Patent Publication Number: US-9837706-B2

Title: Directing electromagnetic waves in vehicle communications

Description:
TECHNICAL FIELD 
     The present disclosure relates to vehicle-to-vehicle communications. 
     BACKGROUND 
     Many vehicles are equipped with systems purposed for communication with other vehicles or objects in the vicinity. These systems may communicate information related to vehicle speed, direction, or other important parameters. Omnidirectional antennas may allow indeterminate communication with all other vehicles and objects in the vicinity. Communication with other vehicles or objects may become unavailable when too many vehicles attempt communication in the vicinity. 
     SUMMARY 
     A vehicle may include a conductive housing surrounding an antenna and defining an aperture having a size at least equal to a wavelength of signals radiated by the antenna. A controller may be configured to orient the housing to point the aperture in a direction opposite the forward vehicle, and after relaying the signal, orient the housing in a direction toward the forward vehicle. The controller may operate in response to receiving a cooperative control signal from a platooned forward vehicle. 
     The controller may be further configured to adjust an elevation angle of the aperture, with respect to the antenna, based on an upcoming gantry having a toll collection system. The controller may be further configured to adjust a size of the aperture to decrease attenuation of electromagnetic radiation transmitted from the antenna to outside the housing. The aperture may be an iris diaphragm. The antenna may transmit a signal having a frequency between 5.850 and 5.925 GHz. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram depicting an example of a vehicle having an apparatus purposed to direct electromagnetic waves; 
         FIG. 2  is a section view of a housing fitted to hold an antenna assembly; 
         FIG. 3  is an isometric view of a mount for the housing; 
         FIG. 4  is an isometric view of a housing defining a rectangular aperture; 
         FIG. 5  is an isometric view of a housing defining a circular aperture; 
         FIGS. 6A and 6B  are schematic diagrams of platoons of vehicles utilizing an apparatus purposed to direct electromagnetic waves; and 
         FIG. 7  is a schematic diagram of a traffic signal fitted with an apparatus purposed to direct electromagnetic waves. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Many vehicles today employ vehicle-to-vehicle (“V2V”) communications to improve cooperation among vehicles and improve customer satisfaction. V2V communications may relay data related to location, velocity, acceleration, traffic conditions, status of traffic signals, and other information as required. V2V communications may use dedicated short-range communication (“DSRC”) and 802.11p protocols to communicate. Many protocols may facilitate V2V communications. These protocols may be based on an ad-hoc or decentralized network design, or a separate protocol requiring a structured network design may be used. 
     A DSRC system may be connected to an antenna assembly to propagate electromagnetic waves. An antenna assembly may include an antenna having a monopole, dipole, or other wave propagation configuration. The antenna assembly may also include a transceiver connected to the antenna. The transceiver may use any frequency on the electromagnetic spectrum to communicate information. For example, the system may use electromagnetic radiation within the radio frequency band. An antenna assembly may also include a processor or array of processors used to create or prepare data for transmission. A frequency band near 5.9 GHz may be used to facilitate V2V communications. These bands may be separated into channels to minimize cross-talk between designated communication paths. 
     The antenna may be omnidirectional. The antenna may be configured to transmit and receive electromagnetic waves from any direction or a plurality of directions. Use of omnidirectional antennas may cause congested communication paths among vehicles and objects, which may result in a poor reception of information. DSRC attempts to address this issue by using the wireless access in vehicular environments (“WAVE”) protocol&#39;s media access control, WAVE simple message protocol, and channel selection. Although these methods may alleviate certain levels of congestion and interference, the methods may provide little benefit in areas with high vehicular traffic. The transmit power and receive sensitivity of omnidirectional antennas may be limited to further prevent congestion. 
     A directional antenna may be adapted to direct waves in a particular direction. For example, the antenna may direct waves using a physical aperture, synthetic aperture, parabolic reflector, fractal structure, horn structure, etc. The antenna may be configured to transmit and receive signals from vehicles or objects within a front and rear acceptance angle. The antenna may be configured to transmit and receive signals in a vertical direction. A directional antenna, as specified above, may have increased transmit power and reception sensitivity with reduced congestion and interference. 
     A housing may surround all or part of the antenna to deflect, impede, attenuate, redirect, stop, or abate signals transmitted or received from the antenna. The housing may surround the other electronic devices associated with the antenna or controllers for the housing. The housing may be made of a conductive material to shield the antenna from electromagnetic radiation. The conductive material may be of any type (e.g., copper, aluminum, graphene, gold, silver, calcium). The conductive material may be grounded to the vehicle. The housing may also be made of a material designed to attenuate magnetic signals. The material designed to attenuate may magnetically attenuate the signal (i.e., materials with high magnetic permeability causes eddy currents to oppose the magnetic field), or the material may impede the signal through structure. The housing may be made of a combination of these materials to provide improved electromagnetic shielding. The housing may attenuate signals from all directions or may allow signals from designated directions (e.g., vertical). 
     The housing may define an aperture. The aperture may be configured to allow signals to be transmitted and received from the antenna in a desired direction or shape. The aperture may have a circular, rectangular, or other geometric shape. The circular aperture may be formed of a diaphragm comprised of blades mounted on the housing. The size of the aperture may be adjusted by the blades to allow variable amounts of electromagnetic radiation or different shapes of electromagnetic radiation. The size may be manually adjustable by a user or automatically adjusted by a controller as is known in the art. The entrance to the housing created by the aperture may be protected from the elements by a piece of glass, screen, or opaque element. 
     A rectangular aperture may be formed using a cutout or adjustable perpendicular plates. The perpendicular plates may be adjusted using a screw drive along with a rack or gear for each of the two directions of movement. The perpendicular plates may be made of materials similar to the housing material. The perpendicular plates may be made of different materials to provide different waveguide characteristics. The rectangular aperture may be formed using two pairs of opposed plates to maintain the center of the aperture in line with the antenna, instead of offset. 
     The housing may be adjusted to change the direction of the aperture. There are numerous ways to adjust the orientation of the housing known to those having skill in the art. For example, a screw drive may cooperate with a rack to rotate the housing about a substantially horizontal plane. This may adjust the direction of the signal about an azimuth angle. The rack may be mounted on bearings to reduce friction between the rack and a chassis mounted to the vehicle. A DC motor connected to a controller may actuate the screw drive. Induction or permanent magnet motors may also be used. The DC motor may be coupled with an encoder or other locating device to provide location feedback to the controller. The controller may be configured with maximum encoder positions to prevent twisting of cabling connecting the antenna to other electronics. 
     The housing may be adjusted about a horizon or elevation angle. For example, a sector gear may provide a range of motion of greater than 90° to adjust the elevation angle of the housing. The sector gear may be mounted to cooperate with a second drive screw mounted to an internal chassis containing the housing. The sector gear may be mounted on a bearing to reduce friction. The screw drive may be actuated by a DC motor. The DC motor may be connected to a controller. The DC motor may also have an encoder to provide feedback to the controller. 
     The aperture may be configured to direct electromagnetic waves, signals, or radiation by being sized at least one wavelength in width or diameter. The aperture may be sized manually or automatically to properly direct the electromagnetic waves of a given wavelength. Waves experience diffraction when confronted with an aperture. An aperture sized too small for the waves will not direct the waves in a desirable direction, if at all. A DSRC signal having a frequency of roughly 5.9 GHz may have a wavelength of about 2.0 inches. The aperture should be sized at least two inches, preferably greater than two, to provide adequate directional control over the signal. 
     The directional antenna as described above may be used in addition to an omnidirectional antenna because V2V standards require at least one omnidirectional antenna. This configuration would allow extended range from the directional antenna through increased transmission or reception strength, yet meet the standard requiring omnidirectional support. 
     The directional antenna may be used in combination with map and location data to communicate with known or expected devices. For instance, the directional antenna may be directed toward an upcoming traffic light, oncoming traffic at an intersection, or directed toward emergency assistance. A disabled vehicle on the side of a road may use the directional antenna to signal only oncoming traffic for assistance because passed vehicles are unlikely to turn around. The directional antenna may also notify oncoming emergency vehicles of the location of the vehicle at an increased range from the omnidirectional DSRC antenna because the directional antenna may have an increased transmission or reception power. The directional antenna may be used by emergency vehicles to notify vehicles in the travel path to move out of the way. For instance, the directional antenna may be used to notify vehicles in the same direction of travel or on a desired travel path. 
     The directional antenna may be oriented vertically to communicate with overhead gantries. For instance, a toll collection system may be mounted to a gantry to collect toll information from vehicles. Vertical orientation of the directional antenna in light of an upcoming gantry may eliminate interference from other vehicles and result in improved communication with the toll collector. 
     The directional antenna may be used to improve congestion and interference in busy intersections by directing DSRC signals from the traffic signal or traffic system to specific traffic lanes or directions. Oncoming traffic may be notified of the approaching signal, while vehicles already through the traffic signal may have reduced congestion and interference. The controller of the housing may orient the housing such that the aperture points to a direction of oncoming traffic and avoids outgoing traffic. 
     The directional antenna may be used to improve cooperative adaptive cruise control. Cooperative adaptive cruise control (“CACC”) provides collaboration among vehicles in a platoon to communicate and match speeds. CACC can reduce oscillations in vehicle speed by removing latency from the system. CACC may be improved using the directional antenna as described above by isolating communications within the platoon. Omnidirectional antennas create substantial interference and handshaking between oncoming platoons and platoons in other lanes. This unfavorable consequence of omnidirectional antennas may be reduced using a directional antenna. 
     CACC may utilize a directional antenna in a platoon of five cars where the first vehicle of the platoon sends a signal in a rearward direction. The second vehicle may then receive the signal and send an acknowledgment to the first vehicle. The first vehicle may then continue to listen for a forward vehicle, by intermittently rotating the aperture of the direction antenna forward, and rotate backward to communicate with the second vehicle. The CACC system may be configured with time-domain multiplexing, which synchronizes the DSRC signal&#39;s transmit and receive sequences. Information communicated throughout the platoon may include speed, direction, intended destination, and other information necessary to facilitate CACC. 
     A vehicle event may necessitate CACC communications among the vehicle platoon. For example, a forward vehicle may receive a flat tire indication from its vehicle control system. The forward or leading vehicle may need to indicate this information to other vehicles in the platoon to notify other vehicles of debris or an impending deceleration. The forward vehicle may orient a housing into a direction opposite of travel, e.g., behind, to notify follower vehicles that there is an emergent situation. 
     Referring now to  FIG. 1 , A vehicle  100  includes a directional antenna  102 . The directional antenna may be mounted to the roof, interior, undercarriage, or other location of the vehicle. The vehicle may have a powertrain control module  104 -A, a body control module  104 -B, a radio transceiver module  104 -C, a communications and entertainment unit  104 -D, a climate control management module  104 -E, a GPS module  104 -F, and a user interface module  104 -G. The modules may be configured to communicate via a communications network  106  (e.g., CAN). A DSRC  108  control unit may be configured to communicate on the communications network  106  or part of the other modules specified above. The DSRC  108  may include a processor  110  and memory to process and send data on the network  106  and prepare data for transmission via the transceiver  112 . 
     Referring now to  FIG. 2 , a cross-section of the directional antenna  102  is shown. The antenna  102  may have a conductive housing  114 . The conductive housing may include separate layers to provide radio wave shielding. The conductive housing  114  may surround at least a portion of the antenna  116 . The antenna  116  may be positioned in the center of the housing  114 . The antenna may be electrically connected to a transceiver  112 . The transceiver  112  may propagate signals to the antenna for transmission or receive signals from the antenna to decipher the contents. The DSRC  108  may communicate with a controller  118  to determine the proper direction of the directional antenna  102 . The DSRC  108  and the controller  118  may be part of the same integrated circuit. The controller  118  may determine the proper direction of the directional antenna  102  by received information from other vehicles or objects. The controller  118  may determine proper direction based on GPS location information or previously receiving data. The controller  118  may be configured to control actuators or motors configured to adjust the relative location of the housing  114 . The controller may be configured to receive indication of relative motion from sensors or encoders on the motors. 
       FIG. 3  depicts an embodiment of the housing movement system. A ring gear  120  has an attached drive screw  122  to rotate the housing about an axis. The ring gear may be mounted to a set of bearings  124 , which allow movement between the directional antenna  102  and the vehicle (not shown). Struts  121  extend radially from the ring gear  120 . Mounted in the center of the struts is a sector gear  126  along with the directional antenna  102 . The directional antenna  102  is moved about the vertical axis or elevation angle via the sector gear  126 . The sector gear  126  may be mounted in a sector gear housing to restrict translational movement. The sector gear  126  may be actuated using a sector gear drive screw  128 . Both of the drive screws  122 ,  128  may be mechanically connected to an electromagnetic drive controlled by a controller (not shown). Each of the drive screws  122 ,  128  may be fitted with encoders to indicate position to the controller. 
       FIG. 4  depicts at least one embodiment of the directional antenna  102 . The directional antenna  102  has a housing  114  capable of attenuating electromagnetic signals and a rectangular aperture  200 . The rectangular aperture  200  is sized to properly direct incoming or outgoing signals from the antenna (not shown). The housing  114  may include two pairs of perpendicular plates  202 ,  208  and  204 ,  206  configured to alter the size of the aperture  200 . The plates  202 ,  208  and plates  204 ,  206  may be actuated by a pair of screw drives (not shown) connected to electric motors and a controller. The size of the aperture  200  may be adapted to have a width and height at least one wavelength of the incoming or outgoing signals to limit diffraction. 
       FIG. 5  depicts at least one embodiment of the directional antenna  102 . The housing  114  may define an aperture  300  having a circular shape. The aperture  300  may be an iris diaphragm type. The aperture may be defined by rotating blades  302  capable of reciprocally changing the size of the aperture. The aperture  300  may be automatically sized to match a specified signal frequency or wavelength. For instance, a 5.9 GHz signal may have a wavelength of about two inches. The aperture may be sized with an internal diameter of at least two inches to provide adequate steering of the signal. 
     Now referring to  FIG. 6A  at least one embodiment of a directional antenna is depicted. The directional antenna may be mounted to the roof of a vehicle  600 A. Vehicle  600 A may include a DSRC transceiver capable of V2V communications. Vehicle  600 A may send a signal  602 A rearward to the platoon of vehicles t 600 B,  600 C,  600 D,  600 E of one lane. The next vehicle in the platoon  600 B receives a signal from vehicle  600 A via a directional antenna facing in the forward direction. The directional antenna of vehicle  600 B may then rotate rearward to direct communications to the rest of the platoon (e.g.,  600 C,  600 D,  600 E, etc.). The directional nature of antenna allows for increased receive sensitivity and transmit strength. As shown in  FIG. 6B  the signals and reception areas  602 A  602 B,  602 C,  602 D,  602 E may be limited to the lane of the platoon  600 A,  600 B,  600 C,  600 D,  600 E. 
     Now referring to  FIG. 7 , in at least another embodiment a directional antenna  702  may be placed on a traffic signal or indicator  700  to notify particular drivers of signal status. Any value a traffic signal  700  can provide a vehicle  704  may be diminished after the vehicle has passed through the intersection. The directional antenna  702  may provide DSRC communication to oncoming vehicles  704  or vehicles that would receive value from the indication. In addition, a vehicle  704  configured with a directional antenna  702  may recognize an upcoming traffic signal through GPS or other V2V communications. The vehicle  704  may then orient the directional antenna  702  to the expected location based on current position and the position of the traffic signal. This could provide early indication of signal status to the vehicle  704  and reduce interference from other signals. 
     The processes, methods, or algorithms disclosed herein may be deliverable to or implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms may be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components. 
     The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.