Position determiner

Abstract

A position determiner is provided comprising: a first antenna; a radio signal modification device, wherein the radio signal modification device is configured to improve the ability to determine whether a portable key device is located on a back side or a front side of the position determiner based on obtaining a channel impulse response, CIR, from an impulse signal transmitted from the portable key device, wherein the position determiner is mountable such that the back side is in a space limited by a physically barrier that is selectively unlockable and the front side is opposite the back side.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a position determiner, and in particular to facilitating determining whether a portable key device is located on a front side or a back side of the position determiner. BACKGROUND

[0002] Locks and keys are evolving from traditional, purely mechanical locks. Today, there are wireless interfaces for electronic locks, for example by interacting with a portable key device. For example, Radio Frequency Identification (RFID) has been used as a wireless interface.

[0003] When using RFID, the user needs to present the portable key device in the vicinity of a reader connected to the lock. Furthermore, RFID requires a relatively large antenna in the reader next to the lock and uses a lot of energy. Importantly, RFID requires the user to actively take out the portable key device (e.g. an RFID card or a smart phone supporting NFC (Near Field Communication)) and bring it within a few centimeters of the lock. This is inconvenient and can be insecure, as the portable key device is more easily stolen by an attacker when it is presented to the lock for access control.

[0004] By using other short-range wireless communication with a slightly longer communication range, such as Bluetooth Low Energy (BLE), Bluetooth or Ultra-Wideband (UWB), the portable key device can be put in a pocket or a handbag and still be used for access control. However, the extended range also brings new problems. If the lock is unlocked every time an authorized portable key device is within range, one problem that arises is that the electronic lock can be unintentionally unlocked when a person inside walks past the electronic lock or hangs a coat inside, and anyone can enter the restricted physical space.

[0005] By determining whether the portable key device (and thus the user) is inside or outside, automatic access control can still be used, but the person inside will not trigger the unlocking process.

[0006] However, it needs to be reliable to determine whether the portable key device is inside or outside. SUMMARY

[0007] It is an object to achieve improved reliability for determining whether a portable key device is located on a front side or a back side of a position determiner.

[0008] According to a first aspect, there is provided a position determiner comprising: a first antenna; a radio signal modification arrangement, wherein the radio signal modification arrangement is configured to improve an ability to determine whether a portable key device is located on a back side or a front side of the position determiner based on obtaining a channel impulse response, CIR, of an impulse signal transmitted by the portable key device, wherein the position determiner is mountable such that the back side is in a space restricted by a physically barrier that is selectively unlockable, and the front side is opposite the back side.

[0009] The radio modification arrangement can be configured to enhance an asymmetry in CIR reception between when the portable key device is located on the back side and when the portable key device is located on the front side.

[0010] The position determiner can further comprise a metal plate on the back side of the first antenna. The metal plate can be a ground plane portion of an antenna assembly that also comprises the first antenna. Alternatively or additionally, when the metal plate is a metal door, the metal plate can be the physical barrier.

[0011] The position determiner can further comprise a second antenna.

[0012] The radio signal modification arrangement can be implemented by a radio asymmetry arrangement configured to increase a difference in how an ultra-wideband, UWB, impulse signal is received by the first antenna and the second antenna when the UWB impulse signal is transmitted from the back side of the position determiner.

[0013] The radio asymmetry arrangement can be implemented by the metal plate being arranged such that a centre of the metal plate is arranged closer to the first antenna than to the second antenna.

[0014] The radio asymmetry arrangement can comprise an edge waveguide arranged alongside an edge of the metal plate that is closer to the first antenna than to the second antenna, whereby the edge waveguide is configured to increase a signal level of the UWB impulse signal at the first antenna more than at the second antenna.

[0015] The radio asymmetry arrangement can comprise a first peripheral wave blocker arranged in contact with an edge of the metal plate that is closer to the first antenna than to the second antenna, whereby the first peripheral wave blocker is configured to increase a path length of the UWB impulse signal to the first antenna compared to a path length to the second antenna.

[0016] The radio asymmetry arrangement can comprise a second peripheral wave blocker arranged in contact with a portion of a second edge of the metal plate that is closer to the first antenna than to the second antenna.

[0017] The radio asymmetry arrangement can comprise a central wave blocker arranged between the first antenna and the second antenna.

[0018] The radio signal modification device can be implemented by a radio wave diffuser configured to diffuse more of the UWB pulse signal when received by the first antenna from the back side 16 than when the UWB pulse signal is received by the first antenna from the front side.

[0019] The radio wave diffuser can comprise a radio frequency, RF, absorber made of RF radiation absorbing material.

[0020] The RF absorber can be arranged so as to reduce deflection of the UWB pulse signal from the back side around the metal plate towards the first antenna.

[0021] The RF absorber can be arranged at the back side of the metal plate.

[0022] The RF absorber can extend beyond an edge of the metal plate when viewed from a direction perpendicular to the metal plate.

[0023] The RF absorber can be arranged at a periphery of the metal plate in a main plane of the metal plate.

[0024] The RF absorber can be a radio asymmetry device configured to increase a difference in how the UWB pulse signal is received by the first antenna and the second antenna when the UWB pulse signal is emitted from the back side of the position determinator.

[0025] The radio wave diffuser can comprise a plurality of edge waveguides arranged beside opposite edges of the metal plate, respectively, and a central waveguide arranged at the front side of the first antenna and the second antenna and in between the first antenna and the second antenna.

[0026] The radio wave diffuser can comprise a rectangular metal plate arranged parallel to the metal plate in front of the first antenna and the second antenna, wherein a hole in the center of the rectangular metal plate provides line-of-sight reception of the UWB pulse signal from the front side.

[0027] The position determinator can further comprise an outer wave blocker attached to an outer edge of the rectangular metal plate, wherein the outer wave blocker is inclined from the rectangular metal plate towards the back side.

[0028] Generally, unless otherwise indicated herein, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of whatever is referred to unless indicated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed unless explicitly stated. BRIEF DESCRIPTION OF DRAWINGS

[0029] Aspects and embodiments are now described, by way of example, with reference to the drawings, in which:

[0030] FIG. 1 is a schematic diagram illustrating an electronic access control system, an environment in which embodiments presented herein can be applied;

[0031] FIGS. 2A-2B is a schematic diagram illustrating a pulse signal from a portable key device and a corresponding channel impulse response;

[0032] FIG. 3A and FIG. 3B is a schematic diagram illustrating how the CIR differs between different antennas;

[0033] FIGS. 4A-4B is a schematic diagram illustrating an embodiment in which the radio signal modification means of the position determiner is implemented by radio asymmetry means comprising an asymmetrically placed ground plane;

[0034] FIG. 5 is a schematic diagram illustrating radio signal modification means of the position determiner implemented by radio asymmetry means comprising an edge waveguide;

[0035] FIG. 6 is a schematic diagram illustrating radio signal modification means of the position determiner implemented by radio asymmetry means comprising a first peripheral wave blocker;

[0036] FIGS. 7A-7B is a schematic diagram illustrating radio signal modification means of the position determiner implemented by radio asymmetry means comprising a plurality of peripheral wave blockers;

[0037] FIG. 8 is a schematic diagram illustrating radio signal modification means of the position determiner implemented by radio asymmetry means comprising a first peripheral wave blocker and a central wave blocker;

[0038] FIGS. 9A-9B is a schematic diagram illustrating radio signal modification means of the position determiner implemented by a radio wave diffuser comprising an RF (radio frequency) absorber in the back side;

[0039] FIGS. 10A-10B is a schematic diagram illustrating radio signal modification means of the position determiner implemented by a radio wave diffuser comprising an RF absorber arranged in the periphery of a ground plane;

[0040] FIGS. 11A-11B and FIGS. 12A-12B is a schematic diagram illustrating radio signal modification means of the position determiner implemented by asymmetric radio wave diffusers;

[0041] FIG. 13 is a schematic diagram illustrating radio signal modification means of a position determiner implemented by a radio wave diffuser comprising a plurality of edge waveguides and a center waveguide; and

[0042] FIGS. 14A-14B is a schematic diagram illustrating radio signal modification means of a position determiner implemented by a radio wave diffuser comprising a rectangular metal plate and optionally an external wave blocker. DETAILED DESCRIPTION

[0043] Aspects of the present disclosure will now be described in greater detail with reference to the drawings, in which certain embodiments of the present application are shown. These aspects are, however, not to be interpreted as limiting; rather, the embodiments are to be provided as examples in order that the present disclosure will be thorough and complete, and will fully convey the scope of all aspects of the present application to those skilled in the art. Throughout the specification, like drawing reference numerals refer to like elements.

[0044] The embodiments presented herein determine when a portable key device is located on the front side or the back side relative to a barrier (e.g. a door) based on a channel impulse response (CIR). A pulse is emitted by the portable key device and the CIR is received by an antenna of the position determiner. The position determiner further comprises radio signal modification means and the position determiner is arranged on the back side (inside) of the barrier. The radio signal modification means are configured such that they increase the ability to determine whether the portable key device is located on the back side or the front side (outside) of the barrier by increasing the asymmetry of the reception of the CIR by one or more antennas. This allows for a convenient and reliable determination of the front side or the back side, such that for example access control is only performed when the portable key device is located on the front side (i.e. outside) of the barrier.

[0045] FIG. 1is a schematic view showing an electronic access control system 10, which is an environment in which embodiments presented herein can be applied. Access to the back side 16 of the position determiner 1 is restricted by a selectively unlockable physical barrier 15. The physical barrier 15 is located between the back side 16 of the position determiner and the front side 14 of the position determiner. The back side 16 of the position determiner 1 is a restricted physical space, and the front side 14 of the position determiner 1 is an accessible physical space. In other words, the position determiner can be installed such that the back side 16 (of the position determiner) is in a space restricted by a selectively unlockable physical barrier 15, and the front side 14 is opposite to the back side 16. Note that the front side 14 of the position determiner 1 can be a restricted physical space itself, but with respect to this particular position determiner 1, the front side 14 of the position determiner is accessible. In other words, the back side 16 of the position determiner 1 is inside the physical barrier 15, and the front side 14 of the position determiner is outside the physical barrier 15. The barrier 15 can be a door, a gate, a hatch, a window, a drawer, etc. The barrier 15 can be, for example, a metal door, such as a fire door or a security door. A handle 17 or a door knob is provided to allow opening of the barrier 15 once unlocked. Alternatively, an electric door opener can be used to open the door. To unlock or lock the barrier 15, an electronic lock 12 is provided. The electronic lock 12 can be in an unlocked state or a locked state. The electronic lock 12 can be separate from but connected to the position determiner 1 (as shown), or can form a part of the position determiner 1 (not shown). In one embodiment, the position determiner 1 further comprises the electronic lock 12. The barrier 15 is provided in a surrounding fixed structure 11, such as a wall, a fence, or a vehicle.

[0046] The position determiner 1 comprises one or more antennas 13a-b. Each antenna is fixedly mounted relative to the electronic lock 12. Each antenna can be a directional antenna, where the gain varies according to the direction of reception or transmission. For example, each antenna can be a patch antenna or other antenna with a ground plane arranged behind the radiating element. In this way, the type and size of the material behind the antenna has little or no impact on the antenna characteristics. When implemented as a directional antenna, the antenna faces the front side 14 of the position determiner 1. This means that the antenna 13 has a line-of-sight with the portable key device in the front side 14 of the position determiner. The line-of-sight is to be interpreted as a line-of-sight in terms of radio signal propagation. In other words, there can be a thin plastic cover or similar protecting the antenna 13 from the space of the front side 14 of the position determiner 1. In practice, the portable key device can even be in a back pocket or similar, in which case there is a body between the portable key device and the antenna. The direction in which the antennas 13a-b face is the direction in which signal reception and transmission takes place best. Thus, when the antenna is a directional antenna, the maximum gain of the antenna faces the front side 14. This can be achieved, for example, with a metal plate, such as a ground plane or other metal plate, arranged on the opposite side (rear side) of the antenna, see below.

[0047] The position determiner 1 is used to determine whether a first portable key device 2a and a second portable key device 2b in the vicinity of the electronic lock 12, for example, are located on the front side 14 or the rear side 16 of the position determiner 1. The determination is based on the relationship to the position determiner 1 and can be based on, for example, UWB (Ultra-Wideband) technology. UWB provides high accuracy of device positioning, but at the cost of relatively large energy usage. Alternatively or additionally, the positioning module 13 can be based on other positioning technologies.

[0048] The electronic lock 12 is capable of receiving and transmitting signals from / to the portable key devices 2a-b over a communication channel, which can be a short-range wireless interface. The electronic lock 12 can use the same antennas 13a-b as used by the position determiner 1 for the short-range wireless interface.

[0049] Optionally, the electronic lock 12 comprises a separate unit for communicating with the portable key devices 2a-b and evaluating access, which is also referred to as an access control reader. In this example, there is a first portable key device 2a and a second portable key device 2b. The portable key devices 2a-b are implemented using any suitable device, which is portable by a user and can be used by the electronic lock 12 to evaluate whether access is granted by communicating on a communication channel. The portable key device can comprise a digital key for electronic authentication.

[0050] The portable key devices 2a-b are typically carried or worn by the users and can be implemented as a smartphone, a wearable device, a key card, etc. In this example, the first portable key device 2a is carried by the first user 4a and the second portable key device 2b is carried by the second user 4b. The first user 4a and the first portable key device 2a are located at the front side 14 of the location determiner 1 (i.e. outside the electronic lock 12) and the second user 4b and the second portable key device 2b are located at the back side 16 of the location determiner (i.e. inside the electronic lock 12).

[0051] The short-range wireless interface between the portable key devices 2a-b and the electronic lock 12 is a radio frequency wireless interface and can for example employ Bluetooth Low Energy (BLE), Bluetooth, ZigBee, Radio Frequency Identification (RFID), any IEEE 802.11 standard, any IEEE 802.15 standard, etc. Using the communication channel, the portable key devices 2a-b can be authenticated and an authorization determination (access control) can be performed by the electronic lock 12 or an access control reader. The communication over the short-range wireless interface can be encrypted.

[0052] When the access control of the electronic lock 12 makes access permissible, the electronic lock 12 is set to an unlocked state. When the electronic lock 12 is in the unlocked state, the barrier 15 can be opened and when the electronic lock 12 is in the locked state, the barrier 15 cannot be opened. In this way, access to the back side 16 of the location determiner 1 is controlled by the electronic lock 12. It should be noted that the electronic lock 12 can be installed in the fixed structure 11 by the physical barrier 15 (as shown) or in the physical barrier 15 itself (not shown).

[0053] The electronic lock 12 can perform access control for any portable key device 2a-b that presents itself to it. However, according to the embodiments presented herein, access can only be granted if the portable key device 2a is determined to be behind the front side 14 of the location determiner. The reason for this is that if the electronic lock 12 granted access whenever a portable key device is within communicable range, the second portable key device 2b in the restricted physical space 16 (i.e. inside) could cause the electronic lock 12 to be unlocked when the second user 4b walks by but does not intend to unlock the electronic lock 12 to open the barrier. Then, an unauthorized person could open the barrier 15 and enter the restricted physical space 16.

[0054] The electronic lock 12 optionally comprises communication capabilities to connect to the server 6 of the electronic access control system 10 via a network 5. This network can be a wide area network such as the Internet, to which the portable key devices 2a to 2b can connect, for example, via WiFi (e.g. any IEEE 802.11x standard) or a cellular network such as LTE (Long Term Evolution), Next Generation Mobile Networks (Fifth Generation, 5G), UMTS (Universal Mobile Telecommunications System) using W-CDMA (Wideband Code Division Multiplexing), etc.

[0055] FIGS. 2A-2B is a schematic diagram showing a UWB pulse signal 29 from a portable key device 2a, 2b and the corresponding Channel Impulse Response (CIR). The horizontal axis represents time, and the vertical axis represents amplitude.

[0056] In FIG. 2A , the UWB pulse signal 29 from the portable key device is shown in the form of generating and transmitting this UWB pulse signal 29 from the portable key device. The UWB pulse signal 29 can be transmitted by the portable key device based on a command triggered by the position determiner.

[0057] In FIG. 2B , the CIR 30 is shown. The CIR 30 is the received version of the UWB pulse signal 29, in this case by one of the antennas 13a, 13b of the position determiner. Due to attenuation, reflections, absorption, antenna shape and other radio environmental factors, the CIR 30 differs in shape from the UWB pulse signal 29.

[0058] Since the radio environmental factors are significantly different if the UWB pulse signal is received from the front side 14 in line of sight and if the UWB pulse signal is received from the back side 16, the CIR can be used to determine whether the transmitter of the UWB pulse signal 29, i.e. the portable key device, is located at the front side 14 or the back side 16 of the position determiner.

[0059] FIG. 3A and FIG. 3B is a schematic diagram showing how the CIR is received by two different antennas. A first CIR 30a is shown, which is the envelope of the signal received by the first antenna. A second CIR 30b is shown, which is the envelope of the signal received by the second antenna.

[0060] In FIG. 3AIn the middle, the first CIR 30a and the second CIR 30b are shown based on the portable key device emitting the UWB pulse signal 29 from the front side 14. It can be seen how the first CIR 30a and the second CIR 30b are very similar and follow each other very well within the measurement time period 32. When receiving the UWB pulse signal 29 from the front side 14, there is a line of sight to the antennas. In this case, the difference between the CIR shapes for the two antennas is very small. Furthermore, the signal amplitudes of the two CIRs 30a to 30b drop off relatively fast.

[0061] In FIG. 3B the middle, the first CIR 30a and the second CIR 30b are shown based on the portable key device emitting the UWB pulse signal from the back side 16. In this case, the radio signals will experience different radio environments and be affected differently by reflections and absorption, resulting in a significant difference between the shapes of the first CIR 30a and the second CIR 30b. In addition, the CIRs are more spread out over time compared to the front side example of FIG. 3A According to the embodiments presented herein, the position determiner further comprises a radio signal modification device configured to improve the ability to determine whether the portable key device 2a, 2b is located at the front side 14 or the back side 16 of the position determiner. This is achieved by a radio modification device that enhances the asymmetry in the CIR reception between when the portable key device is located at the back side and when the portable key device is located at the front side, which applies to both the single antenna case and the multiple antenna case.

[0062] When receiving the UWB pulse signal 29 from the front side, there is a line of sight to the two antennas 13a, 13b, in which case the difference between the CIR shapes for the two antennas 13a, 13b is very small, as shown in FIG. 3A On the other hand, when receiving the UWB pulse signal from the back side of the position determiner, the radio signals will experience different radio environments and be affected differently by reflections and absorption, resulting in a significant difference between the CIR shapes 30a, 30b for the two antennas 13a, 13b, as shown in FIG. 3B In this way, the position determiner 1 can deduce that if the difference between the CIR shapes for the two antennas 13a, 13b is smaller than a threshold value, the portable key device is at the front side 14, and if the difference between the CIR shapes 30a, 30b of the two antennas 13a, 13b is larger than a threshold value, the portable key device is at the back side. The difference can for example be determined as the area between the envelopes of the two CIRs or a measure of the correlation between the two CIR shapes 30a, 30b.

[0063] If the difference between the CIRs for the two antennas 13a, 13b increases when receiving the UWB signal from the rear side 16 of the portable key device, the reliability of the determination increases. Therefore, in some embodiments, the radio signal modification device comprises a radio asymmetry device configured to increase the difference in how the UWB pulse signal 29 is received by the first antenna 13a and the second antenna 13b. Embodiments of such a radio asymmetry device are shown in FIGS. 4A-4B , FIG. 5 , FIG. 6 A to FIG. 6 B and Fig. 7 and are described below.

[0064] Another way for the position determiner 1 to determine when the portable key device is located at the front side 14 or the rear side 16 of the position determiner is based on the shape of the individual CIRs 30a, 30b from either (or both) of the antennas 13a, 13b. Specifically, when receiving the UWB pulse signal 29 from the front side 14, there is a line of sight to both antennas 13a, 13b, in which case the CIRs correspond better to the UWB pulse signal 29 than when receiving the UWB pulse signal 29 from the rear side 16. In other words, the CIRs 30a, 30b when the portable key device is at the rear side 16 are diffuse, as shown in FIG. 3B , and do not have as sharp a peak as the CIRs 30a, 30b when the portable key device is at the front side 14, as shown in FIG. 3A . Therefore, in some embodiments, the radio signal modification device comprises a radio wave diffuser configured to diffuse the UWB pulse signal 29 more when receiving the UWB pulse signal 29 from the rear side 16 than when receiving the UWB pulse signal 29 from the front side 14. This improves the reliability of determining when the portable key device is located at the front side 14 of the position determiner 1 and when the key device is located at the rear side 16 of the position determiner 1. Embodiments of such a radio wave diffuser are shown in FIGS. 9A-9B , FIGS. 10A-10B , FIG. 13 and FIGS. 14A-14B and are described below.

[0065] Embodiments of the radio signal modification device as both a radio asymmetry device and a radio wave diffuser are shown in FIGS. 11A-11B and FIGS. 12A-12B and are described below.

[0066] FIGS. 4A-4Bis a schematic diagram showing an embodiment of the radio signal modification device of the position determiner 1 comprising a radio asymmetric device comprising asymmetrically placed ground planes. The UWB pulse signal 29 is here shown to be emitted from the back side 16. The schematic waves are shown as curves to illustrate the propagation of the waves.

[0067] In this embodiment, the radio asymmetric device 20 is realized by arranging the metal plate 22 such that the center of the metal plate 22 is arranged closer to the first antenna than to the second antenna. The metal plate 22 can for example be a (e.g. copper) ground plane behind the antennas 13a, 13b or a (e.g. steel containing) metal door.

[0068] This enhances the asymmetry in receiving the UWB pulse signal from the back side of the position determiner by blocking more radio waves through the first antenna 13a than through the second antenna 13b.

[0069] In this embodiment, the radio asymmetric device 20 is realized by arranging the metal plate 22 such that the center of the metal plate 22 is arranged closer to the first antenna than to the second antenna. The metal plate 22 can for example be a (e.g. copper) ground plane behind the antennas 13a, 13b or a (e.g. steel containing) metal door. FIG. 4A In this embodiment, the radio asymmetric device 20 is realized by arranging the metal plate 22 such that the center of the metal plate 22 is arranged closer to the first antenna than to the second antenna. The metal plate 22 can for example be a (e.g. copper) ground plane behind the antennas 13a, 13b or a (e.g. steel containing) metal door. FIG. 4B In this embodiment, the radio asymmetric device 20 is realized by arranging the metal plate 22 such that the center of the metal plate 22 is arranged closer to the first antenna than to the second antenna. The metal plate 22 can for example be a (e.g. copper) ground plane behind the antennas 13a, 13b or a (e.g. steel containing) metal door.

[0070] FIG. 5 is a schematic diagram showing the radio signal modification device of the position determiner realized by the radio asymmetric device 20 comprising a first peripheral wave blocker 24a.

[0071] The first peripheral wave blocker 24a is arranged in contact with the edge of the metal plate 22 by the first antenna. In other words, the first peripheral wave blocker 24a is then arranged in contact with the edge (i.e. the upper edge in FIG. 5

[0072] FIG. 6 is a schematic diagram showing the radio signal modification device of the position determiner realized by the radio asymmetric device 20 comprising a first peripheral wave blocker 24a.

[0073] ​As in many of the embodiments presented herein, the position determiner 1 includes a common ground plane 22 behind both the first antenna 13a and the second antenna 13b. The ground plane 22 may be a rectangular metal plate (e.g., made of copper). In one embodiment, the radio asymmetry device 20 is implemented by setting the ground plane such that its center is offset, thereby being positioned closer to the first antenna 13a than the second antenna 13b.

[0074] exist FIG. 6 In the illustrated embodiment, the radio asymmetry device 20 includes an edge waveguide 23 disposed adjacent to the edge of the ground plane 22, which is closer to the edge of the first antenna 13a than the edge of the second antenna 13b. In this way, the edge waveguide 23 improves reception at the first antenna and is therefore configured to increase the signal level of the UWB pulse signal 29 at the first antenna 13a more than at the second antenna 13b. The edge waveguide 23 may be made of a metal such as copper.

[0075] FIGS. 7A-7B This is a schematic diagram showing a radio signal modification device for a position determiner implemented by a radio asymmetry device 20 including multiple peripheral wave blockers 24a to 24c. FIG. 7A The peripheral wave blockers 24a to 24c are shown in the side view, and FIG. 7B The peripheral wave blockers 24a to 24c are shown in the front view.

[0076] In this embodiment, in addition to the first wave blocker 24a, at least one other peripheral wave blocker is present. In this example, a second peripheral wave blocker 24b and a third wave blocker 24c are present. These wave blockers are positioned closer to the vertical edge (along the y-axis) of the first antenna 13a, i.e. FIG. 7A The upper part. In other words, the radio asymmetric device 20 includes a second peripheral wave blocker 24b and a third peripheral wave blocker 24c, both of which are configured to contact a portion of the second edge of the ground plane 22, which is closer to the first antenna 13a than the second antenna 13b.

[0077] The addition of additional peripheral wave blockers 24b to 24c has the same characteristics as FIG. 6 The first peripheral wave blocker has the same effect, but increases the blocking of the first antenna 13a, thereby increasing the asymmetry between the two antennas 13a and 13b.

[0078] The additional peripheral wave blockers 24b to 24c can be made of metal such as copper.

[0079] FIG. 8This is a schematic diagram illustrating a radio signal modification device for a position determiner implemented by a radio asymmetry device 20 including a first peripheral wave blocker 24a and a center wave blocker 26. The center wave blocker 26 is disposed between the first antenna 13a and the second antenna 13b. The center wave blocker 26 may be made of metal such as copper.

[0080] The center wave blocker 26 further reduces any UWB pulse signals from the rear that reach the first antenna 13a and also the second antenna. In this way, the asymmetry between the two antennas 13a and 13b is increased.

[0081] FIGS. 9A-9B and FIGS. 10A-10B This is a schematic diagram showing a radio signal modification device for a position determiner implemented by a radio wave diffuser 18. (See Figures 4 to 5) FIG. 8 Compared to the embodiments shown, these embodiments (and) FIGS. 11A-11B , FIGS. 12A-12B , FIG. 13 and FIGS. 14A-14B The implementation method does not rely on the asymmetry of the CIR between the two antennas 13a and 13b. Instead (or in addition to the asymmetry), the radio signal modification device is implemented here by a radio wave diffuser 18, which is configured to diffuse the UWB pulse signal received from the rear side 16 more than it diffuses the UWB pulse signal received from the front side 14. Thus, the asymmetry on both sides is utilized and enhanced, but it can be achieved using a single antenna. Therefore, the implementation including the radio wave diffuser can be implemented using only one antenna. FIG. 9A and FIG. 9B In the embodiment shown, the radio wave diffuser 18 includes an RF absorber 35 made of an RF radiation absorbing material.

[0082] exist FIG. 9A The image shows how the RF absorber 35 is positioned behind the ground plane 22, i.e., behind the radio wave diffuser 18 at side 16. FIGS. 10A-10B as well as FIGS. 9A-9B As shown, when viewed from a direction perpendicular to the metal plate, the RF absorber 35 can extend beyond the edge of the metal plate 22, that is, beyond the ground plane 22 along the periphery in the x and y directions.

[0083] exist FIGS. 10A-10BIn the middle, the RF absorber 35 is arranged at the periphery of the ground plane. Thus, the RF absorber 35 is arranged around the ground plane 22. The RF absorber 35 is arranged at the periphery of the ground plane 22 in the main plane of the ground plane 22. In other words, the RF absorber 35 is arranged outside the edges of the ground plane 22 (in the plane of the ground plane, i.e. the x-y plane here), but without a significant gap to the edges of the ground plane 22 (e.g. in contact with the edges of the ground plane 22). In the direction perpendicular to the ground plane 22, i.e. in the z-direction in the indicated coordinate system, and relative to the ground plane 22, the RF absorber 35 can be arranged completely at the front side 14, completely at the back side 16, or partially at the front side 14 and partially at the back side 16, as long as the RF absorber 35 has no significant gap to the ground plane in the plane of the ground plane (x-y). A significant gap is here explained as a gap large enough to allow RF waves to pass through.

[0084] FIGS. 11A-11B and FIGS. 11A-11B The RF absorber 35 shown in the middle effectively reduces the ability of the antennas 13a-b to receive the UWB pulse signal 29 from the back side 16, while the reception from the front side is hardly affected. In this way, the first peak in the CIR is significantly spread, which can be used to determine when the UWB pulse signal is received from the front side 14 or the back side 16. The RF absorber 35 is arranged next to the edges of the ground plane 22, thereby reducing the deflection of the UWB pulse signal 29 from the back side 16 around the metal plate 22 to the first antenna 13a (and optionally the second antenna).

[0085] FIGS. 11A-11B and FIG. 11B is a schematic diagram showing the radio signal modification device of the position determiner implemented by the asymmetric radio wave spreader 18. In other words, the radio signal modification device is both a radio wave spreader and a radio asymmetry device. Also here, the radio wave spreader 18 further comprises the RF absorber 35. However, the RF absorber 35 is here the radio asymmetry device 20, which is configured to increase the difference in how the UWB pulse signal 29 is received by the first antenna 13a and the second antenna 13b when the UWB pulse signal 29 is emitted from the back side of the position determiner.

[0086] Looking first at FIG. 12B , the RF absorber 35 is arranged in a rectangular piece behind the ground plane 22. As shown in FIGS. 11A-11B , the RF absorber 35 can extend beyond the edges of the metal plate on three sides. In this case, the RF absorber 35 extends beyond the edges of the metal plate 22 on all sides except the side closer to the second antenna compared to the first antenna.

[0087] Now looking atFIGS. 12A-12B Here the RF absorber 35 is arranged in a U-shape in front of the ground plane 22. Also here, as shown, the RF absorber 35 can extend beyond the edges of the metal plate on three sides. In this case, the RF absorber 35 extends beyond the edges of the metal plate 22 in which it is arranged, i.e. on all sides except the side closer to the second antenna compared to the first antenna. FIG. 13

[0088] In embodiments where the RF absorber is arranged asymmetrically, by arranging an RF reflector in front of the position determiner, it can be detected whether an attacker tries to spoof the system. If the RF absorber 35 is arranged symmetrically with respect to the antennas 13a-b, there is a risk that a UWB pulse emitted from the back side 16 can be reflected back to the antennas 13a-b by the reflector and the UWB pulse is considered to be emitted from the front side 14. However, by arranging the RF absorber 35 asymmetrically with respect to the antennas 13a-b, the position determiner can take both the diffusion of the UWB pulse and the asymmetry between the two antennas into account to determine when a UWB pulse is emitted from the back side 16, which provides a secure determination of the emitting side and becomes more difficult for an attacker to circumvent. FIGS. 14A-14B FIG. 14A

[0089] FIG. 14B is a schematic diagram illustrating the radio signal modification device of a position determiner implemented by a radio wave diffuser 18 comprising a plurality of edge waveguides 23a, 23b and a central waveguide 27.

[0090] The plurality of edge waveguides 23a, 23b are arranged next to opposite edges of the ground plane 22, respectively, and the central waveguide 27 is arranged in front of the first antenna 13a and the second antenna 13b and centrally between the first antenna 13a and the second antenna 13b. This arrangement of waveguides 23a, 23b diffuses UWB pulse signals from the back side 16 while allowing signals from the front side 14 to be received with minimal diffusion.

[0091] The edge waveguides 23a, 23b and the central waveguide 27 can be made of metal, e.g. copper.

[0092] FIG. 14B is a schematic diagram illustrating the radio signal modification device of a position determiner implemented by a radio wave diffuser 18 comprising a rectangular metal plate 21 and an optional external wave blocker 28. FIG. 14A The radio wave diffuser 18 is shown from a side view, and FIGS. 4A-4B The radio wave diffuser 18 is shown from a front view.

[0093] ​​​A rectangular metal plate 21 is arranged in front of the first and second antennas 13a, 13b parallel to the ground plane 22. As shown in FIG. 5 , a hole 32 in the center of the rectangular metal plate 21 provides line-of-sight reception of the UWB pulse signal 29 from the front side 14.

[0094] The rectangular metal plate 21 significantly diffuses the UWB pulse signal from the back side 16 while allowing the signal from the front side 14 to be received with minimal diffusion.

[0095] Optionally, an external wave blocker 28 is arranged to be attached to the outer edge of the rectangular metal plate 21, wherein the external wave blocker 28 is tilted from the rectangular metal plate 21 towards the back side 16 as shown in FIG. 6 . This external wave blocker 28 further diffuses the rectangular metal plate 21.

[0096] The rectangular metal plate 21 and the external wave blocker 28 can be made of metal, e.g. copper.

[0097] It should be noted that FIG. 8 , ​ , ​ , any of the embodiments shown in Fig. 7 and ​ can also diffuse the UWB pulse signal.

[0098] Aspects of the disclosure have been described above with primary reference to several embodiments. However, as is readily understood by those skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the application, as defined by the appended patent claims. Thus, although the various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to limit the true scope of the application, which is set forth in the appended claims.

Claims

1. A position determiner (1), comprising: a first antenna (13a); a second antenna (13b); a metal plate (22) behind the first antenna (13a); radio signal modifying means (18, 20), wherein the radio signal modifying means (20, 18) are configured to improve an ability to determine whether a portable key device (2a, 2b) is located at a back side (16) or a front side (14) of the position determiner based on obtaining a channel impulse response, CIR, (30, 30a, 30b) of a pulse signal (29) emitted by the portable key device (2a, 2b), wherein the position determiner is mountable such that the back side (16) is in a space restricted by a physically barrier (15) that is selectively unlockable, and the front side (14) is opposite to the back side (16), wherein the radio signal modifying means comprise radio asymmetry means (20) configured to increase a difference in how an ultra-wideband, UWB, pulse signal (29) is received by the first antenna (13a) and the second antenna (13b) when the UWB pulse signal (29) is emitted from the back side of the position determiner, wherein the radio asymmetry means (20) are achieved by arranging the metal plate (22) such that a center of the metal plate (22) is arranged closer to the first antenna than to the second antenna; wherein both the first antenna and the second antenna face the front side, wherein the radio asymmetry means (20) comprise an edge waveguide (23) arranged next to an edge of the metal plate (22), the edge being closer to the first antenna (13a) than to the second antenna (13b), whereby the edge waveguide (23) is configured to increase a signal level of the UWB pulse signal (29) at the first antenna (13a) more than at the second antenna (13b); or the radio asymmetry means (20) comprise a first peripheral wave blocker (24a) arranged in contact with an edge of the metal plate (22), the edge being closer to the first antenna (13a) than to the second antenna (13b), whereby the first peripheral wave blocker (24a) is configured to increase a path length of the UWB pulse signal (29) to the first antenna (13a) compared to a path length to the second antenna (13b).

2. The position determiner of claim 1, wherein, the radio modifying means (18, 20) are configured to enhance an asymmetry in CIR reception between when the portable key device is located at the back side and when the portable key device is located at the front side.

3. The position determiner (1) according to claim 1, wherein the radio asymmetry means (20) comprise a second peripheral wave blocker (24b to 24c) arranged in contact with a portion of a second edge of the metal plate (22), the portion being closer to the first antenna (13a) than to the second antenna (13b).

4. The position determiner (1) according to claim 1 or 3, wherein The radio asymmetric device (20) comprises a central wave blocker (26) disposed between the first antenna (13a) and the second antenna (13b).

5. The position determiner (1) according to claim 1 or 2, wherein Each of the first antenna (13a) and the second antenna (13b) is a patch antenna when present.

6. The position determiner (1) according to claim 1 or 2, wherein The radio signal modification device comprises a radio wave diffuser (18), wherein the radio wave diffuser (18) is configured to diffuse more of the UWB impulse signal (29) when received by the first antenna from the back side (16) than when the UWB impulse signal (29) is received by the first antenna from the front side (14).

7. The position determiner of claim 6, wherein, The radio wave diffuser (18) comprises a radio frequency, RF, absorber (35) made of RF radiation absorbing material.

8. The position determiner of claim 7, wherein, The RF absorber (35) is disposed so as to reduce deflection of UWB impulse signals (29) from the back side (16) around the metal plate (22) to the first antenna (13a).

9. The position determiner of claim 7 or 8, wherein, The RF absorber (35) is disposed on the back side (16) of the metal plate (22).

10. The position determiner of claim 9, wherein, The RF absorber (35) extends beyond the edges of the metal plate (22).

11. The position determiner of claim 8, wherein, The RF absorber (35) is disposed in the main plane of the metal plate (22) at the periphery of the metal plate (22).

12. The position determiner of claim 8, wherein, The RF absorber (35) is a radio asymmetric device (20) configured to increase the difference in how the UWB impulse signal (29) is received by the first antenna (13a) and the second antenna (13b) when the UWB impulse signal (29) is emitted from the back side of the position determiner.

13. The position determiner (1) according to claim 6, wherein The radio wave diffuser (18) comprises a plurality of edge waveguides (23a, 23b) disposed beside opposite edges of the metal plate (22) and a central waveguide (27) disposed in front of the first antenna (13a) and the second antenna (13b) and centered between the first antenna (13a) and the second antenna (13b).

14. The position determiner (1) according to claim 6, wherein The radio wave diffuser (18) comprises a rectangular metal plate (21) disposed in front of the first antenna (13a) and the second antenna (13b) parallel to the metal plate (22), wherein a hole in the center of the rectangular metal plate (21) provides line-of-sight reception of the UWB impulse signal (29) from the front side (14).

15. The position determiner (1) according to claim 14, further comprising an outer wave blocker (28) attached to an outer edge of the rectangular metal plate (21), wherein, The external wave blocker (28) is inclined from the rectangular metal plate (21) towards the back side (16).

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