 104 is necessary. It should be appreciated that in some embodiments, the antenna ground 110 is not attached anywhere. However, a local ground is required for the circuit to operate. In some configurations of the antenna, the reference element 104 can be attached to the antenna ground (as in FIG. 1), but when using a differential input (as in FIG. 2), it is not necessary.

[0012] To operate the antenna without a strong ground, the antenna ground 110 should be isolated from the power ground 112 of the power supply 116 (e.g., the DSP board it is powering) by using a DC-DC converter 114. Typically, the DC-DC converter includes an oscillator that oscillates in the frequency band of the antenna. Therefore, care must be taken to both select a converter with particularly low noise and to filter the power. One advantage of this is that it allows the use of a dual-supply operational amplifier, eliminating antenna biasing. An exemplary DC-DC converter 114 is the CC3-0505SF-E, available from TDK-Lambda.

[0013] The amplifier 106 is further connected to a signal output 118, which provides the detected RF signal to, for example, a DSP board (not shown) for analysis and processing into a digital waveform representative of the detected lightning activity. It should be appreciated that in some embodiments, because the antenna gain is based on the effective area of ​​the sensing element 102, the signal level may be somewhat lower than lightning detection sensors utilizing other types of sensing elements (e.g., signal plate designs). To compensate for this, the gain of the sensor's active circuitry can be adjusted, for example, by reducing the C value (and adjusting R accordingly) or by using a gain-bearing follower after the charge amplifier. Because the distance between the reference element 104 and the sensing element 102 is fixed, the passive gain is generally less dependent on position. In contrast, with monopole antenna designs, the distance between the sensing element and external ground varies depending on how the antenna is installed. In some embodiments, the antenna gain is fixed and calibrated prior to sensor installation, advantageously eliminating gain variations or attenuation that may be due to the physical location of the lightning detection sensor (e.g., the height at which the sensor is installed), thereby eliminating the need for a strong antenna ground.

[0014] Figure 2 is a diagram of another antenna circuit design 200 according to one embodiment of the present invention. Many of the components shown in Figure 2 are similar to those shown in Figure 1 above, including the sensing element 102, reference element 104, capacitor 108, antenna ground 110, power ground 112, DC-DC converter 114, power supply 116, and signal output 118. However, as shown in Figure 2, amplifier 202 comprises a fully differential amplifier (such as the AD8274 precision differential amplifier available from Analog Devices, Inc., Norwood, Massachusetts). As can be appreciated, the use of a fully differential amplifier offers several advantages, including lower distortion and improved gain accuracy.

[0015] FIG. 3 is a diagram of a lightning detection sensor design 300 in accordance with one embodiment of the present invention. As shown in FIG. 3 , circuit 100 (e.g., a printed circuit board (PCB)) is housed within plastic housing 302 and connected to sensing element 102 and reference element 104. For example, sensing element 102 and reference element 104 may be a whip antenna attached to plastic housing 302 via a screw plate, which is electrically connected to circuit 100 via wiring. Plastic housing 302 is connected to a mount 304, which may be fixed to a tower, building, or other type of structure. A signal path 306 travels from circuit 100 through mount 304 to, for example, a DSP board or other module (not shown) that receives and processes signals from circuit 100. It should be understood that in some embodiments, the DSP board may be embedded within plastic housing 302.

[0016] 4A and 4B are diagrams of another lightning detection sensor design 400 in accordance with one embodiment of the present invention. FIG. 4A provides an exploded view of sensor design 400 showing the components separated, while FIG. 4B provides a view of the same sensor design 400 with the components fully assembled. As shown in FIG. 4A, sensor body 402 has a cylindrical shape that may be constructed from a water-resistant plastic material (such as polycarbonate or polyvinyl chloride (PVC)). It should be understood that other types of plastic and / or water-resistant materials may be used without departing from the scope of the present invention.

[0017] The circuit 100 (e.g., a PCB) is configured in a circular shape with a diameter slightly smaller than that of the sensor body 402 so that the circuit 100 can be embedded within the sensor body 402 when the sensor is fully configured. In some embodiments, the circuit 100 can be attached to a base plate (not shown) to provide stability and protection for the circuit 100. The circuit 100 and / or the base plate can be attached to the sensing element 102 using, for example, an L-shaped bracket 404 and screws, which provide a connection between the sensing element 102 and the circuit 100. The sensing element 102 is positioned on top of the sensor body 402 and is configured with a diameter slightly larger than that of the sensor body. This allows the sensing element 102 to slide over the sensor body 402 so that at least a portion of the sensing element 102 contacts the outer surface of the sensor body 402. The sensing element 102 is constructed of a conductive metal such as spun 1100 aluminum alloy (although other types of conductive metals may be used within the scope of the present invention). Once the sensing element is slid onto the sensor body 402, the sensing element 102 may be attached to the sensor body 402 using, for example, steel screws 406.

[0018] The reference element 104 is positioned at the bottom of the sensor body 402 and is configured with a diameter slightly smaller than that of the sensor body. This allows the reference element 104 to slide into the sensor body 402 until at least a portion of the reference element 104 is embedded within the sensor body 402 and contacts the inner surface of the sensor body. The reference element 104 is configured from a conductive metal such as spun 1100 aluminum alloy (although other types of conductive metals can be used within the scope of the present invention). Once the reference element is at least partially embedded within the sensor body 402, the reference element 104 can be attached to the sensor body 402 using, for example, steel screws 408. Also, although not shown in FIGS. 4A and 4B , wiring connects the reference element 104 to the circuit 100 to provide a reference signal to the circuit 100.

[0019] 4A and 4B are exemplary, and it should be understood that other configurations of the components are contemplated. For example, in some embodiments, the sensing element 102 may be at least partially embedded inside the sensor body 402, while the reference element may be at least partially disposed on the exterior surface of the sensor body 402. In other embodiments, both the sensing element 102 and the reference element 104 may be at least partially embedded inside the sensor body 402. In yet other embodiments, both the sensing element 102 and the reference element 104 may be at least partially disposed on the exterior surface of the sensor body 402, although these latter two configurations may increase the risk of water bridging or moisture ingress inside the sensor.

[0020] The sensor body 402 is further connected to a mounting bar 510 that holds the sensor in place. As can be appreciated, the sensor may be attached via the mounting bar 410 to another physical object (e.g., a building, tower, or other type of structure) for the purpose of detecting lightning activity. In some embodiments, a cable or wire may be run inside the mounting bar to access the interior of the sensor body 402 for connection to the circuit 100, for example, to carry power to the antenna and carry a signal from the antenna. In one embodiment, an Ethernet cable may be used, although it should be understood that other types of cable, including simple wires, may be used for this purpose. In some embodiments, the circuit 100 may include a network port for interfacing with a cable. This configuration allows the circuit 100 to be connected to a network, for example, for the purpose of transmitting lightning signal data to a remote computing device. In other embodiments, a fiber optic cable may be used to transmit signals from the antenna to an external device.

[0021] As noted above, a significant advantage of the antenna circuit designs of Figures 1 and 2 and the lightning sensor designs of Figures 3, 4A, and 4B is that they eliminate a separate external ground connection to the circuit and instead utilize the antenna ground 110 contained within the lightning detection sensor itself. This can improve the efficiency and costs associated with installing and maintaining the sensor by providing the advantage of not requiring a separate ground cable connected to the lightning detection sensor and running to the ground plane.

[0022] It is to be understood that the embodiments of the invention presented herein are exemplary, and that other configurations of the lightning detection sensor elements described herein may be contemplated as being within the scope of the described technology. "Comprises" and / or each plural form is open-ended and includes the listed parts, and may include additional, alternative, and / or other parts not listed. "And / or" is open-ended and includes one or more of the listed parts and combinations of the listed parts.

[0023] Those skilled in the art will recognize that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments, therefore, are to be considered in all respects as illustrative rather than limiting of the invention described herein.

Claims

1. A lightning detection sensor, a detection element for detecting radio frequency (RF) signals associated with lightning activity; a circuit for receiving the detected RF signal from the detection element and amplifying the RF signal for output to a digital signal processor; a reference element connected to the circuit; Equipped with the reference element is connected to an antenna ground isolated from a power supply ground; A lightning detection sensor, wherein the reference element and the antenna ground are not connected to an external ground plane.

2. The lightning detection sensor of claim 1 , wherein the sensing element and the reference element are made of a conductive metal.

3. 3. The lightning detection sensor according to claim 2, wherein the conductive metal is an aluminum alloy.

4. The lightning detection sensor of claim 1 , further comprising a sensor body housing one or more of the sensing element, the circuitry, and the reference element.

5. 5. The lightning detection sensor according to claim 4, wherein the sensor body is made of a plastic material.

6. 6. The lightning detection sensor according to claim 5, wherein the plastic material is polycarbonate or polyvinyl chloride (PVC).

7. 5. The lightning detection sensor according to claim 4, wherein the sensor body is cylindrical.

8. 8. The lightning detection sensor of claim 7, wherein the circuit is embedded in the sensor body.

9. The lightning detection sensor of claim 8 , wherein at least a portion of the sensing element is disposed on an outer surface of the sensor body, and at least a portion of the reference element is embedded in the sensor body.

10. 9. The lightning detection sensor of claim 8, wherein at least a portion of the sensing element is embedded in the sensor body, and at least a portion of the reference element is disposed on an outer surface of the sensor body.

11. 5. The lightning detection sensor of claim 4, wherein the antenna ground is connected to a ground element disposed inside the sensor body.

12. 2. The lightning detection sensor of claim 1, wherein the gain of the circuit is constant and calibrated.

13. 2. The lightning detection sensor of claim 1, wherein the antenna ground is isolated from the power supply ground using a DC-DC converter.

14. The lightning detection sensor of claim 1 , wherein the circuitry comprises an inverting charge amplifier that amplifies the RF signal.

15. 15. The lightning detection sensor of claim 14, wherein the inverting charge amplifier is a fully differential amplifier.

16. 10. The lightning detection sensor of claim 1, wherein the sensor is attached to a mount that secures the sensor to a physical structure.

17. 10. The lightning detection sensor of claim 1, wherein the circuitry is connected to a remote network via a network port connected to the circuitry.

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