Abstract:
A vehicle communication system mounted in the vehicle and a portable fob for carrying by a user are provided. The vehicle communication system comprises a trigger generator, an LF transmitter for broadcasting an LF wakeup signal, and an RF transmitter for broadcasting a UHF status message including vehicle status data. The vehicle communication system broadcasts a challenge signal after the LF wakeup signal. The portable fob comprises an LF receiver responsive to the LF wakeup signal, a fob controller for determining response data, and an RF transmitter for broadcasting a UHF response signal incorporating the response data. The portable fob further comprises an RF receiver for receiving the vehicle status data, a visual display for visually reproducing the vehicle status data, and a manual input key for activating the fob controller to generate a remote control message. The RF transmitter in the portable fob broadcasts a UHF control signal incorporating the remote control message. The vehicle communication system further comprises an RF receiver responsive to the UHF control signal and a base controller for initiating a corresponding remote control function in response to the UHF control signal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to remote convenience and security systems for automotive vehicles, and, more specifically, to a wireless communication system for integrating functions of a two-way remote keyless entry system and a passive entry system. 
     Remote keyless entry (RKE) systems for vehicles have been in use for many years. These systems provide safety and convenience for a user entering or exiting a vehicle. Some of the typical features offered by these systems allow the user to lock/unlock doors and arm/disarm auto theft systems in a remote manner. In addition, remote starting of the engine and remote control of the climate control temperature setting after starting are commercially available. Typical RKE systems utilize a key fob with a radiofrequency (RF) transmitter which transmits to a base station in the vehicle. When the user is within range, the user actuates a corresponding button on the key fob to send a lock, unlock, or engine start command, for example. Two-way communication is typically implemented in remote start systems so that the user carrying the portable fob can be informed of the status of the vehicle (e.g., engine running status, door lock status, and temperature status). Thus, a two-way fob includes a visual display (e.g., LED indicator lights or an LCD graphical display panel) to convey the information to the user. 
     One disadvantage of this type of system is that the user must manually actuate the key fob to achieve the desired result. In an attempt to eliminate this disadvantage, passive entry systems, which operate in a hands-free manner, are being introduced. In order to avoid excessive battery consumption by periodic radio transmission from the fob, the approach of the user to the vehicle is usually sensed by the vehicle, which then wakes up the fob to perform a security check before actuating a passive entry function. Is it known, for example, to sense the presence of a user who is attempting entry into a locked vehicle via a particular door by detecting the lifting of the door handle. Using a low frequency (LF) wireless signal, the vehicle then interrogates the area around the door for a key fob containing a valid security ID code. 
     Passive entry communication operates over a much shorter range than RKE communication (e.g., 1 meter as opposed to 30 meters). Therefore, an LF signal (e.g., 134 kHz) is used for passive entry while a much higher frequency RF signal (e.g., 315 MHz or 433 MHz) is used for RKE since the LF signal decays over a shorter range. In addition, transponders operative at LF frequencies are readily available. As used herein, LF frequencies range from about 30 kHz to about 300 kHz. RF signals used in RKE systems are typically in the UHF band from about 300 MHz to about 3 GHz. 
     Security ID codes for validating a particular fob for accessing a passive entry function typically include rolling code encryption in order to deter code grabbing and relay attacks by potential thieves. Due to the low frequency signals used by passive entry systems, the exchanging of challenge and response signals used by a rolling code system has transpired using a data rate which is lower than the data rate for performing similar exchanges by RKE systems using RF signals. A slow data rate can result in problems because it is necessary to quickly validate a fob carried by the user after beginning to lift a door handle so that a door unlock mechanism can be activated before the door handle moves beyond an appropriate position. 
     SUMMARY OF THE INVENTION 
     The present invention has advantages of added convenience, faster response times, and increased security as results of integrating functionality of a passive entry system with a two-way RKE system having an active display. 
     In one aspect of the invention, an integrated passive entry and remote keyless entry system is provided for a vehicle, wherein the system comprises a vehicle communication system mounted in the vehicle and a portable fob for carrying by a user. The vehicle communication system comprises a trigger generator, an LF transmitter responsive to the trigger generator for broadcasting an LF wakeup signal, and an RF transmitter for broadcasting a UHF status message including vehicle status data to the portable fob. The vehicle communication system broadcasts a challenge signal to the portable fob after the LF wakeup signal. The portable fob comprises an LF receiver responsive to the LF wakeup signal, a fob controller for determining response data according to the challenge signal, and an RF transmitter for broadcasting a UHF response signal incorporating the response data. The portable fob further comprises an RF receiver for receiving the vehicle status data, a visual display for visually reproducing the vehicle status data, and a manual input key for activating the fob controller to generate a remote control message. The RF transmitter in the portable fob broadcasts a UHF control signal incorporating the remote control message. The vehicle communication system further comprises an RF receiver responsive to the UHF control signal and a base controller for initiating a corresponding remote control function in response to the UHF control signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, block diagram of one preferred embodiment of an integrated two-way RKE and passive entry system according to the present invention. 
         FIG. 2  is a timing diagram of signal exchanges in one preferred embodiment of the invention. 
         FIG. 3  is a flowchart of one preferred method of the present invention. 
         FIG. 4  is a timing diagram of signal exchanges in an alternative embodiment of the invention. 
         FIG. 5  is a timing diagram of signal exchanges in another alternative embodiment of the invention. 
         FIG. 6  is a schematic, block diagram of modified portions of a portable fob and a vehicle base station for providing LF/LF backup functionality. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a vehicle  10  includes a base station or vehicle communication module  11  for communicating with a remote portable fob  12 . Base station  11  includes a microcontroller  13  coupled to an LF transmitter  14 , an RF receiver  15 , and an RF transmitter  16 . In certain embodiments of the present invention, additional LF transmitters or LF antennas may be provided such as an LF transmitter  17 . The additional transmitters or antennas may be located in vehicle  10  remotely from base station  11  at an entry zone being monitored by a passive entry system, for example. A single LF transmitter  14  may also use a plurality of LF antennas at respective locations within the vehicle such as an LF antenna  20  deployed in base station  11  and an LF antenna  21  disposed near a door module  22  in vehicle  10  (e.g., in a side view mirror housing). Door module  22  is coupled to microcontroller  13  and may preferably include a sensing switch for detecting the lifting of a door handle and a power lock mechanism for remotely locking and unlocking a corresponding door lock. If a separate LF transmitter  17  is used, an LF antenna  23  is coupled thereto. 
     An RF antenna  24  is coupled to RF receiver  15  as well as to RF transmitter  16  through a matching circuit  25 . Microcontroller  13  in base station  11  is coupled to an engine controller  26  for controlling an engine  27 . Door module  22  and engine controller  26  act as function actuators for implementing RKE commands received by base station microcontroller  13 . Microcontroller  13  receives vehicle status data from engine controller  26  (e.g., to confirm that the engine has successfully started in response to a remote engine start command) and from door module  22  (e.g., to confirm locking of the vehicle doors). The vehicle status data can be sent to portable fob  12  within a vehicle status message as part of a confirmation following execution of particular RKE commands, for example. 
     Portable fob  12  includes a microcontroller  30  coupled to input buttons  31  typically including separate push buttons for activating RKE commands for locking and unlocking doors, remotely starting or stopping an engine, panic alarm, and others. An RF transmitter  32  is coupled to an antenna  33  through a matching network  34 . RKE commands initiated by depressing a push button  31  are broadcast by RF transmitter  32  and antenna  33 . An RF receiver  35  is coupled to antenna  33  and microcontroller  30  for receiving UHF status messages broadcast by base station  11 , such as engine running status for a remote start function. A display  36  is coupled to microcontroller  30  for displaying vehicle status data from a status message to a user. 
     An LF receiver  37  is coupled to microcontroller  30  and to an LF antenna  38  for detecting wakeup signals broadcast from vehicle  10 . A battery  39  in fob  12  supplies electrical power to all the other components of fob  12  during normal operation. 
     In operation, a typical passive entry sequence begins when a door handle switch in door module  22  generates a trigger pulse provided to microcontroller  13  resulting in executing a trigger generation function within microcontroller  13 . In response to trigger generation, LF transmitter  14  is activated in order to generate an LF wakeup signal to activate LF receiver  37  in fob  12  via antennas  20  and  38 . The LF wakeup signal is also used to localize the fob based on which LF transmitter antenna  20  or  21  generates the strongest received LF wakeup signal in fob  12 . The LF wakeup signal has a known format including an operation code for identifying the signal as a wakeup signal and preferably also including an antenna identifier unique to the antenna being used to transmit each LF wake-up signal. Localization of the fob is necessary to ensure that a person carrying an authorized fob is properly located in the area where the passive function is being requested (e.g., located outside the door with the triggering door handle for a passive entry function and located in the passenger compartment for a passive engine start function). 
     LF receiver  37  preferably includes circuitry for measuring a received signal strength indicator (RSSI) at which the LF wakeup signal is received. The awakened microcontroller  30  stores the RSSI data as part of response data to be sent back to base station  11 . Also after being awakened, RF receiver  35  is activated in order to receive an expected challenge signal from base station  11  as part of a conventional challenge/response validation sequence. For example, microcontroller  13  in base station  11  generates a random number to be used as a seed number in a secret mathematical transformation that is also known to microcontroller  30  in fob  12 . RF transmitter  16  in base station  11  is used broadcast a UHF challenge signal including the random number. RF receiver  35  in fob  12  receives the UHF challenge signal and microcontroller  30  passes the random number through the known mathematical transformation. The resulting transformed number is included in response data together with the RSSI signal and a fob identifier for inclusion in a UHF response signal broadcast via RF transmitter  32  and antenna  33 . The UHF challenge and response signals are sent with a much shorter time delay than if they were sent at the low frequency. The challenge and response may both be sent at 9.6 k baud, for example. The UHF response signal is received by RF receiver  15  via antenna  24  in base station  11  and is processed by microcontroller  13  in a known manner. For instance, microcontroller  13  checks the transformed number as received from fob  12  with its own results of the transformation and determines the UHF response signal to be valid if the transformed numbers match. 
     Fob  12  and base station  11  also function to provide remote keyless entry functions in a conventional manner. Thus, when a user presses a manual input key (i.e., push button)  31  for a desired remote control function, a UHF control signal incorporating a remote control message having a corresponding function identifier and a pre-assigned fob ID is broadcast. When base station  11  receives a UHF control signal, it validates the fob ID and any security codes and then initiates the remote control function via a vehicle message sent from base station controller  13  to an actuator such as door module  22  or engine controller  26 . Typical remote control commands include locking all doors, unlocking a driver&#39;s door, unlocking all doors, unlocking a trunk, activating a panic alarm, remotely starting an engine, activating a climate control, deactivating an engine, deactivating a climate control, and requesting vehicle status data to be provided in a UHF status message. 
     Two-way RKE communication may be initiated by microcontroller  13  automatically after executing certain remote control actions to provide the status data (e.g., engine running status or door lock status) in a UHF status message. The status message is broadcast by RF receiver  15  via antenna  24  to antenna  33  and RF receiver  35  and preferably includes an identifier for properly addressing fob  12  so that information presented by display  36  corresponds to the correct vehicle. The UHF status message may also be prompted by sending a remote control request signal from fob  12 . 
       FIG. 2  shows a first preferred embodiment for localizing a fob in a passive entry sequence wherein it is desired to determine whether the fob is outside the vehicle in the vicinity of a particular door (i.e., when a door unlock request is initiated by a trigger signal from the lifting of a door handle) or inside the vehicle (i.e., a passive engine start sequence is triggered by a user pressing an engine start switch inside the vehicle). A first LF wakeup signal  40  is generated from a first antenna preferentially transmitting to a first area with respect to the vehicle (e.g., outside the vehicle adjacent to a particular door or other closure such as a trunk). After waiting an amount of time sufficient to allow the fob to awaken, the base station sends a challenge signal  41  via the base station RF transmitter and antenna. If the fob is in fact in the first area being preferentially transmitted to, then after receiving the challenge signal and formulating response data the fob RF transmitter sends a UHF response signal  42 . When the fob is located in the area, then the response includes RSSI data showing strong reception. If outside the first area, then the RSSI data will reflect a weak signal. If the fob is not close enough to the target area, the wakeup signal will not have been received and there will no response to the challenge signal at all. In order to poll an additional location, an LF wakeup signal  43  is sent via a second LF antenna preferentially transmitting to a second area (e.g., inside the vehicle). Following sufficient time to allow a fob to awaken, a UHF challenge signal  44  is sent via the RF transmitter in the base station. If a fob was awakened in the desired location being polled, a UHF response signal  45  is sent from the fob RF transmitter to the base station RF receiver. 
     A preferred method of the invention is shown in greater detail in  FIG. 3 . This is just one possible method, and many modifications will occur to those skilled in the art. In step  50 , a trigger event is generated indicating a request for a passive entry function (e.g., lifting a door handle or pressing a start button inside the vehicle). An LF wakeup signal with a corresponding antenna ID is sent in step  51  from the first antenna. At point  52 , either a fob is actually present or not in the area being interrogated by the first antenna. If the LF wakeup signal is received at step  52 , then the fob measures an RSSI signal and determines the antenna ID in step  53 . Whether or not the wakeup signal is received, a UHF challenge signal is sent from the base station as shown at steps  54  and  55 . If the UHF challenge signal is received by a fob, then the fob determines response data and sends a UHF response signal in step  56 . In step  57 , the base station stores the response data. If no fob was awakened or an awakened fob fails to send a valid response signal, then the lack of a response is detected in step  58 . 
     After storing response data in step  57  or detecting that no response was received in step  58 , the base station sends a second LF wakeup signal with a corresponding antenna ID in step  60  from the second antenna. If the second LF wakeup signal is received by a fob in step  61  then the fob determines RSSI data and the antenna ID in step  62 . A UHF challenge signal is sent as shown in step  63  and  64  (although only one challenge signal is sent). If a fob is present, then it determines response data in step  65  and sends a UHF response signal. The base station stores the response data in step  66  or detects the lack of a response in step  67 . 
     A check is made in step  68  to determine whether any valid response was received by a fob. If not, then either the process ends or a batteryless backup procedure may be performed at step  69  as will be described in greater detail in connection with  FIG. 6 . If at least one valid response was detected, then a check is made in step  70  to determine whether a valid response was received only in response to the LF wakeup signal sent from the first antenna. If so, then the person carrying the fob is known to be located in the region interrogated by the first antenna (i.e., region # 1 ). If the requested passive entry function corresponds to region # 1 , then it is performed in step  71  (e.g., a door is unlocked corresponding to the first antenna area). 
     If the only valid response did not correspond to the first LF wakeup signal, then a check is made in step  72  to determine whether the only valid response was in response to the LF wakeup signal sent from the second antenna in step  72 . If so, then the person carrying the fob is known to be located in the region interrogated by the second antenna (i.e., region # 2 ). If the requested passive entry function corresponds to region # 2 , then it is performed in step  73 . If two valid responses were received then a comparison is made in step  74  between the received signal strengths shown by the two responses. If the received signal strength of the first LF wakeup signal is greater then 20 the second RSSI data, then a requested passive entry command for the first region may be performed in step  71 , and otherwise a requested passive entry command for the second region may be performed in step  73 . 
       FIG. 4  shows an alternative message sequence wherein the areas interrogated by respective LF antennas do not overlap. Thus, a first LF wakeup signal  80  and a second LF wakeup signal  81  may be broadcast simultaneously. Since each LF wakeup signal includes an antenna ID, the base station will be able to determine which antenna woke up the fob. Thereafter, just a single challenge signal  82  and a single response signal  83  are necessary. Use of an antenna identifier is optional in the embodiments shown in  FIG. 2 , but is mandatory in the embodiment shown in  FIG. 4 . 
     In another alternative embodiment, a challenge and response sequence can be avoided in the event that a fob is not awakened by a particular LF wakeup signal. Thus, a first wakeup signal  84  is sent from a first LF transmitting antenna and if a fob is awakened then an acknowledgement signal  85  is sent by the fob RF transmitter. This acknowledgement message may also include the RSSI data. Thereafter, a UHF challenge signal  86  and a UHF response signal  87  are exchanged. Additional antenna locations may then be polled in a similar manner if desired. If no acknowledgement signal is received after the first wakeup signal, then a second wakeup signal for interrogating a second area can be broadcast immediately. 
     If no valid responses are received from any LF wakeup signal, it is possible that an authorized fob was in the correct location but that its battery was depleted and the fob was unable to awaken. In order to provide a batteryless backup procedure, a combined two-way RKE/passive entry system having supplemental components as shown in  FIG. 6  may be provided. In fob  12 , the LF received function is performed by a transponder  90 , which includes both a receiver and transmitter and circuitry for storing energy from an external radiated signal. Such transponders are already widely employed in engine immobilizer systems. The LF wakeup signal is of sufficient magnitude and duration that when transponder  90  is within a target area, a sufficient electrical charge is accumulated for powering transponder  90  to communicate a LF response via an internal LF transmitter for performing a passive entry function in a known manner. An LF receiver  91  is provided in base station  11  for receiving an LF response signal from transponder  90  and providing LF response data to microcontroller  13 . LF receiver  91  is coupled to antennas  20  and  21 . A switch  92  may be provided for sharing antennas  20  and  21  between LF transmitter and LF receiver  91 . 
     In view of the foregoing description, the present invention has preserved the short operating range and wakeup capability of a LF system while taking advantage of the higher data rate and resistance to relay attacks of an RF system.