Abstract:
An automotive spoiler-type device to house a suite of sensors is described. Such sensors can include, for example, transmit antennas, receive antennas, video cameras, Infrared (IR) sensors, Electro-Optic (EO) sensors, air sensors, etc. Examples of the information transmitted and received include voice, data, navigation, and other communications functions, including, but not limited to, two-way radios, GPS, wireless Internet applications, etc. In one embodiment, the spoiler antenna installations are lower in profile and more compact than conventional vehicle antennas. In one embodiment, a top-load portion of a monopole antenna is used as a ground plane for a patch-type or cavity type antenna.

Description:
REFERENCE TO RELATED APPLICATION 
     The present application claims priority benefit of U.S. Provisional Application No. 60/381,740, filed May 17, 2002, titled SYSTEM AND METHOD FOR INTEGRATING ANTENNAS INTO A VEHICLE REAR-DECK SPOILER, the entire contents of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to antennas installed on an automobile or other vehicle. 
     2. Description of the Related Art 
     For many years the only antenna found on an automobile or other vehicle was likely to be a monopole whip antenna for an AM/FM radio. Today, a vehicle such an automobile, boat, an the like, is likely to have several antennas for various devices, such as, for example, an AM/FM radio, a cellular telephone, a satellite radio, a GPS receiver, etc. Police, emergency vehicles, and aircraft, have even more antennas for various radio communication and/or data systems. In addition to antennas, other sensors such as electro-optic sensors, cameras, etc. are also becoming more common on vehicles. These antennas and other sensors are often considered to be unsightly. Moreover, sensors that are not integrated into the vehicle are more likely to be damaged by accidents or vandalism, and can reduce gas mileage by creating aerodynamic drag. 
     SUMMARY OF THE INVENTION 
     The present invention solves these and other problems by providing sensors that are integrated into structures typically found on a vehicle such as an automobile, boat, airplane, etc. In one embodiment, sensors such as antennas are integrated into an automotive spoiler-type device to support the transmission and reception of information. Such sensors can include, for example, transmit antennas, receive antennas, video cameras, Infrared (IR) sensors, Electro-Optic (EO) sensors, air sensors, etc. Examples of the information transmitted and received include voice, data, navigation, and other communications functions, including, but not limited to, two-way radios, GPS, wireless Internet applications, etc. In one embodiment, the spoiler antenna installations are lower in profile and more compact than conventional vehicle antennas. 
     The inclusion of sensors in a spoiler, which is installed as a unit, has the additional benefits of concealment (the presence of equipment in the vehicle is not revealed by visible sensors and/or antennas), protection of the sensors from damage, (e.g., car wash damage, vandalism, etc.) robustness, and reduced life-cycle costs. 
     In one embodiment, four antennas and a brake light (the so-called third brake light) are provided in a spoiler. In one embodiment, three antennas cover three transmit/receive frequency bands, namely 150–160 MHz, 423–469 MHz, and 806–869 MHz. The fourth antenna covers the GPS receive bands. These frequency bands represent so-called instantaneous bandwidths of the antennas (where tuning is not needed to achieve a desired transmit/receive performance over the stated bands). These particular transmit/receive frequency bands are currently being used by police, fire and various business radio services. In particular, the 150–160 MHz band demonstrates a relatively long-wavelength case (˜&gt;6 feet). In one embodiment, one or more of the spoiler antennas handle Continuous Wave (CW) transmit power levels of up to approximately 100 Watts. 
     In one embodiment, the spoiler antennas are configured as monopole and top-loaded monopole antennas. In one embodiment, other antennas, such as, for example, GPS antennas, satellite radio antennas, etc. are integrated into the spoiler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and features of the disclosed invention will readily be appreciated by persons skilled in the art from the following detailed description when read in conjunction with the drawings listed below. 
         FIG. 1  shows a suite of antennas integrated into an automobile spoiler-type structure to provide relatively moderate bandwidth coverage. 
         FIG. 2  shows a suite of antennas integrated into an automobile spoiler-type structure to provide relatively wide bandwidth coverage. 
         FIG. 3  shows power reception as a function of aspect angle at 155 MHz for a spoiler-mounted antenna and for a standard monopole whip antenna. 
         FIG. 4  shows power reception as a function of aspect angle at 446 MHz for a spoiler-mounted antenna and for a standard monopole whip antenna. 
         FIG. 5  shows power reception as a function of aspect angle at 837 MHz for a spoiler-mounted antenna and for a standard monopole whip antenna. 
         FIG. 6  shows power reception as a function of aspect angle at 155 MHz for a spoiler-mounted antenna with and without a third brake light in the spoiler. 
         FIG. 7  shows a coax connection for the integrated antenna. 
         FIG. 8  shows one embodiment of a top-loaded antenna for integration in a spoiler. 
         FIG. 9  shows integration of monopoles and top-loaded monopoles into an automobile spoiler. 
         FIG. 10  shows construction of a monopole antenna for integration into an automobile spoiler. 
         FIG. 11  shows integration of a patch-type antenna, including a coaxial signal path, into an automobile spoiler. 
         FIG. 12  shows integration of a cavity-type antenna, including a coaxial signal path, into an automobile spoiler. 
         FIG. 13  shows integration of a coaxial signal path for the antennas of  FIG. 11  or  12  into a monopole antenna. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows one embodiment of a system  100  having an antenna suite integrated into a spoiler-type structure on an automobile or other vehicle. The system  100  includes a spoiler  101 , a low-band antenna  102 , a medium-band antenna  104 , and a high-band antenna  102 . In one embodiment, the antennas  102 – 104  are monopole-type antennas. In one embodiment, the low-band antenna  102  and the medium-band antenna  104  are top-loaded monopoles. In one embodiment, the low-band antenna  103  operates in a band from 150–160 MHz. In one embodiment, the medium-band antenna  104  operates in a band from 423–469 MHz. In one embodiment, the high-band antenna  103  operates in a band from 806–869 MHz. In one embodiment, the low-band antenna  103  is located between the medium-band antenna  104  and the high-band antenna  102 . In  FIG. 1 , the spoiler  101  includes three risers (left, center, and right) that connect the spoiler  101  to the vehicle. The vertical portion of the monopole-type antennas used for the antennas  102 – 104  are located in the three risers. 
     A horizontal-type antenna  105  is also integrated into the spoiler  101 . The horizontal-type antenna  105  can be an annular ring antenna, patch antenna, microstrip antenna, stripline antenna etc. In one embodiment, the horizontal-type antenna  105  is used for receiving satellite signals for systems such as, for example, XM radio, Global Positioning System (GPS) navigation, etc. 
     Spoiler-type structures such as the structure  101  are commonly used on automobiles to improve aesthetics and/or aerodynamic performance of the vehicle. Such spoiler-type structures are also found on boats, aircraft, etc. In one embodiment, the spoiler  101  also incorporates a brake light  110 . The brake light  110  is usually a “third brake light” that is provided in addition to the typical left and right brake lights found on vehicles. In one embodiment, the type of light used for the brake light  110 , and the power connections to the third brake light  110  (e.g., connections to 12 volt power lines) are configured to reduce effects that the power lines might otherwise have on antenna performance (e.g., antenna pattern or impedance). 
     In one example automotive system, the brake light  110  uses a plurality (e.g. sixty) of high-intensity light emitting diodes (LEDs) powered by twelve volts of direct current. The direct current voltage is applied to the LED array through two parallel #18 AWG wires. These wires are molded into a common insulation package that electrically insulates them from one another and their surroundings. The brake light power leads are routed through the spoiler along a tapered path nearly parallel to the vertical portion of the low-band antenna  103 . The average spacing along this taper is approximately 0.75″. In this case, the power lead contributes to the ease of impedance matching with minimal effects upon the monopole radiation pattern by acting as parasitic elements. 
     Greater bandwidths than those listed above can be achieved by various techniques. One technique is to integrate antennas that employ low-profile antenna concepts such as those used in aircraft blade antennas. Additionally, external broadband tuning modules can be used. Broadband antennas can be used to reduce or eliminate the need for fine-tuning of an antenna.  FIG. 2  shows a system  200  that is similar to the system  100  and includes the spoiler  101 , the horizontal-type antenna  105  and, optionally, the brake light  110 . In the system  200 , a low-band antenna  203  operates in a frequency band of 150–250 MHz, a medium-band antenna operates in a frequency band of 250–500 MHz and a high-band antenna operates in a frequency band of 500–2500 MHz. Thus, the system  200  provides bandwidth coverage from 150 MHz to 2.5 GHz. In one embodiment, Radio Frequency (RF) chokes are used to reduce interactions between the antennas  202 – 203 . The upper frequency shown in  FIG. 2  (2500 MHz) is not a limitation and higher frequencies can be accommodated by using additional horizontal-type antennas similar to the horizontal-type antenna  105 . In one embodiment, a top portion of the low-band antenna  203  acts as a ground plane for the horizontal-type antennas such as the horizontal-type antenna  105 . In one embodiment, signal lines (e.g., coaxial cables) for the horizontal-type antennas such as the horizontal-type antenna  105  are routed through the vertical portion of the low-band antenna  203 . 
       FIGS. 3–5  show pattern measurements on embodiments of the spoiler mounted antennas shown in  FIGS. 1 and 2 . Pattern measurements were performed for a spoiler (with integrated antennas) mounted on the vehicle. The spoiler antenna patterns were compared to conventional whip antenna patterns. In one embodiment, the conventional whip antennas used for comparison were mounted near the center of the trunk lid.  FIG. 3  shows 155 MHz data.  FIG. 4  shows 446 MHz data.  FIG. 5  shows 837 MHz data. In  FIGS. 3–5 , the amplitude scale is relative dB, not dBi gain. In general, the spoiler antennas have better pattern coverage than the corresponding whip antenna, especially for aspects where the whip patterns are marginal. 
     Qualitative test results were obtained by mounting the spoiler, with antennas, on a vehicle and using at least one of the antennas to transmit and receive voice data as the vehicle was driven. The quality of the transmission and reception compared favorably to that obtained with a conventional surface mounted whip antenna. 
     The data in  FIG. 6  shows the measured effect of the third brake light power leads on the pattern of the low-band antenna  103  with and without power leads. The power leads has relatively little effect on the antenna pattern. 
       FIG. 7  shows one embodiment of an antenna connection to a coaxial cable. The coaxial cable, located inside the trunk, has a center conductor  701  and a shield  702 . In one embodiment, a metal tab  703  is provided to the shield and a metal tab  704  is provided to the center conductor. The metal tab  703  provided to the shield can be attached to a suitable ground plane, such as, for example, a trunk lid. The metal tab  704  provided to the center conductor can be attached to a monopole-type antenna, such as, for example the antennas  102 – 104  or  202 – 204 . An alternate technique, usually desirable for higher frequencies, is to connect the antenna lead and ground to a conventional bulkhead connector. The configuration shown in  FIG. 7  has the advantage of being relatively low-cost and relatively low-profile. 
       FIG. 8  shows one embodiment of a top load  801  for a monopole such as the low-band antennas  103  and  203 . Top loading increases the effective length of the monopole and therefore allows the monopole to operate a lower frequency with a relatively smaller vertical height than an unloaded monopole. In  FIG. 8 , the top load is constructed from a relatively thin sheet of conducting material and is suitable for use as a ground plane for other antennas. The top load  801  is attached at or near the top of a monopole antenna, as shown, for example, in  FIGS. 1 and 2 . 
       FIG. 9  shows three antenna locations for monopole-type antennas in the spoiler  101 . A first monopole  911  is placed inside a left-hand riser  901  of the spoiler  101 . A base of the first monopole  911  antenna is provided at or electrically near the rear deck surface to which the spoiler is attached (e.g., to the trunk of the vehicle). The monopole  911  is provided to the center conductor of the coaxial cable according to the configuration shown in  FIG. 7 . The monopole  911  extends at least partially up into the left-hand riser  901 . In one embodiment, the monopole  911  is straddled by one or more parasitic rods, each 3.6″ long in order to increase bandwidth. 
     A second monopole  912  is placed inside a center riser  902 . A base of the second monopole  912  is provided at or electrically near the rear deck surface to which the spoiler is attached. The second monopole  912  extends up into the center riser of the spoiler and attaches to a top load as shown in  FIG. 8 . The top load  801  is provided in the horizontal portion of the spoiler  101 . The monopole  912  is provided to the center conductor of a the coaxial cable according to the configuration shown in  FIG. 7 . 
     In one embodiment, the length of the top load  801  is selected to provide desired operation in a band having a center frequency of approximately 155 MHz. In one embodiment, the length of the vertical portion of the second monopole  912  is 6 inches. In one embodiment, the length of the top load  801  is 18½ inches and its width is 4 inches. 
     A third monopole  913  is placed inside a right-hand riser  903  of the spoiler  101 . A base of the third monopole  913  antenna is provided at or electrically near the rear deck surface to which the spoiler  101  is attached (e.g., to the trunk of the vehicle). The third monopole  913  is provided to the center conductor of a the coaxial cable according to the configuration shown in  FIG. 7 . The third monopole  913  extends at into the right-hand riser  903 . A portion of the third monopole  913  extends up into a horizontal portion of the spoiler  101  and continues along inside the horizontal portion for a desired distance to top-load the third monopole  913 . The monopole  913  is provided to the center conductor of a the coaxial cable according to the configuration shown in  FIG. 7 . 
     In one embodiment, the total length (vertical plus horizontal sections) of the third monopole  913  is adjusted to provide desired operation in a band having a center frequency. In one embodiment, the desired center frequency of the third monopole  913  is approximately 446 MHz. In one embodiment, the total length of the third monopole  913  is 7 inches. In another embodiment, the third monopole  913  is straddled by one or more parasitic rods to increase bandwidth. In one embodiment, two parasitic rods each 3.6″ long are used. 
       FIG. 10  shows one embodiment of a top-loaded monopole having a threaded 5/16″ antenna rod. The top load is attached to one end of the antenna rod. A molded dielectric insulator (e.g., nylon) is provided to the feed end of the monopole. 
     In one embodiment, the top load portion of the second monopole  912  (and/or the top load of the third monopole  913 ) is used as a ground plane supporting a horizontal-type antenna such as a patch-type, cavity-type, or slot-type antenna (e.g., a GPS antenna, an XM radio antenna, a wireless Internet antenna, a bluetooth antenna, etc.) The top load  801  serves as the ground plane for a common horizontal-type antenna, such as, for example, a patch-type antenna, a slot-type antenna, a cavity-backed antenna, a cavity-type antenna, a rectangular patch antenna, an elliptical patch antenna, a stacked patch antenna, a spiral antenna, helix antenna, an inverted “F” antenna, a microstrip patch antenna, a stripline antenna, a slot antenna, an annular slot antenna, etc.) 
     As shown in  FIG. 11  a coaxial cable for a patch-type antenna  1101  can be provided from the trunk interior to the antenna  1101  by passing through the monopole  912  (a cross-section “A” of the monopole portion  912  is shown in more detail in  FIG. 13 ). 
     As shown in  FIG. 12  a coaxial cable for a slot-type or cavity-type antenna  1109  can similarly be provided from the trunk interior to the antenna  1101  by passing through the monopole  912  (a cross section “A” of the monopole portion  912  is shown in more detail in  FIG. 13 ). 
     The technique shown in  FIGS. 11 and 12  (using the top loading plate as a ground plane, and the vertical portion as a “conduit for the RF signal) is readily applied to other small antennas to extend frequency coverage to and beyond X-Band. 
       FIG. 13  shows a cross section of the monopole portion of the monopole  912  shown in  FIGS. 11 and 12 . In  FIG. 13 , the monopole  912  is shown as an outer conductor. Concentric layers inward from the monopole  912  include, an insulating ring  1110 , an outer coaxial conductor  1104 , a coaxial dielectric core  1105 , and a coaxial inner conductor  1106 . The coaxial conductor  1104 , the coaxial dielectric core  1105 , and the coaxial inner conductor  1106  form a coaxial feed for the antenna  1101  or  1109 . 
     The horizontal-type antenna (e.g. the antenna  1101  and/or the antenna  1109 ) is shown provided in connection with the monopole antenna  912 . One of ordinary skill in the art will recognize that a horizontal-type antenna (e.g. the antenna  1101  and/or the antenna  1109 ) can also be provided in connection with the top-loaded monopole antenna  913  in similar fashion. Thus, one, two, or more horizontal-type antennas can be provided in the spoiler  101 . Moreover, several coaxial feeds can be provided in parallel in the monopole antenna  912  or  913  to feed several horizontal-type antennas disposed at various locations on the top-load  801 . The outer conductor of the coaxial feed for the horizontal-type antennas can be disposed along the top-load  801  and, optionally, electrically connected to the top-load  801 . 
     Although the foregoing has been a description and illustration of specific embodiments, various modifications and changes can be made thereto by persons skilled in the art. For example, one of ordinary skill will recognize that the spoiler antennas are not limited to the above frequency bands, and that antennas covering other frequency bands, broader bands, or combinations of bands can be provided as well. For convenience, the above disclosure describes embodiments in connection with an automobile spoiler-type structure  101 . One of ordinary skill in the art will recognize that boats, aircraft, and other vehicles have similar spoiler-type structures, and such structures can be used as the spoiler  101 . Therefore, the invention is limited only as defined by the following claims.