Abstract:
A method and system are disclosed for operating a controller of and a RKE system to provide for short distance functions that are actuatable from a key fob at a shorter distance from the vehicle than other long distance functions. This may include receiving a desired type of radio frequency signal; actuating a high gain mode of a receiver of the controller; detecting a message from an acceptable remote keyless entry transmitter; decoding a function code portion of the message; changing the receiver from the high gain mode to a lower gain mode if the function code is not a long distance function; decoding a remaining portion of the message; determining if the remaining portion of the message was decoded properly; and performing the requested function if the remaining portion of the message was decoded properly.

Description:
BACKGROUND OF INVENTION 
     The present invention relates to remote keyless entry types of systems employed with automotive vehicles. 
     Remote keyless entry systems are commonly used with automotive vehicles today. Such systems are including a wider range of functions that can be performed by the remote keyless entry system. For example, not only are the conventional lock, unlock, trunk release, and panic functions available, but also new functions such as remote engine start. 
     For certain functions, such as remote engine start, it is desirable to allow these functions to be performed while the operator is a greater distance from the vehicle than for some of the conventional functions. For example, one may wish to allow for the remote engine start, door lock, and panic alarm functions to be operable when the key fob is as far away from the vehicle as two hundred meters. To obtain this long rage functionality, the remote keyless entry system can be designed to operate at this greater distance. 
     Having the greater range of operation for the remote keyless entry system, however, may be undesirable for certain other remote keyless entry functions. One may wish to avoid inadvertently releasing the trunk if the trunk release button on the key fob is pressed when one is at this long range distance since he will not see or hear the trunk release. Moreover, one may not wish to inadvertently unlock the vehicle doors when at this longer range since one may be out of sight of the vehicle and thus not realize that the doors are unlocked. Accordingly, it may be undesirable for door unlock or trunk release functions to be operable from the same two hundred meter distance. Of course, the shorter range functions are still desirable for the remote keyless entry system, so operators may wish for these short-range functions to be operable only when the operator actuates the key fob at a more conventional range of, for example, about fifty meters or less. 
     Some have attempted to overcome this drawback by designing their remote keyless entry systems to try and detect the distance that the key fob is from the vehicle when the button is pressed, and then determine what function, if any, to perform based on this detected distance. This may be attempted by using received signal strength indicator (RSSI) circuitry. But due to environmental conditions, such as ambient radio frequency noise, this type of method can be very unrepeatable—that is, the range is not always consistently and accurately determined. Such inaccuracy may be undesirable for vehicle operators with these types of remote keyless entry systems. Thus, it is desirable to have a remote keyless entry system that allows for operation of both long-range and short-range functions, while overcoming the drawbacks of the prior art. 
     SUMMARY OF INVENTION 
     An embodiment of the present invention contemplates a method of operating a controller of a remote keyless entry system in a vehicle comprising the steps of: receiving a desired type of radio frequency signal; actuating a high gain mode of a receiver of the controller; detecting a message from an acceptable remote keyless entry transmitter; decoding a function code portion of the message; changing the receiver from the high gain mode to a lower gain mode if the function code is not a long distance function; decoding a remaining portion of the message; determining if the remaining portion of the message was decoded properly; and performing the requested function if the remaining portion of the message was decoded properly. 
     An embodiment of the present invention also contemplates a method of determining whether to perform a remotely requested vehicle function transmitted via an RF signal from a remote transmitter to a vehicle, the method comprising the steps of: actuating a button on the remote transmitter within a predetermined distance from the vehicle to cause the transmission of the RF signal, with the RF signal having a preamble portion and a message portion; receiving the RF signal with a RKE system in the vehicle; actuating a high gain mode of the RKE system; determining whether the remotely requested vehicle function in the message portion is a short distance function; changing the receiver to a lower gain mode if the remotely requested vehicle function is the short distance function; decoding a remaining portion of the message portion; and performing the remotely requested vehicle function if the remaining portion of the message portion is decoded properly. 
     An embodiment of the present invention further contemplates a dual range vehicle remote that includes a key fob and a remote keyless entry (RKE) system. The key fob includes a plurality of buttons, each adapted for indicating a desired remote function, and a transmitter capable of transmitting a signal having a message portion indicative of the desired function when one of the plurality of buttons is actuated. The RKE system may include a receiver capable of receiving the signal, and a controller for setting the RKE system in high gain mode, determining if the desired function in the message portion is a short distance function, changing the RKE system to a lower gain mode if the desired function is a short distance function, decoding a remaining portion of the message portion, and performing the desired function if the remaining portion of the message portion is decoded properly. 
     An advantage of an embodiment of the present invention is that, for certain remote keyless entry functions where it is desirable to operate from a long distance, these functions may operate at these longer distances, while other short distance functions are disabled at such long distances. Thus, inadvertent actuation of short distance functions from a long distance can be avoided. 
     A further advantage of an embodiment of the present invention is that the ability to disable the short distance functions when the key fob is at a long distance may be performed in a consistent and repeatable manner. 
     An additional advantage of an embodiment of the present invention is that no received signal strength indicator (RSSI) or other distance calculating technology is required in the operation of this invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic representation of the vehicle and remote keyless entry system, and the ranges at which the system operates, in accordance with an embodiment of the present invention. 
         FIG. 2  is a block diagram representing an example of a radio frequency transmission from a key fob, in accordance with an embodiment of the present invention. 
         FIG. 3  is a flow chart showing remote keyless entry controller operation in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically shows a vehicle  30  having a remote keyless entry system, indicated generally at  32 . The remote keyless entry (RKE) system  32  includes a controller  34  in communication with a receiver  36 . The controller  34  may be in communication with systems that carry out the desired RKE functions, such as a door lock/unlock actuator (not shown), a vehicle horn and headlights (not shown), an engine ignition system (not shown), and/or a trunk release mechanism (not shown). These systems will not be described in any detail since they are known to those skilled in the art. Moreover, the controller  34  and receiver  36  may be integral or separate components, and may be comprised of various combinations of hardware and software, as is known to those skilled in the art. 
     A key fob  38  includes a set of buttons, such as, for example, lock  40 , unlock  42 , engine start  44 , alarm  46 , and trunk release  48 . Of course, additional or different remote functions may be performed by the key fob  38 , if so desired. For example, power door open and close functions may be included on the key fob. The key fob  38  also has a power source and other electronic circuitry, including a transmitter  50 , which is capable of transmitting a radio frequency (RF) signal  52  in response to the actuation of one of the buttons on the key fob  38 . The details of the transmitter  50  and other electronic circuitry (not shown) and power source (not shown) of the key fob  38  will not be discussed in detail herein since they are known to those skilled in the art. 
       FIG. 1  also provides an illustration of different ranges/distances at which the desired RKE functions may be operable. That is, when the key fob  38  is within a first range/distance D 1 , it is desirable that the RKE system  32  receives the RF signal  52  from the transmitter  50  and that all of the RKE functions are operable. Between the first range/distance D 1  and a second range/distance D 2 , it is desirable that the RKE system  32  only perform long distance functions, while not enabling short distance functions. The actual ranges/distances D 1 , D 2  employed by the system can be set as desired for a particular vehicle, but may be, for example, fifty meters for the shorter range/distance D 1  and two hundred meters for the longer range/distance D 2 . 
     Long distance functions are those that are desired to operate up to the limits of about range/distance D 2 , while short distance functions are those that are desired to only operate up to the limits of about range/distance D 1 . For example, door lock, engine start, and alarm may be long distance functions while door unlock and trunk release may be short distance functions. As an alternative, a function may be applied as a long or short distance function depending upon whether it is being activated or deactivated. For example, if so desired, the alarm function may be treated by the RKE system  32  (in  FIG. 1 ) as a long distance function if it is currently deactivated (i.e., one is pressing the alarm button  46  requesting to activate the alarm), but be treated as a short distance function if it is currently activated (i.e., one is pressing the alarm button  46  requesting deactivation of the alarm). 
       FIG. 2  illustrates a block diagram representing an example of the RF signal  52  from the key fob  38  (of  FIG. 1 ). This RF signal  52  may employ a common format for transmitting an RF signal from the key fob  38 . The RF signal  52  may include a preamble portion  54 , followed by a first frame  56 , a second frame  58  and a third frame  60 . The preamble portion  54  may be just a detectable type of RF transmission at a desired frequency and coding, which may not be specific to a particular key fob, but that the RKE system  32  (in  FIG. 1 ) will recognize as requiring it to wake up from its power saving polling mode to a full run mode. The first frame  56  preferably contains a first complete message  62 , with the second and third frames  58 ,  60  just comprising redundant messages (not illustrated) the same as the first complete message  62 . 
     The first complete message  62  preferably contains a synchronizing (sync) portion  64 , followed by a message identifier (ID) portion  66 , a function code portion  68 , and a rolling code bits portion  70 . The sync portion  64  merely assures that the RKE system  32  has the correct timing for reading the RF signal  52  properly. The message ID portion  66  and function code portion  68  contain information relating to the particular function being requested, (i.e., the function to be performed based on the button that was pressed on the key fob  38 ). The rolling code bits portion  70  relates to the encryption being employed. The messages in the second and third frames  58 ,  60  will just repeat this same information contained in the first frame  56 . While the RF signal  52  is shown with three frames  56 ,  58 ,  60  each containing the same redundant messages  62 , the system can be configured so that a greater or lesser number of redundant frames  56 ,  58 ,  60  can be transmitted with each press of a button on the key fob  38 , if so desired. 
       FIG. 3  illustrates a method of operating the controller  34  (of  FIG. 1 ) in the vehicle  30  as it receives a RF signal  52  (such as that illustrated in  FIG. 2 ). The controller  34  typically starts in a polling mode, which reduces power consumption during long periods of inactivity. In the polling mode, it samples RF data, block  100 , to determine if a preamble is detected, block  102 . If the sampling of the RF data does not detect a preamble, then the sampling of RF data in a polling mode continues. If a preamble is detected, then the controller  34  switches from a polling mode to full run mode with high gain, block  104 . The message is then received and begins to be decoded, block  106 . If no sync portion of the message is detected, then the controller returns to a polling state and again samples RF data. 
     If, on the other hand, a sync portion of the message is detected, the message ID and function code are decoded, block  110 . If the function code is for a long distance function, the remaining portion of the message is decoded, block  116 . If the function code is not for a long distance function, the receiver sensitivity is decreased, block  114 , and then the remaining portion of the message is decoded, block  116 . Thus, for short distance functions, the message is decoded in a low gain mode. Examples of RKE functions that may be long distance or short distance were discussed above relative to  FIG. 1 . 
     The switching from high to low gain mode accounts for the distance from the vehicle  30  that the key fob  38  is when the RKE request is transmitted. Presumably, if the rest of the message becomes corrupted after the receiver  36  is switched to the low gain mode, the user with the key fob  38  must be standing farther away from the vehicle  30  than the range/distance D 1 , so the short distance function should not be carried out. If, in the low gain mode, the rest of the message is successfully decoded, then the user with the key fob  38  is likely within the range/distance D 1  and the function should be carried out. Of course, if the function is a long range function, then the rest of the message is decoded in high gain mode, in which case, it is likely to be decoded properly if the user with the key fob  38  is within the range/distance D 2 . The levels for high and low gain, and the difference between the two, will depend upon various factors, including the actual distances one wishes for ranges/distances D 1  and D 2 . The setting of levels for high and low gain to achieve the desired results are know to those skilled in the art and so will not be discussed further herein. Moreover, while only two levels of gain are employed to distinguish only short and long distance functions, there may be three levels of gain employed to distinguish short, medium and long distance functions, if so desired. 
     Consequently, a determination is made as to whether the remaining portion of the message was decoded properly, block  118 . If it was not decoded properly, a check is made to determine if an additional message was received, block  122 . If an additional message was received, this additional message is decoded, block  124 , and a determination is made as to whether this message was decoded properly, block  118 . The additional messages may be those contained in the redundant frames  58 ,  60  (illustrated in  FIG. 2 ). This continues until a message is decoded properly or until no additional messages are received. If a message is decoded properly, then the requested function is performed, block  120 , and the routine ends, block  126 . If there are no additional messages and no messages were decoded properly, then the routine ends, block  126 , without performing any function. 
     While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.