RU2243912C1 - Vehicle antitheft system - Google Patents

Abstract

FIELD: transport engineering; security systems.

SUBSTANCE: invention relates to devices aimed at preventing unautorized use of vehicles, such as automobiles. Equipment installed on vehicle contains supply source, current-limiting resistor, remote control selector switch with two antiphase windings, light-emitting diode, sealed contact reed relay, ignition key, relay, master oscillator, phase keyer, transmitter and transmitting antenna. Receiving station mounted on board the flying vehicle has measuring and four radio direction-finding channels including five receiving antennas, search unit, three local oscillators, six mixers, six first intermediate frequency amplifiers, two spectrum width meters, frequency doubler, comparison unit, two threshold units, delay line, three switches, frequency meter, six recorder units, second intermediate frequency amplifier, frequency detector, trigger, four multipliers, four narrow-band filters, four phase detectors and correlator. In process of operation false signals (errors) received by mirror and combination channels are suppressed by correlative processing of channel voltages in measuring channel. Invention provides improved noise immunity, reliable reception of alarm signal on frequency, modulating code and location of hi-jacked vehicle at receiving station.

EFFECT: improved antitheft protection.

5 dwg

Description

The proposed system relates to vehicles, in particular to devices for preventing the unauthorized use of vehicles, such as automobiles.

Anti-theft devices and systems for vehicles are known (RF patents N 2006394, 2011574, 2018128, 2021927, 2033352, 2033353, 2033354, 2040416, 2042548, 2058966, 2061320, 2061321, 2186698: Dikarev V.I. et al. Protection of vehicles from hijacking and theft. St. Petersburg, 2000, etc.).

Of the known devices, the closest to the proposed one is the "Anti-theft system for vehicles" (RF patent N 2186698, B 60 R 25/10, 2001), which is chosen as the closest analogue.

The specified system contains a vehicle power source, current limiting resistor, remote switch, LED, reed switch, ignition key, intermittent signal generator, electromagnetic relay, master oscillator, phase manipulator, transmitter and transmitting antenna.

The receiving station located on the aircraft contains receiving antennas, a search unit, local oscillators, mixers, amplifiers of the first intermediate frequency, a detector, spectral width meters, a frequency doubler, a comparison unit, a threshold block, a delay line, keys, a frequency meter, registration blocks, second intermediate frequency amplifier, frequency detector, trigger, multipliers, narrow-band filters and phase detectors. For direction finding of stolen vehicles, the phase method is used, which is implemented using five receiving antennas located in the form of an asymmetric geometric cross.

Having received at the reception point information on the frequency, modulating code and location of the stolen vehicle, police officers take measures to detain the hijacker. Information from the aircraft is transmitted over the air to search and capture groups. The system provides a complete and unambiguous determination of the location of the stolen vehicle.

However, in the known method, the same value of the first intermediate frequency f _pr1 can be obtained by receiving signals at two frequencies f _o and f _s , i.e.

f _pr1 = f _o -f _g1 and f _pr1 = f _s -f _g1 .

Therefore, if the tuning frequency f _of the main take over the reception channel, along with it will be a mirror reception channel, the frequency f _of which differs from the frequency f to 2f _{of pr1} and symmetrically located (mirror) relative to the frequency f _r1 of the first local oscillator. Conversion on the mirror channel of the reception occurs with the same conversion coefficient K _ol as on the main channel. Therefore, it most significantly affects the noise immunity and reliability of the reception at the receiving point of an alarm signal about the frequency, modulating code and location of the stolen vehicle.

In addition to the mirror, there are other additional (combinational) reception channels. In general terms, any combination receive channel takes place when the following conditions are met:

f _pr1 = | ± mf _ki ± nf _g1 |,

where f _ki is the frequency of the Raman reception channel;

m, n are positive integers.

The most harmful combinational reception channels are the channels generated by the interaction of the carrier frequency f _{о of the} received signal with the harmonics of the frequency of the local oscillator of the small order (second, third, etc.), since the sensitivity of the receiver through these channels is close to the sensitivity of the main channel.

So, two combinational channels with m = 1 and n = 2 correspond to the frequency (figure 4):

f _k1 = 2f _g1 -f _pr1 , f _k2 = 2f _g1 + f _pr1 .

The presence of false signals (interference) received via mirror and Raman channels leads to a decrease in noise immunity and reliability of reception at the receiving point of an alarm signal about the frequency, modulating code and location of the stolen vehicle.

An object of the invention is to increase the noise immunity and reliability of reception at the point of reception of an alarm signal about the frequency, modulating code and location of the stolen vehicle.

The problem is solved in that the anti-theft system for vehicles, containing an intermittent signal generator located on the vehicle, one of the supply terminals of which is connected via the ignition key to the plus bus of the power source, an electromagnetic relay, the winding of which is connected to the output of the intermittent signal generator, and the disconnecting the contact is included in the ignition coil circuit in series with the ignition key, a master oscillator, a phase manipulator, a second input to It is connected to the output of the intermittent signal generator, and a transmitter connected to the transmitting antenna, a remote switch with two antiphase windings and opening and closing contacts, a reed switch, a current limiting resistor and an LED, while one of the current limiting resistor leads is connected to the plus bus power supply windings of the remote switch, and through the ignition key - one of the supply terminals of the master oscillator, phase manipulator and transmitter, disconnecting and the make contacts of the first winding of the remote switch are connected between one of the terminals of the reed switch and the second outputs of the first and second windings of the remote switch, the second disconnect contact of the second winding of the remote switch is connected between the second supply terminal of the intermittent signal generator and the negative bus of the power source, the first disconnect contact of the second winding of the remote a switch is connected between the other terminal of the current-limiting resistor and the anode of the LED, the cathode of which and the other output of the reed switch directly, and the other supply terminals of the master oscillator, phase manipulator and transmitter are connected to the negative bus of the power supply via a second disconnecting contact of the second winding of the remote switch, and a measuring channel located at the receiving point, consisting of a series-connected search unit, the first local oscillator , the first mixer, the second input of which is connected to the output of the receiving antenna, and the first amplifier of the first intermediate frequency, sequentially connected to a frequency warrior, a second spectral width meter, a comparison unit, the second input of which is connected to the output of the first spectral width meter, a first threshold block, the second input of which is connected to the output of the delay line, the first key, the second input of which is connected to the output of the first amplifier of the first intermediate frequency, a second mixer, the second input of which is connected to the output of the second local oscillator, an amplifier of the second intermediate frequency, a frequency detector, a trigger, and a first recording unit, and output to the first local oscillator of the second key, the second input of which is connected to the output of the first threshold block, the frequency meter and the second registration unit, while the output of the first threshold block is additionally connected to the inputs of the delay line and the search block, and four direction finding channels, each of which consists of from a series-connected receiving antenna, a mixer, the second input of which is connected to the output of the first local oscillator of the measuring channel, an amplifier of the first intermediate frequency, a multiplier, the second input of which connected to the output of the amplifier of the second intermediate frequency of the measuring channel, narrow-band filter, phase detector and registration unit, while the second inputs of the phase detectors of the first and third direction-finding channels are connected to the output of the second local oscillator, while the second input of the phase detector of the second direction-finding channel is connected to the output of the narrow-band filter the first direction finding channel, the second input of the phase detector of the fourth direction finding channel is connected to the output of the narrowband filter of the third direction finding the receiving channel, the receiving station is located on board the aircraft, the receiving antennas are placed on the aircraft in the form of an asymmetric geometric cross, at the intersection of which is the receiving antenna of the measuring channel common to the receiving antennas of direction finding channels located in the azimuthal and elevation planes, the measuring channel of the system equipped with a third local oscillator, a third mixer, a second amplifier of the first intermediate frequency, a correlator, a second threshold block and a third key, etc. than the third local oscillator, the third mixer, the second input of which is connected to the output of the receiving antenna, the second amplifier of the first intermediate frequency, a correlator, the second input of which is connected to the output of the first amplifier of the first intermediate frequency, the second threshold block and the third key, the second coupled to an output of the first amplifier of the first intermediate frequency, and an output connected to inputs of the first spectrum and measuring the width of the frequency doubler, the frequency f of the first and third f _{r1 r3} geterod ins are spaced twice the value of the first intermediate frequency

f _g3 -f _g1 = 2f _pr1 ,

selected symmetrical with respect to the carrier frequency f _{o the} received signal

f _o = f _g1 = f _g3 -f _o = f _pr1

and rebuild synchronously.

The structural diagram of the equipment installed on the vehicle is presented in figure 1. The structural diagram of the receiving point, placed on board the aircraft, is shown in figure 2. The relative position of the receiving antennas is shown in Fig.3. A frequency diagram explaining the process of forming additional receiving channels is shown in FIG. 4. Timing diagrams explaining the operation of the system are depicted in figure 5.

The anti-theft system for vehicles consists of equipment installed on a vehicle and a reception center located on board an aircraft.

The equipment installed on the vehicle contains: a power source 1, a current-limiting resistor 2, a remote switch 3 with two out-of-phase windings 4 and 5, an LED 6, a reed switch 7, an ignition key 8, an intermittent signal generator 9, an electromagnetic relay 10, a master oscillator 11 , phase manipulator 12, transmitter 13 and transmitting antenna 14.

The receiving station located on board the aircraft contains: receiving antennas 15, 16, 17, 51 and 52, a search unit 18, local oscillators 19, 37 and 65, mixers 20, 21, 22, 38, 53, 54 and 66, amplifiers 23, 24, 25, 55.56 and 67 of the first intermediate frequency, detector 26, spectral width meters 27 and 29, frequency doubler 28, comparison unit 30, threshold blocks 31 and 69, delay line 32, keys 33, 34 and 70, frequency meter 35, registration blocks 36, 42, 49, 50, 63 and 64, second intermediate frequency amplifier 39, private detector 40, trigger 41, multipliers 43, 44, 57 and 58, narrow-band filters 45, 46, 59 and 60, phase Detectors 47, 48, 61 and 62, the correlator 68.

The system operates as follows.

The vehicle can be in two modes: in normal operation, when the anti-theft system is off, and in security mode, when the anti-theft system is on.

In the first mode, the vehicle is translated by bringing the permanent magnet, made, for example, in the form of a keychain, to the reed switch 7, installed behind the skin of the vehicle in a place known only to the owner. In this case, the winding 4 of the remote switch 3 through closed contacts 4.1 and reed switch 7 is connected to a power source 1. Remote switch 3 is transferred to its first stable state, in which contacts 4.2 are closed and contacts 4.1 are opened. Contacts 5.1 and 5.2 are in open state.

When the ignition is turned on, the supply voltage is supplied to the ignition coils and the engine is operating in normal mode, there is no malfunction in the ignition circuit.

To put the vehicle in security mode, that is, to turn on the anti-theft system, the owner again brings the permanent magnet to the reed switch 7. In this case, the coil 5 is activated and the remote switch 3 is transferred to the second stable state, in which contacts 4.1, 5.1 and 5.2 are closed, and 4.2 contacts open. This situation is shown in Fig 1. In this case, the supply voltage through the current-limiting resistor 2 and the closed contacts 5.1 is supplied to the LED 6, which is activated and signals to the owner that the anti-theft system is turned on.

When the ignition is switched on through closed contacts 5.2, the vehicle body is connected to the second inputs of the intermittent signal generator 9, the master oscillator 11, the phase manipulator 12 and the transmitter 13. The generator 9 starts to generate rectangular pulses (Fig. 5, b), periodically opening and closing the contacts 10.1 electromagnetic relay 10, and the master oscillator 11 begins to generate harmonic voltage (Fig.5, a). In this case, the engine is started during the closed state of contacts 10.1, but theft is not possible, because after some time the generator 9 gives a pulse, contacts 10.1 open, the ignition system and the engine turn on.

A person trying to hijack begins to consistently look for the causes of engine failure. At the same time, it is assumed that most of the faults occur in the ignition system. Usually they start checking the ignition system, since it is most simple to verify its serviceability (by the presence of a spark on high-voltage wires suitable for candles).

Suppose a person trying to hijack has brought a high-voltage wire to the ground and cranks the engine. If there is a spark (the period when the 9-pulse generator does not give out), then the hijacker switches to troubleshooting the power supply system and starts to check the power supply sections sequentially, that is, it moves away from the correct search path.

If there is no spark during the test (the period the generator generates 9 pulses), then the hijacker will examine the electrical circuit and look for the damaged area before the break in the pulse and the failure disappears. This serves as an indication for replacing the allegedly faulty part of the circuit, that is, again misleading. Troubleshooting is getting complicated.

Therefore, the absence of an audible alarm does not cause concern and allows an attacker to engage in their criminal activities for a long time. At the same time, the hijacker, having made repeated attempts to start the engine, still has a real opportunity to detect the presence of an anti-theft system, to reveal the principle of its operation and to hijack a vehicle. To prevent theft of the vehicle, a radio channel is used, through which alarm information is transmitted to the reception center, where measures are taken to organize the detention of the hijacker.

When the contacts 5.2 are closed, the supply voltage is supplied to the intermittent signal generator 9, the master oscillator 11, the phase manipulator 12 and the transmitter 13 through the closed ignition key 8.

Harmonic voltage (figure 5, a)

u _о (t) = U _о Cos (2πf _о t + φ _о ),

where U _о , f _о , φ _о is the amplitude, carrier frequency and the initial phase of the voltage, from the output of the master oscillator 11 is supplied to the first input of the phase manipulator 12, the second input of which is supplied with rectangular pulses (modulating code M (t)) (Fig. 5 B). At the output of the phase manipulator 12, a phase-shift (PSK) signal is generated, which, after amplification in the transmitter 13, is radiated by the antenna and received by a receiving station located on board the aircraft.

If an aircraft is used as an aircraft, then the receiving antennas 15, 16, 17, 51 are located on the fuselage from below, and the receiving antenna 52 is located on the left wing (Fig. 3).

If a spacecraft (object) is used as an aircraft, then special panels are used, similar to panels, which, after the spacecraft is put into orbit, open and are located towards the Earth's surface (Fig. 3).

At the receiving point viewing Df predetermined search frequency range and PSK - signals is performed using the search unit 18 which periodically with a period T sawtooth reconstructs synchronous frequency f _r1 and f _r3 geteredinov 19 and 65. Keys 33, 34 and 70 in the initial state always closed.

Received FMN - signals:

u ₁ (t) = U _with Cos [2πf _о t + φ _к (t) + φ ₁ ]

u ₂ (t) = U _with Cos [2πf _о t + φ _к (t) + φ ₂ ]

u ₃ (t) = U _with Cos [2πf _о t + φ _к (t) + φ ₃ ]

u ₄ (t) = U _with Cos [2πf _о t + φ _к (t) + φ ₄ ]

u ₅ (t) = U _with Cos [2πf _о t + φ _к (t) + φ ₅ ], 0≤t≤T _c ,

where U _s , f _о , φ ₁ -φ ₅ , T _s - amplitude, carrier frequency, initial phases and signal duration:

φ _к (t) = {о, π} is the manipulated component of the phase that displays the law of phase manipulation in accordance with the modulating code M (t) (Fig. 5, b), and φ _к (t) = const for кτ _u <t <(k + 1) τ _u and can change abruptly at kτ _u , that is, at the boundaries between elementary premises (K = 1,2, ... N-1); τ _u . N is the duration and number of chips that make up a signal of duration T _c (T _c = .τ _u ) with an output of antennas 15-17, 51 and 52 fed to the first inputs of the mixers 20-22, 53, 54 and 66, respectively, the second inputs of which a voltage of linearly varying frequency is supplied from the outputs of the first 19 and third 65 local oscillators:

u _g1 (t) = U _g1 Cos (2f _g1 t + πϒ $\genfrac{}{}{0ex}{}{\text{2}}{\text{one}}$ + φ _g1 )

u _g3 (t) = U _g3 Cos (2f _g1 t + πϒ $\genfrac{}{}{0ex}{}{\text{2}}{\text{one}}$ + φ _g3 ), 0≤t≤T _p ,

where u _g1 , u _g3 , f _g1 , f _g2 , φ _g1 , φ _g3 , T _p are the amplitudes, initial frequencies, initial phases and the repetition period of the local oscillator voltages:

ϒ ₁ = Df T _p - the rate of change of the frequency of the heterodynes 19 and 65.

Moreover, the frequencies f _g1 and f _{g3 of the} local oscillators 19 and 65 are spaced by twice the value of the first intermediate frequency

f _g3 -f _g1 = 2f _pr1 ,

selected symmetrical relative to the carrier frequency f _{o the} received signals

f _o -f _u1 = f _u3 -f _o = f _ol and rebuild synchronously.

This circumstance leads to a doubling of the additional receiving channels (Fig. 4), but creates favorable conditions for their suppression due to the correlation processing of channel voltages.

At the terminals of the mixers 20-22, 53, 54 and 66, the voltages of the combination frequencies are formed. Amplifiers 23-25, 55, 56 and 67 are allocated the voltage of the first intermediate frequency:

u _pr1 (t) = U _pr1 Cos (2πf _pr1 t + φ _k (t) -πϒ ₁ t ² + φ _pr1 )

u _pr2 (t) = U _pr1 Cos (2πf _pr1 t + φ _k (t) -πϒ ₁ t ² + φ _pr2 )

u _pr3 (t) = U _pr1 Cos (2πf _pr1 t + φ _k (t) -πϒ ₁ t ² + φ _pr3 )

u _CR4 (t) = U _CR1 Cos (2πf _CR1 t + φ _k (t) -πϒ ₁ t ² + φ _CR4 )

u _CR5 (t) = U _CR1 Cos (2πf _CR1 t + φ _k (t) -πϒ ₁ t ² + φ _CR5 )

u _CR6 (t) = U _CR1 Cos (2πf _CR1 t + φ _k (t) -πϒ ₁ t ² + φ _CR6 ), 0≤t≤T _s ,

where u _pr1 = (1/2) K ₁ U _with U _g1 :

u _pr3 = (1/2) K ₁ U _with U _g3 :

K ₁ - gear ratio of mixers

F _CR1 = f _o -f _g1 = f _u3 -f _o first intermediate frequency:

φ _pr1 = φ ₁ -φ _g1 ; φ _pr2 = φ ₂ -φ _g1 ;

φ _pr3 = φ ₃ -φ _g1 ; φ _pr4 = φ ₄ -φ _g1 ;

φ _pr5 = φ ₅ -φ _g1 ; φ _pr6 = φ ₆ -φ _g1 ;

The _voltages u _pr1 (t) and u _pr6 (t) from the outputs of amplifiers 23 and 67 of the first intermediate frequency are supplied to two inputs of the correlator 68, the output of which produces a voltage proportional to the correlation function R (τ). Since the channel voltage u _CR1 (t) and u _CR6 (t) are formed by the same QPSK signal u ₁ (t), received on the main channel at a frequency f _o (Fig. 4), there is a strong between these channel voltages correlation relationship. The output voltage of the correlator 68 reaches a maximum value of U _max (τ), which exceeds the threshold voltage U _then in the threshold block 69. The threshold level U _{then 1} is selected so that it does not exceed random interference. The threshold level U _{por1 is} exceeded only at the maximum value of the correlator output voltage 68. It should also be noted that the correlation function R (τ) of the PSK signals has a remarkable property: it has a maximum main lobe and a low level of side lobes. When the threshold level U _pore1 is exceeded, a constant voltage is generated in the threshold block 69, which is supplied to the control input of the key 70 and opens it. In this case, the voltage u _pr1 (t) from the output of the amplifier 23 of the first intermediate frequency through the public key 70 is supplied to the input of the detector 26, consisting of measuring instruments 27 and 29 of the spectral width, frequency doubler 28, block 30 comparing the threshold block 31 and the delay line 32.

A voltage is generated at the output of the frequency doubler 28

u ₆ (t) = U _CR1 Cos (2πf _CR1 t-2πϒ ₁ t ² + 2φ _CR1 ), 0≤t≤T _c ,

in which phase manipulation is already absent.

The width of the spectrum of the second harmonic Δf ₂ is determined by the duration T of the signal Δf ₂ > 1 / Tc). Whereas the width of the spectrum of the QPSK signal of the first intermediate frequency is determined by the duration τ _{u of} its elementary premises (Δfс = 1 / τ _u ).

Therefore, when the first intermediate frequency is multiplied by two spectra of the PSK signal, it “folds” N times (Δfc / Δf ₂ = N). This circumstance makes it possible to detect and select the QPSK signal even when its power at the input of the receiving device is less than the power of noise and interference.

The spectral width Δfc of the QPSK signal is measured using a spectral width meter 27, and the spectral width of the second harmonic of the signal is measured using a spectral width meter 29. Voltages U ₁ and U ₂ proportional to Δfc and Δf _2, respectively, from the outputs of the meters 27 and 29 of the spectral width are fed to two inputs of the comparison unit 30. Since U ₁ >> U ₂ , a constant voltage is generated at the output of the comparison unit 30, which is compared with the threshold level U _por1 in the threshold block 31. The threshold level U _por1 is selected so that this level does not exceed random interference. The threshold level U _{por1 is} exceeded only when a complex PSK signal is detected. When the threshold level U _pore1 is exceeded, a constant voltage is generated in the threshold unit 31, which is supplied to the control inputs of the keys 33 and 34, opening them to the input of the delay line 32 and to the control input of the search unit 18, putting it in the stop mode. From this point in time, viewing the specified frequency range Df and searching for the PSK signals stops for the time of analysis and registration of the detected PSK signal, which is determined by the delay time τz of the delay line 32.

The frequency of the local oscillator 19 is measured by a frequency meter 35 and is fixed by the recording unit 36. Knowing the frequency of the tunable local oscillator 19 at the time of detection of the PSK signal, it is possible to determine the carrier frequency f _{about the} detected PSK signal.

Vehicles of certain territories and areas may have their own carrier frequencies, which is an additional sign of recognition of a stolen vehicle.

When the tuning of the local oscillators 19 and 65 ceases, the following voltages are allocated by the amplifiers 23-25, 55, 56, and 67 of the first intermediate frequency:

u _CR7 (t) = U _CR1 Cos [2πf _CR1 t + φ _k (t) + φ _CR1 ]

u _pr8 (t) = U _pr1 Cos [2πf _pr1 t + φ _k (t) + φ _pr2 ]

u _pr9 (t) = U _pr1 Cos [2πf _pr1 t + φ _k (t) + φ _pr3 ]

u _pr10 (t) = U _pr1 Cos [2πf _pr1 t + φ _k (t) + φ _pr4 ]

u _pr11 (t) = U _pr1 Cos [2πf _pr1 t + φ _k (t) + φ _pr5 ]

u _PR12 (t) = U _CR1 Cos [2πf _CR1 t + φ _k (t) + φ _CR6 ], 0≤t≤T _c ,

Voltages u _pr8 (t) -u _pr11 (t) from the outputs of amplifiers 24, 25, 55 and 56 of the first intermediate frequency are supplied to the first inputs of the multipliers 43, 44, 57 and 58, respectively.

The voltage u _pr7 (t) from the output of the amplifier 23 of the first intermediate frequency through the public key 33 is supplied to the first input of the mixer 38, the second input of which is supplied with the voltage of the second local oscillator 37, the frequency of which is stabilized by quartz

u _g2 (t) = U _g2 Cos (2πf _g2 t + φ _g2 ),

where U _g2 , f _g2 , φ _g2 - amplitude, frequency and initial phase of the local oscillator voltage 37.

The output of the mixer 38 is formed voltage Raman frequencies. The amplifier 39 is allocated the voltage of the second intermediate frequency (figure 5, g)

u _CR13 (t) = U _CR2 Cos [2πf _CR2 t + φ _k (t) + φ _CR13 ], 0≤t≤T _c ,

_WP2 where U = (1/2) K _{pr1 1} U U _r2

_np2 f = f _r2 -f _pr1 - second intermediate frequency;

φ = φ _{pr13 pr1} -φ _r2, which is input to the frequency detector 40.

At the output of the latter, short bipolar pulses are generated (Fig. 5, e), corresponding to the moments of the abrupt change in the phase of the received PSK signal of the second intermediate frequency u _pr13 (Fig. 5, g). These pulses are fed to the input of trigger 11. With each positive short pulse, trigger 11 is transferred to one stable state, and with each negative short pulse it is transferred to another stable state. At the output of the trigger 41 are formed rectangular (figure 5, e) corresponding to the modulating code M (t) (figure 5, b). These pulses are recorded by the registration unit 42. In addition, each vehicle has its own modulating code, which consists of address and information parts. The address part consists of n elementary parcels and is used to transmit information, for example, about the number of a parking lot, garage, district, etc. The information part consists of m elementary premises

(m = N-n)

and is used to transmit information about the license plate of the vehicle and its owner. The reception of the modulating code M (t) is extracted from the received QPSK signal without a traditional reference voltage. For this, the structural properties of the QPSK signals, a frequency detector 40, and a trigger 41 are used.

Direction finding of a vehicle that is stolen or stolen is carried out by the phase method, which is characterized by a contradiction between the requirements of measurement accuracy and the uniqueness of the angle reading. To resolve this contradiction, the multiscale direction finding method is used.

The voltage u _pr13 (t) from the output of the amplifier 39 of the second intermediate frequency simultaneously enters the second inputs of the multipliers 43, 44, 57 and 58, at the outputs of which harmonic voltages are formed:

u ₇ (t) = U ₇ Cos (2πf _g2 t + φ _g2 + Δφ ₁ ),

₈ u (t) = U ₇ Cos (2πf _r2 t + φ _r2 -Δφ ₂₎

u ₉ (t) = U ₇ Cos (2πf _g2 t + φ _g2 + Δφ ₃ ),

₁₀ u (t) = U ₇ Cos (2πf _r2 t + φ _r2 -Δφ _4), 0≤t≤T _c,

where U ₇ = (1/2) K ₂ U _pr1 U _pr2 :

To ₂ - the transmission coefficient of the multipliers.

Δφ ₁ = φ ₁ -φ ₁ = 2πd ₁ / λ Cosα,

Δφ ₂ = φ ₁ -φ ₁ = 2πd ₂ / λ Cosα,

Δφ ₃ = φ ₁ -φ ₁ = 2πd ₃ / λ Cosβ,

Δφ ₄ = φ ₁ -φ ₁ = 2πd ₄ / λ Cosβ,

α, β are the angular coordinates of the vehicle (azimuth and elevation).

The indicated voltages are distinguished by narrow-band filters 45, 46, 59, 60 and are supplied to the first inputs of phase detectors 47, 48, 61, 62, respectively. The second inputs of phase detectors 47 and 61 are supplied with voltage u _g2 (t) of the second local oscillator 37. The second inputs of phase detectors 48 and 62 are supplied with harmonic voltages u ₇ (t) and u ₉ (t) from the outputs of narrow-band filters 45 and 59. Accordingly the signs "+" and "-" before the phase shifts Δφ ₁ , Δφ ₂ and Δφ ₂ , Δφ ₄ correspond to diametrically opposite positions of the antennas 16, 17 and 51, 52 relative to the antenna 15.

At the outputs of the phase detectors 47, 48, 61 and 62, constant voltages are formed:

u _n1 (α) = U _n1 CosΔφ ₁ ,

u _n2 (α) = U _n2 CosΔφ ₅ ,

u _n3 (β) = U _n1 CosΔφ ₃ ,

u _n4 (β) = U _n2 CosΔφ ₆ ,

where Un ₁ = (1/2) K ₃ U ₇ U _g2 ,

Un ₂ = (1/2) K ₃ U $\genfrac{}{}{0ex}{}{\text{2}}{\text{7}}$ ,

Δφ ₅ = Δφ ₁ + Δφ ₂ = 2π d ₅ / λ CosAα, d ₅ = d ₁ + d ₂ ;

Δφ ₆ = Δφ ₃ + Δφ ₄ = 2π d ₆ / λ Cosβ, d ₆ = d ₃ + d ₄ ;

which are fixed by blocks 49, 50, 53 and 64 registration.

The receiving antennas 15, 16, 17, 51 and 52 are placed in such a way that the measuring bases form an asymmetric geometric cross, at the intersection of which the antenna 15 of the measuring channel is placed (Fig. 3). In this case, smaller bases d ₁ and d ₃ form coarse, but unequivocal direction finding scales, and large bases d ₅ and d ₆ form accurate, but ambiguous direction finding scales:

d ₁ / λ <1/2 <d ₅ / λ, d ₃ / λ <1/2 <d ₆ / λ

Knowing the flight altitude h of the aircraft and measuring the angular coordinates α and β, it is possible to accurately and unambiguously determine the location of the stolen vehicle.

So, it is supposed to use the phase method of direction finding of stolen vehicles using five receiving antennas located in the form of an asymmetric geometric cross.

Having received at the reception point information on the frequency, modulating code and location of the stolen vehicle, police officers take appropriate measures to detain the hijacker. For this, the received information from the aircraft is transmitted over the air to the search and capture groups, and is also entered in the data bank.

The operation of the system described above corresponds to the case of receiving useful QPSK signals on the main channel at a frequency f _o (Fig. 4).

If a false signal (interference) is received through the first mirror channel at a frequency f _s1 , then the output of the mixers 20 and 66 produces the voltages of the following frequencies:

f _z11 = f _g1 + γ ₁ tf _z1 = f _up1 + γt;

f _s13 = f _g3 + γ ₁ tf _s1 ;

f $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{h11}}$ = 2f _g1 + γ ₂ tf _s1 ;

f $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{h13}}$ = 2f _g3 + γ ₂ tf _s1 ; γ ₂ = 2γ ₁ .

where the first index denotes the number of the local oscillator, the frequency of which is involved in the conversion of the carrier frequency of the received signal:

- the index in power denotes the number of the harmonic of the local oscillator frequency involved in the conversion of the carrier frequency of the received signal.

However, only the voltage with a frequency f _s11 falls into the passband Δf _{p of the} amplifier 23 of the first intermediate frequency. Since there is no voltage in the passband Δf _{p of the} amplifier 67 of the first intermediate frequency, the output voltage of the correlator 68 is zero, the key 70 does not open, and a false signal (interference) received through the first mirror channel at a frequency f _s1 is suppressed.

For a similar reason, false signals (interference) received on the second mirror channel at a frequency f _s1 or on the first combinational channel at a frequency f _k1 or any other additional channel are also suppressed.

If false signals (interference) are simultaneously received through the first and second mirror channels at frequencies f _s1 and f _s2 , then the outputs of the mixers 20 and 66 generate voltages of the following frequencies:

f _z11 = f _g1 + γ ₁ tf _z1 = f _up1 + γ ₁ t;

f _s13 = f _g3 + γ ₁ tf _s1 ;

f $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{h11}}$ = 2f _g1 + γ ₂ tf _s1 ;

f $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{h13}}$ = 2f _g3 + γ ₂ tf _s1 ;

f _z31 = f _z3 -f _g1 -γ ₁ t;

f = f _{z33 P3} -f _r3 -γ ₁ t = f _up1 + γ ₁ t;

f $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{z31}}$ = 2f _g1 + γ ₂ tf _s3 ;

f $\genfrac{}{}{0ex}{}{\text{(2)}}{\text{s33}}$ = 2f _g3 + γ ₂ tf _s3 ;

In this case, the voltage at frequencies f and f _{z11 z33} fall within the bandwidth Δfp amplifiers 23 and 67 of the first intermediate frequency. However, the key 70 does not open. This is explained by the fact that channel voltages with frequencies f _s11 and f _{s33 are} formed by different signals (interference) received at different frequencies f _s1 and f _s3 . There is a weak correlation between them, the output voltage of the correlator 68 is insignificant and does not exceed the threshold level _Uop1 in the threshold block 69. The key 70 does not open and false signals (interference) received simultaneously on the first and second mirror channels at frequencies f _s1 and f _s3 are suppressed.

For a similar reason, other false signals (interference) received simultaneously on two or more other additional channels are suppressed.

Thus, the proposed system in comparison with the prototype provides increased noise immunity and reliability of reception at the point of reception of an alarm signal about the frequency, modulating code and location of the stolen vehicle. This is achieved by suppressing false signals (interference) received via mirror and Raman channels by correlating channel voltage in the measuring channel. In this case, a remarkable property of the correlation function of the QPSK signals is used.

Claims (1)

An anti-theft system for vehicles, containing an intermittent signal generator located on the vehicle, one of the supply terminals of which is connected via the ignition key to the plus bus of the power source, an electromagnetic relay, the winding of which is connected to the output of the intermittent signal generator, and an NC contact is included in the ignition coil circuit sequentially with the ignition key, the master oscillator, the phase manipulator and the transmitter connected to the transmitting antenna are connected in series, a switch with two antiphase windings and opening and closing contacts, a reed switch, a current-limiting resistor and an LED, while one of the terminals of the current-limiting resistor and the windings of the remote switch is directly connected to the positive bus of the power source, and through the ignition key, one of the supply terminals of the master oscillator, phase manipulator and transmitter, opening and closing contacts of the first winding of the remote switch are connected between one of the terminals of the reed switch and the second and the terminals of the first and second windings of the remote switch, respectively, the second NC contact of the second winding of the remote switch is connected between the second supply terminal of the discontinuous signal generator and the negative bus of the power source, the first NC contact of the second winding of the remote switch is connected between the terminal of the current-limiting resistor and the anode of the LED, the cathode of which and the other output of the reed switch directly, and the other supplying conclusions of the master oscillator, phase manipulator and the sensor through the second NC contact of the second winding of the remote switch is connected to the negative bus of the power source, the second input of the phase manipulator is connected to the output of the intermittent signal generator, and the measuring channel located at the receiving point, consisting of a series-connected search unit, the first local oscillator, the first mixer, the second input which is connected to the output of the receiving antenna, and the first amplifier of the first intermediate frequency, series-connected frequency doubler, the second spectrum width, a comparison unit, the second input of which is connected to the output of the first spectrum width meter, the first threshold block, the second input of which is connected to the output of the delay line, the first key, the second input of which is connected to the output of the first amplifier of the first intermediate frequency, the second mixer, the second the input of which is connected to the output of the second local oscillator, the amplifier of the second intermediate frequency of the frequency detector, the trigger and the first registration unit, and from the first local oscillator connected in series to the output the second key, the second input of which is connected to the output of the first threshold block, the frequency meter and the second registration block, while the output of the first threshold block is additionally connected to the inputs of the delay line and the search block, and four direction finding channels, each of which consists of a series-connected receiving antenna mixer, the second input of which is connected to the output of the first local oscillator of the measuring channel, the amplifier of the first intermediate frequency, a multiplier, the second input of which is connected to the output of the amplifier second intermediate frequency of the measuring channel, narrow-band filter, phase detector and registration unit, while the second inputs of the phase detectors of the first and third direction-finding channels are connected to the output of the second local oscillator, the second input of the phase detector of the second direction-finding channel is connected to the output of the narrow-band filter of the first direction-finding channel, the second input the phase detector of the fourth direction-finding channel is connected to the output of the narrow-band filter of the third direction-finding channel, the receiving point is located on and on board the aircraft, the receiving antennas are placed on board the aircraft in the form of an asymmetric geometric cross, at the intersection of which is placed the receiving antenna of the measuring channel, common to the receiving antennas of direction finding channels located in the azimuthal and elevation planes, characterized in that the measuring channel of the system is equipped with a third the local oscillator, the third mixer, the second amplifier of the first intermediate frequency, the correlator, the second threshold block and the third key, and to the output of and a third heterodyne, a third mixer, the second input of which is connected to the output of the receiving antenna, a second amplifier of the first intermediate frequency, a correlator, the second input of which is connected to the output of the first amplifier of the first intermediate frequency, the second threshold block and the third key, the second input of which is connected in series with the output of the first amplifier of the first intermediate frequency, and the output is connected to the inputs of the first meter of the width of the spectrum and the frequency doubler, the frequencies of the first f _g1 and third f _g3 local oscillators are spaced twice the value of the first intermediate frequency f _g1 -f _g3 = 2f _pr1 , selected symmetrical relative to the carrier frequency f _{o the} received signal f ₀ -f _g1 = f _g3 -f ₀ = f _pr and rebuild synchronously.

Images