DE102021202319A1 - Antenna arrangement for an electronic vehicle key - Google Patents

Abstract

An antenna arrangement for an electronic key has an antenna (10) and an antenna circuit (20) designed to control the antenna (10), the antenna (10) and the antenna circuit (20) being arranged on a circuit board (30) which Antenna arrangement is designed for transmitting and receiving ultra-wideband signals or signals according to a Bluetooth standard and the antenna circuit (20) has a filter arrangement (24) designed for filtering signals which are received by the antenna (10) and are to be sent, wherein the filter arrangement (24) has a capacitance which is formed by at least two conductor tracks formed on the printed circuit board (30).

Description

The present invention relates to an antenna arrangement, in particular an antenna arrangement for an electronic vehicle key.

Most of today's vehicles can be unlocked and remotely started using an electronic vehicle key. Some "start/stop" entry systems are known in which the user has to press an unlock button of the electronic remote key in order to, for example, unlock or lock the vehicle, start the engine of the vehicle or open a trunk of the vehicle. Such an electronic vehicle key must usually be inserted into an immobilizer station located in the vehicle, which recognizes the vehicle key and allows the user to start the vehicle. Such systems replace the originally known ignition switch systems. Other "start/stop" entry systems do not require the user to press a button or insert the key into an immobilizer to unlock or lock the vehicle or start the engine. Such a "start/stop" access system is referred to as a passive start and access system or radio locking system (RKE - Remote Keyless Entry). With passive starting and entry systems, the vehicle can be automatically unlocked when the key is detected within a certain distance of the vehicle. To start the vehicle, a start button in the vehicle usually has to be pressed.

Such an electronic vehicle key communicates with the vehicle using wireless technology. An electronic vehicle key therefore usually has two or even more different antennas. For example, an electronic vehicle key may have at least one of a long wave (LF) antenna, a decimeter wave (UHF) antenna, an ultra wide band (UWB) antenna, and an antenna for Bluetooth communication. For example, Bluetooth or Bluetooth Low Energy (BLE) communication can be used to transmit various information (e.g. tire pressure, fuel status, etc.) from the vehicle to the vehicle key or to a handheld electronic device (e.g. a smartphone). be used. A filter stage must be provided for each antenna. The filter stage is typically expensive and requires a certain amount of space.

There is a need to provide an antenna arrangement for an electronic vehicle key that has comparatively small space requirements and can be implemented at comparatively low costs.

This problem is solved by an antenna arrangement according to claim 1 and an electronic vehicle key according to claim 12. Configurations and further developments of the invention are the subject of the dependent claims.

An antenna arrangement for an electronic key includes an antenna and an antenna circuit designed to control the antenna, the antenna and the antenna circuit being arranged on a printed circuit board, the antenna arrangement being designed to transmit and receive ultra-wideband signals or signals in accordance with a Bluetooth standard, and the antenna circuit a filter arrangement configured to filter signals received by the antenna and to be transmitted, the filter arrangement having a capacitance formed by at least two conductor tracks formed on the printed circuit board.

Such an antenna arrangement can be formed in a cost-effective manner since the filter arrangement can be formed extremely cost-effectively.

Only the material for forming the at least two conductor tracks on the printed circuit board is required to form the filter arrangement.

The capacitance may have a double helix shape having a first helical trace and a second helical trace spiraling into one another.

A filter assembly can thus be formed which has satisfactory performance for many applications.
The first spiral conductive pattern and the second spiral conductive pattern may each have a width in a horizontal direction of between 0.1 and 0.2 mm, the horizontal direction being a direction parallel to a surface of the circuit board on which the first spiral conductor track and the second spiral conductor track are formed.

A filter assembly can thus be formed which has satisfactory performance for many applications.

The first spiral wiring and the second spiral wiring may each have a width in the horizontal direction of 0.14 mm.

The first spiral conductive trace may be coupled to a first conductive trace and the second spiral conductive trace may be coupled to a second conductive trace.

The first conductive line and the second conductive line may each have a width in the horizontal direction of between 0.5 and 1.5 mm.

The first conductive pattern and the second conductive pattern may each have a width in the horizontal direction of 0.9 mm.

The first conductive line and the second conductive line may be 50Ω microstrip lines.

A filter arrangement can thus be formed which has satisfactory performance for many applications, in particular for ultra-wideband and Bluetooth antennas.

The at least two conductor tracks can have copper.

This allows the filter arrangement, and hence the antenna arrangement, to be formed in a very cost-effective manner.

The at least two conductive lines may have a thickness in a vertical direction of between 0.4 and 0.6 mm, the vertical direction being a direction perpendicular to a surface of the circuit board on which the conductive lines are formed.

A filter assembly can thus be formed which has satisfactory performance for many applications.

The antenna can have a conductor track on the printed circuit board.

The antenna can be a monopole antenna or an inverted-F antenna.

For example, a monopole antenna can be used for UWB transmission, and an inverted-F antenna can be used for Bluetooth or Bluetooth Low Energy transmission.

An electronic vehicle key has an antenna arrangement.

• 1 veranschaulicht schematisch eine Antennenanordnung gemäß einem Beispiel.
• 2 veranschaulicht schematisch eine Antennenanordnung, die auf einer Leiterplatte angeordnet ist, gemäß einem Beispiel.
• 3 veranschaulicht schematisch eine Filteranordnung gemäß einem Beispiel.
• 4 veranschaulicht schematisch in einem Diagramm verschiedene Graphen mit Bezug auf die Filteranordnung von 3.
• 5 veranschaulicht schematisch eine Filteranordnung gemäß einem weiteren Beispiel.
• 6 veranschaulicht schematisch in einem Diagramm verschiedene Graphen mit Bezug auf die Filteranordnung von 5.

Examples will now be explained with reference to the drawings. In the drawings, the same reference numbers designate the same features.

• 1 FIG. 12 schematically illustrates an antenna arrangement according to an example.
• 2 FIG. 12 schematically illustrates an antenna arrangement arranged on a printed circuit board, according to an example.
• 3 FIG. 12 schematically illustrates a filter arrangement according to an example.
• 4 FIG. 12 schematically illustrates in a diagram various graphs related to the filter arrangement of FIG 3 .
• 5 FIG. 12 schematically illustrates a filter arrangement according to a further example.
• 6 FIG. 12 schematically illustrates in a diagram various graphs related to the filter arrangement of FIG 5 .

Only elements useful for understanding the present invention are illustrated in the following figures. The filter assembly, antenna assembly, and electronic vehicle key described below may include more than the exemplary elements illustrated in the figures. However, any additional elements not necessary for the implementation of the present invention have been omitted for the sake of clarity.

1 illustrates an antenna arrangement that may be implemented in a vehicle electronic key. Signals can be sent between a vehicle and the electronic vehicle key (vehicle and electronic key in 1 not specifically illustrated). For example, the electronic vehicle key can send request signals to the vehicle to indicate a user's desire to unlock/lock the vehicle. Furthermore, authentication signals can be sent between the electronic vehicle key and the vehicle, for example to prevent unauthorized users (unauthorized keys) from unlocking or starting the vehicle. Numerous other signals can be sent between the electronic vehicle key and the vehicle for many different applications.

An electronic vehicle key can therefore have different antennas. An antenna 10 and a corresponding antenna circuit 20 are in 1 schematically illustrated. The antenna 10 may be an ultra wideband (UWB) antenna, for example. Ultra wideband is a radio technology that can use a very low level of energy for short-range, high-bandwidth communications over a large portion of the radio spectrum. However, the antenna 10 can also be an antenna, for example for transmitting and receiving signals according to FIG a Bluetooth standard with a frequency of 2.4 GHz.

In the 1 The antenna arrangement illustrated has an antenna circuit 20, the antenna circuit 20 having a matching circuit 22, a filter stage or filter arrangement 24 and a control unit 26. The matching circuit 22 can be designed to match the input impedance of the antenna 10 to the output impedance of the antenna circuit 20 . The matching circuit 22 can have capacitors and inductances, for example. The filter arrangement 24 is designed to filter the signals received by the antenna 10 and the signals to be transmitted. The filter arrangement 24 may comprise a front-end bandpass filter, for example to reduce or even avoid spurious emissions during the transmission of signals and to reduce or even avoid in-band noise which has a negative effect on demodulation during the reception of signals. The control unit 26 is designed to control the function of the antenna circuit 20 and to process the received signals and/or the signals to be transmitted via the antenna 10 .

Filter arrangements for antenna circuits often contain ceramic filters or so-called SAW filters. Such filters generally have extremely satisfactory performance, but are quite expensive.

Referring now to FIG 2 a circuit board 30 is illustrated schematically. The antenna 10 is arranged on the circuit board 30 . For example, the antenna 10 can be formed by a conductor track arranged on the printed circuit board 30 . The antenna 10 can be, for example, a monopole antenna or an inverted-F antenna. In 2 a monopole antenna is illustrated schematically. The antenna circuit 20 can also be arranged on the printed circuit board 30 . The filter arrangement 24 can have a capacitance which is formed by at least two conductor tracks on the circuit board 30 . this is in 3 schematically illustrated. In the 3 The filter arrangement 24 illustrated can be used for a Bluetooth antenna 10, for example. The filter assembly 24 has a double helix shape. The dual helix form includes a first spiral trace 2412 and a second spiral trace 2422 . The first helical conductive trace 2412 may be coupled to a first conductive trace 2410 and the second helical conductive trace 2422 may be coupled to a second conductive trace 2420 . The second spiral trace 2422 is in 3 illustrated by a dashed line for purposes of illustration only, and particularly to clearly distinguish the second helical trace 2422 from the first helical trace 2412 . However, the second spiral conductive line 2422 is formed by a continuous conductive line on the circuit board 30 . The first spiral conductive line 2412 and the second spiral conductive line 2422 each form a spiral and spiral into one another, thereby forming a capacitor. The first helical trace 2412 and the second helical trace 2422 may each form at least three complete turns, for example. According to one example, the first spiral trace 2412 and the second spiral trace 2422 each form between three and ten complete turns.

The first spiral conductive pattern 2412 and the second spiral conductive pattern 2422 have a small width d2 in a horizontal direction compared to the width d1 of the first conductive pattern 2410 and the second conductive pattern 2420 in a horizontal direction. The horizontal direction is a direction parallel to a surface of the circuit board 30 on which the first spiral wiring 2412 and the second spiral wiring 2422 are formed. The width d1 of the first conductive line 2410 and the second conductive line 2420 can be between 0.5 and 1.5 mm (millimeters), for example. According to an example, the width d1 of the first conductive line 2410 and the second conductive line 2420 is 0.9 mm. The width d2 of the first spiral conductor track 2412 and the second spiral conductor track 2422 can be between 0.1 and 0.2 mm, for example. According to one example, the width d2 of the first spiral conductive line 2412 and the second spiral conductive line 2422 is 0.14 mm. A thickness of the first conductive line 2410, the second conductive line 2420, the first helical conductive line 2412 and the second helical conductive line 2422 in a vertical direction z can be between 0.4 and 0.6 mm, for example. According to an example, the thickness is 0.5 mm. The vertical direction z is a direction perpendicular to a surface of the circuit board 30 on which the first spiral conductive pattern 2412 and the second spiral conductive pattern 2422 are formed.

The first conductive line 2410 and the second conductive line 2420 may be configured to operate as an input line and an output line, respectively, and may be implemented as 500 microstrip lines, for example.

The first conductive line 2410, the second conductive line 2420, the first helical conductive line 2412 and the second helical conductive line 2422 may comprise copper, for example.

The filter arrangement 24 can therefore be implemented in a very cost effective manner. The material required to form the filter assembly 24 on the circuit board 30 is generally very inexpensive. The filter assembly 24 occupies only a certain amount of space on the circuit board 30. The performance of the filter assembly 24 described is somewhat inferior compared to SAW filters or ceramic filters, but may be acceptable for many applications in favor of reduced cost.

A similar filter arrangement 24 is in 5 illustrated schematically for an ultra wideband antenna.

The filter assemblies 24 described above provide satisfactory transmission and low insertion loss for those frequencies common to ultra wideband and Bluetooth transmission. Outside of the affected frequency bands, insertion losses are increased, blocking any unwanted signals outside of the desired frequency bands. this is in 4 (for Bluetooth) and 6 (for ultra wideband) illustrated.

As in 4 As can be seen, insertion losses for in-band reception (between about 2.4 and 2.5 GHz) are about 1.79 dB (curve marked with triangle). Insertion losses increase to 10 dB or more for frequencies above 2.7 GHz. Also the frequency response for input (curve marked with cross) and output (curve marked with dot) is in 4 illustrated.

As in 6 As can be seen, insertion losses for in-band reception (between about 6.5 and 7.2 GHz) are about 2 dB (curve marked with triangle). The bandwidth is around 500 MHz, which is sufficient for an ultra-wideband channel. Insertion losses increase to 8 dB or more for frequencies above 7.3 GHz or below 6.2 GHz. Also the frequency response for input (curve marked with cross) and output (curve marked with dot) is in 6 illustrated.

The filter assembly 24 has been described above in relation to Bluetooth and ultra wideband transmission. However, the filter arrangement can be adapted for other frequency bands. The quality of the filter assembly 24 may depend on the quality of the circuit board 30 .

Reference List

10

antenna

20

antenna circuit

22

matching circuit

24

filter arrangement

2410

first track

2412

first spiral track

2420

second track

2422

second spiral conductor track

26

control unit

30

circuit board

Claims (13)

An antenna assembly for an electronic vehicle key, comprising: an antenna (10); and an antenna circuit (20) configured to control the antenna (10); whereby the antenna (10) and the antenna circuit (20) are arranged on a circuit board (30), the antenna arrangement is designed to transmit and receive ultra-wideband signals or signals in accordance with a Bluetooth standard, and the antenna circuit (20) has a filter arrangement (24) designed to filter signals which are received by the antenna (10) and are to be transmitted, the filter arrangement (24) having a capacitance which is determined by at least two on the printed circuit board ( 30) formed conductor tracks is formed. antenna arrangement claim 1 , wherein the capacitance has a double helix shape comprising a first helical trace (2412) and a second helical trace (2422) spiraling into one another. antenna arrangement claim 2 , wherein the first spiral conductive line (2412) and the second spiral conductive line (2422) each have a width (d2) in a horizontal direction of between 0.1 and 0.2 mm, the horizontal direction being a direction parallel to a surface of the circuit board (30) on which the first helical trace (2412) and the second helical trace (2422) are formed. antenna arrangement claim 3 , wherein the first spiral conductive line (2412) and the second spiral conductive line (2422) each have a width (d2) in the horizontal direction of 0.14 mm. Antenna arrangement according to one of claims 2 until 4 wherein the first helical conductive trace (2412) is coupled to a first conductive trace (2410) and the second helical conductive trace (2422) is coupled to a second conductive trace (2420). antenna arrangement claim 5 , wherein the first conductive line (2410) and the second conductive line (2412) each have a width (d1) in the horizontal direction of between 0.5 and 1.5 mm. antenna arrangement claim 6 , wherein the first conductive line (2410) and the second conductive line (2420) each have a width (d1) in the horizontal direction of 0.9 mm. Antenna arrangement according to one of Claims 5 until 7 , wherein the first conductive line (2410) and the second conductive line (2420) are 50Ω microstrip lines. Antenna arrangement according to one of the preceding claims, wherein the at least two conductor tracks comprise copper. Antenna arrangement according to one of the preceding claims, wherein the at least two conductor tracks have a thickness in a vertical direction (z) of between 0.4 and 0.6 mm, the vertical direction (z) being a direction perpendicular to the surface of the Circuit board (30) runs on which the conductor tracks are formed. Antenna arrangement according to one of the preceding claims, wherein the antenna (10) has a conductor track on the circuit board (30). antenna arrangement claim 11 , wherein the antenna (10) is a monopole antenna or an inverted-F antenna. Electronic vehicle key, which has an antenna arrangement according to one of Claims 1 until 12 having.

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