RADAR SYSTEM FOR REGISTERING THE ENVIRONMENT FOR A MOTOR VEHICLE AND A CIRCUIT BOARD FOR SUCH A RADAR SYSTEM

Abstract

The disclosure relates to a radar system for registering the environment for a motor vehicle, with a circuit board includes a wave termination with a termination line, a signal line connected to it for the transmission of a high frequency signal, and a first substrate layer which is produced from a material with a first loss factor. The radar system also includes a first tier attached onto the first substrate layer, which includes the signal line, a second substrate layer which is produced from a second material with a second loss factor, which is greater than the first loss factor, and a second tier applied to the second substrate layer, which includes the termination line. Additionally, the disclosure relates to a circuit board for such a radar system.

Claims

1. A radar system for registering the environment of a motor vehicle, with a circuit board, the radar system comprising: a wave termination with a termination line; a signal line connected with this for the transmission of a high frequency signal; a first substrate layer produced from a first material with a first loss factor; a first tier attached onto the first substrate layer, the first tier includes the signal line; a second substrate layer produced from a second material with a second loss factor which is greater than the first loss factor; and a second tier attached onto the second substrate layer, the second tier includes the termination line.

2. The radar system of claim 1, wherein the termination line and the signal line are connected by means of a hollow line.

3. The radar system of claim 2, wherein the hollow line comprises a first section arranged in the first substrate layer and a second section arranged in the second substrate layer.

4. The radar system of claim 1, further comprising a first mass tier arranged between the first and the second substrate layers.

5. The radar system of claim 4, further comprising a coupling slit inserted into the first mass tier.

6. The radar system of claim 4, wherein the first layer, the second layer, and the first mass layer are connected by means of a number of through contacts.

7. The radar system of claim 6, wherein the through contacts form a hollow line wall of the hollow line.

8. The radar system of claim 6, wherein the through contacts are arranged in a U shape.

9. The radar system of claim 1, wherein the termination line is designed in a meandering form.

10. The radar system of claim 1, wherein the termination line comprises a line end on which a through contact is arranged.

11. The radar system of claim 1, wherein the termination line is designed as a stripline.

12. The radar system of claim 1, wherein the termination line is arranged between the second and a third substrate layer.

13. The radar system of claim 12, wherein the second and third substrate layers are produced from the same material.

14. The radar system of claim 12, wherein on the side of the third substrate layer opposite the second tier, a second mass tier is arranged.

15. A circuit board for a radar system of claim 1, the circuit board comprising: a wave termination with a termination line; a signal line connected with this for the transmission of a high frequency signal; a first substrate layer produced from a first material with a first loss factor; a first tier attached onto the first substrate layer, which comprises the signal line; a second substrate layer produced from a second material with a second loss factor which is greater than the first loss factor; and a second tier attached onto the second substrate layer, which comprises the termination line.

Description

DESCRIPTION OF DRAWINGS

[0034] FIG. 1 shows a schematic and profile depiction a radar system with a circuit board designed as a multiple layer circuit board,

[0035] FIG. 2 shows a schematic and perspective depiction a section of the circuit board according to FIG. 1 with a wave termination,

[0036] FIG. 3 shows a top view the section according to FIG. 2 and a first tier,

[0037] FIG. 4 shows a top view a first mass tier of the section according to FIG. 2,

[0038] FIG. 5 shows a top view a second layer of the section according to FIG. 2,

[0039] FIG. 6 shows a top view a second mass tier of the section according to FIG. 2, and

[0040] FIG. 7 shows a simulated and a measured reflection behaviour of the wave termination according to FIG. 2.

[0041] The dimensions and values named in the description below should merely be regarded as examples. Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0042] A radar system 2 with a circuit board 4 and a housing 6 is shown in FIG. 1. The radar system 2 is in particular suitable for use in a motor vehicle not shown here, for example, as a distance warning device. The radar system may include suitable transmission and receiving devices not shown further here, such as antennae. The housing 6 additionally includes a connection 8, via which the radar system 2 is for example connected to systems not shown here for the purpose of data exchange. The radar system 2 may be connected to a control and/or data processing system of the motor vehicle. Alternatively or in addition, the radar system 2 may include a control facility not shown in greater detail, such as for the purpose of evaluating data or a control of the radar system 2.

[0043] The circuit board 4 includes an upper side 10 on which a number of HF components 12 is arranged, and an underside 14 on which additional electronic components 16 are arranged. In some examples, the circuit board 4 is a multiple layer system and includes several tiers and substrate layers which form a stack. The circuit board 4 shown in FIG. 1 includes in the stacking direction 18, i.e., starting with the upper side 10 and in the direction of the underside 14 (or also from top to bottom) the following tiers and substrate layers: a first tier 20, a first substrate layer 22 (shown as shaded here), a first mass tier 24, a second substrate layer 26, a second tier 28, a third substrate layer 30, and a second mass tier 32.

[0044] A section of the circuit board 4 according to FIG. 1 is shown in FIG. 2. In both figures, the multiple layer structure of the circuit board 4 can clearly be seen. The tiers 20, 24, 28, 32 are respectively produced form a conductive material (such as copper). Here, parts of the respective layer 20, 24, 28, 32, may be left out, i.e., a tier 20, 24, 28, 32 may also include areas 34 in which no conductive material is attached. For example, the two mass tiers 24, 32 are designed on the section shown essentially as areas made of conductive material; however, the two tiers 20, 28 include free areas in order to form line structures made of conductive material. The latter may be particularly clearly seen for the first tier 20, which here forms an external tier or top tier. Equally, the second tier 28 may include free areas; in FIG. 2 this is indicated by different line thickness of the second tier.

[0045] As shown, the first substrate layer 22 is produced from an HF material, for example a material known under the brand name RO3003; the second and third substrate layers 26, 30 are respectively produced from a standard material, and in some examples, both from the same material, such as the material known under the material name FR4. The materials are usually dielectric and respectively include a loss factor which represents a measure for the absorption behaviour of the respective material. Here the HF material a lower loss factor compared to the standard material, in particular for electromagnetic signals with a high frequency, for example from a frequency range between 10 GHz and 100 GHz. In other words, the first substrate layer 22 is low loss and the two remaining substrate layers 26, 30 are high loss. The first tier 20 attached to the first substrate layer 22 may serve to guide or transmit high frequency signals.

[0046] FIG. 2 shows a wave termination 36 which is connected to a signal line 38. This is only partially visible in FIG. 2 and runs further outside of the section shown. In some examples, the signal line 38 is designed as a micro-stripline. This serves to transmit a signal with a specified frequency. The signal may be high frequency, for example, the frequency is selected from a frequency range between 10 GHz and 100 GHz, and amounts to approximately 77 GHz, for example.

[0047] The signal line 38 is connected to a hollow line 42, which is a part of the wave termination 36, by means of a transition area 40 which here has a funnel shape. FIG. 2 merely shows a horizontal hollow line wall 44 of the hollow line 42. This hollow line wall 44, the transition area 40, and the signal line 38 are made of a conductive material and are attached as part of the first tier 20 onto the first substrate layer 22. Additionally, the first tier 20 is usually covered with a protective paint not shown here.

[0048] Further, a number of through contacts 46 may be seen, which are arranged in a U shape and in this manner form two side arms and a middle arm which connects these. The through contacts 46 extend in the stacking direction 18, as a result of which the side arms respectively form a vertical hollow line wall 48 of the hollow line 42; the middle arm in particular forms a closed end 50 of a first section 52 of the hollow line 42.

[0049] The through contacts 46 are at a specified distance 54 from each other and have a specified diameter 56. The distance 54 and the diameter 56 may be suitably selected in dependence on the frequency of the signal. For example, the distance 54 is approximately 0.5 mm and the diameter 56 is approximately 0.3 mm.

[0050] Additionally, a further through contact 46 is arranged away from the through contacts 46. This is in particular designed according to the same manner as the through contacts 46. In some examples, the through contacts 46, 46 are designed as so-called Vias, i.e., holes with metallised inner walls, for example, bore holes, and extend over all four tiers 20, 24, 28, 32 and through all three substrate layers 22, 26, 30. Alternatively, the holes are not only metallised on their inner walls, but are also completely filled out with conductive material, for example, a suitable pin is inserted into the hole.

[0051] FIGS. 3 to 6 each show one of the four tiers 20, 24, 28, 32 in a top view. As shown, the wave termination 36 extends over several of the tiers 20, 24, 28, 32 and substrate layers 22, 26, 30 of the circuit board. The first layer 20 is shown in FIG. 3. The through contacts 46 forming the hollow line 42 arranged in a U-shape may be clearly seen, as can the transition area 40 which connects the signal line 38 with the hollow line 42.

[0052] The hollow line 42 has a width 58 and a length 60 that are specified by the arrangement of the through contacts 46. In a suitable manner, this arrangement and thus the width 58 and the length 60 of the hollow line 42 is selected depending on the frequency of the signal. For example, the width 58 is approximately 2 mm and the length 60 is approximately 3.5 mm.

[0053] FIG. 4 shows the mass tier 24 which follows the first substrate layer 22 in the stacking direction 18, which includes a horizontal hollow line wall 62 in the area of the through contacts 46 arranged in a U shape. This hollow line wall 62 in combination with the hollow line wall 44 formed in the first tier 20 and the through contacts 46 enclose a chamber area in the first substrate layer 22 and thus form the first section 52 of the hollow line 42. In some examples, as a result of the U-shaped arrangement of the through contacts 46 and the connection with the first mass tier 24, this section 52 is short circuited.

[0054] The first mass tier 24 may be produced in the section shown essentially entirely from conductive material; exceptions are only the through contacts 46 and an opening designed as a coupling slit 64. This coupling slit 64 is inserted into the horizontal hollow line wall 62 and in particular enables a coupling of the first section 52 with a second section 66 of the hollow line 42 arranged underneath. In other words, the signal coupled into the first section 52 of the hollow line 42 starting from the signal line 38 may be further transmitted by means of the coupling slit 64 into the second section 66. This is essentially arranged in the second substrate layer 26.

[0055] The coupling slit 64 is designed in such a manner that the signal may be transmitted in as reflection-free a manner as possible from the first section 52 into the second section 66. As shown in FIG. 4, the coupling slit 64 is designed as a rectangle with a slit width 68 that is less than the width 58 of the hollow line 42, and with a slit length 70 that is approximately one size less than the slit width 68. In some examples, the slit width 68 and/or the slit length 70 are selected depending on the frequency. For example, the slit width 68 is 1.4 mm and the slit length 70 is 0.1 mm. Further, the coupling slit 64 is arranged at a certain distance 72 from the closed end 50 of the hollow line 42 and is for example 1.5 mm, i.e., approximately half of the wavelength of a signal with a frequency of approximately 77 GHz.

[0056] FIG. 5 shows the second tier 28 arranged in the stacking direction 18 below the second substrate layer 26. The through contacts 46 arranged in a U shape enclose a part of the second tier 28 which in this manner forms a horizontal line wall 74 of the horizontal line, in particular of the second section 66. This is consequently formed by means of the horizontal line walls 62, 74 and the through contacts 46 arranged in the second tier 28 and the first mass tier 24. As shown, the through contacts 46 accordingly form at the same time vertical hollow line walls 48 of the first and second section 52, 66. A hollow line 42 designed in this manner is particularly space saving in its design due to the sections 52, 66 arranged one on top of the other in the stacking direction 18. Here, the horizontal hollow line wall 52 formed in the first mass tier 24 serves both as a lower hollow line wall of the first section 52 and as an upper hollow line wall of the second section 66.

[0057] In some implementations, the two sections 52, 66 are not arranged one on top of the other (not shown). In particular, further through contacts 46 are then possibly required in order to form accordingly suitable hollow line walls 48. However, the first and second sections 52, 66 may overlap at least partially in the stacking direction 18, and in such a manner that these are connected by means of the coupling slit 64 for transmitting the signal.

[0058] Since the through contacts 46 in some examples, form vertical hollow line walls 48 of the first section 66, the latter is thus essentially formed in mirror symmetry to the first section 52 with regard to the first mass tier 24.

[0059] The second section 66 includes an open end 76 due to the U-shaped arrangement of the through contacts 46. This is connected by means of a further transition area 40 to a termination line 78, which is here designed as a so-called stripline. Since the termination line 78 is surrounded by the second and third substrate layer 26, 30, which are both respectively produced from a material with a high loss factor, the signal experiences accordingly high losses during transmission via the termination line 78. The longer the termination line 78, the greater the losses. In order to realise as long a termination line 78 as possible, while at the same time requiring little space, the line runs in an essentially meandering form in the variant shown in FIG. 5. In other examples, not shown here, the termination line 78 is however spiral in form.

[0060] The termination line 78 includes a line end 80 on which the through contact 46 is arranged. On the one hand, this connects the line end 80 over a particularly short route to the two mass tiers 24, 32, while on the other offering access to the termination line 78 for the purpose of measuring transmission in order to determine the absorption effect of the wave termination 42.

[0061] FIG. 6 shows the second mass tier 32, which in the section shown is fully designed as a surface made of conductive material, with the exception of the through contacts 46, 46. In particular, the second mass tier 32 like the first mass tier 24 includes conductive material throughout in the area below or above the termination line 78, as a result of which the termination line 78 is in particular designed as a stripline.

[0062] The through contacts 46, 46 are designed to be continuous in the examples shown, in other words, they connect all four tiers 20, 24, 28, 32 with each other. In particular, in the section of the circuit board 4 shown here, the areas of the four tiers 20, 24, 28, 32 that are equipped with conductive material are connected to each other in an electrically conductive manner and are in particular short circuited with a mass potential.

[0063] FIG. 7 shows a graph 82 with two curves 84, 86 for the purpose of clarifying the functionality of the wave termination 36. Here, functionality is intended to mean in particular a low reflection acceptance or absorption of a high frequency signal. While the input signal is being fed into the wave termination 36, a certain part is reflected and accordingly is present as an output signal. In order to determine a weakening achieved by means of the wave termination 36, respective signal strengths of the input and output signal are measured. The relationship between the signal strength of the output signal and the signal strength of the input signal then corresponds to a reflection parameter, in particular to a so-called S parameter (S.sub.1.1). In the graph 82 the reflection parameter S.sub.1.1 is applied in decibels as a function of the frequency f of the input signal in Gigahertz. The reflection parameter S.sub.1.1 is applied along the coordinates of the graph 82, and the frequency f along the x-axis.

[0064] Here, the curve 84 shows a measurement result, while the curve 86 shows a simulation result. In both cases, a weakening in a target range 88 may clearly be seen, which here includes a frequency range of 76 GHz to 78 GHz. The wave termination 36 measured or simulated here has a particularly low reflection level with a frequency of approximately 77 GHz. In particular, both curves 84, 86 show a similar progression. The wave termination 36 shown here is therefore in particular suited for operation at a frequency of approximately 77 GHz. Due to suitable changes made accordingly to the various dimensions of the wave termination 36, it is advantageously possible to achieve at least a similar behaviour with other frequencies.

[0065] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

LIST OF REFERENCE NUMERALS

[0066] 2 Radar system [0067] 4 Circuit board [0068] 6 Housing [0069] 8 Connection [0070] 10 Upper side (of the circuit board) [0071] 12 HF component [0072] 14 Underside (of the circuit board) [0073] 16 Component [0074] 18 Stacking direction [0075] 20 First tier [0076] 22 First substrate layer [0077] 24 First mass tier [0078] 26 Second substrate layer [0079] 28 Second tier [0080] 30 Third substrate layer [0081] 32 Second mass layer [0082] 34 Free area [0083] 36 Wave termination [0084] 38 Signal line [0085] 40 Transition area [0086] 42 Hollow line [0087] 44 Hollow line wall (horizontal, in the first tier) [0088] 46 Through contact [0089] 46 Through contact [0090] 48 Hollow line wall (vertical) [0091] 50 Closed end [0092] 52 First section (of the hollow line) [0093] 54 Distance (between two through contacts) [0094] 56 Diameter (of the through contact) [0095] 58 Width (of the hollow line) [0096] 60 Length (of the hollow line) [0097] 62 Hollow line wall (horizontal, in the first mass tier) [0098] 64 Coupling slit [0099] 66 Second section (of the hollow line) [0100] 68 Slit width [0101] 70 Slit length [0102] 72 Distance (coupling slit to closed end) [0103] 74 Hollow line wall (horizontal, second tier) [0104] 76 Open end [0105] 78 Termination line [0106] 80 Line end [0107] 82 Graph [0108] 84 Curve (measurement result) [0109] 86 Curve (simulation result) [0110] 88 Target range