CA1336722C - Passive keyless entry system - Google Patents

Abstract

A passive keyless entry system is disclosed that is specifically adapted for use with automotive vehicles. The system is designed to automatically unlock the vehicle as the operator approaches the vehicle. The system is further designed to automatically lock the vehicle as the operator, carrying the beacon, moves away from the vehicle. The system includes a portable beacon that is carried by the operator, a receiver/controller located in the vehicle, and an antenna connected to the receiver/controller for receiving the encoded transmission from the beacon. The beacon includes a motion sensor to conserve battery life when the beacon is stationary. Transmission between the beacon and the receiver/controller is characterized by a magnetically coupled radio frequency signal embodying differential phase encoded data with error correction coding of the data to enhance noise immunity and signal discrimination.

Description

1 33~7~2 PASSIVE ~F~F~S ENTRY SYSTEM

Background and Summary of the Invention The ~-es~,L invention relates to electr~nic keyless entry systems and in par~;c~ r to a passive keyless entry ys~" that is parti~ll~rly adapted for use with au~.~Live vehicles.
Automotive keyless entry systems, when first intro~lce~, typically inClu~ a numerical keypad located on the exterior door panel of the vehicle. m e opera~L entered a unique multiple digit code on the keypad to automatically unlock or lock the vehicle.
Recently, more sophisticated keyless entry systems for vehicles have been proposed which use a portable remote transmitter that is carried by the u~e~a~ol and a receiver located in the vehicle that is adapted to unlock the vehicle in response to the detection of a coded radio frequency signal or a coded optical signal received flom the ~r~n~m;tter. Such systems require that the operator actuate a button o~ switch on the transmitter to initiate the tr~ncmi~s;~n~ s;m;l~r to the operation of a ~ ional automatic garage door opener, in order to conserve battery life and prevent inadvertent actuation.
While re convenient to ~perate than the keypad-type keyless entry systems, the latter transmitter/receiver-type systems nonetheless require that the uye~a~b~ physicAlly locate the transmitter and actuate a button to unlock the vPh;cle. Hence, the convenien oe provided by such a system versus a w lv~.~ional key and lock a,la,~lt~.~ is not s~L~L~- ially ~l~lo~a.
In addition, while other types of "keyless" entry systems are known and presently used in other applications, these systems for various reasons are generally not suitable for au~ ive use. This 6 ~ 2 2 wDuld i ncl ~lAP systems employing magnetic card readers, inLe~oyaLion/tran~pn~Apr-type systems, and ~,J~,Lional automatic garage door openers. A magnetic card-type system is probably adaptable to auL~.vLive use, but provides little added benefit to justify the PXpPn.CP. I~lLeL~ydtor/L~ lpr-type ~y~L~ls~ though adaptable to o~e~aLe in a totally passive manner, are more complex and therefore more PxrPnsive~ and ~les~lL a power cnn~r~?tion problem as the intP~LoyaLo~ therefore must be on and i..Le~uyaLing at all times.
In a~dition, the transponder in such systems must be capable of receiving as well as transmitting data, thus adding to cost. Lastly, au~ aLic garage door systems, while appearing to employ 5;m;lAr technology have su~sL~-Lially different operating requirements which result in significantly different circuit designs. In part;~llAr, an automDtive keyless entry system must possess a level of noise immunity and signal discrimination that is substantially greater than that required for an ~uL~uaLic garage door opener. This is due to several factors ;ncl~lA;ng the many different enviluluænLs in which vehicles may be located, the greater number of vehicles that may be e~l;FpeA
with oomparable systems, and the fact that large numbers of vPh;cles are fL~u~ly located within close proximity to one another, such as in parking lots. In addition, au~.~Lic garage door systems require that the ~y~aLo~ actuate a transmitter, and therefore are not totally passive. Also, garage door u~ -type ~y~ have a substantial range and therefore can ~o~- ially activate a function, such as unlocking the trunk of the vehicle, when the o~erator is some distance away from the VPhiclP and unaware the trunk has b en opened.

1 33~722 Accordingly, it is the primary object of the present invention to provide a totally passive keyless entry system that is espec; A 1 1 Y
adapted for use with automotive vehicles.
It is also an object of the present invention to provide an auL~,oLive keyless entry system that is adapted to auL~,~Lically unlock the vehicle as the u~eLdtoL apprDaches the vehicle.
In addition, it is an object of the present invention to provide a passive keyless entry system having a beacon/transmitter that is e~ LL~I~1Y small in size and includes a mDtion sensing switch that a~L~.aLically activates the tran.smitter in the beacon whenever ll~V~I~ of the beacon is sensed.
It is a further object of the ~leserl~ invention to provide a passive keyless entry system that employs electronic circuitry which permits the system to function in the micr~power range while in its ;escPnt state.
Addi~;~nAlly, it is an object of the present invention to provide a passive keyless entry system having an acceFtable operating range between the beacon and receiver while providing a projected beacon baLLeLy life in excess of one year.
Further, it is an object of the present invention to provide a passive keyless entry system that employs signal trancm;cs;~n and ccding ter-hn~ s which provide a high level of noise imm~nity and signal discrimination.
It is also an bbject of the ~es~ invention to provide a passive keyless entry system that is rpli~hle and yet is relatively ;ne~rPncive to mAmlfA~ture.

In general, the passive keyless entry system acoording to the present invention w mprises three basic onm~n~ts: a transmitter or beacon, a re oe ivertcontroller, and a re oe iving antenna. m e beacon, which is small enough to be attached to a keychain, is carried by the operator and ino~L~u-~ es a motion sensor that is used to energize the transmitter portion of the beacon. m e transmitter in the beacon is adapted to emit a ooded r~;o L~ y signal that w ntains both identification and function information and an error w L~ ion code.
m e beacon is designed to continue to transmit repeatedly its c~ded signal until no motion is detected for a predet~rm;ne~ period of time.
m us, the motion sensor serves to ~L~L~ heAcnn battery life and enables the present system to function in a totally passive manner.
e receiving antenna w mprises a c;~le coil of wire, wound to be sensitive at the transmitted f~ y of the ~eAo~n. The antenna is located at a position on the vehicle to optimize the ~e~ro~,~nce of the system. It has been found desirable to adapt the system so that the receiver/controller is responsive to the signal from the beacon when the ~eAo~n comes within 3 - 6 feet of the vehicle.
m e receiver/controller is lLU~l~e~ inside the vehicle and is adapted to o~e~e on the v~hicle's 12 volt negative ground batter~.
Vpon receipt of a radio frequency 5;~nAl from the antenna, the re oe iver/ w ntroller is adapted to pro oe ss the coded radio frequency signal and evaluate the serial data oontained therein. If the signal is d~ in~ to be valid, the re oe iver/oontroller automatically unloc~s the driver's-side vehicle door.
Op~ Ally, the heAonn may be provided with function switches which, when depressed by the operator, change the function code contained in the radio frequency signal, thus directing the receiver/oontroller to open the vehicle trunk and/or ~elf~ , other functions. In addition, the receiver/controller in the p~es~lL system is adapted to automatically lock the vehicle doors when the operator leaves the vehicle and carries the heAo~n out of range of the receiver/oontroller, A~ ~ing the proper status of the ignition and doorjamb switches.
Additional objects and advantages of the present invention will hecnr~ apparent upon reading the following description of the preferred ~mho~;mPnt of the present invention which m2kes refe,~c~ to the drawings in which:

Brief Description of the Drawings Figure 1 is a diagrammatical view illustrating the preferred A~l;cAtion of the ~le~L invention;
Figure 2 is a partial cutaway view of the receiving antenna used in the present invention;
Figure 3 is a timing diagram illustrating the Miller eno~ding ter~n;que used in the preferred embodiment;
Figure 4 is a ~e~e~Live view of the hP~nn/transmitter of the es~.~ invention;
Figure 5 is a circuit diagram of the beaoon/transmitter shown in Figure 4;
Figure 6 is a block diagram of the heAOnn/ ~ l; tter shown in Figure 5;
Figure 7 is a timing diagram illustrating the various signals pr ~ ~ce~ by the timing ~vl~Ll~ller 54 shown in Figure 6;

Figure 8 is a block diagram of a linear Np stage shift register used to generate the error correction code polyn~m; Al used in the preferred em~o~;mPnt;
Figure 9 is a diagrammatical view of the steps used to y~leLaLe the L~ tted ~PAC~n ccde;
Figure 10 is a detailed circuit diagram of the antenna driver circuit 66 of Figure 6;
Figure 11 is a oombined timing and circuit diagram illustrating the ll~lt~ in which the bipolar driver signal is generated;
Figure 12 is a signal diagram illustrating the waveform of the resulting bipolar drive signal sl~plie~ to the hPAc~n antenna;
Figures 13a - 13c are circuit diagrams of the receiver/controller according to the present invention;
Figure 14 is a block diagram of the bipolar F~ont end and digital data detect custom in~eyra~ed circuits used in the receiver/controller;
Figure 15 is a detailed block diagram of the clock generator circuit shown in Figure 14;
Figure 16 is a detailed block diagram of the carrier s~ll~ ~ullizer circuit shown in Figure 14;
Figure 17 is a detailed block diagram of the lock de~e~o~
circuit shown in Figure 14; and ll Figure 18 is a detailed block diagram of the data extraction circuit shown in Figure 14.

Detailed Description of the Preferred Embodiment Referring to Figure 1, a diayr~l~Lic view illustrating the application of the present invention as an entry system for an aul~ ilP 10 is shown. As depicted in the drawing, the h~Ao~n (o~n oe ~ ) is adapted to be carried by the driver 12 and is ~es~ollsive to the motion created as the driver waLks to energize the transmitter portion of the hPAoon. While energized, the transmitter portion of the hp~oQn continuously L~ ~ts a ooded radio r-~U~l~y signal which inclu~es identification and function data, and an error correction code. When the driver oomes within range of the vehicle ~ a~ u~imately three feet in the preferred Gmh~;mPnt- the receiving antenna (also conceAle~) located on the vPhicle magnetically couples the transmitted beacon eneryy into the re oe iver/controller.
The antenna 14 (Figure 2) in the preferred embcdiment is located in the B-pillar 16 of the vehicle as this location has been experimentally determined to produce the most favorable results.
However, other locations on the vehicle have been found to be ac oe ptable. Mb-~ov~r, in view of the llay,leLic coupling between the heA~n and re oe iver, it is poss;hl~ to co~ ul the field of the antenna b~ LU~' iate plA~Pmpnt~ orientation, and confiy-uration of the antenna, and in this m~nn~r provide c w e~ay~ in selected areas, such as in the vicinity of the trunk lid or the driver-side door hA~le.
The re oe iver/oDntroller, which is located in the vehicle, is adapted to p~uuxss the ooded radio fre~uency 5;g~Al received fm m the antenna and ~e~ro ,- the function requested if the identification code is deLe~l,ined to be "valid", where a "valid" code oorr~p~n~c to the code prestored in the reoeiver/controller. Optionally, the beacon may be provided with one or mDre input switches that can be used to transmit up to sixteen different function codes to control various functions in a~dition to unlocking the driver's side door, such as unlocking the trunk, tnrn;~g on the interior lights, etc. Preferably, however, when none of the function switches are depressed, the receiver/controller is adapted to ill~el~leL the ~fAlllt function ccde as a ~-~ for unlocking the driver's side door of the vehicle.
Alternatively, the "~efAlllt" function of the system can be selected to unlock all doors of the vehicle, or any other function desired by the automabile manufacturer. In A~ition, the system is adapted to respn~ to the condition where the driver leaves the vehicle by au~ ically locking all doors of the vehicle a ~edeLermined period of time after the hPAQ~n signal hecnmPs too weak to receive.
Turning to Figure 2, a partial cutaway view of the re oe iving antenna 14 used in the preferred ~mho~;rPnt is shown. The antenna 14 merely comprises a single wire, such as 34-gauge magnet wire, that is ~LCy~ed as shcwn at 18 the number of turns required to provide the desired inductance. Preferably, the magnet wire is w-d~e~ around a stable form to maintain the shape of the antenna rigid so that the inductan oe of the antenna does not vary. A plastic shield 20 may be rlAce~ over the ooil of wire 18 for ~Lo~ec ion. Although the drawing shows the antenna as having a circular shape, other configurations can be used (e.g., lecL~lar) to A~ At,e spa oe ~vnsL~dints at the desired mcunting location. In addition, it may be desirable to add a secon~ grounded wire to the coil for electrical shielding purposes to i"~uv~ the performAnr,P of the antenna. However, this also adds to the cost of the anntena.
1~ 1 CrnT~ln;c~tion Channel In order to conserve the battery pow_r of the beacon and the vPhicl~ ~a--ery, the trAnqm;ss;o~ frequency in the preferred o~imPnt is selected to be a relatively low 98.3 KHz. The frequency of the trAncm;~si~n signal is therefore substantially above most of the low frequency noise that emanates from an automobile and yet the fifth hArmnn;c of the trAn~m;Csion frequency is still below the AM
radio band. Accordingly, interference with AM radio frequency signals is avoided. The beacon antenna comprises a coil of wire as described that is tuned to the selected carrier frequency. m e antenna creates a magnetic field which couples to the coil of wire used for the receiving antenna. The nhA~P in flux caused by the receipt of a signal at the carrier frequency generates a vDltage across the receiving antenna ~Prm;nAl~. When the he~on is placed in the center of the receiving antenna, the resulting voltage can be as high as 2 volts peak-to-peak. Hcwever, as the hPAcnn mDves a few feet away from the C~ L of the re oe iving antenna, the voltage may drop to less th~n 15 mic m volts p~ak-to-peak. m is wide variation in signal level comprises one of the major constraints in the selection of a wLu~liate crnT~m;CAtion ~hAnnPl architecture.
Although many dif~e~ typPs of carrier "n~ tion sr~ es may be employed, i~ frequency shift keying, amplitude shift keying, etc., phase shift keying (nPSKn) has been selected for the preferred Fnho~imPnt. In PSK PnoC~;ng~ the frequency stays the same, but the _g_ .
phase is shifted exactly 180 degrees to dif~e~ iate a logical "1"
from a logical "0". This srh~mP uses a m;n;~ ~ bandwidth, and is very simple to im~lem nt in the transmitter. In particular, PSK encoding may be Aconr~lich~ using an exclusive-OR gate with the carrier ~ Cy supplied to one input and the data signal provided to the other. An additional benefit of PSK e~o~inq is energy efficiency.
SpecifirAlly, PSK ~c~ing uses all of the transmitted energy for informAtion with no energy being separately applied to generate a carrier. Mbl~uvtL~ front end signal ~L~esfiinq of PSK ~nco~in~ can be ~cc~mplished at the receiver using a limiter instead of an a~ ~tic gain control circuit. Hence, sin oe PSK ~nco~inq is defined in terms of phase, the received signal will not suffer when passed through a limiter. The prim~ry disadvantage of PSK encoding, on the other hand, is the need to ~ey~e~a e the carrier at the receiver and thus properly s~ ize the re oe iver to the coded transmitted signal.

Error Correction Code While the use of many different coding schemes is possible, the preferred ~kn~im~nt of the present keyless entry system uses a ooding scheme that employs an error correction oode to improve system ~eLr~.~ e. .~pecifi~Ally~ the use of an error colL~oLion code allows the sysbem to ~lo~elly receive a c~ded trAncm;ssion which may have been partially altered by noise. This ill~LUv~s reception ~eLr~l~la~lce and the respon~e time of the system. In addition, the use of error ~LL~ ion oodes results in a reduction of false de~ec~ions. A false detection occurs any time the receiver/oontroller indicates the detection of a ~alid h~nn key oode when the valid oode was not 1~l 1 3 3 6 7 2 2 transmitted. This can occur due to ~d~" noise, or the presence of another beacon with a s;mil~r ccde that is inooLL æ ~ly ~Pco~e~ into a valid code.
The ooding scheme used in the preferred Pmho~imPnt comprises a 48-bit code with two repetitions. m e first four bits in the coded LL~ II; ssi~ oomprise preselected s~-l~lLo~lization bits which produ oe eight transitions that are ; 1 1eg~1 under the Miller code. m e four SYNC bits are followed by a 4-bit ~ CN oode and a 20-bit IDENTIFICAIICN code. A 24-bit error ooLL~ction code (nECC") is then added to the 24 bits of FuNcTIoN and IDENTIFICATION code. The 4-bit FUNCTION code, as previously noted, provides up to sixteen different FUNCTION codes to selectively control the activation of additional functions as desired, such as trunk unlock, unlock all doors, turn on interior lights, etc. In addition, it will be a~L æ iated that the 20-bit IDENTIFICATION code provides in excess of one m;llion different ID codes, thereby signifir~ntly reducing the probability that tw~
ke~c~nq with the sam~P ID code will be present in the sam~ vicinity at the same tim~.
In that the SYNC bit pattern is the only mechanism that the re oe iver/controller has to s~ ize onto the data for the purposes of Miller ~eco~i~g and ex*raction of the data bits, it is possible for noise to generate a pattern which will cause the re oe iver/controller to begin to read a oode word at the wrong plaoe. Moreover, it is the nature of cyclic oodes that any shifted versian of a legal oode word is itself a legal oode w~rd. The i~ ly synchrcnized oode word oould, therefore, ~ a valid code w~rd for another vehicle and thus cause an i -~ u~er unlocking of a door or activation of another function. To overcome this problem, the coding scheme in the preferred embcdirent ~mploys an anti-slip pattern that is su~erimposed onto the 48-bit code word making an i,~ pe1ly synchronized code word invalid on other vehicles. .~p~c;ficAlly, the 48-bit FUNCTION, IDENTIFICArION, and ECC code word is P~ tcive-OR'ed with a p~de~ ned 48-bit anti-slip pattern. The resulting output from the exclusive-OR gate is then provided to a Miller ~,~del which produ oe s the final ~noc~ transmitted word.
The reason for employing the Miller ~nco~ing techni~le is as follows. One of the characteristics of PSK encoding is the ambiguity at the receiver. This occurs hec;tllce of the exact 180 degree phase shift. Since the signal received for a digital "1" is essentially the negative of the signal transmitted for a digital "On, it is impossible !11 to distinguish one from the other with~ut some prior knowledge. This problem is effectively eliminated by using an edge sensitive data ~n~o~i~g scheme such as Miller ~nao~in~ which has been selected for the present keyless entry system. In Miller e~o~i~g, when a logical "1" is transmitted, a transition always occurs in the mi~le of the bit oe ll. When a logical "0" is transmitted, a transition occurs at the beg;~t;ng of the bit oe ll only if the previously transmitted bit was also a logical "0n. Otherwise, no transition occurs. Miller ~n~o~in~ iS u~ e~ in the preferred P~ho~;mPnt hec~n~e it is relatively simrlP to implement at both the transmitter and receiver/controller.
Miller ~n~n~;n~ is ~Pf;n~ by the followIng table:

n-1 Dn TD2n TD2n+
' O O 1 0 where n is an ill~eytL O.. last n.
Dn_l is the previously transmitted data bit.
When n = O, Dn 1 is defined to be 1.
Dn is the ~u~r~l~ data bit.
TD2n is the first of two transition bits for each data bit.

where 1 indicates a change in the state of the encoded data signal, and O indicates no change.

TD2n+1 is the secnn~ of tw~ transition bits for each data bit.
where 1 indicates a change in the state of the ~nco~F~ data signal, and O indicates no change.
e Miller ~co~;ng table is illustrated for convenient referen oe in Figure 3.
As previously noted, it is ne oe ssary for the receiver to identify the beginning of the encoded tran~mi~sion word and for this ~ ose a 4-bit SYNC ~a~ e ll is added at the beginning of the code word which presents an i 1 l e~ l pattern for Miller ~nco~ing. Rec~ e of this ;ll~g~l nature of the SYNC ~a-L~L,., it can always be dif~e~l iated by the receiver from the oode wDrd. The SYNC pattern used in the preferred ~m~c~impnt is ~efinP~ by the transition string: 01000001, where "1" in~;c~tes a change in the state of the encoded data signal and "O" ;n~ic~tes no change.
In addition, it will be recognized that the re oe iver/controller must separate the signal coming ~ uyll the data channel into individual bits. Sin oe the bits are separated in tim_, this requires a clock. The preferred solution to this problem is a self-clocking code. A self-clocking code is characterized by a reasonable number of transitions that are w~ ef;nP~ with respect to the data bits. It will be a~ ciated, therefore, that sin oe Miller PncD~i~q ensures the presen oe in the transmitted PTlOO~P~ word of a reasonable number of transitions, the use of Miller PnCo~ing also satisfies the requirement for a self-clocking code.

Beacon/Transmitter I

Turning now to Figur_ 4, a Prspective view of the beaoon/transmitter 24 according to the ~les~ invention is shown. In the preferred ~mho~;mPnt, the beacon is packaged in a relatively small, generally rectangular housing 26 approximately 2 inches by 1.5 inches by 0.5 inches in size and having an opPning 28 for conveniently attaching the bPA~nn to a keychain. m e beacon 24 illus-~c~ed in Figure 4 includes two mu ~lAlly actllAhle switches 30 and 32 that are operative to unlock the trunk of the vehicle and unlock the passenger doors. As previously indicated, the beacon may alternatively be provided with additional function switches to control the selective activation of additional functions, such as turning on the interior lights of th_ vehicle. As also previcusly noted, in the default mDde where none of the function switches are de~e5sed, the hPAo~n is a~ e~ to transmit the nlmlork driver's-side door~ function code.
Referring naw to Fi~ure 5, a circuit diagram of the heAonn/transmitter 24 acoording to the ~-es~n~ invention is shown. In the preferred ~mh~;mpnt~ the bPAcon circuit is oomprised of a single custom integrated circuit 40, a battery 42, a coil of wire acting as a transmitting antenna L1, a motion detector 44, a quartz crystal 46, and the two function switches 30 and 32, all mounted to a printed circuit board. The battery 42 utilized in the preferred embodiment is a conventional 3 volt lithium manganese dioxide watch battery. Similarly, the quartz crystal 46 used in the preferred embodiment comprises a conventional 32.768 KHz watch crystal that is used to control the operating frequency of the beacon. In particular, the energy contained in the third harmonic of the crystal frequency signal is used in the antenna driver. The beacon antenna L1 consists of a coil of wire and a tuning capacitor Cl, the values of which are tuned to the third harmonic, 98.304 KHz. The motion detector 44 is a device that is responsive to very slight movements and is adapted to continuously cycle on and of when movement is sensed. In addition, the preferred motion detector is equally sensitive to motion in any orientation of the beacon. A motion detector suitable for use in the present application is disclosed in applicant's U.S. Patent No. 4,833,281, issued May 23, 1989 and entitled "Motion Sensing Switch".
A block diagram of the beacon/transmitter 24 according to the present invention is illustrated in Figure 6. The signal from the motion sensing switch 44 is provided to a motion detector and oscillator enable circuit 50. This interface circuit 50 is always active and is adapted to monitor the state of the motion sensing switch 44 and produce a timed oscillator enable signal at its output 51 whenever a change in the state of the motion sensing switch 44 is detected. In the preferred embodiment, the timed oscillator enable rn/

signal oomprises a 26-secnn~ pulse. If motion continues to be detected, succ~ss;ve enable signals will be produced so that the osc;ll~tor enable signal on line 51 will t~nm;nAte 26 æ conds after all motion of the ~Acnn has oe Ace~. To oonserve battery life, the mDtion detector and oscillator ~nAhl~ circuit 50 is the only circuit that remains active at all times.
In respon~e to the osc;llAtor ~nAhl~ signal on line 51, the osr;llAtor circuit 52 is activated to produ oe the 32.768 KHz crystal clock signal (nXTAL~) at its output. The 32.768 KHz crystal clock signal is provided to a tlming controller circuit 54 that is adapted to produce the various timing signals used for generating the code word, initi~l;7;ng the various circuits, and sequen oe control. The various timing signals pro~ e~ at the output of the timing c~ltroller 54 are illustrated in the timing diagram shown in Figure 7. In part;clllAr, the XIAL divide-by 16 and XIAL divide-by 32 clock signals are prc~ure~ at the Clock [0-2] output lines: the 0-51 State Count corresponding to the 48-bit oode word plus the four SYNC bits, is pro~oe~ at the State Count [0-5] output lines; and the Parity, Miller, FUNCTICN, and IDENIIFICAIION signals are pro~u~e~ at the Oontrol [0-3] output lines. The State [0-1] output line is provided to the ~nc~e~ data ~ ~LaLoL 64 and supplies a sync pulse or end-of-message pulse at the end of each oomplete cycle.
A ~Phypln oe circuit 56 is shown co~ c~e~ to four function switches although, as previously noted, the preferred ~mhc~;mPnt herein u~ es only two function switches 30 and 32. m e four outputs from the debounce circuit 56 are ~ul~e~ ed to the ~PssAqe y~le~a~o~ circuit 58 which oontrols the oonL~,~ of the IDENTIFICATIoN

and FUNCTION ;nformAtion produced at the MES5AOE output. m e status of the four function inputs deter~inPs the ~ L of the 4-bit FUNKTION code. The 20-bit IDENTIFICAIION code, on the other hand, is set at the mAmlf~cturing stage by connecting the 20 input lines (ID0 -IDl9) to the m~SSA9e y~a~O~ 58 to prewnred fused-link jumpers, or to a ~Le~oyL~.~Ied EEPRoM m~n~ry. m e ME~SA~E output from the m~ssAge y~le~aL~L 58 comprises a serial output signal that is provided to the e r o~L~Lion code (ECC) ~oo~r 60. m e EoC ~,~er 60 is adapted to y~eLate a 24-bit error oorrection code based upon the oollLe~lL of the MESSAGE code received from the mPssAge generabor 58.
m e parity bits, or error correction code, are generated using a linear Np stage shift register connected as illusLl~ed in Figure 8, where:
gi is the ith ooefficient of the y~e~aLol polynnm;Al g(X) = 1 + g1X + g2X2 + ... + gn k lXn k 1 + gn kXn k n is the total number of bits in the code w~rd, in this case 48, k is the number of mPssAge bits in the code wDrd, in this case 24, bi is the value stored in the ith register, + ;n~; CAteS an exclusive OR-gate, AND ;n~;CAtes an AND-gate, ll switch is a m~ltiplexer, and "Message" is the bit ~aL~ consisting of the FUNCTION code follcwed by the ID code.
The specific generator polyn~mi~l used in the preferred Pmho~imPnt is as follows:

( ) 1 + X x2 + X4 + ~ + x6 + x8 + X9 + X10 + X13 +

X16 + X17 + Xl9 + X20 + X22 + X23 + X2 .

The anti-slip pattern generator 62 y~elaLes a fixed 48-bit pattern at the samP clock rate as the serial output from the ECC
enco~Pr 60. As previously noted, the anti-slip pattern is super; ~serl onto the oode word to prohibit the receiver from detecting a valid code from another heAcon with a 5imilAr code that is shifted in position relative to the valid beacon oode. ffl is serves to redu oe the prnh~hil;ty of false detection from other heAcnn~. The anti-slip pattern used in the preferred ~mho~impnt which begins in bit position 0 is as follows:

0000 1111 1010 1101 0011 0011.

The two serial outputs flall the anti-slip pattern generator 62 and the ECC Pnco~ 60 are prcvided to the ~oo~ed data generator 64.
me ~n~o~ data yeneraLoL 64 is adapted to exclusively-OR the 48-bit anti-slip pattern with the 24-bit ME~ 3E and 24-bit ECC code w~rd and then Miller encode the data. In addition, the ~ rl~ data genera~or 64 also adds the 4-bit SYNC code to the beginning of the Miller ~n~ d data word. The resulting Pnno~P~ data w~rd is serially provided to an antenna drive circuit 66 which is c~ e~Led to the tuned antenna circuit 68.
To summarize, the various steps for generating the transmitted beacon code are diayla~ ~Lically illusLLaLed in Figure 9. Initially, the 4-bit FUNCTIoN oode is de-~ . ;ne~ in accordance with the status of the various ~ loN switches. The 20-bit IDE~ ATIaN code which is stored in the beaoon chip, is combined with the 4-bit ~N~ ON ccde to m2ke a MESSAOE . Based upon the o~ .L of the MES5AOE , 24 parity bits are generated using the E~r poly~nm;~l. The parity bits are then A~pPn~ to the MESSAGE resulting in a 48-bit code word. Each of the 48 bits in the code word is then Pxcl~lcive-oR~ed with each bit of a ~ ele~,ine~ 48-bit anti-slip pattern. The resulting 48-bit code w~rd is then Miller ~n~Q~e~ and a 4-bit SYNC ~a~Lell" ;11PgAl under the Miller ccde, is added to the he~;nn;n~ of the Miller Pnoo~ word.
Turning now to Figure 10, a detailed circuit diagram of the antenna drive circuit utilized in the preferred ~mho~i~Pnt is shown.
The antenna drive circuit is ~Psigne~ to meet the following objectives: (1) high output efficiency; (2) average battery drain of less than 40 microamps over normal operating o~lditions; (3) frequency tripling to allow the use of an ;l~kL~cive 32.768 KHz crystal osc;llAtor; (4) a reAcnnAhly clean signal ~e~LL~m; (5) freedom fr~m latch-up during normal operation; and (6) a small n~lLe~ of external v~ s. m e preferred ~mho~;m~nt of the present ..
eAo~n/transmitter utilizes a bipolar antenna drive circuit 66 which serves to inject as much energy as possible into the antenna to improve the effic;~cy of the he~r~nn. me bipolar drive circuit 68 ~u~uc~s narrow drive pulses that are provided to the ~ a circuit every 1.5 cycles, alternately driving the antenna circuit toward the baLL~ly voltage and boward ground. With this approach, an output cAr~r;tor C2 is required, and the signal decays for anly 1.5 cycles between pulse injection. An additional benefit of the bipolar drive circuit is that the antenna oscillates at a peak-to-peak voltage equal to the ~a~Le~y voltage.

--1~

To generate the bipolar drive signal, the XTAL clock signal is provided th mugh a time delay circuit 70 to produ oe a DELAYED XTAL
clock signal. ffl e XTAL and DELAYED XTAL clock si~nA 1 ~ are then pr~vided to the inputs of an AND-gate equivalent 72 and a NOR-gate 74 to produ oe a first narrow pulse train on line 76 and a second na w pulse train on line 78 shifted by 180 degrees relative to the signal on line 76. The waveform illus ~ aLe~ above the narrow pulse train waveforms represents the phase-shifted difference between the XTAL and DELAYED XTAL clock signals. The ~Jo~ded Data signal on line 80 is clocked thr~ugh a D flip-flop 82 by the XTAL clock signal to p m vide non-inverted and inverted ~ ~de~ Data 5;9~ on output lines 84 and 86, Le~e~Lively.
The non-inverted and inverted ~,~ Data signals on lines 84 and 86 and the first and secon~ narrow pulse train signals on lines 76 and 78 are provided to a logic gate netwDrk 90 having tw~ output lines 92 and 94. The logic gate network 90 functions in the following manner. When a clock pulse is present on line 76, the presen oe of a logic "1" in the Encoded Data word will result in a HI signal pulse being pro~ure~ on output line 94 and the presen oe of a logic "0" in the ~oo~ Data w~rd will result in a LO signal pulse being pr ~ l~e~
on output line 92. C~llv~lsely, when a clock pulse is ~le~ on line 78, the ~le~,oe of a logic "1" in the ~..~1~1 Data word will result in a HI S;9nA1 pulse being produced on u~4~uL line 92 and the presen oe of a logic ~0" in the ~I~ P~ Data word will result in a LO signal pulse ~eing Fr~hlce~ on cutput line 94. The output signal on line 92 is lnverted by i~lve~Lel 96 and the tWD resulting parallel data signals are then provided to the gates of tWD N-type and P-type transistors Ql and Q2, as illustrated in Figure 11. Note that the period of the tw~ resulting signals provided to the FEIS Ql and Q2 is equal to 1/32.768 KHz or 30.52 microseonn~-~. The resulting bipolar drive signal supplied to the antenna circuit 68 is illustrated in Figure 12. As can be seen LLall the waveform illusLLaLed in Figure 12, the bipolar drive circuit 66 injects energy into the tuned antenna circuit 68 every one-and-a-half cycles, Ll~eL~bY OPt;m;7;ng the amDunt of energy injected into the antenna Ll and improving the eff;ciPncy of the bP~o~.

Re oe iver/Controller Referring now to Figures 13a - 13c, a circuit diagram of the re oe iver/controller 100 according to the present invention is shown.
The re oe iver/controller 100 is adapted to re oe ive the radio frequency signal re oe ived by the antenna, detect the presence of a beacon signal, ~m~nl~Ate the signal, and de~e~--ine the oDnL~ of the serial ;nformAtion being tra ~mitted. If the trAncmi ss;nn is detPrmine~ to be a valid beacon oode, the re oe iver/ccntroller 100 further performs the instructed function corresponding to the function code in the re oe ived transmission.
In general, the re oe iver/oontroller 100 comprises a mi~L~ ter 102 for ~e~ru~ g logical and .-~Lhhl~Lical oAl~llAtions, receiver circuitry for receiving and detecting the ~L~sen oe of a beaoon trAncmi.csion, a non-volatile mEmory devi oe 120 for storing valid identification codes, and output circuitry for controlling various vehicle features such as door and trunk locks. The tw~ inputs 116 and 118 from the re oe iving antenna are provided to an analog receiver 1 3~6722 circuit that is implemented in the preferred PmhQ~;mPnt with a custom ilLeyL~ ed circuit 104. The analog bipolar re oe iver circuit 104 comprises a single conversion supeLl~ elu~yne ~e oe iver having an ~ ;Ate frequency of 4.274 KHz. m e signal received from the tuned antenna coil comprises a voltage proportional-to the magnetic field re oe ived from the h~Aonn. This signal is amplified by a preamplifier, filtered, and mixed with a voltage o~l~Llolled oscillator (nVCOn) frequency signal to create an in~ermP~;Ate frequency (nIF").
m e intPrmP~;Ate frequency signal is further Am~l;f;~ filtered, and limited to CMCS signal levels for process;ng by the digital data detector circuit 106.
The digital data detector circuit 106, which is also i~lP~pnted in the preferred Pmho~imPnt with a custom inLey~aLed circuit, is adapted to detect the presence of a beacon signal and produce an autput signal to "wake up" the mi~lu-vul4~ter 102. The digital data detection circuit 106 also ~mn~ tes the PSK enc~ea signal from the heAo~n. Data S~ ~ ~lization circuitry extracts-the clock from the resulting Miller Pnoo~P~ signal and clocks the data into the mi~ouu~ter. Tb ~mi nimi ~e dvtlaye power cansumption of the receiver/controller 100, the digital data detection circuit 106 also S;gnA1~ the mi~ u~ L~r 102 to g~ into a stand-by mode when the heACnn is aut of range.
In this regard, the bipolAr frDnt end receiver circuit 104, the digital data detection circuit 106, and the voltage regulator 112 are the only circuits that remain active at all tlmes. In the preferred PmhC~imP~t the total quiesoent current draw for the receiver/controller 100 is less than one mill;Am~re. m us, vehicle battery power is conserved.
m e m~i~,o. -,~hlter 102 used in the preferred Pmho~;mPnt oomprises an 840 Series 8-bit miu~K~ ter n~mlf~Lu~ by National Semiconductor. The mi~ ter is ~oy~ d to ~Pco~e the Miller CC~ signal received from the digital data detection circuit 106 and o~ e the resulting bit patterns with the data previously stored in a non-volatile mem~ry 120. Based upon the results of this comparison, the miuL~ lter 102 is further ~uyL~I~l~d to oontrol the activation of various functions such as door and trunk locks. A
separate algorithm stored in the micrc~r~lter is provided for y~ulling new identification codes into the non-volatile mem~ry 120.
Significantly, in the preferred PmhC~;mpnt~ the EEPRoM 120 has the capacity for storing and the mi~Lu~x~ ter 102 is ~oyr~.læd to accept and check for more than one valid he~on oode. In this manner, several different hPao~n.~ can be validated and used in oonjunction with a single receiver/oontroller 100.
In addition, the re oe iver/controller 100 includes interface circuitry 112 ; n~ ; n~ a power regulator and a transient suppressor to isolate the receiver/controller circuitry fram noise on the 12-volt battery lines. The interface circuitry 112 also provides various regulated pcwer supply voltages.
m e various additional inputs to the receiver/oontroller circuit 100 serve the fo~ g functions. m e Rey Switch input is gIr~ ed when the key is in the ignition and serves to inhibit the keyless entry system by gr~nn1in~ the various output lines from the microon~rllter 102 to the relay driver circuits that activate the doors . 1 336722 and trunk lock mech~n;c~. m e Doorjamb input is used by the microcomputer 102 in oombination with the Key Switch input to du~l~Lically lock all of the vehicle dbors when the beacon is out of re oe iving range. In par~ r~ the mi~-loK~ ter 102 is ~Lu~ ~d to au~.aLically lock all of the vehicle dbors a predele~ine~ period of time after the hP~con is out of range and all of the vehicle doors have been clo~e~, but only if the key is not in the ignition. The Hatch or trunk lid input ~;gn~l is provided as a fee~h~k signal to the mi~-~o~ ter 102 to ~ repetitive actuation of the trunk or hatch unlock solenoid. me P1UYLW~ input is used to activate the receiver/controller ~y~ ing mode. A new identification code can then be ~Loy-~,-,ed into the non-volatile memory 120 of the receiver/controller 100. Specifically, to ~1UYL~ a new beacon ID
code into the controller, the Ploy~ input line is y r o~.ded and a hP~Gon is brought within range of the receiving antenna. The ID code from the he~o~n is the~u~l read by the mi~-,u~ ter 102 into the EEPR~M 120. In this manner, if a beacon is lost, a new hP~con with a different identification oode can be provided and the new beacon ID
code conveniently ~uy~ d into the receiver/oontroller 100 by an au~Lized servi oe ~s~nlllel. The Manual Lock and Manual Unlock inputs are provided to the receiver/oontroller 100 to ~ml~lly override the system regardless of the state of the mliuL ~ .,~ ter 102.
In par~ Ar, actuation of the rq~Al lock and/or unlock buttnns on the vPh;cl~ ~rill override the mi~la~ ter 102 and activate the a~ iate lock and!or unlock solenoids regardless of the state of the cxA.LLol outputs fram the mi~la~ Ler 102.

e output tprm;nAlq from the mi~ c~lJ,~ter 102 are provided to various relay driver circuits that serve to activate the various lock and unlock door and trunk mPchAn;qm-q. In a~dition, it is preferred that the relay driver circuits that interface with external relays or 501Pno;~q ir~ e _hort circuit ~l~Le~ ion circuitry to ~u e~L the microc~ LeL 102 and the relay driver circuits in the event of a short in the external relays or solPno;~.
e various relay driver circuits function in essentially the samP manner. Therefore, the following description of the Unlock Driver's Door relay driver circuit can be oonsidered applic~hl~ to the r~mAining relay driver circuits as well.
When the mi~L.~s.,~lter 102 determines from ~cc~ing the function code from a valid hPAo~n tra~mi~sion that the driver's door is to be unlocked, the mi~l~k~ uter 102 produces a logic Hl 5iq~Al at output port L5 on pin 16. The Hl signal on line 124 serves to bias the Darlington transistor Q4 into full oonduction, thereby energizing the relay ooil of relay RXl. Energization of relay ooil RYl in turn serves to energize a motor (not shown) that is operatively connected to the lock mechanism of the driver's door and is effective to unlock the door. As previously not~, if the mAmlAl lock or unlock buttons in the vPhi~le are actuated, the receiver/controller 100 is overridden regardless of the state of the mi~-~o~ ter 102. In part;~llAr, if the manual unlock ~utton is actuated, a positive signal pulse is p mYhl~e~ on line 126 which results in a o~L~ ~ing positive signal pulse being provided at node 128, designated "Point A~ in the circuit diagram. m e positive signal pulse at node 128 is effective to ;mmP~; Ately turn o,n Darlington transistor Q4 as well as Darlington ~ 336722 transistor Q5 to thereby energize both relays RXl and RX2 and unlock the driver's side and pA~s~er doors. S;milArly, if the mAmlAl lock button is actuated, a positive signal pulse is provided on line 130 which results in a positive signal pulse being provided at node 132, designated "Point B" in the circuit diagram. The positive signal pulse at node 132 is effective to turn on Darlington transistor Q6 which in turn energizes relay ooil RX3 and locks all of the vehicle doors.
As also previously noted, the receiver/controller 100 in the present keyless entry system is adapted to inhibit system operation whenever the ignition key is in the ignition. SpecificAlly, upon insertion of the key in the ignition, a LO signal pulse is pro~lce~ on line 134, designated "Point C" in the circuit diagram, which results in a corresponding LO si~nAl being provided on line 136 to the positive input of a comparator 138. This in turn causes the output of comparator 138 to go LO, thereby plllin~ nodes 140 and 142 to ground ~o~lLial and inhibiting the output ports L5 - L7 and G0 of the mi~,o~ ter 102. Accordingly, it will be a~eciated that when the key is in the ignition, the mi~c~ ter 102 is inhibited from activating switching control transistors Q4 - Q6 and Q9 in the various relay driver circuits, thereby effectively inhibiting operation of the ~ysL_...
The additional circuitry 144 shown in the "unlock hatch" drive circuit is provided to deL~-L a short cir~uit in the remotely located unlock hatch solenoid (not shown) and, in such event, pulse width nrY~1lAte the Darlington transistor Q9. Opti~nally, additional circuitry 114 m~y also be provided at the antenna input 118 to provide a oontinuity test for the antenna connections.
Turning now to Figure 14, blocked diagrams of the custam ill~eyL~ed circuits 104 and 106 u~;1i7e~ to process and ~PmY~llAte the ;ncnm;n~ s;q~Al from the antenna are shown. The ~nAlog re oe iver IC
104 comprises a very low power amplifier, filter, and O~ tL el circuit. m e circuit acoepts a n~rrcwtand PSK signal at 98.304 KHz from the tuned antenna circuit. m e signal is am~l;f;~ and muxed down to an in-P~ te frequency (nIFn) of 4.274 KHz in the preferred embodimPnt. m e resulting IF signal is filtered and amplified with the last stage ~L fu~lling a limiting function. The resulting output signal is a 0 - 5 volt square wave signal with an a~l~xImately 50 per oe nt duty cycle.
With part;~ll~r ref~L~Ioe to the drawing, the two output lines, 116 and 118, from the antenna are provided to a differential ~,~lifier 150 which m;n;m;7es common mLde noise and amplifies the antenna signal. The output from the diff~ ial amplifier 150 is provided to a high Q, very narrow bandwidth, hAn~55 filter having a center frequency of 98.304 KHz, the f~yu~lcy of the beacon trancm;ss;~n.
The output from the h~n~r~cs filter 152 is in turn provided to a mixer 154 which o~ LLs the incnring s;gnAl down to an intprmp~;~te ~ i9nAl of 4.274 KHz in the preferred Pmhc~impnt. Mbre par~ lArly, the mixer 154 is adapted to take the difference in LL~tllcy be~ ^n the incnmin~ signal fm m the hAn~cs filter 152 and the ~L~uL signal from the voltage controlled o~cillAtor ~VCO) circuit 160. m e voltage oontrolled osci 11 Ator 160 in the preferred kc~imPnt is designed to lock onto a frequency signal of 102.578 KHz, thus providing the 4.742 KHz differential ~ e~"~l;Ate frequency between the VCO frequency signal and the beacon frequency 5;~nAl. The IF signal on line 155 is A~l;f;e~ by an amplifier circuit 156 and thereafter provided to a limiter circuit 158 which converts the signal to a square wave signal having a~uximately a 50 percent duty cycle.
The resulting output sigTAl from the limiter circuit 158 on line 159 is provided to the digital data detectian circuit 106.
The digital data detector 106 perfoLms the following functions.
A clock generator circuit 162, shown in greater detail in Figure 15, has an oscillAtor circuit 184 which uses the 32.768 KHz crystal 110 (Figure 13a) to generate a 32.768 KHz crystal clock signal (XTAL CLK).
The clock generator circuit 162 also receives the VCO clock signal, and contains divider circuits 163 and 165 which divide down the VCO
clock signal. ffl ese signals are used in the other blocks as timing signals. The carrier S~ wlizer 164 oombines with the voltage controlled oscillAtor 160 in the bipolar front end chip 104 to make up a phase lock loop circuit (PLL). The PLL circuit recreates the carrier frequency ne oe ssAry to de~de the PSK signal. Rapid frequency aoquisitian and phase synchronization with a detected ~eAc~n signal are enhanced by a r,~ y sweep circuit that is controlled by a c~ L~l circuit which ~~ es the VCO Lley~ to the crystal oscillAtor IL~u~ncy when a heA~on is not in range. In this ~ L, the rl~ U~l~y of the VCO circuit is m~de to grAAllAlly sweep up and down around the 102.578 RHz frequency to thereby keep the frequency of the VCO si~nAl within the vicinity of the ~e~Le~ frequency of a beacon trAncmi-csi~n. m e lock detector circuit 166 is adapted to produce a " ~P wake-up si~n~l" when a beacon sigTAl has been dc~ecLed and the receiver is properly synchronized to the beacon signal. In other words, the lock detector circuit 166 is adapted to activate the microcomputer 102 when it is determined that a beacon is present and the beacon signal has been "locked" onto. The microcomputer 102 is programmed thereafter to determine if the received beacon signal contains a valid beacon code. The lock detector circuit 166 essentially comprises a quadrature lock detector and a digital filter. When the phase lock loop circuit acquires both phase and frequency, the lock detector output from the lock detector circuit 166 goes HI. The ~P wake-up signal similarly comprises a pulse which causes the microcomputer 102 to enter its active state. The data extraction circuit serves to demodulate the received signal to recover the data bit stream. A matched filter is included to remove noise from the signal and additional circuitry decodes the Miller encoded recovered transition bit stream. The decoding circuitry includes a clock synchronizer to regenerate and synchronize to the data sample clock which is required to demodulate the Miller encoded signal.
Referring now to Figure 16, a more detailed block diagram of the carrier synchronizer circuit 164 is shown. As previously noted, the purpose of the carrier synchronizer 164 is to recreate the carrier frequency signal in proper phase with the received beacon transmission. The regenerated carrier signal is required to demodulate the PSK encoded beacon transmission. The carrier synchronizer 164 includes the circuit components which, together with the VC0 circuit 160 in the bipolar front end IC 104, comprise a long loop phase locked loop circuit with frequency doubling. In particular, the output signal from the bipolar front end IC 104 on rn/sg line 159 is provided to a shift register 170 which shifts the phase of the ;ncnm;~ s;gnAl by a~laxImately 90 degrees. m e incoming signal on line 159 together with the phase shifted signal on line 171 are then provided to a ~L~U~lCy doubler 172 which mixes the two signals to provide a resulting output signal on line 174 having a frequency double that of the input Ll~u~lcy s;~nAl on line 159. m e doubled L-~u~l~y output s;gnAl (DBL OUT) on line 174 is provided to one input of a phase error circuit 176 which has its other input ~o"lecLe~ to the output of a 90-degree delay cirruit 173. m e 90-degree delay circuit 173 delays the V~O DrV 12 signal from the clock generator circuit 162 by 90 degrees. The phase error block 176 in the preferred hc~;m~t oomprises an exclusive-OR gate which, in a digital system, provides a very close ~ u~Lmation to the mixer used in analog phase lock loop circuits. The duty cycle of the output signal fram the phase error circuit 176 refiects the amcNnt of phase error between the V~O DIV 12 signal and the doubled IF signal on line 174. Exactly 50 ~el ~ lL duty cycle OOLL~UI~S to a zero phase error. Any other duty cycle causes the charge pump circuit 178 to produce a voltage signal on output line 180 which is fed back to the V~O circuit 160 to wLLe~
the V~O frequency and reduce the phase error. When the phase lock l w p circuitry has acquired both the frequency and phase of the h~Aoon signal, the LOCK ~ W signal provided to the charge pump circuit 178 to disable the fn~ncy sweep function.
In order to minLmize the amDunt of time it takes for the receiver/oontroller bo lock onto t~e h~Con transmission, a 32.768 KHz watch crystal 110 (Figure 13a) oomparable to the watch crystal 46 in the beaoon, is ;n~ e~ in the reoeiver circuitry to provide a fixed I .

frequency signAl that closely d~ximates the expected frequency of the heAcon trAncm;-~sion. Re~lr~;ng to Figure 15, the clock geneLaLoL
circuit 162 i~Clll~PS a 32.768 KHz oscillAtor circuit 184 th_t is connected to the watch crystal 110 and is adapted to produce a fixed frequency output signAl on line 185 (XTAL CLR1 substantially equal to the crystal frequency of the hPAQ~n signal. The XIAL CIK signal on line 185 is provided through a pulse ~t~ ~ aL~L 186 which divides the frequency of the XIAL clock signAl by a factor of 3. The resulting pulse y~elaLoL output signal on line 182 is provided to the carrier synchronizer circuit 164 and is used to keep the frequency of the output s;gnAl from the voltage controlled o.scillAtor 160 within the vicinity of 102.578 KHz. In particular, the pulse generator output signal on line 182, together with the VOO DIV 3 signal, are provided to a VCO frequency counter 178 and VCO frequencv counter ~ecodpr 179 which essentially compare the frequency of the V~O signal to the frequencv of the XTAL clock signal. m e output is then provided to a sweep control latch circuit 188 which in turn directs the charge pump circuit 178 to slowly sweep the frequency of the output signal LLC
the voltage controlled oscillator 160 up and down within a couple hundred Hertz of 102.578 KHz. In other words, the VCO frequency ocunter, ~e~X~1P~ ~ and sweep control latch circuits 178 - 180 serve to provide a fee~hA~k loop for the charge pump circuit 178 when no heAoon is within range of the re oe iver antenna bo thereby slowly dither the fre~lPn~y of the V~O si~n~l within the vicinity of 102.578 KHz. In this ~n~r, the re oe iver/oontroller 100 is able to rapidly lock onto the phase of the he~Aoon frequency signal when a valid beaoon signal is deLe~ed. On oe a hPAcr~ oomes within range of the re oe iving antenna, I' I! !

the charge pump circuit 178 is primarily inflll~nce~ by the phase error circuit 176 and thus functions as a w "v~ional phase lock loop circuit. Accordingly, circuits 178 - 180 have no effect on the operation of the phase lock loop circuitry on oe a beacon is within range. ffl is is AC~nm~l;.C~e~ by the lock de~e~ o. circuit 166 which a LOCK ~h'l'~'l' output signal on line 190 when a hPA~n signal is detected that is provided to the charge pump circuit 178 and is effective to dicAhle the frequency sweep function.
Referring now to Figure 17, a detailed block diagram of the lock deLeoLor circuit 166 is shown. As previously noted, the lock detector circuit 166 determines when the re oe iver has de~e~ed and prcperly synchronized to a ~eAnO~ signal and produ oe s a ~ P wake-up signal to turn on the mi~L~al~ter 102. The mi~L~ ~uter 102 thereupon determines if the received signal is from a valid hP~o~n. m e lock de e~oL circuit 166 oomprises an exclusive-OR quadrature circuit 192, a lock detector interval oounter 194, a lock detector low pass filter and comparator 196, a hold-on circuit 198, and a ~ P wake-up circuit 200. In particular, the DBL OVT signal on line 174 fm m the carrier synchronizer circuit 164 and the VCO DTV 12 from the clock generator circuit 162 are provided to the inputs of the exclusive-OR quadrature circuit 192. It will be rec~lle~ that the DBL OUT signal on line 174, which has a frequency twi oe the frequency of the IF C;q~A1 on line 159, has been phase shifted 90 degre_s relative to the IF signal.
Thus, the V~O DTV 12 s;gnAl is 90 deg~ees out of phase with the DBL
OUT signAl on line 174, thereby naking the circuit a true quadrature de~e~Lul. When a hPAnon signal is present and the PLL circuit has aoquired both proFer LL~ and phase, the ~xc~ ;ve-oR quadrature circuit 192 will provide a HI output signal on line 193 mDst of the time. When the PLL circuit is unlocked, the output signal on line 193 will toggle up and dcwn with an average HI time of a wlu~Lmately 50 ~e~c~L. Lock deLecLo~ circuits 194 and 196 are adapted to sample the quadLaLul~ output line 193 over a fixed pPric~ of time and count the JlWl~e~ of samples which are in quad~aLule. In the preferred ~mhQ~imP~t~ lock is in~ic~ted when 384 or re sam.~les are in quadrature out of a possible 511. .~rerif;cAlly, the lock detector counter 196 and interval counter 194 are reset at the same time and clocked by the same VCO DIV 6 clock signal. Interval counter 194 is in~l~lc~ltFrl each clock pulse while the lock de~ecLor counter 196 is in~L~Iæ~Led at a clock pulse only if the output signal on line 193 is HI. If the count total in lock de~e~Lo~ counter 196 is equal to or greater than 384 at the time of the next reset pulse, the hold-on circuit 198 is activated. Hold-on circuit 198 oomprises a retriggerable one-shot circuit that is adapted to m, intain the lock ccndition to the mi~r~A,~uter 102 for a~-u~mately 500 millicec~s aftPr it is no longer 1n~icAted by the oounters 194 and 196. In this el~ the lock deLeuL~L circuit 166 ignores dLu~uuLs in the beacon signal or short-term noise bursts. m e ~P wake-up circuit 200 comprises a D flip-flop that produces a 7.8 milli~pQnn~ output pulse on line 202 that is prcvided to the mi~-L w ~ ter 102 in response to the prodhction of the LOCK ~ output s;gnAl ~r~ll the hold-on circuit 198.
Turning now to Figure 18, a d_tailed block diagram of the data extraction circuit 168 is shawn. As previously noted, the data extraction circuit 168 ~rrY~ tes the inonm;ng PSK ~ P~ signal and runs the resulting data bit stream through a matched filter to remcve noise. Initial ~eco~ing of the Miller ~n~c~ data is pe~,æd and the synchr~n; 7;ng data clock is y~e~a~e~ to ~ Yrl~ the Miller code and clock the data bit stream into the ni~ oc~l~uter 102.
Spec;f;rAlly, the data ~LLa~Lian circuitry 168 includes a data e~LLau ion circuit 204 which comprises an exclusive-OR gate having the PSK ~c~ signAl on line 159 provided to one input and the Syll~l~ V~ 1; 7P~ V~O DIV 24 signal provided to its other input. Once locked onto the heAo~n signal, it will be a~leciated that the frequency of the VCO signal (102.578 XHz) divided by 24 equals the same 4.274 KHz signal as the in~rmP~;Ate frequency (IF) signal on line 159. It will further be a~.eciated, therefore, that the synchronized V~O DIV 24 clock signal contains the recreated carrier phase locked to the in~ ,P~;Ate frequency s;g~Al on line 159. The data extraction exclusive-OR gate 204 ~mn~l-lAte5 the PSK P~co~e~
S; ~A 1 and the output is filtered through a digital ua~ff~d filter circuit 206. The early-late gate data sy~ Lullizer circuit 208 generates the clock signal used to ~Fro~ the Miller e~co~P~ data and clock the data bit stream into the mi~Y ~ q~lter 102. Init;Al ~Pcc~;n~ of the Miller ~co~ transition bit stream is then ~e~roL,~d by the transition data bit stream y~Ld~5l 210. The serial data bit stream is pro~vided to the miuL~ uLe~ 102 on output line 214. The ~ P data hucYl~hlhe circuit 212 interfaces with the mi~L.~ Ler to control the serial inputting of the ddta bit stream into the microoo~puter 102. In the preferred ~mhc~;mPnt, final ~Po~;n~ of the data bit stream is peL~o~l~;rl in the mi~Lo~,4~l~, 102 by software.

While the above description oonstitutes the preferred embodiment of the invention, it will be appreciated that the invention is susceptible to mn~ific~tion~ variation, and change without departing from the ~lu~e~ scope or fair meaning of the ~rQnr~nying claims.

Il

Claims (8)

1 . A keyless entry system for a vehicle having an electric door lock mechanism, and including:
a portable beacon adapted to be carried by the operator of the vehicle and comprising transmitter means for transmitting a coded beacon signal; and receiver means associated with the vehicle and including antenna means for receiving said beacon signal and controller means for decoding said beacon signal and activating a predetermined function associated with the vehicle in response thereto, said controller means being further adapted to automatically activate said electric door lock mechanism to lock the doors of the vehicle after the operator leaves the vehicle and carries said beacon away from the vehicle.

2 . The keyless entry system of claim 1 further including means for producing a first output signal when the ignition key of the vehicle is in the ignition.

3 . The keyless entry system of claim 2 wherein said controller means is adapted to automatically activate said electric door lock mechanism to lock the doors of the vehicle after the operator leaves the vehicle and carries said beacon away from the vehicle only if said first output signal is not present.

4 . The keyless entry system of claim 3 wherein said controller means is adapted to automatically activate said door lock mechanism to lock the doors of the vehicle a predetermined period of time after said beacon signal is out of range of said antenna means.

5 . The keyless entry system of claim 1 wherein said beacon further includes a portable power source, motion sensing means for sensing physical motion of said beacon, and circuit means responsive to said motion sensing means for activating said transmitter means to transmit said beacon signal.

6 . The keyless entry system of claim 5 wherein said transmitter means is inactive and only said circuit means of said beacon is active when said beacon is stationary.

7 . The keyless entry system of claim 3 further including means for producing a second output signal when the doors of the vehicle are open.

8 . The keyless entry system of claim 7 wherein said controller means is adapted to automatically activate said electric door lock mechanism to lock the doors of the vehicle after the operator leaves the vehicle and carries said beacon away from the vehicle only if both said first and second output signals are not present.