Abstract:
A receiver/controller unit ( 14 ) of a remote convenience system ( 10 ) receives an electromagnetic signal ( 18 ). The signal ( 18 ) is comprised of a plurality of pulses that convey a remote convenience function request. In response to the receipt of the signal ( 18 ), the receiver/controller unit ( 14 ) causes performance of the requested function. The receiver/controller unit ( 14 ) has a comparator ( 82 ). A first input of the comparator ( 82 ) is connected to receive an electrical signal ( 78 ) with an electrical characteristic that varies to convey the remote convenience function request. A second input of the comparator ( 82 ) is connected to receive a signal 86 that has a threshold electrical characteristic value. Preferably, the electrical characteristic is voltage amplitude. An output of the comparator ( 82 ) provides a signal indicative of the occurrence of the electrical characteristic of the electrical signal ( 78 ) exceeding the threshold value, and that conveys the remote convenience function request. A microprocessor ( 100 ) adjusts the threshold electrical characteristic value.

Description:
FIELD OF THE INVENTION 
     The present invention relates to remote convenience systems, and is particularly directed to systems that include an adjustable pulse detection receiver. 
     BACKGROUND OF THE INVENTION 
     Remote convenience systems are known in the art. Such remote convenience systems permit remote control of certain functions. One example type of a remote convenience system is for remotely controlling vehicle functions. Other example types of remote convenience systems include garage door opener systems and entry light activation systems. Focusing on the remote convenience vehicle systems, remotely controlled vehicle functions include locking and unlocking functions of one or more vehicle doors. A remote convenience system that permits remote locking and unlocking is commonly referred to as a remote keyless entry system. Such remote convenience vehicle systems may provide for control of other vehicle functions. For example, a remote vehicle locator function may be provided. The vehicle locator function causes a horn to emit a horn chirp and/or the headlights of the vehicle to flash “ON”. This allows a person to quickly locate their car within a crowded parking lot. 
     Known remote convenience vehicle systems include a receiver/controller unit mounted in an associated vehicle and at least one portable hand-held transmitter unit located remote from the receiver/controller unit. Each transmitter unit is provided with one or more manually actuatable switches. Each switch is associated with a vehicle control function to be performed. The transmitter unit includes circuitry that responds to the actuation of one of the switches to transmit a function request message, along with a security code, in the form of a digital signal. A signal that is received by the receiver/controller unit is processed such that the vehicle performs the requested function. 
     The remote convenience systems operate in the ultrahigh frequency (UHF) portion of the radio frequency (RF) spectrum. Specifically, the signals from the transmitter units are in the UHF portion of the spectrum that is allocated by the United States Federal Communications Commission (FCC) for unlicensed transmission devices. FCC regulations stipulate that such unlicensed devices cannot have a transmitted signal strength that exceeds a preset maximum. Some countries other than the United States only permit very low levels of transmitted power. The transmitted power level in these countries is lower than the permitted level in the United States. For example, in Japan, remote convenience transmitter units have typical transmission power levels 30 dB below that of a typical United States remote convenience transmitter unit. In addition, within the United States, FCC regulations stipulate that the unlicensed devices must not cause undo radio interference and must operate despite the presence of any radio interference. 
     Often, it is desirable to accomplish remote control performance of certain functions at a longest possible distance. One example of such a function that is performed at the longest possible distance is the remote vehicle locator function. To illustrate such a scenario, consider a shopping mall patron exiting a shopping mall building and being faced with the task of visually locating their car within a vast shopping mall parking lot. It will be beneficial to be able to actuate the remote vehicle locator function from a location near the exit door of the shopping mall, before proceeding into the parking lot. 
     In order for a receiver/controller unit located within the associated vehicle to receive a low power signal, the receiver/controller unit must have a high sensitivity and must have a high ability to differentiate the signal from any noise. 
     Another issue which presents itself for remote convenience systems is that the type of the circuitry hardware that is used within the receiver/controller unit is often dependent upon the type of signal that is transmitted from the associated transmitter unit. Specifically, if the transmitted signal contains a pulse string that has a duty cycle that is approximately fifty percent, the receiver/controller unit typically includes an average detector for discriminating pulses within the transmitted signal. A threshold level, used to determine the occurrence of pulses, is set at an average signal level. 
     However, if the transmitted signal contains a pulse string that has a duty cycle that is much lower than fifty percent, the receiver/controller unit typically requires the use of a peak detector to discriminate the occurrence of pulses within the transmitted signal. A threshold level is set at some percentage of a peak value of the signal. 
     It is to be appreciated that an average detector does not perform well for low duty cycle signals and the peak detector does not perform well for high duty cycle signals. Thus, different hardware setups must be provided in the receiver/controller units, dependent upon the type of transmitted signal. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect, the present invention provides a receiver/controller apparatus for receiving an electromagnetic signal comprised of a plurality of pulses that convey a remote convenience function request, and for causing performance of the requested function. A comparator of the apparatus has a first input for receiving an electrical signal with an electrical characteristic that varies to convey the remote convenience function request. A second input of the comparator receives a threshold electrical characteristic value. An output of the comparator provides a signal that is indicative of the occurrence of the electrical characteristic of the electrical signal exceeding the threshold value and that conveys the remote convenience function request. The apparatus includes means for adjusting the threshold electrical characteristic value. 
     In accordance with another aspect, the present invention provides a receiver/controller apparatus for a remote convenience system. The apparatus is responsive to a remote convenience function request conveyed via an electromagnetic signal transmitted from a portable transmitter for controlling performance of an associated function. Antenna means picks-up the electromagnetic signal and outputs a respective, electrical antenna-output signal conveying the function request. Receive circuitry means of the apparatus processes the antenna-output signal and outputs an electrical signal that conveys the function request in response to the processing of the antenna-output signal. The receive circuitry means includes a comparator that has a first input for receiving an electrical signal with a voltage that varies to convey the remote convenience function request. A second input of the comparator receives a threshold voltage value. An output of the comparator provides a signal indicative of the occurrence of the voltage of the electrical signal exceeding the threshold voltage value. The receive circuitry means includes means for adjusting the threshold voltage value. 
     In accordance with another aspect, the present invention provides a method of receiving an electromagnetic signal comprised of a plurality of pulses that convey a remote convenience function request, and for causing performance of the requested function. The electromagnetic signal is picked-up. An electrical antenna-output signal conveying the function request is output. A first signal with a voltage is derived from the antenna-output signal. The voltage of the first signal varies to convey the remote convenience function request. A second signal that has a threshold voltage value is provided. The first and second signals are compared. An output signal that indicates the occurrence of the voltage of the first signal exceeding the threshold voltage value is provided to convey the function request. The threshold voltage value of the second signal is adjusted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, wherein: 
     FIG. 1 is a schematic illustration of a remote convenience vehicle system in accordance with the present invention; 
     FIG. 2 is a schematic illustration of a first embodiment of-a receiver portion within a receiver/controller unit of the system of FIG. 1; and 
     FIG. 3 is a second embodiment of the receiver portion. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A remote convenience vehicle system  10  is schematically shown in FIG.  1 . The system  10  includes a transmitter unit  12  and an associated receiver/controller unit  14  that is mounted in a vehicle  16 . The transmitter unit  12  is operable to communicate, via an electromagnetic signal  18 , with the receiver/controller unit  14  to achieve remote control performance of at least one convenience function (e.g., unlock doors) at a vehicle system  20  (e.g., vehicle door lock actuator) of the vehicle  16 . The transmitter unit  12  is operated when it is desired to cause performance of the requested remote convenience function at the vehicle  16 . 
     The transmitter unit  12  is a portable hand-held unit with a housing that encloses its electronic components. The transmitter unit  12  includes at least one manually actuatable pushbutton electric switch. In the example shown in FIG. 1, there are three pushbutton selector switches  24 - 28 . A first pushbutton switch  24  and a second pushbutton switch  26  are associated with door lock and unlock functions, respectively. A third pushbutton switch  28  is associated with a vehicle alarm or “panic” function. It will be appreciated that the system  10  could be configured to control different remote convenience functions, and that the transmitter structure (e.g., the number, type, and the location of the pushbutton switches on the transmitter) would be accordingly different. 
     Each actuation or predefined series of actuations, of one of pushbutton switches (e.g.,  24 ) of the transmitter unit  12  is a request to perform a corresponding predefined remote convenience function. For example, actuating pushbutton switch  24  is a request to lock the doors of the vehicle  16 . The pushbutton switches  24 - 28  are operatively connected to a transmit radio frequency (RF) circuitry  32  within the housing of the transmitter unit  12 . The transmit RF circuitry  32  is, in turn, operatively connected to a broadcast transmission antenna  34 . 
     In response to pushbutton actuation, transmit RF circuitry  32  generates/assembles a “packet” of information to be transmitted. The transmission packet includes a start/wake-up portion, a security code, and at least one command that represents the remote function request. The transmit RF circuitry  32  then provides an appropriate electrical signal  36  that conveys the transmission packet to the antenna  34 . In response to the stimulus of the electrical signal  36 , antenna  34  broadcasts the signal  18 , which is intended to be received by the receiver/controller unit  14  at the vehicle  16 . Preferably, the transmitted signal  18  is a pulse-width-modulated (PWM) signal that has a radio frequency (RF) carrier frequency. It is to be appreciated that other signal types (e.g., frequency modulation, frequency shift key) can be used without deviating from the present invention. 
     Within the receiver/controller unit  14 , an antenna array  40  is operatively connected to a receiver portion  42 . The antenna array  40  provides a RF electrical signal  44  that conveys the contents (e.g., a security code and a function request message) of the transmitted signal  18  that has been received. The receiver portion  42  processes the conveyed information and provides a signal  46  to a controller portion  48 . Specifically, in one preferred embodiment, the receiver portion  42  includes an amplifier, a mixer that beats the signal with a local oscillator signal, a buffer, and a bandpass filter. Thus, the signal is converted to an intermediate or baseband frequency having a plurality of pulses. Each pulse has amplitude that is dependent upon the strength of the transmitted signal  18 . 
     Within the controller portion  48 , the information-conveying pulses are processed to determine if the transmitted signal  18  includes a proper security code and to determine the function that is requested. If the transmitted signal  18  includes the proper security code, the controller portion  48  provides an appropriate signal  50  to the corresponding vehicle system  20  (e.g., door lock actuator system) to cause performance of the requested function. 
     With regard to the convenience functions that are remotely controlled via the system  10 , the person of ordinary skill in the art will understand the vehicle systems  20  and the operation of such functions, as they are known in the art. Accordingly, detailed descriptions of such systems and functions are not provided herein and for brevity. Also, it will be appreciated that the present invention is applicable to other non-automotive, remotely controlled functions (e.g., garage door opening or entry light activation). 
     Within the receiver portion  42 , the RF signal  44  provided from the antenna array  40  is converted to a lower frequency in order to permit processing. Accordingly, the receiver portion  42  includes a carrier frequency processing circuitry  54 . In one example, the. carrier frequency processing circuitry  54  includes a front-end amplifier  56  that receives the RF signal  44  that is output from the antenna array  40 . A signal  58  output from the amplifier  56  is provided as a first input to mixer  60 . A local or reference oscillator  62  provides an oscillating signal  64  at a reference frequency as a second input to the mixer  60 . 
     The mixer  60  combines the two input signals and outputs a signal  66  that has frequency component values that are at the sum and difference of the frequency values of the two input signals. In other words, the mixer  60  “beats” the first input signal  58  with the second input signal  64 . The “difference frequency” value is at the IF frequency. 
     The carrier frequency processing circuitry  54  includes a buffer  68 , a bandpass filter  70 , and an amplifier  72  for handling the IF frequency signal output from the mixer  60 . The buffer receives the signal  66  output from the mixer  60 , and provides an output  74  to the bandpass filter  70 . The bandpass of the filter  70  is centered on the IF frequency. Thus, other frequency components, such as the “sum frequency” produced in the mixer  60 , are removed. The amplifier  72  amplifies a signal  76  output from the filter  70 , and provides an IF signal  78 , which is the output from the carrier frequency processing circuitry  54  and provided to a first node  80 . 
     It is to be appreciated that the signal  78  is comprised of a series of pulses that convey the contents (e.g., start portion, security code, function request) of the transmitted signal  18 . Each pulse of the signal  78  has amplitude that is dependent upon signal strength. Preferably, amplitude is represented by voltage amplitude. 
     The signal  78  output from the carrier frequency processing circuitry  54  must be further processed to differentiate between pulses that convey information and pulses that are the result of noise and the like. Also, this further processing permits transmitted signals  18  that have insufficient strength to be ignored by the receiver/controller unit  14 . Thus, only pulses that meet certain criterion are passed along to the controller portion  48  for decoding, etc. The criterion used to screen-out certain pulses is adjustable and is provided by the structure set forth below. 
     The first node  80  is connected to a first input terminal of the comparator  82 , and the signal  78  is provided as a first input to the comparator. A second node  84  is connected to a second input terminal of the comparator  82 , and a reference voltage is supplied as a second input signal  86  to the comparator. When the voltage amplitude of the first input signal  78  is greater than the voltage amplitude of the second input signal  86 , the output of the comparator  82  is a HIGH. The duration of the HIGH is dependent upon the time that the pulse voltage exceeds the reference voltage (i.e., generally equal to the duration of the pulse of the first input signal  78 ). When the voltage amplitude of the first input signal  78  is less than the reference voltage of the second input signal  86 , the output of the comparator  82  is LOW. Thus, the reference voltage is a threshold value. 
     The reference voltage at the second node  84  is the voltage across a capacitor  88  that is connected between the second node and electrical ground. Electrical energy is supplied to the second node  84  by a regulated voltage source voltage source V cc  (e.g., a battery of the vehicle  16  and regulation circuitry) connected to the second node  84  via a resistor  90 . 
     The first and second nodes  80  and  84  are connected together via a resistor  92 . Thus, the first input signal  78  is capable of influencing the reference voltage at the second node  84 . It is to be appreciated that the amount of influence caused by the first input signal  78  is dependent upon pulse duration and pulse voltage amplitude of the first input signal. 
     In order to compensate for the influence, a microprocessor  100  is provided. The microprocessor  100  has the capability to either draw current from or supply current to the second node  84 . The microprocessor  100  is connected, via a line  102 , to the second node  84  to monitor the reference voltage. A current-supply terminal  104  of the microprocessor  100  is connected to the second node  84  via a diode  106  and a resistor  108 . A current-sink terminal  110  of the microprocessor  100  is connected to the second node  84  via a diode  112  and a resistor  114 . Thus, the reference voltage of the second input signal  86  is controlled by the microprocessor  100 . The current flow between the microprocessor  100  and the second node  84  can maintain the reference voltage despite influence of the first input signal  78 . Thus, threshold saturation (i.e., the reference voltage rising toward the level of the pulse amplitude) and threshold depletion (i.e., the reference voltage sinking to the signal noise floor) are avoided. 
     The current flow between the microprocessor  100  and the second node  84  can also change (increase or decrease) the reference voltage to a new level. Decreasing the reference voltage results in a weaker signal (i.e., with lower amplitude pulses) being permitted to “pass” the comparator  82 . Increasing the reference voltage results in the opposite effect. This provides an ability to accept certain signals and to ignore other certain signals, dependent upon signal strength. 
     During operation, when the first input signal  78  goes HIGH at the beginning of a pulse, a certain amount of electrical energy flows through the resistor  92  to add charge to the capacitor  88 . Similarly, when the first input signal  78  goes LOW, electrical energy from the capacitor  88  can flow through the resistor  92  and discharge the capacitor. 
     If the reference voltage at the second node  84  is not controlled, the duty cycle of the first input signal  78  may cause a migration of the reference voltage value away from its intended amount. Specifically, if the duty cycle of the first input signal  78  is close to fifty percent, the signal-induced charge time (i.e., the time that the signal  78  adds charge to the capacitor  88  during each pulse) has about the same duration as the signal-induced discharge time (i.e., the time that charge is detracted from the capacitor  88  during the absence of a pulse). Thus, the reference voltage level would not tend to migrate. However, if the duty cycle of the first input signal  78  is much higher than fifty percent, the charge time is much longer than the discharge time. The result is that the reference voltage at the second node  84  migrates to a higher level. It is possible that the reference voltage (i.e., the threshold level) could reach the level of the pulse HIGH value of the first input signal  78 . At this point, the data would be corrupted by any noise on the first input signal  78 . If the duty cycle of the first input signal  78  is much lower than fifty percent, the charge time would be much less than the discharge time. The reference voltage would decay toward a noise floor. Again, noise would be a corrupting factor. 
     However, in the present invention, the microprocessor  100  monitors the reference voltage and can provide an offsetting charging energy, via the terminal  104 , or drain energy, via the terminal  110 , to hold the reference voltage at a near constant level. Further, as noted above, the microprocessor  100  can be used to adjust the reference voltage to a new level and hold the new level for the entire comparison process. This is accomplished without changing any of the circuitry. Specifically, without changing any of the values of the resistors or the capacitor. Thus, the receiver portion  42 , in accordance with the present invention, can be used with transmitter units that have different signal duty cycles and different signal strengths. Also, different control ranges can be established. 
     FIG. 3 illustrates a second embodiment of the receiver portion in accordance with the present invention. The receiver portion of FIG. 3 is designated  42 ′ and is similar to the receiver portion  42  of FIG.  2 . Structures that are identical for the two embodiments are identified by identical reference numerals. 
     The second embodiment of the receiver portion  42 ′ (FIG. 3) differs from the first embodiment in that electrical energy is not provided via the source V cc  and resistor  90  of the first embodiment shown within FIG.  2 . Instead, the second node  84  (FIG. 3) is connected to a bank of parallel resistors  202 A- 202 N. Each of the resistors  202 A- 202 N has a different resistance value. For example, resistor  202 A may be 1M ohms,  202 B may be 2M ohms (i.e., double), etc. Each of the resistors  202 A- 202 N is connected to a respective terminal (e.g.,  204 A) of a microprocessor  200 . 
     Each of the terminals  204 A- 204 N may output electrical energy that is transferred, via its associated resistor, to the second node  84 . The different resistor values result in different amounts of electrical energy provided from each terminal. Accordingly, dependent on which terminals  204 A- 204 N of the microprocessor  200  are activated to output electrical energy, a variable amount of electrical energy is provided to the second node  84  to charge the capacitor  88 . Thus, the resistor network acts as a digital-to-analog converter. 
     One or more diodes (not shown) can be added to control the flow of current. The microprocessor  200  is connected, via a line  206 , to the second node  84  to monitor the reference voltage. 
     In addition, the terminals  204 A- 204 N of the microprocessor  200  can permit current to flow into the microprocessor from the second node  84  (i.e., the microprocessor can act as a current sink). The amount of current that flows at each of the terminals  204 A- 204 N is dependent upon the value of the associated resistor. Accordingly, the amount of total energy drawn from the second node  84  by the microprocessor  200  is dependent upon which terminals of the microprocessor are activated to draw current. One or more diodes (not shown) can be added to control the flow of current. 
     Thus, it is to be appreciated that electrical energy can flow from the microprocessor  200  to the second node  84 , or from the second node to the microprocessor. Thus, the reference voltage value at the second node  84  is provided and adjusted by the microprocessor  200 . Adjustment can be for either maintaining a constant reference voltage value, or to change the reference voltage value for the entire signal duration. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.