WO2019105850A1

WO2019105850A1 - Method and device for determining the position of mobile identification transmitters

Info

Publication number: WO2019105850A1
Application number: PCT/EP2018/082309
Authority: WO
Inventors: Christian Morhart; Josef Schinagl
Original assignee: Continental Automotive Gmbh
Priority date: 2017-11-28
Filing date: 2018-11-23
Publication date: 2019-06-06
Also published as: DE102017221285A1; CN111344752A

Abstract

The invention relates to a device for determining the position of a mobile identification transmitter (30) in relation to a vehicle (10), comprising a first antenna (31) arranged in the mobile identification transmitter (30) and at least two antennas (2n) arranged in the vehicle (10). The device is designed to determine the reception field strength (P31->2n) of signals (S2n, S31) transmitted between the first antenna (31) and the respective at least two antennas (2n) arranged in the vehicle (10), to form at least one relationship from two different measured reception field strengths ((P31->2n), and to compare each of the at least one formed relationships with at least one threshold. The position of the mobile identification transmitter (30) is determined on the basis of the comparison of the at least one relationship with the at least one threshold.

Description

description

Method and device for determining the position of mobile identification transmitters

The invention relates to a method and a device for determining the position of mobile identification encoders, in particular in a vehicle.

Keyless vehicle entry and start systems such as the Passive Start Entry (PASE) system are automated systems to unlock a vehicle without actively using a car key and start by merely pressing the start button. In the vehicle while a Sen deeinheit is arranged, which emits signals. These are, for example, electromagnetic signals in the LF (Low Frequency) or HF (High Frequency) range. These signals are received by a transponder unit when it is in the vicinity of the vehicle, and then evaluated and / or further processed. Following the evaluation and / or further processing in the transponder unit corresponding response signals can be sent back to the transmitting unit in the vehicle. The response signals are sent, for example, in the UHF frequency band and can be evaluated in the vehicle by an evaluation unit. If a response signal is recognized as correct and thus the transponder unit is identified as belonging to the vehicle, the vehicle can be unlocked or started. Other functions in the vehicle can also be controlled in this way.

In some cases, the position of the

Transponder unit determined. The permitting and / or releasing of a function can then additionally depend on the position of the transponder unit. For example, a startup Operation of the vehicle only be released when the transponder unit is detected as being located inside the vehicle.

There are various ways known how the position of a transponder unit can be determined. In newer systems, the functions of the transponder unit (driving key) are increasingly being taken over by portable electronic devices, such as smartphones. For the communication between the portable electronic devices and the vehicle signals often come in accordance with a Bluetooth standard, for example the Bluetooth Low Energy

(BLE) standard, used. The known Po sitionsbestimmung methods can not be readily applied to the communication via Bluetooth, since signals according to a Bluetooth standard, in contrast to LF signals, for example, due to shading effects (for example, by the body of the user) can be greatly attenuated. Due to shading, the position determination with the forth conventional methods when using Bluetooth devices can be very inaccurate.

The object of the invention is to provide an improved device and an improved method for determining the position of mobile identification devices (portable electronic devices) be.

This object is achieved by a device according to claim 1 and a method according to claim 12. Embodiments and developments of the inventive concept are the subject of dependent claims.

An apparatus for determining the position of a mobile identification transmitter with respect to a vehicle has a first one arranged in the mobile identification transmitter antenna and at least two antennas arranged in the vehicle. The apparatus is configured to determine the reception field strengths of signals transmitted between the first antenna and the at least two antennas arranged in the vehicle, to form at least a ratio of two different measured reception field strengths, and to each of the at least one formed ratio each with at least one threshold to compare. The position of the mobile identification transmitter is determined on the basis of the comparison of the at least one ratio with the at least one threshold.

By forming ratios of different reception field intensities, interference of the signals or specific characteristics of the particular mobile identifier used can be compensated. Specific characteristics may include, for example, the type of antennas used or the orientation of the antennas used. The determination of the position becomes more accurate and less susceptible to interference.

Of the antennas arranged in the vehicle, at least one antenna may be arranged in the interior of the vehicle and at least one antenna in the exterior of the vehicle.

As an alternative or in addition to the antennas arranged in the interior and exterior of the vehicle, at least one antenna can be arranged in the region of the hood of the vehicle and at least one antenna in the region of the trunk of the vehicle and / or an antenna in the region of the right side of the vehicle and at least one antenna Antenna may be arranged in the region of the left side of the vehicle and / or two antennas may be arranged at two obliquely opposite corners of the vehicle. This results in particularly high-contrast positions, whereby the accuracy of the position determination can be improved.

The ratio can be formed from two reception field strengths, which relate to antennas in the vehicle having a distance of more than 10cm, more than 50cm, more than lm or more than 2m to each other. This also results in possible high-contrast positions of the antennas, which in turn can be improved accuracy of positioning.

The signals can be sent to the mobile identification transmitter by the antennas arranged in the vehicle, and the mobile identification transmitter can be designed to determine the reception field strengths of the received signals. However, it is alternatively also possible to send the signals from the first antenna arranged in the mobile identification transmitter to the antennas arranged in the vehicle. In this second case, the device can furthermore have a control unit, which is connected to the antennas arranged in the vehicle and which is designed to determine the reception field strengths of the received signals. The position determination can thus follow both in the vehicle and in the mobile identification transmitter.

For each of the ratios formed, the same threshold can be used. Alternatively, however, it is also possible to use different thresholds for at least two of the ratios formed. Various zones can be defined in and / or around the vehicle in which a mobile identification transmitter can be detected. The thresholds may depend on the size and shape of desired zones. The reception field strength with respect to an antenna arranged in the vehicle depends on the distance of the mobile identification transmitter to the corresponding antenna.

Each ratio can be compared to a first threshold and a second threshold. As a result, the size and shape of the zones can be changed.

The device can furthermore be designed to determine an attenuation of the signal between the two antennas based on a signal transmitted between two antennas arranged in the vehicle. The at least one threshold may then depend, for example, on the particular attenuation.

A mobile identification transmitter has a first antenna and a vehicle has at least two antennas. A method for determining the position of the mobile identification transmitter with respect to the vehicle comprises determining the reception field strengths of signals transmitted between the first antenna and the at least two antennas disposed in the vehicle, forming at least a ratio of two different measured reception field strengths and the Ver equalize each of the conditions formed with at least one threshold. The position of the mobile identification transmitter is determined on the basis of the comparison of the conditions with the at least one threshold.

The invention will be explained in more detail with reference to the figures of the drawing, wherein the same or similar elements are provided with the same reference numerals. It shows:

FIG. 1 shows a sketch of the principle of a keyless vehicle access and starting system; FIG. 2 shows a sketch-like depiction of different zones in a vehicle and the principle of a system for determining the position of a mobile identification transmitter;

3 shows in a block diagram a system for determining the position of a mobile identification transmitter according to an embodiment of the invention, FIG.

Figure 4 in a sketchy representation of a system for

Position determination of a mobile identification encoder according to an embodiment of the invention, and

FIG. 5 shows a flowchart of a method for determining the position of a mobile identification transmitter according to an embodiment of the invention.

Figure 1 shows a schematic representation of the principle of a keyless vehicle access and start system. In the vehicle 10, a transmitting unit 20 is arranged, which is adapted to emit signals. These signals are received by a transponder unit or a mobile identification encoder 30 when it is in the vicinity of the vehicle 10, and then evaluated and / or further processed. Conventional transponder units are arranged in example in a vehicle key. With newer systems, however, more and more portable electronic devices (mobile identification transmitter) are taking over the functions of conventional vehicle keys. Portable electronic devices may be, for example, smartphones, tablets, laptops, smartwatches or the like. Following the evaluation and / or Wei terverarbeitung in the mobile identification transmitter 30 corresponding response signals can be sent back to the transmitting unit 20. The response signals can in the vehicle 10th be evaluated by a, not shown in Figure 1, evaluation.

To receive the signals sent by the transmitting unit 20, the mobile identification transmitter 30 must be within a certain radius around the vehicle 10, since the transmitted signals have only a limited range. This radius can be for example 10 meters. This is just an example. The range can also be larger or smaller.

The transmitting unit 20 may continuously transmit signals or only to a specific event. Such an event may be, for example, touching or actuating a door handle or a vehicle start button. Any other suitable type of event is also possible. If the mobile identity transmitter 30 sends a correct response signal to a signal received by the transmitting unit 20, the vehicle 10 is unlocked.

For some functions in the vehicle 10 often also the current position of the mobile identification transmitter 30 plays a role. For example, it may be necessary for the mobile identification transmitter 30 to be located inside the vehicle 10 so that the vehicle 10 can be started. For this purpose, different zones A, B, C, D can be defined in or around the vehicle 10. This is shown by way of example in FIG. A first zone A is located, for example, in the interior of the vehicle 10. Further zones B, C, D can be defined, for example, in the area in front of the driver's door, the front passenger's door or the boot. The zones A, B, C, D shown in FIG. 2 are merely examples. In the simplest case, for example, a first zone in the interior of the vehicle 10 and a second zone in a certain radius around the vehicle 10 are defined. Both the interior and the exterior of the However, vehicles 10 may also be divided into more than one zone. For example, a zone in the area of the driver's seat and other zones can be defined in the area of the front passenger seat, the rear seat and the parcel shelf. The various zones can differ in shape and size from each other.

In which of the zones A, B, C, D is a mobile Identifika tion transmitter 30 can be detected using one or more antennas 21, 22, 23 in the vehicle 10. In Figure 2, three antennas 21, 22, 23 are shown. In the vehicle 10, however, more or less antennas may in principle be arranged at any suitable positions. At the antennas 21, 22, 23 may be connected to a controller 40. The control unit 40 may be configured to emit signals via one or more of the antennas 21, 22, 23. Signals received by the antennas 21, 22, 23 can in turn be sent to the control unit 40 for further evaluation. For example, signals which are received by the mobile identification transmitter 30 can be emitted by the antennas 21, 22, 23 arranged in the vehicle 10. The mobile identification transmitter 30 may measure the reception field strength of each of the received signals. The reception field strength of a signal decreases with increasing distance from the transmitting antenna. Since the position of the antennas in the vehicle 10 is known, the distance to the respective antennas 21, 22, 23 and thus the position of the transponder unit 30 with respect to the vehicle 10 can be determined from the received signal strengths of one or more signals received at one time ,

In principle, it is also possible that the mobile identification transmitter 30 emits signals and each of the antennas 21, 22, 23 determines the reception field strength of these signals. The mobile identification transmitter 30 thus serves in this case as Transmitter and the antennas 21, 22, 23 in the vehicle 10 as a receiver. The farther the respective antenna 21, 22, 23 away from the mobile identification transmitter 30, the lower the measured reception field strength of the signals. From the measured reception field strengths, it is then possible in turn to deduce the distance of the mobile identification transmitter 30 to each of the antennas 21, 22, 23. When the distance to each one of the antennas 21, 22, 23 is known, the position of the mobile identification transmitter 30 with respect to the vehicle 10 can be deduced.

However, it is often not necessarily required that the exact position of the mobile identification transmitter 30 is known. It is basically sufficient to detect in which of the zones A, B, C, D the mobile identification transmitter 30 is located. For example, it can be detected that the mobile identification transmitter 30 is located in the zone A in the interior of the vehicle 10 when the received field strength measured with respect to an antenna located in the vehicle 10 exceeds a certain threshold.

By other devices in the vehicle emitted by the antennas 21, 22, 23 or the mobile identification transmitter 30 signals can be disturbed. It may be both equally shaped interferers, such as mobile devices or radios, which permanently superimpose the signals of the antennas 21, 22, 23, or so-called peak interferers act, eg ignition pulses which the signals of the antennas 21, 22, 23 briefly overlap. In addition, the measured reception field strength depends on a wide variety of other factors. This can be, for example, shading effects, which can be caused for example by the vehicle body or the body of the user. Nowadays, classic car keys, as already described above, are becoming more and more popular with smartphones or other portable ones electronic devices or mobile identification transmitter replaced, which can take over the key function. The communi cation between mobile identification transmitter and vehicle often takes place via Bluetooth or WiFi.

However, different electronic devices (eg, different types of smartphones) may have different characteristics (eg, different types of antennas, different antenna orientation, etc.), thereby increasing the absolutely measured reception field strength of the transmitted signals, depending on the type of electronic device used can vary. Especially with measured reception field strengths in the GHz range, very large fluctuations can occur. As a result, the above-described position determination may be erroneous and the mobile identification transmitter 30 may be detected in a wrong zone A, B, C, D. The fluctuations of the measured absolute values can be, for example, in the range of 20 dB (factor 100) and more.

These disadvantages are intended to be prevented or minimized by the present invention.

FIG. 3 schematically shows a system for determining the position of a mobile identification transmitter according to an embodiment of the invention. About a plurality of antennas 21, 22, 23 in the vehicle, an electromagnetic signal S21, S22, S23 is respectively out sends. The signals transmitted between the antennas 21, 22, 23 and the mobile identification transmitter 30 may be, for example, signals according to a Bluetooth standard, for example the Bluetooth Low Energy (BLE) standard.

Bluetooth is an internationally standardized data interface. For example, data or files can be exchanged between two devices or music and Bluetooth via Bluetooth Be transmitted. Bluetooth devices transmit at a frequency of 2.4 GHz and allow data transmission with a short range of usually less than 50m. Currently, various Bluetooth standards are known, for example, Bluetooth 1.0 and 1. OB 1999, Bluetooth 2.0 + EDR 2004 or Bluetooth 4.0 2009. It is not important in the present invention, according to which standard the vehicle 10 and the mobile identification transmitter 30 communicate with each other cate. However, in order to enable communication, it is usually necessary for two Bluetooth-enabled devices between which a connection is to be established to communicate according to the same standard. However, some of the standards are also compatible with each other.

Bluetooth devices usually consume a relatively large amount of power. However, especially in vehicles or the associated mobile identification transmitters (for example, smartphones), the power consumption is usually critical. As a result, so-called Bluetooth Low Energy (BLE) devices are increasingly found in vehicles and external devices. Bluetooth Low Energy is often referred to as Bluetooth Smart. BLE is based on the classic Bluetooth technology, but has a significantly lower power consumption and is usually cheaper. When using BLE devices in a mobile identification transmitter 30, the battery of the mobile identification transmitter 30 (or of the electronic device) is thus subjected to less load than with conventional Bluetooth devices.

However, the signals sent between the antennas 21, 22, 23 and the mobile identification transmitter 30 can also be, for example, signals in accordance with the WiFi standard. Any other kind of signals is also possible. In FIG. 3, by way of example, three antennas 21, 22, 23 arranged in the vehicle are shown. This is just an example. In principle, a number of n antennas can be used, with n> 2. The larger the number of antennas 2n, the larger, however, is usually the accuracy in determining the position, as will be described below.

The mobile identification transmitter 30 has a further antenna 31. About this further antenna 31, the electromagnetic signals S2n can be received. The reception field strengths P3i> 2i, P3i> 22 _/ P3i> 23 of the individual signals S2n can then be determined in the mobile identification transmitter 30. These are, for example, a first reception field strength P3i_ _> 2i of a first signal S21 which is transmitted from a first antenna 21 in the vehicle to the mobile identification transmitter 30, a second reception field strength P3i_> 22 of a second signal S22 which from a second antenna 22 in the vehicle to the mobile Identi fikationsgeber 30 is sent and a third reception ^¬ field strength P3i-> 23 of a third signal S23 which is sent from a third arranged in the vehicle antenna 23 to the mobile identification transmitter 30. In principle, the mobile identification transmitter 30 detects a larger reception field strength P3i_ _> 2 _{n of} a signal S2n the closer it is to the corresponding antenna 2n. The value of the reception field strength determined is P3i_> 2 _n thus depends on the distance between the respective antenna 2n and tifikationsgeber the mobile Iden 30 inaccuracies in the measurement, which are caused for example by the type of the electronic apparatus used as the mobile ID Case ^¬ onsgeber 30, contact while measuring each of the reception field strengthen P32_> 2 _n on.

Instead of an absolute measurement of the reception field strengths P3i_ _> 2 _n and a comparison of each of the reception field strengths P3i_ _> 2 _n with one or more thresholds (absolute value), the measured values of at least two of the reception field strengths _{P3i_>} 2 _n ^¬ he inventively in a ratio to each other. Unsi ^¬ uncertainties, which occur in all the measurements equally, characterized occur both in the numerator and the denominator and be compensated.

This will be described in more detail with reference to Figure 4 the example of an arrangement with two antennas 21, 22 in the vehicle. In the example in FIG. 4, two antennas 21, 22 are arranged in the vehicle. For example, an antenna 21 can be arranged in the interior of the vehicle and a second antenna 22 can be arranged outside the vehicle, for example on the vehicle ^roof . If a mobile identification transmitter 30 (or a portable electronic device) is located with an antenna 31 in the vicinity of the vehicle, the mobile identification transmitter can receive signals from both antennas 21, 22 on the vehicle and the corresponding reception field strengths P3i _> 2i, P3i> 22 to measure these signals. These reception field strengths P3i _> 2i, P3i> 22 are then set in relation to one another and this ratio is compared with a threshold, for example:

P _3i-> 2i / P3i->22> threshold

If the mobile identification transmitter 30 is located inside the vehicle as shown by way of example in FIG. 4 (zone A, cf., FIG. 2), the reception field strength P3i_ _> 2i measured in relation to the first antenna 21 in the vehicle is substantially greater than that in relation to the second one Antenna 22 Reception field strength P3i- _> 22 measured outside the vehicle, assuming that the signals are transmitted with the same strength. The signals emitted by the second antenna 22 are attenuated in example by the vehicle roof, while the signals of the first antenna 21 almost unattenuated in the mobile Identification transmitter 30 arrive. That is, for the ratio of the two values shown above results in this case, a relatively large value (eg> 1). The threshold can be selected, for example, as 1 (threshold = 1). Any other value greater or less than 1 is also possible (eg threshold = 0.5, threshold = 2 or threshold = 3). The selected threshold depends, for example, on the shape and size of the ^different zones and on the arrangement of the antennas 21, 22 in the vehicle.

If the mobile identification transmitter 30 is located, for example, outside the vehicle, the reception field strength P3i_> 22 measured in relation to the second antenna 22 outside the vehicle would be significantly greater than the reception field strength measured in the vehicle relative to the first antenna 21 _P3i-> 2i · the signals from the first antenna 21 would be weakened in this case from the car body, while the signals of the second antenna 22 is substantially unimpaired would be in the mobile identification transmitter 30th Thus, in the example described, the ratio of the two values shown above would result in a relatively small value (eg <1).

In the same way, different zones can be defined in and around the vehicle. For example, the first antenna 21 may be attached to the driver's door (eg, left side) while the second antenna 22 is mounted on the passenger's door (eg, right-hand side) on the opposite side of the vehicle. Would be a user with the mobile identifi ^¬ cation encoder 30 exactly in the middle behind the vehicle, a ratio of the reception field strengths P3i_ would _result> 2i / P3i-> 22 close to 1 if it is assumed that the signals are emitted at each of the same thickness. The further the mobile identification transmitter 30 would move towards the driver's door, the more so the received field strength P3i_ _> 2i measured with respect to the first antenna 21 would be larger and the reception field strength P3i_ _> 22 measured with respect to the second antenna 22 would be smaller. The calculated ratio would thus yield ever greater values. For example, it could be determined that the mobile identification transmitter 30 is detected in a zone B (see FIG. 2) in front of the driver's door, if it is valid

P31-> 2l / P31-> 22> 2.

Another possibility is, for example, to attach an antenna to the hood and a further antenna in the region of the trunk and to bring the measured reception field strengths in turn to a relationship and to compare with a suitable threshold. Likewise, it is possible to play at ^¬ to mount two antennas on each diagonally opposite corners ^¬ opposite the vehicle 10. So for example one antenna at the right front corner and the other antenna at the diagonally opposite left rear corner.

In the simplest case, two antennas 21, 22 are arranged in or on the vehicle. However, any other number n of antennas (with n> 2) is also possible. In this case, the measured with respect to an antenna receive field strength can be set only with a further reception field strength in a ratio, or with several different reception field strengths.

For example, three different antennas 21, 22, 23 could be arranged in the vehicle. A first antenna 21 may be arranged in the interior of the vehicle, a second antenna 22 on the driver's door and a third antenna 23 on the passenger's door. The mobile identification transmitter 30 could, for example, be recognized in one of the zones if: R ₃ i- _{> 2ΐ} / R3ΐ- _{> 22} > threshold_l, AND

P _{3i-> 2i} / P _{3i-> 23} > Threshold_2, AND

P _{3i-> 22} / P3i- _{> 23} > Threshold_3.

For example, various antennas, as already described above, can be arranged in particularly high-contrast positions in the vehicle. For example, different antennas are not arranged in close proximity to each other. For example, the distance between two antennas may be more than 10cm, more than 50cm, more than 1m, or more than 2m. For example, two antennas can also be arranged in close proximity to one another if one antenna is located in the interior of the vehicle, while the other antenna is arranged on the outside of the vehicle. Examples of high-contrast positions are e.g. Interior / exterior, right / left, front ne / rear, diagonally opposite corners, etc.

In the example shown above, a mobile Identifika tion is recognized as located in a zone when the ratios formed are each greater than a predetermined threshold. This is just an example. It is also possible, for example, to specify lower threshold values which must be exceeded correspondingly by one or more of the ratios:

P _{3i-> 2i} / P3i- _{> 22} > threshold_l, AND

P _{3i-> 2i} / P _{3i-> 23} <threshold_2, AND

P _{3i-> 22} / P3i- _{> 23} > Threshold_3.

For example, two different threshold values can also be defined for one or more of the ratios formed. These may be a lower threshold Xnmin and an upper threshold Xnmax. It can then be determined whether the respectively determined ratio of the reception field strengths is greater or less than the respective thresholds. By suitable combination of the threshold values, different zones can be defined, for example by means of intersection formation. For example, a mobile identification transmitter 30 may be detected as being in a first zone A, if:

Xlmin_A 2i} / P _{3i> 22} <Xlmax_A AND

X2min_A 2i} / P _{3i> 23} <X2max_A AND

X3min_A 22} / P _{3i> 23} <X3max_A.

For example, a mobile identification transmitter 30 may be detected as being in a second zone B if:

Xlmin_B 2i} / P _{3i> 22} <Xlmax_B AND

X2min_B 2i} / P _{3i> 23} <X2max_B AND

X3min_B 22} / P _{3i-> 23} <X3max_B.

These are just examples. Different zones may be determined by any such combination of thresholds. The values of the threshold values can be selected according to the desired size and shape of the zones.

For example, by creating ratios, shading effects are cut out. This will be explained below with reference to an example. For example, a user stands in front of his vehicle with a view of the vehicle. His smartphone, which acts as a car key, is located in a back pocket of the user. That is, signals sent between the antennas in the vehicle and the smartphone are shadowed by the user's body. This applies both to an antenna arranged in the interior and to an antenna arranged in the exterior of the vehicle. Both signals are thus attenuated substantially equally by the user's body. The relationship between the two fangsteidstärken each other thus gives substantially the same value as for the non-attenuated signals. Comparing the ratio of the signals to each other with one or more thresholds thus provides substantially the same result (eg, user is in zone A) as in the case where the signals are not attenuated.

After the reception field strengths P3i_ _> 2 _{n have been} determined in the mobile identification transmitter 30, it can emit a response signal S31 via the further antenna 31 (see FIG. The response signal S31 is also an electromagnetic signal. The signal S31 thereby contains information on the measured reception field strengths _{P3i_>} 2 _n · It can be emitted a single signal which has information about all ge ^¬ measured reception field strengths _{P3i_>} 2 _n. However, it may S2n are sent out to each of the received signals which are respectively received by the antennas ent ^¬ speaking 2n also each have their own response signal S31. Each of these Ant word signals S31 may then comprise information about the reception field strength P3i_ ^_¬> 2 _n of the signal of the respective antenna 2n. The antennas 2n are connected to a control unit 40. Response signals S31 received via the antennas 2n can be sent to the control unit 40 for further processing. The controller 40 thus receives the information on the measured reception field strengths _P3i-> 2 _n, the entspre ^¬ sponding ratios can form and may determine therefrom the position of the mobile identification transmitter 30, and determine in which zone the mobile identification transmitter is thirtieth However, it is also possible that a position determination already takes place in the mobile identification transmitter 30 and the mobile identification transmitter 30 in the response signal S31 sends an information about the particular position or the specific zone. In the above example, the antennas are 2n in the vehicle 10 as the transmitting antennas and the antenna 31 in the mobile identifica tion ^¬ encoder 30 serves as a receiving antenna. The determination of the reception field strengths _{P3i_>} 2 _n is done in the mobile identifica ^¬ tion encoder 30. However, it is alternatively also possible that the determination of the reception field strengths _{P3i_>} 2 _{n is} not in the mobile identification transmitter 30 is performed. Instead of transmitting signals S2n from each of the antennas 2n in the vehicle, the mobile identification transmitter 30 may transmit one or more signals S31 received from the antennas 2n. In such a case, the antenna 31 is thus used in the mobile Iden ^¬ tifikationsgeber 30 as a transmitting antenna and the antennas 2n in the vehicle 10 serve as receiving antennas. In the control apparatus 40, the reception field strength can then _{P3i_>} 2 _n each of the received signals are determined S31 and the reception field strengths _{P3i_>} 2 _n corresponding to each other and compared with appropriate thresholds in ^¬ speaking conditions. As a result, in turn, the position of the mobile identification transmitter 30 with respect to the vehicle 10 can be determined.

In the mobile identification transmitter 30 and / or in the STEU ergerät 40, the position and shape of the zones A, B, C, D is known. Based on the determined reception field strengths _P3i-> 2 _n, or the relationships formed, can thus be determined, in which zone A, B, C, D the mobile identification transmitter is thirtieth Depending on the zone in which the mobile identification transmitter 30 is located, a corresponding function in the vehicle can then be allowed or prevented.

The system can be libriert example, during operation nachka ^¬. As shown schematically in FIG. 4, it is possible, for example with the aid of signals between the first antenna 21 and the second antenna 22, to determine the attenuation of the signals. That is, it can be determined how strong a signal on the path x3 between the first antenna 21 and the second antenna 22 is attenuated. For example, it can be detected if changes in damping occur over time. For example, a signal between the first antenna 21 and the second antenna 22 may initially not be significantly attenuated. However, for example, due to changes to the vehicle, there may be occurrences of objects in the radio link between the first antenna 21 and the second antenna 22 at a later time causing significant attenuation of signals transmitted between the first and second antennas 21, 22 , The specific attenuation can be used, for example, for diagnostic purposes, in particular for self-calibration of the system, for example in order to estimate and adapt the value of the (relative) threshold (s) with which the determined ratios are compared. If, for example, the (relative) threshold (s) at delivery of a vehicle have preset values, these can, if necessary, be recalibrated at a later time in order to adapt the system to possible changes.

FIG. 5 shows in a flowchart a method for determining the position of a transponder unit with respect to a vehicle. The transponder unit has a first antenna and the vehicle has at least two antennas. One method includes determining the receive field strengths of signals transmitted between the first antenna and the at least two antennas disposed in the vehicle, respectively (step 501). At least two of the determined receive field strengths are set in relation to each other (step 502). Each of the at least one formed ratio is compared to at least one threshold (step 503). The position of the transponder unit is determined based on the comparison of the ratios with the at least one threshold (step 504). LIST OF REFERENCE NUMBERS

10 vehicle

20 transmitting unit

2n antennas

S2n electromagnetic signals

30 mobile identification transmitter

31 antenna

S31 electromagnetic signal 40 control unit

A, B, C, D zones

Claims

claims

1. Device for determining the position of a mobile

An identification transmitter (30) relative to a vehicle (10), the device comprising a first antenna (31) arranged in the mobile identification transmitter (30) and at least two antennas (2n) arranged in the vehicle (10), and wherein the pre ^¬ direction is designed to

the reception field strengths _(P3i-> _n 2) of between the first antenna (31) and said at least two in the vehicle (10) disposed antennas (2n) transmitted signals (S 2n, S31) to determine;

to form _(> 2 _n P3i-) at least one ratio of two different measured reception field strengths; and

comparing each of the at least one formed ratio with at least one threshold, respectively

the position of the mobile identification transmitter (30) is determined on the basis of the comparison of the at least one ratio with the at least one threshold.

2. Device according to claim 1, wherein arranged in the vehicle (10) antennas (2n) at least one antenna in the inner space of the vehicle (10) and at least one antenna in the outer space of the vehicle (10) is arranged.

3. Device according to claim 1, wherein at least one of: antennas (2n) arranged in the vehicle (10) have at least one antenna in the region of the hood of the vehicle (10) and at least one antenna in the region of the trunk of the vehicle (10 ) is arranged;

at least one antenna in the region of the right side of the vehicle (10) and at least one antenna in the region of the left side of the vehicle (10) are arranged by the antennas (2n) arranged in the vehicle (10); and of the antennas (2n) arranged in the vehicle (10), two antennas at obliquely opposite corners of the antenna

Vehicle (10) are arranged.

4. Apparatus according to claim 1, 2 or 3, wherein the ratio of two reception field strengths (P3i- _> 2 _n ) is formed which relate to antennas in the vehicle (10), which is a distance of more than 10cm, more than 50cm, more as lm or more than 2m to each other.

5. Device according to one of claims 1 to 4, wherein

the signals (S2n) from those in the vehicle (10) arranged

Antennas (2n) to the mobile identification transmitter (30) are sent and the mobile identification transmitter (30) adapted _(> 2 P3i- _n) to determine the reception field strengths of the received signals (S 2n), or

the signals (S31) are transmitted from the first antenna (31) arranged in the mobile identification transmitter (30) to the antennas (2n) arranged in the vehicle (10) and the device further comprises a control unit (40) which is in line with the vehicle arranged antennas (2n) is connected and which is adapted to determine the reception field strengths (P3i- _> 2 _n ) of the received signals (S31).

6. Device according to one of claims 1 to 5, wherein for each of the ratios formed the same threshold is used.

7. Device according to one of claims 1 to 5, wherein for at least two of the ratios formed different thresholds are used.

8. Device according to one of the preceding claims, wherein the reception field strength (P3i- _> 2 _n ) with respect to a vehicle in ^¬ ordered antenna (2n) of the removal of the mobile Identity encoder (30) to the corresponding antenna (2n) depends.

9. Apparatus according to any one of the preceding claims, wherein each ratio is compared to a first threshold and a second threshold.

10. Device according to one of the preceding claims, which is further adapted to determine a damping of the signal between the two antennas (2n) by means of a signal between two in the vehicle (10) arranged antennas (2n) signal.

11. The device of claim 10, wherein the at least one threshold depends on the determined attenuation.

12. A method for determining the position of a mobile identification transmitter in relation to a vehicle, wherein the mobile identification transmitter has a first antenna and the vehicle has at least two antennas, and wherein the method comprises

Determining the reception field strengths _(P3i-> _n 2) of between the first antenna (31) and arranged to at least two in the vehicle (10) antennas (2n) transmitted signals;

Forming at least one ratio of two different measured reception field strengths _(P3i-> 2 _n); and

Comparing each of the formed ratios to at least one threshold, respectively

the position of the mobile identification transmitter (30) is determined on the basis of the comparison of the ratios with the at least one threshold.