Vehicle anti-theft alarm system

A vehicle anti-theft alarm system comprises a microwave transmitter and receiver for transmitting microwave frequency signals from one location in the vehicle against a target in the vehicle at a given distance from the transmitter-receiver and for receiving the signals reflected back from the target and producing a monitoring signal representative of a time, frequency or distance parameter for sending and receiving the signals. If, for example, an object is interposed in the path of the transmitted signals, the parameter and thus the monitoring signal changes and a control signal is produced for actuating an alarm. A holding circuit provides for the alarm to remain actuated when the article is removed from the path of the transmitted signals.

BACKGROUND OF THE INVENTION 
The present invention relates to the art of vehicle anti-theft devices and 
systems and, more particularly, to systems producing an audio and/or 
visual alarm in response to unauthorized entry into, or attempted 
unauthorized entry into a vehicle. 
The present invention finds particular utility in connection with detecting 
the unauthorized entry into the driver and passenger compartment of a 
vehicle and, accordingly, will be described in detail herein in connection 
with such use. At the same time, however, it will be appreciated that the 
invention has other utility such as detecting the unauthorized opening of 
a vehicle compartment enclosure such as a door for the driver and 
passenger compartment, the hood closing a vehicle motor compartment and/or 
a vehicle trunk lid. 
Over the past several years, there has been an increasing demand by vehicle 
owners for security devices to deter or prevent vehicle theft and 
unauthorized entry into the interior of a vehicle or into the engine 
compartment or trunk. A wide variety of anti-theft devices and systems 
have been developed in an effort to minimize the foregoing and other 
security problems. Such devices include, for example, steering wheel 
locks, alarm systems and devices which disable certain components of the 
vehicle when a theft is attempted, and electronic security systems which 
actuate an alarm in response to the detection of vibration or other motion 
of the vehicle when the security system is activated. Steering wheel locks 
are of course a good deterrent against theft of a vehicle in that they 
preclude steering thereof. At the same time, they do not preclude a thief 
from breaking into the vehicle driver and passenger compartment or opening 
the hood and/or trunk for the purpose of stealing items such as radio 
equipment, the vehicle battery, a spare tire and any other valuable 
objects which may have been left in the vehicle. The electronic systems 
heretofore provided are intended, primarily, to deter unauthorized entry 
into any compartment of the vehicle and, in this respect, function in 
response to vibration of the vehicle to actuate horns, sirens and/or 
blinking lights to frighten a would be thief away. A persistent problem 
with such vibration responsive security systems is the difficulty to 
adjust the sensitivity thereof so that they are neither over or under 
sensitive. In this respect, if they are too sensitive, the alarm can be 
actuated by wind or other minor movement of the vehicle. On the other 
hand, if they are not sensitive enough, it is possible to carefully gain 
entry to the vehicle without setting the alarm off. This sensitivity 
problem negatively affects the efficiency of such a security system for 
its intended purpose and negatively affects customer acceptance of such 
systems as a viable deterrent to unauthorized entry and/or theft of a 
vehicle or articles therein. In particular in this respect, the actuation 
of such alarm systems in response to movement of a vehicle other than that 
created by a would be thief has become prevalent to the extent that the 
audio and/or visual alarms are often ignored by persons who might 
otherwise intervene and/or take notice of a thief so as to be able to 
identify the latter to authorities. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a vehicle anti-theft security 
system is provided which minimizes or overcomes the foregoing 
disadvantages in connection with systems intended primarily to deter 
unauthorized entry into a vehicle compartment. More particularly in this 
respect, a security system in accordance with the present invention is not 
actuated in response to vehicle motion or vibration but, rather, to the 
unauthorized opening of a vehicle closure member and/or to the 
unauthorized physical entry into the driver and passenger compartment of 
the vehicle. Accordingly, the system cannot be actuated other than by 
physical displacement of a closure member such as a door, trunk lid or 
hood of a vehicle from the closed position thereof, or by a person opening 
a door of the vehicle and entering the driver and passenger compartment 
thereof. This, other than for accidental actuation of the system by the 
vehicle owner, advantageously limits actuation of the system to a positive 
unauthorized attempt to enter the vehicle and thus promotes awareness that 
the audio and/or visual alarm signal from the system is indicative of a 
real theft situation. 
Further, in accordance with the invention, the anti-theft system operates 
in a manner similar to radar in that microwave frequency signals are 
transmitted against a fixed target in the vehicle and reflected back from 
the target to enable establishing a monitoring signal representative of 
the frequency, time and distance parameters for the transmitted and 
reflected signals. For example, a microwave transmitter-receiver can be 
mounted on the interior side of the fire wall of a vehicle on the driver's 
side thereof so as to transmit signals of microwave frequency against the 
front of the driver's seat which provides the target. The signals are 
reflected back to the transmitter-receiver from the target in a 
predetermined time depending on the distance between the 
transmitter-receiver and the seat or target. The interposition of an 
object between the transmitter-receiver and seat or target, such as the 
legs of a would be thief, increases the frequency of the signals and 
reduces the time for the signals to be transmitted and returned to the 
transmitter-receiver and, therefore, changes the monitoring signal. Such 
change in the monitoring signal causes actuation of an audible and/or 
visible alarm, such as a siren, the vehicle horn and/or the vehicle 
lights. In accordance with one aspect of the invention, the alarm or 
alarms when so actuated are maintained operable by a holding circuit 
therefor, regardless of whether or not the object is removed from between 
the transmitter-receiver and target, or the remainder of the system is 
disabled by the would be thief. Preferably in this respect, the security 
system is energized by the vehicle battery and the holding circuit 
connects the audible and/or visible alarm directly to the battery so as to 
maintain the alarm signal independent of the remainder of the security 
system. 
In accordance with another aspect of the invention, the target for the 
transmitted microwave frequency signals can be a closure member for a 
vehicle compartment, such as a door to the driver and passenger 
compartment, the trunk lid and/or the vehicle hood. In an arrangement of 
this character, the transmitter-receiver would be mounted in the 
corresponding compartment at a fixed location relative to the closure 
member when the latter is in its closed position relative to the 
compartment. The monitoring signal in this instance changes upon opening 
of the closure member, whereupon the alarm signal is actuated. Again, a 
holding circuit is preferably provided for maintaining the alarm signal or 
signals, regardless of whether the closure is returned to its closed 
position relative to the compartment and/or the remainder of the system is 
disabled. 
It is accordingly an outstanding object of the present invention to provide 
an improved vehicle anti-theft security system operable upon unauthorized 
opening of a vehicle compartment closure and/or unauthorized entry into 
the driver-passenger compartment of a vehicle to actuate audible and/or 
visible alarms. 
Another object is the provision of a security system of the foregoing 
character which is operable to eliminate actuation of the alarm or alarms 
in the absence of an actual unauthorized intrusion into a compartment of 
the vehicle. 
Yet another object is the provision of a security system of the foregoing 
character which is operable, when actuated, to maintain the audible and/or 
visible alarm signals independent of the actuating portion of the alarm 
system and independent of removal of the intrusive action. 
Still a further object is the provision of a security system of the 
foregoing character employing a microwave frequency signal 
transmitter-receiver for transmitting a signal against a target in or 
associated with a vehicle compartment and receiving the signal reflected 
back from the target to provide a monitoring signal which changes in 
magnitude in response to an unauthorized intrusion into the vehicle 
compartment and provides the basis for actuating the alarm signal or 
signals.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now in greater detail to the drawings wherein the showings are 
for the purpose of illustrating a preferred embodiment of the invention 
only and not for the purpose of limiting the invention, FIG. 1 
schematically illustrates the driver's side of the driver-passenger 
compartment 10 of a motor vehicle and which compartment includes a 
driver's seat 12 supported on the compartment floor 14 for adjustment 
relative thereto toward and away from the vehicle fire wall 16. In the 
embodiment illustrated, the vehicle anti-theft alarm system comprises a 
microwave transmitter-receiver 18 and a microprocessor 20 mounted on the 
compartment side of fire wall 16 with the transmitter-receiver 18 being 
positioned to transmit microwave frequency signals S.sub.T towards seat 12 
and to receive reflected or echo signals S.sub.E. Preferably, the 
microwave signals are transmitted at a frequency of about 2.5 GHz. The 
front of seat 12 provides a target for transmitted signal S.sub.T and, if 
the material of the seat is inappropriate for reflecting echo signal 
S.sub.E, seat 12 can be provided with a target 22 of suitable material for 
this purpose. 
The security system is preferably powered by the vehicle battery 24 located 
in engine compartment 26 of the vehicle, and the system further includes 
an alarm device 28 such as a siren, horn or the like which is actuated, as 
described hereinafter, through a holding switch 30. Holding switch 30 is 
an electronic flip-flop switch which is responsive to sequential pulse 
signals from microprocessor 20, as described hereinafter, to alternately 
change between open and closed modes and which remains in each of the 
modes until pulsed to the other. Preferably, both alarm 28 and holding 
switch 30 are mounted on the engine compartment side of fire wall 16. 
Battery 24 is connected to microprocessor 20 by line 32 and is adapted to 
be connected to alarm 28 through holding switch 30 such as by a line 34 
between line 32 and holding switch 30 and line 36 between holding switch 
30 and alarm 28. The system functions to be described hereinafter, 
including activation and de-activation of the system, are controlled by 
and through microprocessor 20 and, preferably, the system is activated and 
de-activated by a remote, hand held encoder 38 adapted to transmit radio 
frequency or infrared signals 40 to microprocessor 20. In a well known 
manner, microprocessor 20 includes a receiver responsive to sequential 
signals from encoder 38 to sequentially turn the system on and off. For 
the purposes set forth more fully hereinafter, microprocessor 20 includes 
a timer 42, and the system includes an adjustable reference monitoring 
signal generator 44. 
When microprocessor 20 is activated by remote control encoder 38, the 
component parts of the system are connected in circuit with battery 24 
through the microprocessor. In this actuated condition of the system, 
holding switch 30 is in the open mode whereby the circuit from battery 24 
to alarm 28 is open. Microwave frequency transmitter-receiver 18 is 
activated by the microprocessor through line 46 and transmits microwave 
frequency signals S.sub.T toward target 22 and receives the echo signals 
S.sub.E therefrom and produces a monitoring signal which is representative 
of the frequency of the transmitted and received signals as well as the 
distance between transmitter-receiver 18 and target 22 and the time 
required for a given microwave frequency signal to travel from the 
transmitter-receiver to target 22 and back to the transmitter-receiver. 
This monitoring signal is outputted from transmitter-receiver 18 to 
microprocessor 20 through line 48 and is compared in the microprocessor 
with a reference monitoring signal from reference signal generator 44 
which is representative of the actual frequency, distance and time 
criteria for the transmitter-receiver and target as relatively positioned 
in conjunction with installing the security system. The foregoing 
comparative function is continuous and the system remains in a stand-by 
mode so long as there is no deviation between the monitoring and reference 
monitoring signals. If there is no unauthorized entry, as described below, 
the system can be deactivated by remote controller 38 and holding switch 
30 remains open. 
Prior to describing the operation of the system in response to an 
unauthorized entry into the vehicle, reference is made to FIG. 1 wherein 
the illustration is indicative of the fact that the frequency, distance 
and time criteria are variables in connection with the disclosed 
embodiment as a result of the adjustability of driver's seat 12 toward and 
away from transmitter-receiver 18. Such adjustability provides for the 
front of the driver's seat and/or target 22 if the latter is applied 
thereto to be located between distances D1 and D2 relative to 
transmitter-receiver 18. Accordingly, it will be appreciated that the 
frequency of the monitoring signal will be greater when the seat is 
positioned to provide distance D2 between target 22 and 
transmitter-receiver 18, and that the time for transmitting and receiving 
a reflected microwave signal will be less when the seat is positioned to 
provide the distance D2 between the target and transmitter-receiver. It 
will likewise be appreciated that the difference d between the distances 
D1 and D2 provides a distance-time-frequency window which is preferably 
accommodated in the system so as to preclude having to adjust the 
reference signal generator 44 each time the driver's seat is adjusted to a 
position between distances D1 and D2. This is achieved by programming 
microprocessor 20 to respond only to a deviation between the monitoring 
signal and reference monitoring signal which is not within the 
distance-time-frequency window. This would not be necessary, of course, if 
the target were not adjustable relative to a transmitter-receiver. 
Assuming now that the vehicle operator leaves the vehicle and activates the 
security system through remote control encoder 38 as described above, the 
system functions as follows and as indicated in FIG. 3A. Until such time 
as there is an unauthorized entry into the vehicle, the monitoring signal 
from transmitter-receiver 18 to microprocessor 20 through line 48 is 
within window d, whereby the system takes no action and remains in a 
standby mode in preparedness to respond the an unauthorized entry. Upon 
unauthorized entry, in the embodiment illustrated, the legs of a person 
entering compartment 10 to sit on driver's seat 12 will traverse the 
microwave signals S.sub.T transmitted by transmitter-receiver 18 towards 
target 22 at some point designated in FIGS. 1 and 2 by broken line 50 at a 
distance D3 from the transmitter-receiver and which distance is less than 
the distance D2 and thus outside the window d. Therefore, the distance and 
time for the transmission and return of the microwave frequency signals is 
decreased and the frequency thereof is increased, whereby the monitoring 
signal thereafter outputted from the transmitter-receiver through line 48 
to microprocessor 20 is indicative of the fact that the monitoring signal 
is no longer within the window d. The monitoring signal is then compared 
in the microprocessor with the reference monitoring signal from reference 
signal generator 44 and, in response to the difference therebetween, the 
comparator outputs a control signal which in response to which 
microprocessor 20 outputs a pulse signal through line 52 to holding switch 
30. This pulse signal actuates the holding switch to its closed mode 
completing the circuit between battery 24 and alarm 28, whereby the latter 
is actuated. Since holding switch 30 will remain in the closed mode until 
such time as it is pulsed back to the open mode, alarm 28 is connected to 
battery 24 independent of the remainder of the system and will continue to 
be actuated even if the object interposed between transmitter-receiver 18 
and target 22 is removed or microprocessor 20 is disabled such as by 
removal from the fire wall or physical destruction. In the event of the 
latter, the alarm can be deactivated only by disconnecting the alarm from 
battery 24 such as by severing one of the leads 34 and 36 or disconnecting 
the battery. 
When the system is actuated in the foregoing manner in response to an 
unauthorized entry, and the microprocessor is not disabled, the system can 
be deactivated through the use of the remotely controlled encoder 38. In 
this respect, as will be seen from FIGS. 3A and 3B, the comparator output 
control signal indicative of unauthorized entry provides an "enable" 
signal which prepares microprocessor 20 to deactivate the system in 
response to a subsequent signal received from remotely controlled encoder 
38. Upon receiving such signal from the encoder, microprocessor 30 outputs 
a signal to timer 42 and outputs a pulse signal through line 52 to holding 
switch 30, whereby the latter is actuated to its open mode to disconnect 
alarm 28 from battery 24. Timer 42 provides a delay sufficient to assure 
such opening of holding switch 30 and then deactivates the microprocessor 
and thus the security system. This feature advantageously enables the 
vehicle owner to deactivate the alarm and the system in the event he or 
she accidentally actuates the alarm by entering the vehicle without first 
deactivating the system. Furthermore, this feature enables the vehicle 
owner to deactivate the alarm if a would-be thief has entered the vehicle 
and left without disabling the microprocessor. 
While the embodiment illustrated in the drawings shows the 
transmitter-receiver and target respectively on the vehicle fire wall and 
driver's seat, it will be appreciated that numerous mounting arrangements 
are possible and that the system can be actuated in response to an 
unauthorized entry which would increase the distance between the 
transmitter-receiver and target rather than decreasing the distance by 
interposing an object therebetween. In this respect, for example, a 
transmitter-receiver could be mounted on the passenger side door and the 
target on the driver's side door, whereby opening of either door would 
increase the distance between the transmitter-receiver and target, thus 
changing the monitoring signal and causing the comparator to output a 
control signal in response thereto. Similarly, one of the 
transmitter-receiver and target could be in a fixed location in the 
driver-passenger compartment and the other on one of the compartment doors 
whereby opening of the door would actuate the alarm. Another possible 
arrangement would be to mount the transmitter-receiver on the ceiling of 
the driver-passenger compartment with the compartment floor, seat or other 
object therebeneath providing the target. It will likewise be appreciated 
that the security system could be provided in the trunk compartment or 
motor compartment of a vehicle such that opening of the trunk lid or hood 
would actuate the alarm. These and other mounting arrangements and 
locations will be obvious from the foregoing description. 
While considerable emphasis has been placed herein on the embodiment 
illustrated and described, it will be appreciated that other embodiments 
of the invention can be made and that changes can be made in the disclosed 
embodiment without departing from the principles of the invention. In this 
respect, for example, while the alarm is disclosed as being a siren, it 
will be understood that other alarm devices can be used alone or in 
combination with such a siren. For example, the vehicle horn and/or lights 
can be connected in the alarm circuit. It will be obvious too that the 
hold switch can be mounted in any suitable inconspicuous location in a 
vehicle such as behind the dashboard for example. These and other 
modifications of the disclosed embodiment, as well as other embodiments of 
the invention, will be obvious and/or suggested to those skilled in the 
art upon reading the description herein, whereby it is to be distinctly 
understood that the foregoing descriptive matter is to be interpreted 
merely as illustrative of the present invention and not as a limitation.