DE19602316C1 - Device for transmitting data or energy - Google Patents

Description

The invention relates to a device for transmitting Data or energy. Such a device can in particular turned on for an anti-theft system for a motor vehicle are set in which coded information from a Key and to a lock and in the opposite direction be sent.

A known device (DE 44 30 360 C1) has a sta tional transceiver that contains an oscillating circuit. In the transceiver gets an oscillation by an excitation variable forced to transfer their energy to a transponder becomes. The transponder also has an oscillating circuit, through which the energy is received and encoded data to the Transceiver to be retransmitted.

In the case of this known device when it is first detected the encoded data is initially unsuccessful, so the oscillating circuit of the transceiver is "detuned". For this becomes the resonant frequency of the resonant circuit or its excitation frequency changed. If the resonant circuit as a result of construction element tolerances are out of tune, so this out of tune remains also when using the transceiver in an anti-theft device system received. Therefore, every transmission process must then be carried out at least twice.

The problem of the invention is a device for over carry data or create energy at which the ener or the data are transmitted as effectively as possible.

The problem is solved according to the invention by the features of Pa Claim 1 solved. A stationary transcei shows ver a first resonant circuit with a coil and a con capacitor on. The resonant circuit is determined by an exciter size  excited with an excitation frequency to an oscillation. Of the Current and / or the voltage of the exciter size are measured and if the current or voltage depend on a setpoint gives way, a correction value is generated.

Advantageous embodiments of the invention are in the Un marked claims. This is advantageous Correction value saved and for later inductive over Carrying data or energy in an anti-theft system used.

Exemplary embodiments of the invention are described below the schematic drawings explained in more detail. Show it:

Fig. 1 is a schematic block diagram of the erfindungsge MAESSEN device,

Fig. 2 is a resonance curve of a resonant circuit of the device according to Fig. 1 and

Fig. 3 is a diagram of a transceiver of the apparatus of FIG. 1.

A device according to the invention for transmitting data or energy has a stationary transceiver 1 ( FIG. 1) which interacts with a portable transponder 2 via a transformer coupling when the transpon of FIG. 2 is in the vicinity of the transceiver 1 . The transceiver 1 initially transmits energy to the transponder 2 . In the transponder 2 , code information is stored, which is transmitted back to the transceiver 1 (energy transmission and data retransmission are represented by a double arrow drawn in broken lines).

To transmit energy or data, the transceiver 1 has an antenna 3 in the form of a coil which, together with a capacitor 4, forms a first resonant circuit (hereinafter referred to as antenna resonant circuit 3 , 4 ). The antenna 3 is inductively or transformer-coupled to a coil 5 of the transponder 2 . The coil 5 of the transponder 2 forms, together with a capacitor 6 arranged in series or in parallel therewith, a second resonant circuit (hereinafter referred to as a transponder resonant circuit 5 , 6 ).

The antenna resonant circuit 3 , 4 is fed by a generator or an oscillator 7 with an alternating voltage or an alternating current in cycles with an excitation frequency f _E as soon as a supply unit 8 of the oscillator 7 is switched on. As a result, the antenna resonant circuit 3 , 4 is excited to oscillate at the excitation frequency f _E. The field excited by the antenna 3 induces a voltage in a coil 5 of the trans ponder 2 when the transponder 2 is arranged in the vicinity of the transceiver 1 .

The transponder resonant circuit 5 , 6 is in turn excited by the vibration of the antenna resonant circuit 3 , 4 to vibrate. The transponder resonant circuit 5 , 6 can be loaded by a connected transponder IC 9 , in which code information is stored, in the rhythm of the code information. As a result, the antenna resonant circuit 3 , 4 is loaded or modulated due to the transformer coupling in the rhythm of the code information.

The antenna resonant circuit 3 , 4 is forced by the oscillator 7 with an excitation size to oscillate with an excitation frequency f _E. The output voltage or current of the oscillator 7 is used as the excitation variable. The oscillator 7 oscillates at the oscillator frequency f₀. A frequency divider (not shown ) can also be arranged between the oscillator 7 and the antenna resonant circuit 3 , 4 , which divides the oscillator frequency f₀ down to the desired excitation frequency f _E. The excitation size creates a stationary, forced oscillation of the antenna resonant circuit 3 , 4 , which then oscillates at the excitation frequency f _E.

Each resonant circuit has a natural frequency or also called resonance frequency f _R , which is determined by the components of the resonant circuit, ie by the inductance of the antenna 3 and the capacitance of the capacitor 4 in the antenna resonant circuit 3 , 4 . The excitation current flowing through the antenna 3 is greatest when the resonant circuit is excited with the excitation frequency f _E equal to the resonance frequency f _R (cf. solid curve in FIG. 2). As a result, the magnetic field which is generated by the current I flowing through the antenna 3 becomes the greatest. Thus most of the energy is transferred to the trans ponder 2 . The maximum amplitude of the current I depends on the quality of the resonant circuit. With a high quality, the amplitude of the current I is large, and with a low quality, the amplitude of the current I is smaller.

The power balance is illustrated using a resonance curve ( FIG. 2) in which the frequency f is plotted on the abscissa (x-axis) and the amplitude of the current I through the antenna 3 on the ordinate (y-axis).

The excitation frequency f _E can be kept very constant by a controlled oscillator 7 , while the resonance frequency f _R is dependent on the components and their tolerances. If the excitation frequency f _{E is} equal to the frequency f 1 and the resonance frequency f _{R is} also equal to the frequency f 1 , the current I flowing through the antenna 3 is greatest with a maximum amplitude of I 1.

If the resonance frequency f _R (= frequency f₂) from the excitation frequency f _E (dashed resonance curve in Fig. 2), the antenna resonant circuit 3 , 4 is no longer optimally excited and only a current with the amplitude I₂ flows through the antenna 3 . The magnetic field thus generated can then be too low for the transmission of data or energy.

In the manufacture of the transceiver 1 , deviations from setpoints in the ductility of the antenna 3 and the capacitance of the capacitor 4 can occur as a result of component tolerances. Thus, the resonance frequency f _R of the resonant circuit 3 , 4 changes compared to the constant excitation frequency f _E. If the device according to the invention is operated under such conditions, the maximum energy is no longer transmitted to the transponder 2 and the data received from there can likewise only be received with a very small amplitude.

After the manufacture of the transceiver 1 it must first be determined whether the resonance frequency f _R deviates from the excitation frequency f _E by more than a certain predetermined amount. For this purpose, the amplitude of the current I through the antenna 3 or the voltage U across the capacitor 4 is measured using a measuring device 10 . The measured amplitude is compared with a predetermined and stored target value. If the deviation is too large, a correction value is generated and stored in the measuring device 10 . Depending on the correction value, the antenna resonant circuit 3 , 4 is subsequently corrected for all transmissions between transceiver 1 and transponder 2 , so that the most effective possible transmission between transceiver 1 and transponder 2 takes place.

The antenna resonant circuit 3 , 4 can be changed in two different ways depending on the correction value, so that the most effective possible energy and data transmission takes place. On the one hand, the resonance frequency f _{R of} the antenna oscillation circuit 3 , 4 can be approximated to the excitation frequency f _E and, on the other hand, the current I through the antenna 3 , ie the excitation current, can be increased.

First, the change in the resonance frequency f _{R is} considered (path shown in dashed lines in FIG. 1). By measuring the current I through the antenna 3 , its maximum amplitude is first compared with a target amplitude. If the current deviates too much from a target current, then the resonance frequency f _R deviates from a target resonance frequency.

By measuring the phase of the current and the voltage, it can be determined whether the antenna resonant circuit 3 , 4 is inductively or capacitively detuned. Because with an inductive detuning the current I rushes through the antenna 3 of the voltage U by a phase angle ϕ and with a capacitive detuning the current I leads to the voltage U by the phase angle ϕ. The magnitude of the detuning is known from the measured amplitude of the current I. By comparing the phases of current I and voltage U, the direction of the detuning is known. The amplitude I and the phase angle ϕ then determine the correction value.

The antenna resonant circuit 3 , 4 is then connected or disconnected with a capacitance ΔC or an inductance ΔL depending on the correction value via a capacitive and / or inductive network 11 . As a result, the resonance frequency f _{R of} the antenna resonant circuit 3 , 4 changes . The capacitance .DELTA.C and the inductance .DELTA.L are determined such that the resonance frequency f _R approximates the excitation frequency f _E by adding or removing the capacitance .DELTA.C and / or the inductance .DELTA.L. In FIG. 2, this corresponds to a shift of the resonance curve drawn in dashed lines to the left into the solid resonance curve. Thus, a current I flows through the antenna 3 at the excitation frequency f _E , the amplitude of which is approximated to the target amplitude I 1.

The connection or disconnection of the capacitance ΔC and / or the inductance ΔL occurs only once after the trans ceiver 1 has been manufactured . These corrections, ie the addition or removal of the capacitance ΔC and / or the inductance ΔL, are retained for subsequent transmission processes. The antenna resonant circuit 3 , 4 is thus adapted to the excitation unit with the oscillator 7 . The antenna resonant circuit 3 , 4 is advantageously manufactured in such a way that its resonance frequency f _{R is} above the excitation frequency f _E or the target resonance frequency, taking into account manufacturing tolerances. This makes the device simpler since only capacitors need to be switched.

If the antenna resonant circuit 3 , 4 is only slightly capacitively tuned, the resonance frequency f _R can be changed by removing a capacitance ΔC. In contrast, if the antenna resonant circuit 3 , 4 is inductively detuned, the resonance frequency f _{R can be changed} by adding a capacitance ΔC.

Next, consider a change in current I through antenna 3 . If the antenna resonant circuit 3 , 4 is out of tune, so at the excitation frequency f _E only a current with the amplitude I₂ flows through the antenna 3 , the excitation current can also be increased to such an extent that the amplitude of the current through the antennas is approximately equal to that Amplitude I 1 is (dotted resonance curve in Fig. 2).

For this purpose, the current I₂ is first measured. Since the amplitude I 1 of the ideal current is known, the correction value can be determined by which the current I 2 must be amplified. In this approach, the amplitude of the I₃ ma imum current increased by the antenna 3 when the frequency f₂ would be stimulated with a He excitation frequency f _e equal. Since the current is increased, more energy must be fed into the device before, ie the excitation current must be increased significantly.

The excitation current is increased depending on the correction value only once after the transceiver 1 has been manufactured . These corrections are retained for subsequent transmission processes, ie the excitation current determined by the correction value remains constant in all subsequent transmissions of data or energy. This has the advantage that a constant magnetic field is generated. Sufficient voltage is thus induced in the transponder oscillating circuit 5 , 6 , in order to conversely transmit data back from the transponder 2 to the transceiver 1 .

The correction value can be saved and with each over the excitation current or the addition or displacement switch the capacitance ΔC and / or the inductance ΔL rivers.

In the device according to the invention, both corrections can also be carried out in succession, ie first changing the resonance frequency f _R and then changing the current I by correcting the excitation current. This can be the case if a good approximation to the target resonance frequency is not yet achieved by changing the resonance frequency f _R.

In FIG. 3, a circuit diagram is shown of the invention Before direction. The antenna 3 is controlled via a bridge circuit, in the branches of which there is a switching transistor T₁ to T₄. The transistors T₁ to T₄ are in pairs, ie the pair T₁ and T₃ and the pair T₂ and T₄, on or off. The transistors T₁ to T₄ are driven during this time with the excitation frequency f _{E in} such a way that a positive and a negative voltage are applied to the antenna 3 alternately. As a result, a sinusoidal current with the frequency f equal to the excitation frequency f _{E flows} through the antenna 3 .

Between the antenna 3 and the capacitor 4 is a handle from which is connected to the measuring device 10 for measuring current 1 and voltage U. Both the amplitude and the phase of current I and voltage U can be measured with the measuring device 10 . The measured values are compared with target values which are based on the design of the device and which are stored in the measuring device 10 . If there is a deviation beyond a specified tolerance range, the correction value is generated and saved.

The transistors T₁ to T₄ can each consist of several parals lel switched individual transistors exist, the Ein cell transistors are switched on depending on the correction value. For example, the individual transistors can directly individual memory cells of a memory, not shown be connected in which the correction value is a binary value stores. The correction value determines the number of individual transistors arranged in parallel to each other and are controlled according to the correction value.

The memory can be contained in the oscillator 7 , via which the antenna 3 is then controlled in accordance with the correction value. The oscillator 7 then acts as a current driver stage of the antenna 3rd

The transistors T₁ to T₄ in the bridge circuit can also be controlled by a pulse width modulated signal via the Oszilla gate 7 . Depending on the length of the switch-on pulse and a subsequent variable pulse pause (duration of the pulse and pause depend on the correction value), the pairs of transistors T₁ and T₃ or T₂ and T₄ are switched on and off for different lengths. The current I through the antenna 3 can thus be controlled as a function of the correction value.

Driving with a pulse width modulated signal has the advantage that an amplitude modulated signal can be transmitted to the transponder 2 at the same time.

The excitation current and thus the current I through the antenna 3 is only changed within a predetermined tolerance range depending on the correction value. If a major change would be necessary, it can be concluded that the corresponding transceiver 1 is afflicted with errors that are too large and is therefore sorted out.

In the device according to the invention, the correction value is determined at least once at the end of the band after the transceiver 1 has been manufactured. In all subsequent transmissions, the correction value is already included, so that the efficiency of the transmission is high, ie so that the received amplitudes of the transmitted signals are large enough.

The correction value can be determined in the device according to the invention if the transponder 2 is arranged in the vicinity of the transceiver 1 . The transponder resonant circuit 5 , 6 , however, has only a minor effect on the resonance frequency f _{R of} the antenna resonant circuit 3 , 4 and the current I through the antenna 3 , since its coil 5 and its capacitor 6 have only low impedance values due to the small dimensions of the transponder 2 exhibit. For this reason, the resonance frequency f _{R of} the antenna resonant circuit 3 , 4 and the current I through the antenna 3 can also be determined without the transponder 2 .

The target values for the resonance frequency f _R and the current I 1 can be determined in advance on a laboratory sample. The setpoints can also be calculated using a model.

A device according to the invention is advantageously used in an anti-theft system for a motor vehicle. Energy is transmitted from transceiver 1 to transponder 2 , which uses this energy to transmit coded data back from transponder 2 to transceiver 1 . The vibration of the transponder resonant circuit 5 , 6 is advantageously load-modulated or frequency-modulated in the rhythm of the code information. As a result of the inductive coupling, the vibration of the antenna resonant circuit 3 , 4 is also modulated.

The modulated vibration of the antenna resonant circuit 3 , 4 is detected either by the measuring device 10 or by an evaluation unit, not shown. A demodulator demodulates the code information from the modulated vibration and forwards it to a comparator. The comparator compares the detected code information with a target code information and, if they match, gives an enable signal to a security unit. Such a security unit can be, for example, an immobilizer or a door lock.

The transceiver 1 can be arranged on a door or ignition lock, while the transponder 2 is located on an ignition key or a chip card.

The measuring device 10 can be a microprocessor, which detects the current via an A / D converter and takes over the connection of the capacitance ΔC and / or the inductance ΔL or the control of the excitation current. The microprocessor can perform other functions, such as demodulation and size comparison.

Instead of the amplitude of the current, the amplitude of the voltage at the antenna 3 can also be measured. To measure the phase angle ϕ and the capacitive or inductive detuning of the antenna resonant circuit, the phase is measured by both the voltage and the current through the antenna 3 . Such measurements are well known. It is therefore not necessary to go into them here.

The capacitive and / or inductive network 11 , through which the capacitance .DELTA.C or the inductance AL the antenna oscillation circuit 3 , 4 added or removed as a parallel or series impedance, consists of various impedances, such as capacitors and coils. The size of the impedance of the antenna resonant circuit 3, 4 changed, thereby depends on the detuning of the antenna resonant circuit 3, 4 and hence of the resonant frequency f _R and the excitation frequency f from _E.

Claims (7)

1. Device for transmitting data or supply energy from / to a transponder, in particular for an anti-theft protection system in a motor vehicle, with

• - A stationary transceiver ( 1 ) having a first resonant circuit ( 3 , 4 ) with an antenna ( 3 ) in the form of a coil and a first capacitor ( 4 ), the resonance frequency (f _R ) being determined by its components ,
• - A portable transponder ( 2 ) having a second resonant circuit ( 5 , 6 ) with a second coil ( 5 ) and a second capacitor ( 6 ), and
• - An excitation unit ( 7 ) which vibrates with an oscillator frequency (f₀) and whose output variable is used as an excitation variable with an excitation frequency (f _E ) for forcing an oscillation of the first resonant circuit ( 3 , 4 ), and
• - An evaluation unit ( 10 ) in which the current (I) and / or the voltage (U) in the first resonant circuit ( 3 , 4 ) is measured and in which a correction value in the event of a deviation of the current or the voltage from a desired value is generated, with the aid of which the first resonant circuit ( 3 , 4 ) is subsequently corrected in all transmissions between the transceiver ( 1 ) and the transponder ( 2 ), so that the most effective possible transmission takes place between the two.

2. Device according to claim 1, characterized in that the current (I) and / or the voltage (U) in the first resonant circuit ( 3 , 4 ) are measured according to magnitude and phase (ϕ) and that the correction value is determined as a function thereof . 3. Apparatus according to claim 2, characterized in that the resonance frequency (f _R ) of the first resonant circuit ( 3 , 4 ) depending on the correction value by adding or removing at least one series or parallel inductance (ΔL) and / or at least one series or parallel capacitance (ΔC) to the antenna ( 3 ) or to the first capacitor ( 4 ) is changed. 4. The device according to claim 2, characterized in

• - That the excitation unit ( 7 ) has a driver stage, which is controlled depending on the correction value, whereby the current (I) in the first resonant circuit ( 3 , 4 ) is increased or decreased,
• - That the correction value is stored in a memory of the excitation unit ( 7 ) and
• - That the memory is connected to the driver stage.

5. The device according to claim 4, characterized in that the current (I) in the first resonant circuit ( 3 , 4 ) is changed by the correction value only within a predetermined tolerance range. 6. The device according to claim 1, characterized in that the first resonant circuit ( 3 , 4 ) via the antenna ( 3 ) and the second coil ( 5 ) with the second resonant circuit ( 5 , 6 ) is inductively coupled when the transponder ( 2 ) is located near the transceiver ( 1 ). 7. The device according to claim 6, characterized in that

• - That the transponder ( 2 ) has code information that generates a modulated oscillation of the first resonant circuit ( 3 , 4 ) as a result of the inductive coupling,
• - That the modulated vibration is detected by the evaluation unit ( 10 ),
• - That the code information from the modulated vibration is de-modulated,
• - That the detected code information is compared with a Sollcodeinforma tion and
• - That a release signal for releasing a security unit is generated if there is a match.