Abstract:
An apparatus and method of determining bearing and distance measurements between a mobile device and an object using Rf based measurements. The mobile device communicates with a control in the object to determine the relative bearing between the mobile device and the object with respect to magnetic north and, optionally, the distance between the mobile device and the object. An indicator on the mobile device aid in directing s the user of the mobile device toward the object as the mobile device is moved relative to the object. The mobile device can be a key fob and the object can be a vehicle.

Description:
BACKGROUND 
     The present invention relates, in general, to object locator apparatus and methods and, also, to wireless vehicle key fobs for remotely activating vehicle control functions. 
     The difficulty of finding a vehicle in a large parking lot, at shopping centers, sporting or music events, multi-level parking structures, etc., is a common problem experiences by all drivers on a regular basis. Long range key fobs have historically been used to activate a vehicle horn and exterior lights which can alert a driver to the vehicle location via audible and/or visual cues. This approach works well if the driver is within hearing or visual range of the vehicle and there are no obstructions or structures which would interfere with hearing or seeing the vehicle. This method does, however, create a nuisance in the form of noise pollution and possible embarrassment to the driver since many people could also hear the horn. 
     It has been proposed to incorporate a GPS receiver and a high accuracy compass into a key fob to facilitate determining the location of a parked vehicle with respect to the key fob location. This approach, however, has a significant cost and size/weight increase to the key fob for the GPS and compass components. 
     SUMMARY 
     A mobile object locator key fob with range and bearing measurements is disclosed. 
     In one aspect, a method for determining the location of an object by a remote, mobile apparatus comprises the steps of generating a bearing signal from the object with respect to magnetic north, receiving the bearing signal by the mobile apparatus, determining by the mobile device the relative bearing between the mobile device and the object, and providing direction information, including the relative bearing to the user of the mobile apparatus to aid in directing the user to the object. 
     The method can also include the step of updating the direction information provided to the user of the mobile apparatus as the mobile apparatus is moved relative to the object. 
     The method may also include the step of determining distance between the mobile device and the object, and the step of providing direction information to the user may include providing a relative distance between the mobile apparatus and the object. 
     An object remote location apparatus includes a control coupled to a transmitter and a receiver and adapted to be mounted on an object to transmit and receive wireless signals with respect to a remote mobile device, a mobile device having a transmitter and a receiver and one input member carried on the mobile device for activating an object location determining sequence between the mobile device and the control to aid the user of the mobile device to locate the object. 
     An antenna, responsive to the control generates an angularly rotating signal containing a signal angle information relative to magnetic north. The mobile device is operative to detect the angularly rotating signal and to decode the signal angle information in the rotating signal to determine a relative bearing to magnetic north between the mobile device and the object. 
     The mobile device includes an indicator carried on the mobile device for providing direction information including at least the relative bearing to the user of the mobile device to provide the location of the object relative to the mobile device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The various features, advantages, and other uses of the present invention will become more apparent by referring to the following detailed description and drawing in which: 
         FIG. 1  is a pictorial representation of a vehicle key fob for locating the vehicle using range and bearing measurement; 
         FIG. 2  is a schematic diagram of the components of the key fob shown in  FIG. 1 ; 
         FIGS. 3A and 3B  are plan views of the key fob having alternate indicators or displays; 
         FIG. 4  is a schematic diagram of the components of the remote keyless entry control and antenna; 
         FIG. 5  is a pictorial representation of the bearing determination of the key fob and remote keyless entry control; 
         FIG. 6  is a flow chart showing the major steps in the range and bearing measurement method; and 
         FIG. 7  is a pictorial representation of the use of the key fob with range and bearing measurement to assist a vehicle driver in locating the vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawing, and to  FIGS. 1-4  in particular, there is depicted a vehicle  10  having a remote keyless entry or RKE apparatus  12  mounted therein. A wireless key fob and transmitter  14  is associated with the RKE  12  and is identifiable by a unique frequency match to enable only the fob  14  to transmit signals to the RKE  12  which are recognized by the RKE  12  as being valid for vehicle control functions. 
     As shown in detail in  FIG. 2 , the fob  14  includes a control  20 , which may be a processor based control executing a control program stored in a memory  21 . One or more input members or buttons  22  are mounted on the housing  24  of the fob  14 . The input members or buttons  22  are associated with a particular vehicle function, such as locking or unlocking the vehicle doors and/or trunk or hatch, lowering the vehicle windows, remotely starting the vehicle engine, flashing the vehicle horns and/or lights, etc. An indicator  26 , such as an LED display  27  shown in  FIG. 3B , or one of more illuminatable devices, such as LEDs  28 A,  28 B and  28 C shown in  FIG. 3A , may also be mounted in the fob housing  24  to display vehicle status or button  22  selection information. 
     It will be understood that the shape of the fob housing  24 , the number and functions designated by the buttons  22 , and the type and shape of the optional display  26  can have any configuration. 
     A power supply  30  is contained in the housing  24  for powering the components of the fob  14  as shown in  FIG. 2 . A transmitter or a transmitter/receiver, transceiver or transponder  32  is mounted in the housing  24  for transmitting a data signal generated by the control  20  in response to depression or activation of one of the buttons  22  through an antenna  34 . The transmitter  32  has a frequency of operation between 300 MHz to 915 MHz, for example only. 
     The user depresses or activates one of the buttons  22  associated with the desired vehicle function that the user wishes to initiate. The input signal from the button  22  wakes up or activates the processor in the control  20  which outputs a data stream to the transmitter  32 . The data stream may include a data preamble, the actual vehicle function command, i.e., unlock vehicle doors, etc., an optional rolling code for vehicle to vehicle security, and possibly one or more check bits. This signal is sent by the transmitter  32  through the antenna  34  to the RKE  12  where it is received by a receiver  40  through an antenna  42 . The signal is demodulated by a vehicle access controller  44  which can also be a microprocessor based controller  44 . The controller  44  outputs a signal to a vehicle function control device or to a vehicle body computer which implements the desired vehicle function. 
     It will be understood that the description of the fob  14  and vehicle RKE  12  for remotely controlling various vehicle functions, such as locking and unlocking doors, activating vehicle horn and/or lights, etc., is by way of example only as the following description of a method and apparatus for determining range and bearing measurement between the vehicle and the key fob can be implemented without remote vehicle control functions provided by the fob and by the vehicle RKE. 
     In one aspect, the control  20  of the fob  14  and the RKE  12  in the vehicle or stationary object are programmed with appropriate transmit and receive capabilities to perform both relative bearing or angle and range or distance measurement using radio frequency signals. The relative bearing or angle and the range or distance measurement use processing techniques similar to Automatic Direction Finder (ADF) or VHF Omni-Range (VOR) using a radio frequency transmitter on a stationary object to be located, such as the vehicle  10 , which broadcasts a unique signal which the mobile or remote device, such as the fob  14  in the present implementation, receives and analyzes to determine the relative or absolute angle between the mobile device and the stationary transmitter. 
     For example, as shown in  FIG. 4 , an antenna  46  which generates a circumferential, rotating signal carrying absolute or relative angle of the antenna  46  relative to local magnetic north. The antenna  46  may be a phase array antenna continuously generating rotating or circumferentially oriented signals, such as signals A, B, and C in  FIG. 5 , which carry relative angle or bearing information of each signal A, B, or C, relative to magnetic north  48  as detected by compass or other equipment used to measure the earth&#39;s magnetic field at the location of the antenna  40 . The signals A, B, and C, respectively carry different angle information as each signal is generated by the antenna  46 . 
     As shown in  FIG. 5 , depending on the position of the fob  14  relative to the antenna  46  which is mounted on the vehicle  10 , the fob  44  will detect and receive one of the angular rotating signals A, B, and C generated by the antenna  46 . The control  20  of the fob  10  decodes the angular signals A, B, and C, and determines an angle or bearing between the fob  14  and the vehicle  10  on which the antenna  46  is mounted. 
     The control  20  in the fob  14  also can determine approximate distance between the mobile device of fob  14  and the vehicle  10  by signal propagation time delay of an Rf signal between the mobile device  14  and the vehicle  10  or by other means, such as the relative signal strength of a return signal from the RKE  12  in response to a distance request signal from the fob  14 . 
     As shown in  FIG. 6 , for power conservation purposes, the vehicle or object locator sequence would only be enabled when the vehicle owner initiates it via depression of one of the input members  22  on the fob  14  as shown by step  50  in  FIG. 6 . The object locate sequence would be active only for a set time as established by a time window in step  52 . The fob  14  sends an initiation signal in step  52  to the vehicle RKE  12  which activates the antenna  46  of the vehicle RKE  12  in step  54 . In this step, the antenna  46  generates the circumferentially spaced continuously rotating angle containing signals A, B, and C, etc., as shown in  FIG. 5 . One of these signals A, B, C, etc., is received and decoded by the fob  14  in step  56 . The control  46  in the fob  14  uses this angular information to determine the relative angle or bearing between the fob  14  and the vehicle  12  with respect to magnetic north in step  58 . 
     Simultaneous with the activation signal in step  52  or as an independent time space signal, the fob  14  transmits a distance measurement signal in step  60  to the RKE  12  Immediately upon receiving the distance measurement signal, the vehicle access controller  44  in the RKE  12  retransmits a return signal via the transmitter  46  and antenna  48  which is received by the fob  14  in step  62 . The time propagation delay between the start of transmission of the distant signal by the fob  14  in step  60  until the return signal is received by the fob  14  in step  62  is used by the control  20  in the fob  14  to determine the approximate distance between the fob  14  and the vehicle  10  in step  64 , taking into account the propagation delay of an Rf signal in air and the short signal processing time required by the RKE  12  upon receiving the distant signal from the fob  14  before the RKE  12  retransmits a return signal to the fob  14  in step  64 A. 
     Alternately, the fob control  120  measures the return signal strength in step  64 B and compares it to pre-established distance versus signal strength relationships to determine the approximate distance between the fob  14  and the vehicle  10 . 
     The fob  14  can provide the bearing and/or range information to the user of the fob  14  in different ways in step  65 . In one aspect shown in  FIG. 3A , one or more illuminatable devices, such as LEDs  28 A,  28 B, and  28 C are mounted on the housing  24  of the fob  14 . Each LED  28 A,  28 B,  28 C may be a different color or the centrally located LED  28 B in the illustrated example of three LEDs,  28 A,  28 B, or  28 C can be one color to indicate that the user is following a direct path to the vehicle, and the other LEDs  28 A and  28 C located to the left and right of the central LED  28 B can be used to indicate that the user is diverging from the direct bearing or path to the vehicle  10 . This use of the LEDs  28 A,  28 B, and  28 C, which also can include flashing signals from one or more of the LEDs  28 A,  28 B, and  28 C, with the flash cycle indicative of the approximate distance, whether increasing or decreasing, between the fob  14  and the vehicle  10  to guide the user via a “cold, warm, hot” dead reckoning-type locator system. 
     Referring briefly to  FIG. 7 , the fob  14 , after determining the bearing and distance between the fob  14  and the vehicle  10 , determines a direct path shown pictorially by reference number  70  to the vehicle  10 . As long as the user of the fob  14  follows this path  70 , only the LED  28 B would be lit. As the LED  28 B could flash at a periodic rate which decreases in time as the distance between the fob  14  and the vehicle  10  decreases. The flash rate of the LED  28 B could also decrease if the user of the fob  14  were to move away from the direct path to the vehicle  10  into the area denoted by reference number  72  in  FIG. 7 . 
     The LEDs  28 A and  28 C would be illuminated by the control  20  of the fob  14  when the user diverges from the path  70 , while still decreasing the distance between the fob  14  and the vehicle  10 , by moving into the areas  74  and  76  to the left and right, respectively, of the direct path  70 . 
     It will be understood that the direct path  70  could also cover a slight diversion sector area  78  which is still close enough to the direct path  70  to be useful in leading the user of the fob  14  to the relative area of the vehicle  10 . 
     In another aspect shown in  FIG. 3B , a visual graphical display  27  on the fob  14  can include display  27 , such as an LCD display, for example, which is capable of displaying graphic representations, such as the main compass points, north, south, east, and west, all denoted by reference number  80 , and a line depicting the direct path  70  from the location of the fob  14  denoted at a center point  82  on the display  27  to the vehicle  10 . The relative angle of the direct path  70  to one of the main compass directions  80  would be changed by the control  20  in the fob  14  if the user were to turn in a circle or otherwise diverge from the direct path  70  to the vehicle. 
     The display  27  can also include a flashing signal whose flash rate is proportional to the changing distance between the fob  14  and the vehicle  10 . 
     The fob control  20  will continue to update the bearing and/or range information as the user moves relative to the vehicle  10  as long as the total time of the locate sequence is within the total time established by the locate sequence time window in step  52 . The total time is checked in step  66  and the locate sequence terminated if the total preset time has been exceeded, or continued as explained above if time remains in the time window. 
     The use of Rf based bearing and distance measurement techniques in a fob  14  and the vehicle RKE controller  12  results in a low cost, light and small fob whose functional range is limited only by the effective Rf range of the system. The use of Rf signals for bearing an arranged measurement enables the fob  14  to be used in locating the vehicle  10  in ranges up to one mile or more in open air as well as at shorter distances in covered structures, such as parking garages. 
     In addition, the range and measurement features described above may be incorporated into existing configurations for vehicle fobs  14  and vehicle RKE controls  12  without requiring additional space, complex components, or external ground or satellite infrastructure.