Patent Application
20250079702
The present disclosure relates to radio frequency (RF) devices, and, more particularly, to an RF device carried by a remotely controlled unmanned vehicle and associated methods.
Remotely controlled unmanned vehicles include airborne, land and water vehicles. Unmanned airborne vehicles (UAVs) are commonly referred to as drones. An operator uses radio frequency (RF) signals to remotely control an unmanned vehicle. In some cases, the unmanned vehicle may have reduced signal reception due to its operating environment.
Reduced signal reception may be caused by an RF interference source within the operating environment of the unmanned vehicle. The RF interference source may be intentional or unintentional.
Intentional RF interference may be from an RF jammer, for example. In this case, the RF jammer operates within the same frequency band as an RF receiver being carried by the unmanned vehicle. Unintentional RF interference may be from RF transmitters operating in close proximity to the unmanned vehicle.
There is a need to operate unmanned vehicles in the presence of an RF interference source. If RF signal reception at the RF device is degraded too much due to the RF interference source, then an operator of the unmanned vehicle may lose control.
A radio frequency (RF) device for a vehicle may include an antenna, an RF receiver and a controller. The antenna may include a housing, a rotatable base carried by the housing, an actuator to selectively rotate the base, a pair of spaced apart antenna elements carried by the rotatable base, and a phase sifter coupled to the pair of antenna elements to define an antenna pattern having a pair of opposing nulls. The RF receiver is coupled to the antenna, and the controller may drive the actuator to steer the antenna pattern based upon the RF receiver. The vehicle may be unmanned.
The pair of opposing nulls in the antenna pattern may be 180 degrees apart. The controller may be configured to steer the antenna pattern so that one of the nulls is directed toward an RF interference source. The RF receiver may operate over a frequency range, and the pair of opposing nulls are aligned over the frequency range.
The phase shifter may include at least one discrete component. In another embodiment, the phase shifter may include a pair of feeds coupled to respective antenna elements in a reverse configuration.
The controller may be configured to steer the antenna pattern based upon received signal strength. A spacing between the pair of antenna elements may be in a range of 0.1-0.7 wavelength of an operating frequency of the RF receiver.
The pair of antenna elements may comprise a pair of dipole antenna elements extending upwardly from the base. The RF receiver may comprise a frequency-hopping spread spectrum (FHSS) receiver, a direct sequence spread spectrum (DSSS) receiver, or an orthogonal frequency-division multiplexing (OFDM) receiver.
Another aspect is directed to an RF device for a vehicle that may include an antenna comprising a housing, a rotatable base carried by the housing, an actuator configured to selectively rotate the base, a pair of spaced apart dipole antenna elements extending upwardly from the base, and a phase sifter coupled to the pair of antenna elements to define an antenna pattern having a pair of opposing nulls. An RF receiver is coupled to the antenna. A controller is coupled to the RF receiver and may drive the actuator to rotate the antenna pattern while determining received signal strengths of received RF signals, and to stop rotation of the antenna pattern at a desired received signal strength.
Yet another aspect is directed to a method for operating an RF device for a vehicle as described above. The method may include operating the RF receiver coupled to the antenna, and operating the controller to drive the actuator to steer the antenna pattern based upon RF signals received by the RF receiver.
The present description is made with reference to the accompanying drawings, in which exemplary embodiments are shown. However, many different embodiments may be used, and thus the description should not be construed as limited to the particular embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout, and prime notations may be used to indicate similar elements in different embodiments.
Referring initially to
Control of the vehicle 20 is based on the RF device 30 receiving RF control signals 42 from a remote control station 40 controlled by an operator 44. The RF device 30 needs to have good reception of the RF control signals 42 to ensure control of the vehicle 20. If an RF interference source 50 within the operating environment of the unmanned vehicle 20 is transmitting RF interference signals 52, then these signals may disrupt control of the vehicle 20. If control of the vehicle 20 is disrupted or lost, then the vehicle may not complete its intended goal or mission.
The RF device 30 includes an antenna 60, an RF receiver 24 and a controller 26. Although not shown, the RF device 30 may also include a transmitter to communicate with the remote control station 40. The antenna 60 includes a housing 61, a rotatable base 62 carried by the housing, an actuator 64 configured to selectively rotate the base, a pair of spaced apart antenna elements 66 carried by the rotatable base, and a phase sifter 68 coupled to the pair of antenna elements 66 to define an antenna pattern 70 having a pair of opposing nulls 72. The pair of opposing nulls 72 in the antenna pattern 70 may be 180 degrees apart.
The controller 26 is configured to drive the actuator 64 to steer the antenna pattern 70 based upon the RF receiver 24. RF signals received by the RF receiver 24 may be passed on to the controller 26 to determine received signal strength of the RF signals. The controller 26 may then steer the antenna pattern 70 based up the determined received signal strengths. For example, the controller may steer the antenna pattern 70 so that one of the nulls 72 is directed toward an RF interference source 50. This allows the antenna 60 to be resilient in the presence of an RF interference source 50 without changing orientation or a direction of travel of the vehicle 20.
The antenna elements 66 may be loop antennas, horn antennas, patch antennas, helical antennas, monopole antennas or dipole antennas, for example. For discussion purposes, the antenna elements 66 are configured as dipole antenna elements. Spacing between the antenna elements 66 is in a range of 0.1-0.7 wavelength of the operating frequency of the RF device 30. Typically, the wavelength is determined based on a highest operating frequency of the RF device 30.
The RF device 22 is not limited to a particular frequency band. The operating frequency may be within 0.3-3.0 GHz, for example. For discussion purposes, the dipole antenna elements 66 are sized to operate between 1.35-2.4 GHz. In this configuration, the dipole antenna elements 66 are about 5 inches in height with a spacing of about 2.5 inches therebetween. This corresponds to the antenna 60 having a height of about 6 inches and a diameter of about 3.5 inches, with a weight being less than 16 ounces. This allows the antenna 60 to be small, lightweight and low cost.
The antenna 60 operates as a linear array while the dipole antenna elements 66 are combined 180 degrees out of phase from one another. This causes the antenna pattern 70 to be circular-shaped with the pair of opposing nulls 72. In one embodiment, the phase shifter 68 includes at least one discrete component so that the dipole antenna elements 66 are combined 180 degrees out of phase from one another.
In another embodiment, the phase shifter 68 may include a pair of coaxial or stripline type feeds coupled to respective dipole antenna elements 66 in a reverse configuration so that the dipole antenna elements 66 are combined 180 degrees out of phase from one another. For the coaxial feeds, each coaxial cable has a center conductor and an outer conductor. The center and outer conductors of one of the coaxial cables for one of the dipole antenna elements is connected opposite of how the center and outer conductors of the other coaxial cable are connected to the other dipole antenna element.
As will be discussed below, the antenna 60 may also be configured to operate with one dipole antenna element 66 by switching out the other dipole antenna element 66. Operation with a single dipole antenna element 66 generates an omni-directional antenna pattern without any nulls. The omni-directional antenna pattern may be used when the signal strength of received RF signals is above a threshold. This typically indicates that the RF signals received by the RF receiver are not being degraded by an RF interference source 50.
If RF interference signals 52 from an RF interference source 50 are not being detected by the RF device 30, then the antenna pattern 70 may be positioned by the controller 26 so that the pair of nulls 72 is directed away from the operator 44, as shown in
As the antenna pattern 70 is steered by the controller 26, orientation of the frame 22 via the propulsion arrangement 23 may remain the same. This allows the RF interference signals 52 to be mitigated without having to change a flight path of the vehicle 20.
An advantage of the antenna 60 having a pattern 70 with a pair of opposing nulls 72 is that the nulls are aligned over an operating frequency range of the RF device 30, as shown by graph 100 in
Line 102 corresponds to the antenna pattern 70 at 1.35 GHz, line 104 corresponds to the antenna pattern 70 at 1.60 GHz, line 106 corresponds to the antenna pattern 70 at to 1.875 GHz, line 108 corresponds to the antenna pattern 70 at 2.10 GHz, and line 110 corresponds to the antenna pattern 70 at 2.40 GHz.
The respective antenna patterns 70 corresponding to lines 102-110 basically overlap one another. Consequently, the nulls 72 remain consistent or aligned across a wide frequency band. This allows the RF receiver 22 to receive fixed frequency or frequency hopping RF control signals 42 while mitigating interference from an RF interference source 50.
To provide further resiliency in the presence of an RF interference source 50, the RF receiver 24 may be a spread spectrum receiver, for example. In one embodiment, the RF receiver 24 may be a frequency-hopping spread spectrum (FHSS) receiver to receive RF control signals 42 that are spread over a wide range of frequencies using frequency hopping. In another embodiment, the RF receiver 24 may be a direct sequence spread spectrum (DSSS) receiver to receive RF control signals 42 that are spread over a wide range of frequencies using a code. In yet another embodiment, the RF receiver 24 may be an orthogonal frequency-division multiplexing (OFDM) receiver to receive RF control signals 42 that are based on closely spaced narrowband subchannel frequencies instead of a single wideband channel frequency.
For comparison purposes, reference is directed to graph 120 in
Line 122 corresponds to the antenna pattern 80 at 1.35 GHz, line 124 corresponds to the antenna pattern 80 at 1.60 GHz, line 126 corresponds to the antenna pattern 80 at to 1.875 GHz, line 128 corresponds to the antenna pattern 80 at 2.10 GHz, and line 130 corresponds to the antenna pattern 80 at 2.40 GHz.
With the nulls 82 changing at different frequencies, this makes it more difficult to operate with a frequency hopping or spread spectrum receiver. It would be difficult to point a null 82 of the antenna pattern 80 toward an RF interference source 50 at a particular frequency and then try to point the moving null 82 toward the RF interference source 50 at a different frequency.
Referring now to
Operation with a single dipole antenna element 66(1) generates an omni-directional antenna pattern without any nulls. The omni-directional antenna pattern may be used when the strength of received RF signals is above a threshold. In this case, RF switch 63 is switched so that coaxial cable 140 is connected to dipole antenna element 66(1). Consequently, coaxial cable 142 is not connected to dipole antenna element 66(1). RF switch 65 is switched so that coaxial cable 140 is connected with coaxial cable 148, which is connected to the RF receiver 24. Coaxial cable 146 from the phase shifter 68 is not connected to coaxial cable 148.
If the strength of received RF signals falls below a threshold, the controller 26 controls the RF switches 63, 65 so that the RF device 30 operates with both of the dipole antenna elements 66(1), 66(2). An RF interference source 50 may be causing the RF signals to fall below the threshold, for example.
The controller 26 controls RF switch 63 so that coaxial cable 142 is connected to dipole antenna element 66(1) instead of coaxial cable 140. The phase shifter 24 now receives RF signals from dipole antenna element 66(1). The phase shifter 24 also receives RF signals from dipole antenna element 66(2) via coaxial cable 144. The phase shifter 24 may include one or more discrete components, for example. The controller 26 controls RF switch 65 so that coaxial cable 146 is connected with coaxial cable 148, which is still connected to the RF receiver 24.
The controller 26 is connected to the RF receiver 24 to determine strength of the received RF signals. A value of the received signal strength may be determined as a signal-to-noise ratio (SNR) or as a received signal strength indicator (RSSI). Based on the strength of the received RF signals, the RF device 30 will control the RF switches 63, 65 accordingly.
Initial operation of the RF device 30 may be with dipole antenna element 66(1), for example. If the signal strength of the received RF signals drops below an initial threshold, then the controller 26 controls the RF switches 63, 65 so that the RF device 30 is operating with both of the dipole antenna elements 66(1), 66(2).
The controller 26 may then apply a control loop to mechanically sweep the antenna pattern 70 so that one of the nulls 72 maintains being directed towards the RF interference source 50 causing the initial threshold drop. The controller 26 may be a proportional derivative (PD) controller, for example. An output of the PD controller varies in proportion to the error signal as well as with the derivative of the error signal. An advantage of the PD controller is to increase the stability of steering one of the nulls 72 of the antenna pattern 70 toward an RF interference source 50 by improving control since it has the ability to predict future errors.
Another aspect is directed to a method for operating the RF device 30 for a vehicle 20 as described above. The RF device 30 includes an antenna 60 comprising a housing 61, a rotatable base 62 carried by the housing, an actuator 64 to selectively rotate the base, a pair of spaced apart antenna elements 66 carried by the rotatable base, and a phase shifter 68 coupled to the pair of antenna elements to define an antenna pattern 70 having a pair of opposing nulls 72. The method includes operating an RF receiver 24 coupled to the antenna 60, and operating a controller 26 to drive the actuator 64 to steer the antenna pattern 70 based upon RF signals received by the RF receiver 24.
Referring now to
The vehicle 220 includes a frame 222 carrying a propulsion arrangement 223 to provide lift and maneuverability and to orient the frame 222. The frame 222 may also be referred to as a chassis or fuselage. The propulsion arrangement 223 may be based on one or more propeller blades, for example. The vehicle 220 may operate in low-to-medium altitude airspace, such as up to 100 meters, for example.
Control of the vehicle 220 is based on the RF device 230 receiving RF control signals 242 from a remote control station 240 controlled by an operator 244. The RF device 230 needs to have good reception of the RF control signals 242 to ensure control of the vehicle 220. If an RF interference source 250 within the operating environment of the unmanned vehicle 220 is transmitting RF interference signals 252, then these signals may disrupt control of the vehicle 220. If control of the vehicle 220 is disrupted or lost, then the vehicle may not complete its intended goal or mission.
The RF device 230 includes an antenna 260, an RF receiver 224 and a controller 226. Although not shown, the RF device 230 may also include a transmitter to communicate with the remote control station 240. The antenna 260 includes a housing 261, a base 262 carried by the housing, a pair of spaced apart antenna elements 66 carried by the base, and a phase sifter 268 coupled to the pair of antenna elements 266 to define an antenna pattern 270 having a pair of opposing nulls 272. The pair of opposing nulls 272 in the antenna pattern 270 may be 180 degrees apart.
Controller 226 is configured to control the propulsion arrangement 223 to orient the frame 222 to steer the antenna pattern 270 based upon the RF receiver 224. RF signals received by the RF receiver 224 may be provided to the controller 226 to determine received signal strength of the RF signals. The controller 226 may then orient the frame 222 to steer the antenna pattern 270 based up the determined received signal strengths. For example, the controller 226 may orient the frame 222 to steer the antenna pattern 270 so that one of the nulls 272 is directed toward an RF interference source 250. This allows the antenna 260 to be resilient in the presence of an RF interference source 250 by changing orientation or a direction of travel of the vehicle 220.
The antenna elements 266 may be loop antennas, horn antennas, patch antennas, helical antennas, monopole antennas or dipole antennas, for example. For discussion purposes, the antenna elements 266 are configured as dipole antenna elements. Spacing between the antenna elements 266 is in a range of 0.1-0.7 wavelength of the operating frequency of the RF device 230. Typically, the wavelength is determined based on a highest operating frequency of the RF device 230.
The RF device 222 is not limited to a particular frequency band. The operating frequency may be within 0.3-3.0 GHz, for example. For discussion purposes, the dipole antenna elements 266 are sized to operate between 1.35-2.4 GHz. In this configuration, the dipole antenna elements 266 are about 5 inches in height with a spacing of about 2.5 inches therebetween. This corresponds to the antenna 260 having a height of about 6 inches and a diameter of about 3.5 inches, with a weight being less than 16 ounces. This allows the antenna 260 to be small, lightweight and low cost.
The antenna 260 operates as a linear array while the dipole antenna elements 266 are combined 180 degrees out of phase from one another. This causes the antenna pattern 270 to be circular-shaped with the pair of opposing nulls 272. In one embodiment, the phase shifter 268 includes at least one discrete component so that the dipole antenna elements 266 are combined 180 degrees out of phase from one another.
In another embodiment, the phase shifter 268 may include a pair of coaxial or stripline type feeds coupled to respective dipole antenna elements 266 in a reverse configuration so that the dipole antenna elements 266 are combined 180 degrees out of phase from one another. For the coaxial feeds, each coaxial cable has a center conductor and an outer conductor. The center and outer conductors of one of the coaxial cables for one of the dipole antenna elements is connected opposite of how the center and outer conductors of the other coaxial cable are connected to the other dipole antenna element.
As will be discussed below, the antenna 260 may also be configured to operate with one dipole antenna element 266 by switching out the other dipole antenna element 266. Operation with a single dipole antenna element 266 generates an omni-directional antenna pattern without any nulls. The omni-directional antenna pattern may be used when the signal strength of received RF signals is above a threshold. This typically indicates that the RF signals received by the RF receiver are not being degraded by an RF interference source 250.
If RF interference signals 252 from an RF interference source 250 are not being detected by the RF device 230, then the antenna pattern 270 may be positioned by orienting the frame 222 so that the pair of nulls 272 is directed away from the operator 244, as shown in
Referring now to
Operation with a single dipole antenna element 266(1) generates an omni-directional antenna pattern without any nulls. The omni-directional antenna pattern may be used when the strength of received RF signals is above a threshold. In this case, RF switch 263 is switched so that coaxial cable 340 is connected to dipole antenna element 266(1). Consequently, coaxial cable 342 is not connected to dipole antenna element 266(1). RF switch 265 is switched so that coaxial cable 240 is connected with coaxial cable 248, which is connected to the RF receiver 224. Coaxial cable 346 from the phase shifter 268 is not connected to coaxial cable 348.
If the strength of received RF signals falls below a threshold, the controller 226 controls the RF switches 263, 265 so that the RF device 230 operates with both of the dipole antenna elements 266(1), 266(2). An RF interference source 250 may be causing the RF signals to fall below the threshold, for example.
The controller 226 controls RF switch 263 so that coaxial cable 342 is connected to dipole antenna element 266(1) instead of coaxial cable 340. The phase shifter 224 now receives RF signals from dipole antenna element 266(1). The phase shifter 224 also receives RF signals from dipole antenna element 266(2) via coaxial cable 344. The phase shifter 224 may include one or more discrete components, for example. The controller 226 controls RF switch 265 so that coaxial cable 346 is connected with coaxial cable 348, which is still connected to the RF receiver 224.
The controller 226 is connected to the RF receiver 224 to determine strength of the received RF signals. A value of the received signal strength may be determined as a signal-to-noise ratio (SNR) or as a received signal strength indicator (RSSI). Based on the strength of the received RF signals, the RF device 230 will control the RF switches 263, 265 accordingly.
Initial operation of the RF device 230 may be with dipole antenna element 266(1), for example. If the signal strength of the received RF signals drops below an initial threshold, then the controller 226 controls the RF switches 263, 265 so that the RF device 230 is operating with both of the dipole antenna elements 266(1), 266(2).
The controller 226 may then apply a control loop to orient the frame 222 to steer the antenna pattern 270 so that one of the nulls 272 maintains being directed towards the RF interference source 250 causing the initial threshold drop. The controller 226 may be a proportional derivative (PD) controller, for example. An output of the PD controller varies in proportion to the error signal as well as with the derivative of the error signal. An advantage of the PD controller is to increase the stability of orienting the frame 222 to steer one of the nulls 272 of the antenna pattern 270 toward an RF interference source 250 by improving control since it has the ability to predict future errors.
Another aspect is directed to a method for operating a vehicle 220 with a radio frequency (RF) device 230 as described above. The RF device 230 includes an antenna 260 comprising a housing 261, a base 262 carried by the housing, a pair of spaced apart dipole antenna elements 266 extending upwardly from the base, and a phase sifter 268 coupled to the pair of antenna elements 266 to define an antenna pattern 270 having a pair of opposing nulls 272. The method includes operating an RF receiver 224 coupled to the antenna 261, and operating a controller 226 to control the propulsion arrangement 223 to orient the frame 222 to steer the antenna pattern 270 based upon the RF receiver 224.
Many modifications and other embodiments will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the foregoing is not to be limited to the example embodiments, and that modifications and other embodiments are intended to be included within the scope of the appended claims.
