POWER SAVING REMOTE KEYLESS ENTRY

Abstract: A keyless entry system for a vehicle such as an automobile. A signal processor (18) can power down processor operating sections such as a data amplifier (12.6) to conserve battery power. The power down sequence takes place after a function is performed in response to an instruction from a hand held transmitter (10). The power up sequence is initiated by transmitting to the processor an encoded signal (N) instructing the processor to power up. A data signal (DB) follows the power-up signal and causes the processor to initiate a function, such as unlocking doors. The processor only initiates this function after the power-up signal disappears. The power-up signal consists of a plurality of tone encoded pulses (TP). A tone decoder decodes these pulses and an instruction signal (DB) from a demodulated electromagnetic signal.

Description: Description Power Saving Remote Keyless Entry Technical Field This invention relates to remotely controlled systems for vehicles, such as automobile keyless entry systems. Background Art Remotely controlled ("keyless") security systems are becoming increasingly popular in automobiles. These systems typically use a small key chain transmitter. The operator presses a button sending a command as a transmitted coded electromagnetic signal using an infrared or RF carrier. The signal is received at a receiver in the vehicle. At the receiver, a signal processor interprets the decoded information and causes the command function to take place, such as unlocking the doors and providing an audible signal heard (a "chirp") audible some distance away from the vehicle, confirming that the command has been received and completed. The receiver and the processor are always in a full power stand-by condition waiting for the command, creating considerable battery drainage, especially if a vehicle is parked for a length of time in colder climates, where available battery power is significantly reduced by lower temperatures. A driver, away for several weeks may return to the vehicle finding a dead battery caused by this continuous power drain in the otherwise "de-powered" vehicle, except perhaps for the clock, although clocks usually blank the A splay when the vehicle is parked to save power. Summary of the Invention According to the present invention, portions of the receiver are "powered down" (a "sleep mode") after security functions are carried out, for example, after the doors are locked. When the user presses the remote transmit, coded signal is transmitted, causing the signal receiver to power-up ("wake up"). It then accepts the coded command. According to the present invention, the signal processor waits until the power-up signal is removed before responding to a command. According to one aspect of the invention, the power-up signal, which proceeds the alarm inactivation signal, comprises a plurality of tone coded pulses. The receiver contains a tone decoder that responds only to particular received pulses. The frequency of the transmitted pulses corresponds to the detection frequency of the decoder and a specified number of pulses must be received. The decoder produces a control signal when those conditions are satisfied. The control signal causes the battery to power the powered down portions of the receiver. According to another aspect of the invention, thus the receiver goes to sleep after the command is completed. According to another aspect of the invention, the last tone pulse (last pulse in the "wake-up signal") initializes a microprocessor routine that interprets the digital command following the wake-up signal. Brief Description of the Drawings FIG. 1 is a functional block diagram of a keyless entry system embodying the present invention. FIG. 2 is a time graph showing the wake-up and command signals. Best Mode for Carrying Out the Invention In FIG. 1, a portable remote-control transmitter 10 contains a transmit button 10.1. A user presses the button to cause the transmitter 10 to transmit a carrier (RF or infrared) modulated by "tone pulses" TP and data bits DB shown in FIG. 2. Those signals consist of a "wake-up signal", first "burst" of tone puises at a particular audio frequency and a command, a digital word of data bits. Pressing the button activates a tone-generator 10.2, connected to an RF/digital output 10.3 that produces the modulated carrier RF which is applied to an antenna 10.4. The modulated carrier RF. comprising the tone puises TP and data bits DB in FIG. 2, is transmitted to a remote receiver 12, associated with the vehicle and powered by the vehicle's battery 14. The carrier RF is received by an antenna 12 and applied to a super regenerative receiver 14 that demodulates the carrier RF producing, on the line 12.2, the two signals TP and DB (one audio pulses at frequency F of the tone pulses TP and the other a "pulse width" modulated digital word with the data characteristics of the data bits of signal DB where a zero is distinguished from a one (zero is "0" and one is " 1 ") by the duty cycle. The signal TP is applied to a tone decoder 12.3, which is responsive to signal TP having the correct audio frequency and number of puises to provide an output "wake-up" signal SIG. 1 on the line 12.31. The wake-up signal is applied to a signal processor 12.4. which controls a switch SW that applies power to a data amplifier 12.6 in response to the wake-up signal, which the decoder only produces when N pulses at frequency F are detected. As discussed below, the processor includes a microprocessor 12.6 that begins a command detection routine when the wake-up signal disappears (when the last pulse of the N + X pulses in signal TP disappears), and if the code is correct, the command is carried out, e.g. the doors are iocked or unlocked. - 3 - The data amplifier 20, though shown as a separate item, should be viewed as part of the signal processor "system" 18, but receives power separately from the battery. The data amplifier 20 provides the signal DB to the processor I/O section on the line 20.1 as a signal DATA. When the signal DATA is received, the processor initiates a decode routine of the signal DATA and sends a signal SIG. 2 to an alarm system 22 that controls the door locks 24. Once the function associated with the command DB is completed (e.g. the door locks are latched or unlatched, the microprocessor again goes into its sleep mode; the power to the data amplifier and the microprocessor is removed by operating switch SW. With the benefit of the foregoing description, one skilled in the art may make modifications in whole or in part through the embodiment of the invention that has been described with departing from the true scope and spirit of the invention embraced by the claims that follow.

Claims: Claims 1. A remote control security system, characterized by: a portable transmitter comprising means for transmitting a signal comprising a code of finite duration preceding a data signal for performing a security function; a battery powered receiver comprising means for receiving said signal, means for detecting said code and said data signal, first control means for initiating said security function in response to said data signal, second control means for providing a first signal to power said first control means in response to said code and discontinuing said first signal after said security function is performed. 2. The invention described in claim 1 further characterized in that: said code comprises N audible tone pulses of finite duration and said second control means comprises a tone decoder that provides an output signal in response to said tones. 3. The invention described in claim 2 further characterized in that said commanded function is identified by a duty cycle of pulses in said data signal and said first control means determines said duty cycle with reference to the last one of said N tone pulses. 4. The invention described in claim 3 further characterized in that said first control means comprises a signal processor having a clock and a data amplifier, said clock and said data amplifier operating from the battery in response to said first signal and being unpowered when said first signal is absent and said clock is triggered by said last tone pulse. 5. A method of battery conservation in a vehicle having a remotely accessed security control system comprising a signal processor, characterized by the steps of: putting sections of the signal processor in a powered down state after a function is performed by the control system; remotely transmitting a signal that contains a coded instruction to power-up said sections and a coded instruction to perform a commanded security function; and waiting until said coded instruction is discontinued to decode said instruction and perform said commanded function. 6. The invention described in claim 5 further characterized in that said sections includes a data amplified and processor clock. 7. The invention described in claim 6 further characterized in that said coded instruction comprises a plurality of tone coded pulses preceding said commanded instruction and said commanded instruction is decoded with reference to the last of said tone encoded pulses.

Inventors: BREHMER GERALD M, FLEISSNER THOMAS, BREHMER, GERALD, M., FLEISSNER, THOMAS
Applicants: UNITED TECHNOLOGIES AUTOMOTIVE, UNITED TECHNOLOGIES AUTOMOTIVE, INC.
Application year: 1993
Main classification: G08C19
IPC codes: B60R25, G07C9, G08C19, H04B1, H04Q9