EP2489095B1 - Antenna coupler - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to the field of radio frequency line technology; It relates to an antenna coupler for connecting a high-frequency antenna according to the preamble of claim 1.

BACKGROUND OF THE INVENTION

In many technical devices that contain a high-frequency transmitter or receiver and at the same time are galvanically exposed to an earth-related high voltage (mains voltage), an antenna is to be connected via a coaxial cable. The corresponding antenna and the coaxial cable must be galvanically isolated from the device, otherwise there is danger to life when touched.

The problem has been solved for example by two parallel arranged dipole antennas in the device, in which, however, by the unwanted radial radiation, a high transmission loss of at least 6dB for the useful signal. The decoupled power was fed into a coaxial cable to be routed to a remote antenna.

A known decoupling via capacitors ( US4987391 ) has either a low withstand voltage (1 kV) or a high transmission loss, because a high design resistance of the capacitors a large design is a prerequisite, which has a negative effect on the damping due to high inductive reactance and unwanted radiation.

From the publication by SS BEDAIR and INGO WOLF: "Fast and accurate analytical formulas for calculating the parameters of a general broadside-coupled coplanar waveguide for (M) MIC applications" IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol. 37, No. 5, 1. May 1989 (1989-05-01), pages 843-850, XP002605986 Piscataway, USA , An antenna coupler for connecting a high-frequency antenna to a galvanically operable with a high voltage device is known, comprising a multilayer printed circuit board with conductor planes which are electrically isolated from each other in the depth direction (z) of the multilayer printed circuit board, at least one to be coupled or coupled to the high-frequency antenna first High-frequency line in a first conductor level, at least one second high-frequency line to be coupled or coupled to the device in a second conductor level of the multilayer printed circuit board, wherein the multi-layer printed circuit board has an electrically insulating PCB core layer, wherein the first and second conductor level extend on the same side of the PCB core layer, wherein the device side is arranged to be coupled or coupled second radio-frequency line at a greater distance from the PCB core layer than the first radio-frequency line, and wherein the antenna coupler a electrically conductive shield structure extending in part on the opposite other of the two sides of the circuit board core layer and is adapted to shield the first high-frequency line against an interaction in the conduction of high-frequency signals.

Furthermore, the following publications also show embodiments of antenna couplers, namely

"Chapter 10: Coplanar waveguides" in Franco di Paolo: "Networks and devices using planar transmission lines" 2000, CRC Press LLC, Florida, USA, XP002605987, ISBN: 0-8493-1835-1 .

CHIEH-PIN CHANG ET AL: "A 3-dB Quadrature Coupler Using Broadside-Coupled Coplanar Waveguides" IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, IEEE SERVICE CENTER, NEW YORK, NY, US, Vol. 18, No. 3, March 1 2008 (2008-03-01 pages 191-193, XP011205042, ISSN: 1531-1309 and

US 2005/017821 A1 ,

It is from the document US7545243 It is known that line structures are suitable for galvanic decoupling. However, a disadvantage of this known solution is also the low dielectric strength.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to further develop an antenna coupler for connecting a high-frequency antenna to the effect, wherein the above-mentioned disadvantages can be solved.

The object underlying the invention is achieved by the totality of the features of claim 1. Further embodiments are the subject of the dependent claims 2 to 7. The antenna coupler according to the invention for galvanic isolation of the antenna from the transmitter / receiver achieves a high insulation voltage of up to 12kV DC and AC line voltage, but at the same time an extremely low transmission loss for the high frequency useful signal , The antenna coupler according to the invention can achieve a particularly low transmission loss within desired frequency limits, since the coupling lines, so the first and second high-frequency line, can be arranged with a very small distance from each other in the depth direction of the multilayer printed circuit board. The commonly used layer thickness of the multilayer printed circuit board can be used as the distance between the coupling lines. A distance of 0.3 mm, for example, can be realized.

There is a large usable high-frequency bandwidth can be more than one octave, for example, from 800 MHz to 2200 MHz. It can be produced inexpensively by using multilayer printed circuit boards, for example 2-fold or 4-fold multilayer printed circuit boards.

The antenna coupler is thus preferably designed as a multilayer printed circuit board. The coupler is formed of two appropriately coupled high frequency lines. The geometric arrangement of the metal surfaces (in particular copper surfaces) of the high-frequency lines forms the coupler. The distances between the copper surfaces and the electrically insulating carrier material of the multilayer printed circuit board provide the necessary insulation voltage strength.

In the present case, the high-frequency lines are two coplanar lines which are embedded in two different layers of the multilayer printed circuit board one above the other. These lines preferably each consist of at least one strip line for the inner conductor and at least two strip lines for the outer conductor.

These two times three conductors are selected in a preferred embodiment in the distance and in the width of the lines so that the resulting line has a characteristic impedance of 50 ohms. This allows a shock-free and thus low-loss forwarding of high-frequency power from the coaxial cable to the transmitter / receiver inside the device.

The thickness of the dielectric (dielectric material) is preferably selected such that a voltage resistance required in the respective application is achieved.

In preferred embodiments, the terminals of the coplanar leads to the surface of the circuit board hold a required for the desired dielectric strength leakage current path. For this purpose, in one embodiment, located in the inner layer of the circuit board (typically antenna side) coplanar line beyond the coupling zone with modified geometry, eg changed conductor width and / or conductor distances extended before contacting the surface is made.

The preferred embodiment of the inventive antenna coupler is designed as a one-sided shielded coupling structure. The device-side coplanar line is supplemented by an additional shielding surface connected to PCB vias. According to the invention, the shielding surface is arranged in such a way that, together with the strip conductors of the device-side coplanar line, it partially encloses the coaxial line, that is to say the antenna-side coplanar line. In this way, at least the screen side is less sensitive to interference from metal parts inside the device.

To achieve a high dielectric strength is suitable as insulating support material of the multilayer printed circuit board, for example, the known material FR-4, a glass fiber reinforced, epoxide-based material having a dielectric strength of more than 30kV / mm.

It is necessary to ensure sufficiently large leakage current paths on the surface of the printed circuit board between the galvanically isolated parts. For a dielectric strength of 12kV, for example, a leakage current of a little more than 10mm is needed.

The antenna coupler according to the invention will be described below with reference to the figures. Only a section of the antenna coupler, namely the coupling region in the multilayer printed circuit board is shown in each case.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. The following color coding of the illustrated structural elements is used in the figures:

Light blue: air

• Dunkelgrün: Dielektrische Schichtisolation
• Hellgrün: Deckelisolation oder Kernschicht (Core) der Mehrlagenleiterplatte.

Orange-red and yellow-green: metal surfaces of strip lines. Dark blue and dark green sections at ends of strip lines (center conductors) are to be read as orange-red sections, so to understand as integral components of the respective stripline, and have these structural elements, despite their other colors no different from an orange-red or yellow-green color meaning.

• Darkgreen: Dielectric layer insulation
• Light green: cover insulation or core layer (core) of the multilayer PCB.

Fig. 1

eine perspektivische Ansicht eines erfindungsgemässen Antennenkopplers mit zwei von einander durch eine Schichtisolation beabstandete und isolierte Koplanarleitungen auf einer Seite einer Leiterplattenkernschicht und mit einer elektrisch leitfähigen Abschirmstruktur, die sich zum Teil auf der gegenüberliegenden anderen der beiden Seiten der Leiterplattenkernschicht erstreckt und die ausgebildet ist, die erste Hochfrequenzleitung und geräteseitige Metallteile, die nicht Teil des Antennenkopplers sind, gegen eine Wechselwirkung bei der Leitung von Hochfrequenzsignalen abzuschirmen;

Fig. 2

vergrößerte perspektivische Ansicht eines geräteseitigen Endabschnitts des Antennenkopplers gemäss Fig. 1;

Fig. 3

vergrößerte perspektivische Ansicht des gegenüberliegenden antennenseitigen Endabschnitts des Antennenkopplers gemäss Fig. 1;

Fig. 4

Schnittansicht des eingangsseitigen Abschnitts -dargestellt: yz-Ebene- des Antennenkopplers; und eine

Fig. 5

weitere Schnittansicht -dargestellt: xz-Ebene- des Antennenkopplers.

Show it:

Fig. 1

a perspective view of an inventive antenna coupler with two mutually separated by a layer insulation and insulated coplanar lines on one side of a PCB core layer and with an electrically conductive shielding structure which extends partly on the opposite other of the two sides of the PCB core layer and which is formed, the first To shield high-frequency line and device-side metal parts that are not part of the antenna coupler from interference in the conduction of high-frequency signals;

Fig. 2

enlarged perspective view of a device-side end portion of the antenna coupler according to Fig. 1 ;

Fig. 3

enlarged perspective view of the opposite antenna-side end portion of the antenna coupler according to Fig. 1 ;

Fig. 4

Section view of the input-side section -represented: yz plane- of the antenna coupler; and a

Fig. 5

further sectional view -shown: xz-plane of the antenna coupler.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows in a perspective view of an inventive antenna coupler 1 with two of each other by a layer insulation 13 spaced and isolated coplanar lines 3a, 3b, 4a, 4b. Since the first coplanar line 3a, 3b is consequently concealed by the second coplanar line 4a, 4b in this illustration, it is Fig. 4 for the arrangement of both coplanar lines 3a, 3b, 4a, 4b to each other to help.

The coplanar lines 3a, 3b, 4a, 4b are disposed on one side of a circuit board core layer 6 and shielded with an electrically conductive shielding structure 5, this shielding structure 5 extending in part on the opposite one of the two sides of the circuit board core layer 6 and formed so that the first high-frequency line 3a, 3b and not shown here, device-side metal parts that are not part of the Antennenkopplers, do not interact in the conduction of high-frequency signals.

In Fig. 1 are both coplanar lines 3a in the y direction of the illustrated coordinate system. 3b, 4a, 4b respectively in the sequence outer conductor 3b, 4b- inner conductor 3a, 4a-outer conductor 3b, 4b arranged. In the z-direction of the coordinate system follow one another metal surface or screen surface 9 - an intermediate layer of dielectric material 8 - antenna side, (first) coplanar 3a, 3b - layer insulation 13 - device side (second) coplanar 4a, 4b.

The coplanar lines 3a, 3b, 4a, 4b extend parallel to one another in the longitudinal direction x in the multilayer printed circuit board (2); Apart from short antenna-side and device-side longitudinal sections (strip lines 10a, 10b, 11a, 11b), the coplanar lines 3a, 3b, 4a, 4b completely overlap in the longitudinal direction and completely overlap in their transverse direction y perpendicular to the longitudinal direction x.

• Breite Innenleiter 3a, 4a: 3mm
• Breite Aussenleiter 3b, 4b: 2mm
• Länge Koplanarleitungen 3a, 3b, 4a, 4b: 25mm
• Dicke Schichtisolation 13: 0,3mm
• relative Dielektrizitätszahl der Schichtisolation 13: ε_r=4,5
• seitlicher Abstand Innenleitern 3a, 4a und Aussenleitern 3b, 4b: 1,2mm

As an example of mass for the embodiment of the antenna coupler according to the invention shown here, the following values are helpful, whereby the values of the width given here in the y-direction are to be considered, the length values in the x-direction and the thickness values in the z-direction:

• Wide inner conductor 3a, 4a: 3mm
• Width outer conductor 3b, 4b: 2mm
• Length of coplanar lines 3a, 3b, 4a, 4b: 25mm
• Thick layer insulation 13: 0.3mm
• relative dielectric constant of the layer insulation 13: ε _r = 4.5
• lateral distance inner conductors 3a, 4a and outer conductors 3b, 4b: 1.2mm

In Fig. 1 strip lines 10a, 10b are also visible which project in the longitudinal direction x of the first coplanar line or the first high-frequency line 3a, 3b via the second coplanar line or second high-frequency line 4a, 4b for connection to an unillustrated coaxial line to an antenna; in the following synopsis with Fig. 3 this situation becomes even clearer.

With 7 is in Fig.1 Air as the medium surrounding the antenna coupler 1 represented; In addition to insulating properties, the air has no other function.

Fig. 2 shows an enlarged perspective view of a device-side end portion of the antenna coupler according to Fig. 1 , Here it becomes clear that the second high-frequency line 4a, 4b with strip lines 11a, 11b projecting in the x-direction over the first high-frequency line 3a, 3b for the purpose of connection to a device not shown in detail here.

As already for Fig. 1 indicates, shows Fig. 3 in an enlarged perspective view of the antenna-side end portion of the antenna coupler with the strip lines 10a, 10b to the first high-frequency line 3a, 3b.

In the Fig. 4 is shown in a sectional view to the yz plane visible as the second high-frequency line 4a, 4b with its outer conductor 4b, but not with its inner conductor 4a, electrically conductive through the PCB core layer 6 through with the metal surface 9 on the opposite other of the two sides of the PCB core layer 6 is connected for shielding. Another sectional view shows in Fig. 5 the xz plane of the antenna coupler. It becomes clear that a large number of connections or printed circuit board plated-through holes 12 hold the outer conductor 4b with the metal surface 9 at the same potential.

Of course, the invention presented here is not limited to the embodiments shown but to the features of the claims. It is, for example, the second high-frequency line 4a, 4b of course coupled on the antenna side, while the first high-frequency line 3a, 3b can be coupled device side.

LIST OF REFERENCE NUMBERS

1

antenna

2

Multilayer printed circuit board

3a, 3b

first high-frequency line with inner conductor and outer conductor, first coplanar line

4a, 4b

second high-frequency line with inner conductor and outer conductor second Koplanarleitung

5

shield

6

PCB core layer

7

air

8th

dielectric material

9

Metal surface, screen surface

10a, 10b

Stiff line to 3a, 3b

11a, 11b

Stripline to 4a, 4b

12

Connection, printed circuit board vias

13

layer insulation

Claims (7)

1. An antenna coupler (1) for connecting a high frequency antenna to a device to which a high voltage may be galvanically applied during operation, comprising

   - a multilayer printed circuit board (2) having conductor levels that are electrically insulated from one another in the depth direction (z) of the multilayer printed circuit board (2),

   - at least one first high frequency line (3a, 3b) that is coupleable or coupled to the high frequency antenna in a first conductor level,

   - at least one second high frequency line (4a, 4b) that is coupleable or coupled on the device side in a second conductor level of the multilayer printed circuit board (2),

   wherein the multilayer printed circuit board (2) has an electrically insulating printed circuit board core layer (6),

   - wherein the first and second conductor levels extend on the same side of the two sides of the printed circuit board core layer (6),

   - wherein the second high frequency line (4a, 4b) that is coupleable or coupled on the device side is situated at a greater distance from the printed circuit board core layer (6) than is the first high frequency line (3a, 3b), and

   - wherein the antenna coupler (1) has an electrically conductive shielding structure (5), part of which extends on the opposite, other of the two sides of the printed circuit board core layer (6) and which is designed for shielding the first high frequency line (3a, 3b) from interaction with the conduction of high frequency signals, characterized in that

   - the second high frequency line (4a, 4b) is situated on an outer surface of the multilayer printed circuit board (2),

   - the shielding structure (5) has a metal surface (9) that partially sheathes the first high frequency line (3a, 3b),

   - wherein the second high frequency line (4b) is electrically conductively connected by its outer conductor (4b), through the printed circuit board core layer (6), to the metal surface (9) on the opposite, other of the two sides of the printed circuit board core layer (6), and the first high frequency line (3a, 3b) is at the same time insulated with respect to the second high frequency line (4a, 4b) and with respect to the metal surface (9).
2. The antenna coupler (1) according to Claim 1, characterized in that the first and second high frequency lines (3a, 3b, 4a, 4b) in the multilayer printed circuit board (2) extend parallel to one another in the longitudinal direction (x) of the first and second high frequency lines (3a, 3b, 4a, 4b).
3. The antenna coupler (1) according to Claim 1 or 2, characterized in that the high frequency lines (3a, 3b, 4a, 4b), except for short longitudinal sections of the high frequency lines (3a, 3b, 4a, 4b) on the antenna side and on the device side, completely overlap in the longitudinal direction.
4. The antenna coupler (1) according to one of the preceding claims, characterized in that the spaced-apart high frequency lines (3a, 3b, 4a, 4b) completely overlap one another in their transverse direction (y) extending perpendicularly to the longitudinal direction.
5. The antenna coupler (1) according to one of the preceding claims, characterized in that the high frequency lines (3a, 3b, 4a, 4b) are designed as coplanar lines.
6. The antenna coupler (1) according to one of the preceding claims, characterized in that each conductor level has at least one stripline (10a, 11a) for coupling to an internal conductor on the antenna side and on the device side, respectively, and at least two striplines (10b, 11b) for coupling to an external conductor on the antenna side and on the device side, respectively.
7. The antenna coupler (1) according to Claim 6, in which the striplines (10a, 10b, 11a, 11b) of the first and second high frequency lines (3a, 3b, 4a, 4b) have a respective lateral distance from one another, i.e., a distance that is measurable perpendicular to the longitudinal direction (x) of the striplines (10a, 10b, 11a, 11b), in the respective conductor level, and have a respective width that is measurable in the lateral direction (y) in the conductor level in question, which in combination result in the respective high frequency line having a characteristic impedance of 50 ohms.

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