Antenna arrangement for receiving and transmitting electromagnetic waves with different polarisations

Abstract

An antenna arrangement, in particular an RFID antenna arrangement, for receiving and transmitting electromagnetic waves of different polarizations comprises an antenna having at least two spaced-apart feed points, wherein the antenna is configured to transmit a polarized electromagnetic wave. The antenna arrangement further comprises a signal input for a high-frequency input signal and a coupler circuit coupled to the signal input, which includes a first coupler input connected to a first node, a second coupler input connected to a second node, a first coupler output connected to a third node, and a second coupler output connected to a fourth node.Furthermore, the first and third nodes are electrically coupled to each other via a first line, the second and fourth nodes are electrically coupled to each other via a third line, the first and second nodes can be electrically coupled to each other via a second line by means of a first switching device, and the third and fourth nodes can be electrically coupled to each other via a fourth line by means of a second switching device. Furthermore, the signal input can be coupled to the first coupler input or to the second coupler input, with the first and second coupler outputs each being connected to a feed point of the antenna.

Description

[0001] The invention relates to an antenna arrangement for receiving and transmitting electromagnetic waves of different polarization as well as a corresponding method and a coupler circuit.

[0002] Such antenna arrangements can include a feed network. A feed network is used to couple signals from a transmit / receive unit into an antenna structure with the lowest possible losses at more than one feed point. The feed network ensures, for example, by means of a coupler circuit, that predefined portions of the input signal are present at the network outputs with a desired phase angle in order to achieve a desired polarization of the transmitted signal. The lower the losses in the network (for signal splitting and forwarding), the higher the amplitude of the output signal(s) fed to the antenna. This effect is particularly pronounced with RFID antennas, since the same antenna (of the RFID reader) is used for transmitting and receiving.

[0003] Depending on the application, different polarizations can be advantageous. If the orientation of a transponder is unknown, the use of a circularly polarized antenna, i.e., an antenna that receives and transmits circularly polarized electromagnetic waves, offers significant advantages, as the variance in the transponder's orientation can be better compensated, allowing information to be read more easily. However, since transponders in most cases only have a linearly polarized antenna, the transponder can (ideally) only absorb half of the received energy of the electromagnetic wave.In applications where the transponders have a predetermined, known orientation to the reader, it would be advantageous to use an antenna with linear polarization in the reader so that, with correct orientation (of the reader in relation to the transponder), the transponder can absorb more energy, thus achieving a greater identification range.

[0004] Consequently, there is a need for an antenna array that can generate signals of different polarization.

[0005] It is an object underlying the invention to provide an antenna arrangement and a method for receiving and transmitting electromagnetic waves of different polarization as well as a coupler circuit.

[0006] This problem is solved by the subject matter of the independent claims.

[0007] The invention relates to an antenna arrangement, in particular an RFID antenna arrangement, for receiving and transmitting electromagnetic waves of different polarization, comprising: an antenna having at least two feed points arranged at a distance from one another, the antenna being configured to emit a polarized electromagnetic wave; a signal input for a high-frequency input signal and / or with a high-frequency input signal; a coupler circuit coupled to the signal input, comprising: a first coupler input connected to a first node; a second coupler input connected to a second node; a first coupler output connected to a third node;and a second coupler output connected to a fourth node, wherein the first and third nodes are electrically coupled to one another via a first line, wherein the second and fourth nodes are electrically coupled to one another via a third line, wherein the first and second nodes are electrically coupled via a second line by means of a first switching device, wherein the third and fourth nodes are electrically coupled via a fourth line by means of a second switching device, wherein the signal input is coupled to the first coupler input or to the second coupler input, wherein the first and second coupler outputs are each connected to one or more feed points of the antenna. ;

[0008] In other words, the first and third nodes and the second and fourth nodes are fixedly and preferably directly electrically coupled to one another by means of the first and third lines, respectively. The electrical connection between the first and second nodes and between the third and fourth nodes can be selectively established via the first switching device or the second switching device. For example, the first switching device can be switched such that an electrical connection can be established between the first and second nodes via the second line (and in particular the first switching device). This state is described below as the coupling state of the switching device. However, the first switching device can also be operated such that there is no electrical connection between the first and second nodes, which is referred to below as the decoupling state.This applies accordingly to the second switching device and the third and fourth nodes.

[0009] The signal input can preferably only be coupled with either the first coupler input or only with the second coupler input.

[0010] According to a first embodiment, the coupler circuit is operable in a decoupling mode and in a coupling mode, wherein the coupler circuit is configured in the decoupling mode such that the first and second switching devices are operated in a decoupling state, such that the signal input is connected only to the first or second coupler output. In the decoupling mode, the antenna is preferably configured to emit a linearly polarized electromagnetic wave. Furthermore, the coupler circuit can be configured in a coupling mode such that the first and / or second switching devices are operated in a coupling state, such that the signal input is connected to the first and second coupler output. In the coupling mode, the antenna is preferably configured to emit a circularly polarized or elliptically polarized electromagnetic wave.

[0011] In decoupling mode, for example, the first node is electrically coupled to only one other node, namely the third node. The second node can accordingly only be electrically coupled to the fourth node. The input signal present at either the first or second coupler input is then forwarded to only one coupler output, namely either the first or second coupler output. Accordingly, the antenna receives the input signal at only one feed point, which preferentially generates a linearly polarized electromagnetic wave from the antenna.

[0012] In coupling mode, however, an input signal at one coupler input can be split between both coupler outputs. For this example, we assume an input signal at the first coupler input and thus at the first node. Furthermore, we assume that the first to fourth lines each generate a phase shift of 90°.

[0013] In coupling mode, the input signal can travel from the first node to the third node via the first line, experiencing a phase shift of 90°. At the same time, the input signal can travel via the second and third lines to the fourth node, experiencing a phase shift of 90° twice, for a total of 180°. The input signal is accordingly split between two feedpoints of the antenna, with the signals at the two feedpoints having a phase shift of 90° from each other, thus making it possible to transmit, for example, a circularly polarized wave.

[0014] The antenna arrangement is thus capable of setting different operating modes by means of the first and second switching devices, in which different output signals are provided at the coupler outputs by determining the forwarding of the input signal, for example a radio-frequency signal, based on the state of the switching devices. In particular, depending on the operating state of the first and second switching devices, it is determined at which coupler outputs an output signal is provided. Furthermore, depending on the operating state of the switching devices, the phase and / or amplitude of the output signals of the coupler outputs, in particular with respect to the input signal, can be set, wherein the state of the switching devices determines whether the input signal is split or not. The operating state of the respective switching device can be controlled, for example, by means of a controller of the antenna arrangement.When reference is made to a "phase shift" in the following, this refers specifically to a phase shift with respect to the input signal, unless otherwise stated.

[0015] The phase shift of the output signals at the first and second coupler outputs with respect to the phase of the input signal depends particularly on the electrical length of the lines. The "electrical length" of an electrical line refers to the length of the line through which the signal is transmitted. Electrical signals propagating through lines are subject to various phase shifts, delays, and distortions. The phase shift depends particularly on the electrical length of the line. In the following, the term "electrical length" can also be used synonymously with a phase shift caused by an electrical line or an electrical component.

[0016] Furthermore, the amplitude of the output signals output at the first and second coupler output depends in particular on the impedance of the lines and on the amplitude of the input signal.

[0017] By utilizing the above properties, the high-frequency signal applied to the signal input can be forwarded and adapted by means of the coupler circuit in such a way that different output signals are provided at the coupler outputs.

[0018] In the following, it is assumed that the signal input is connected to the first coupler input. However, a corresponding functionality of the coupler circuit can also be achieved if the signal input is connected to the second coupler output, in which case the output signals at the coupler outputs described below would then be swapped. In particular, depending on which coupler input the input signal is applied to, a polarization direction, i.e., left-circulating or right-circulating, and / or a polarization angle, for example, of a linearly polarized electromagnetic wave, can be specified.

[0019] If the switching device is operated in the coupling mode, i.e. when the first and / or second switching device is in the coupling state, i.e. in a state in which there is an electrical connection between the first and second nodes and / or the third and fourth nodes, for example by a switch of a respective switching device being closed, the high-frequency signal present at the signal input can be processed as follows: The input signal can be passed via the first coupler input and via the first line to the first coupler output, so that an output signal is present at the first coupler output which corresponds to a converted, in particular phase-shifted and amplitude-changed, input signal. The output signal of the first coupler output therefore has in particular a phase offset corresponding to the electrical length of the first line and a respective amplitude.

[0020] Furthermore, the input signal can be routed to the second coupler output via two possible paths. The input signal can be routed to the second coupler output via both paths when both the first and second switching devices are operated in the coupled state. Alternatively, the input signal can only be routed to the second coupler output via one of the two paths when one of the two switching devices is operated in the uncoupled state and the other of the two switching devices is operated in the coupled state. The following describes the case where the input signal is routed to the second coupler output via both paths.

[0021] The input signal can, for example, be routed via a first path from the first node via the second line to the second node and from the second node via the third line to the fourth node. Furthermore, the input signal can be routed via a second path from the first node via the first line to the third node and from the third node via the fourth line to the fourth node. In particular, the input signal routed via the first path and via the second path are combined at the fourth node, so that the output signal output at the second coupler output corresponds to an addition of the signals transmitted via the first path and via the second path. In particular, the electrical length of the first path, iethe common electrical length of the second line, including the electrical length of the first switching device and the third line, is at least substantially equal to the electrical length of the second path, i.e. the common electrical length of the first line and the fourth line, including the electrical length of the second switching device. In particular, the phase offset of the signals transmitted via the first path and via the second path is thus the same. Furthermore, the cumulative impedances of the first path and the second path, i.e. the common impedance of the second line and the third line, and the common impedance of the first line and the fourth line, can also be at least substantially equal in magnitude.

[0022] In particular, the phase shift of the combined output signal of the second coupler output corresponds to the phase shift of the signals transmitted via the first path and the second path. The amplitude of the output signal of the second coupler output is determined in particular by the impedances of the respective lines. The output signal of the second coupler output has, for example, a phase shift corresponding to the electrical length of the first path and / or the second path and a respective amplitude.

[0023] The output signal of the first coupler output and the output signal of the second coupler output can thus have a different phase offset and, depending on the impedance of the lines, also a different amplitude. Accordingly, the output signal of the first coupler output and the output signal of the second coupler output can be fed into the antenna, for example a patch antenna, via the feed points of the antenna in order to generate and emit a circularly polarized or elliptically polarized electromagnetic wave. In order to generate a circularly polarized or elliptically polarized polarization, two feed lines of the feed points are attached to the antenna, for example offset from one another by 90°. An offset of the feed points by 90° can be provided, for example, in a patch antenna, wherein the angle is measured, for example, from a center point or center of gravity of the antenna.The arrangement of the feed points can be selected, for example, depending on the phase position of the output signals and the output impedance (matching) of the coupler circuit. In particular, for a patch antenna, the position of the feed point, e.g., between the patch center (approx. 0 ohms) and the patch edge (approx. 200 ohms), is selected so that the impedance is matched to the impedance of the coupler circuit.

[0024] As already indicated above, in a symmetrical patch design (e.g., circle, square, octagon, etc.), the geometric angle of the feedpoint arrangement in the patch antenna can also correspond to the phase angle of the feed signals. For example, two input signals with a 90° phase offset are preferably fed into two orthogonally arranged feedpoints. For asymmetrical patch contours, e.g., a rectangle, triangle, oval, etc., other orientations are conceivable.

[0025] In the coupled state, the coupler circuit can thus be operated as a branch line coupler.

[0026] If the switching device is operated in the decoupling mode, i.e. when the two switching devices are in the decoupling state, i.e. in a state in which an electrical connection between the first and second or the third and fourth node is interrupted, for example by a switch of a respective switching device being open, the high-frequency signal present at the signal input can be fed in as follows: The input signal can be passed via the first coupler input and via the first line to the first coupler output, so that an output signal is present at the first coupler output which corresponds to a converted, in particular phase-shifted and amplitude-changed, input signal. The output signal of the first coupler output therefore has in particular a phase offset corresponding to the electrical length of the first line and a respective amplitude.Due to the decoupling state of the switching devices, the input signal cannot be passed to the second coupler output, thus isolating the second coupler output. In particular, the input signal is essentially completely passed to the first coupler output. The output signal of the first coupler output can be fed into the antenna via a feedpoint of the antenna and results in a linearly polarized electromagnetic wave being generated and emitted. For example, a feed line of the feedpoint or feedpoints is positioned in a straight line or at a specific angle to the orientation of the antenna. The resulting radiation can be linearly polarized, for example, horizontally, vertically, or at any other angle, depending on the orientation of the feed line.

[0027] In both operating modes of the coupler circuit, the second coupler input can be short-circuited to ground, in particular via a terminating resistor, in order to achieve the best possible termination, in particular total reflection of the transmission signal.

[0028] The antenna arrangement according to the invention thus makes it possible to switch between a mode of linear polarization, i.e., decoupling mode, and a mode of circular or elliptical polarization, i.e., coupling mode. This allows the polarization to be flexibly changed depending on the respective application. For example, if an antenna arrangement, such as an RFID reader, is to be used to identify an indefinite number of transponders, the RFID reader can identify a first number of RFID transponders in a first "coarse" readout process using circularly polarized RF waves and, in a second "fine" readout process, identify additional RFID transponders that could not be identified in the first readout process due to the lower transmission power using linearly polarized RF waves, which have a higher transmission power than the circularly polarized RF waves.

[0029] A further advantage of the invention lies in the fact that a standard branch line coupler can be adapted with just a few additional components to generate both linear and circular or elliptical polarization. The invention can thus be implemented particularly cost-effectively and in a space-saving manner.

[0030] The antenna may, in particular, comprise a double bifilar helix antenna, a patch antenna, a cross-fed antenna, or a quadrature antenna. The electromagnetic waves emitted by the antenna may further comprise microwaves, infrared waves, RF waves, and / or laser beams, or the like. The high-frequency input signal may furthermore have a wavelength that is less than 500 cm, less than 100 cm, or less than 50 cm, in particular 32 cm. Preferably, the high-frequency input signal may have a frequency in an ISM band (Industrial, Scientific, and Medical Band), in particular in the frequency range between 902 and 928 MHz.

[0031] According to a further embodiment, an electrical length of the first line substantially corresponds to an electrical length of the third line, wherein the electrical length of the first and / or third line in each case corresponds to an electrical length L1, wherein an electrical length of the second line substantially corresponds to an electrical length of the fourth line, wherein the electrical length of the second and fourth lines in each case corresponds to an electrical length L2, wherein an electrical length of the first switching device substantially corresponds to an electrical length of the second switching device, wherein the electrical length of the first and second switching devices in each case corresponds to an electrical length LS, wherein a phase offset L 2S caused jointly by the electrical lengths L2 and LS corresponds at least substantially to an odd integer multiple of 90°.The same can also apply to L1, i.e. L1 causes a phase shift which at least essentially corresponds to an odd integer multiple of 90°.

[0032] Thus, in coupling mode, it can be ensured that the output signal of the first coupler output is phase-shifted by an electrical length L1, while the output signal of the second coupler output is phase-shifted by an electrical length L12S = L1 + L2S. In particular, the phase shift between the output signal of the first coupler output and the output signal of the second coupler output corresponds to the electrical length L2S, which corresponds to an odd integer multiple of 90°, in particular 90°. Thus, the signals fed into the two feed points of the antenna also have a phase shift of 90° with respect to one another, so that a circularly polarized or at least elliptically polarized electromagnetic wave is emitted.In principle, it is also possible for the second and fourth lines and the first and second switching devices to be configured such that the phase offset L2S assumes a value that does not correspond to an odd integer multiple of 90°. In such a case, an elliptically polarized electromagnetic wave results. The electrical lengths L2 and Ls are, in particular, matched to one another such that the phase offset L2S does not assume a value that corresponds to an even integer multiple of 180°, since in this case, a linearly polarized electromagnetic wave would be generated.

[0033] According to a further embodiment, the first and third lines each have a first impedance Z 1 , in particular substantially equal in magnitude, wherein the second and fourth lines each have a second impedance Z 2 , in particular substantially equal in magnitude, wherein the first impedance Z 1 and the second impedance Z 2 are selected such that output signals with substantially equal amplitude are output at the first coupler output and at the second coupler output.

[0034] In particular, the impedances Z 1 and Z 2 are matched to one another. When matching the impedances, an impedance ZS of the switching device can also be taken into account, wherein the first and second switching devices preferably have an impedance that is essentially the same in magnitude. When matching the impedances, it is also taken into account, for example, that the output signal of the second coupler output in coupling mode is generated based on a combination of the input signal conducted via the first path and the second path. Z 2 can, for example, be 50 ohms, so that Z 1 assumes a rounded value of 35.35 ohms. The coupler circuit can, for example, be designed such that the power of the input signal is divided into two parts of equal amplitude, i.e. output signals, which each have 3 dB less power than the input signal.

[0035] According to a further embodiment, the coupler circuit is operable in a partial coupling mode in which the first switching device is operated in the coupling state and the second switching device is operated in the decoupling state, or vice versa, wherein the antenna is configured to emit an elliptically polarized electromagnetic wave in the partial coupling mode.

[0036] In partial coupling mode, the input signal can therefore only be routed to the second coupler output via the first path or the second path. Consequently, this also affects the amplitude of the output signal of the second coupler output. In particular, the amplitude of the output signal of the first coupler output is not equal to the amplitude of the output signal of the second coupler output. Furthermore, the phase offset between the output signal of the first coupler output and the output signal of the second coupler output in partial coupling mode can also be other than an odd integer multiple of 90°. This allows the electromagnetic wave generated by the antenna to have an elliptical polarization. More precisely, to generate an elliptical polarization, preferably only one of the two switches is operated in coupling mode, whereby signals with a phase offset of 90° are produced at the outputs of the coupler circuit.However, due to the impedance differences between L1 and L2, different amplitudes can result. For example, in a symmetrical patch structure, feeding at two orthogonal feed points with a 90° phase shift and unequal amplitude results in elliptical polarization. Using the coupler circuit in partial coupling mode can thus generate an additional, i.e., elliptical, polarization, which may be desirable in some applications, for example, when only a predefined area is to be scanned with higher transmission power.

[0037] According to a further embodiment, the first switching device is arranged at an end of the second line closer to the first line, in particular in the immediate vicinity of the first node, and the second switching device is arranged at an end of the fourth line closer to the third line, in particular in the immediate vicinity of the fourth node, or the first switching device is arranged at an end of the second line closer to the third line, in particular in the immediate vicinity of the second node, and the second switching device is arranged at an end of the fourth line closer to the first line, in particular in the immediate vicinity of the third node.

[0038] According to a further embodiment, the first switching device is arranged between a first sub-line of the second line and a second sub-line of the second line and / or the second switching device is arranged between a first sub-line of the fourth line and a second sub-line of the fourth line.

[0039] In particular, the first subline of the second line and the second subline of the second line are designed such that a phase shift caused jointly by an electrical length L21 of the first subline of the second line, by an electrical length L22 of the second subline of the second line, and by the switching device essentially corresponds to an odd integer multiple of 90°. In particular, this also applies to the electrical length L41 of the first subline of the fourth line and an electrical length L42 of the second subline of the fourth line. In particular, the impedances of the first and second sublines for the second line and / or for the fourth line are of equal magnitude.

[0040] According to a further embodiment, the first and / or second switching device, in the decoupling state, is configured to connect the first or second sub-line to a ground line, i.e., a line element shorted to ground. In particular, the ground line has an impedance ZM and is shorted to ground at one end. This additional line element can optimize the transmission attenuation, i.e., the isolation of the second coupler output, in the decoupling mode, since mismatches in the coupler circuit, in particular the impedances, the electrical lengths of the lines, and the switching devices, can be partially compensated.

[0041] According to a further embodiment, the first and / or second switching device, in the decoupling state, is configured to connect the first or second sub-line to an additional line with an open end. This means that instead of a non-contacted open port on the first and / or second switching device, the first or second sub-line is connected to the additional line, which has an open end and an impedance Z 3 . In this embodiment, too, the additional line element in the decoupling mode can optimize the transmission attenuation, i.e., the isolation of the second coupler output, since mismatches in the coupler circuit, in particular the impedances, the electrical lengths of the lines, and the switching devices, can be partially compensated.

[0042] In particular, the choice of the additional line element, i.e., whether the ground line or the additional line is used, can be made depending on the type of switching device, in particular depending on the phase response or phase shift of the transmitted signal generated by the switching device. The ground line and / or the additional line with an open end are, in particular, designed such that total reflection of the high-frequency signal occurs through the ground line and / or the additional line.

[0043] According to a further embodiment, the lines comprise microstrip lines, coplanar lines, stripline lines and / or coaxial lines. Particularly in coupler circuits with microstrip lines, the microstrip lines are generally designed to utilize the greatest possible substrate height, as this results in the lowest possible losses through the line. However, if a distance to a ground plane (reference ground) of the microstrip line is increased, the conductor track width of the microstrip line must be increased in order to keep the impedance the same. Consequently, in such a case, more area on the substrate is taken up by the microstrip line. Particularly in coupler circuits that use microstrip lines, there is a need to save space on a circuit board. Consequently, the advantages of the invention are particularly evident when using microstrip lines.

[0044] According to a further embodiment, the first and / or second switching device each comprises an SPDT semiconductor switch (SPDT for "single pole double throw," i.e., a changeover switch), a mechanical switching relay, or a PIN diode. In particular, the transmission power of the antenna arrangement depends on and / or is limited by the type of switching device.

[0045] According to a further embodiment, the coupler inputs are connected to a DPDT switch (DPDT for "Double Pole Double Throw"), which is configured to couple the signal input to the first coupler input or the second coupler input and to short the other coupler input to ground. When the signal input is connected to the first coupler input, the input signal is forwarded to the first coupler output in decoupling mode, and the second coupler output is isolated. Conversely, when the signal input is connected to the second coupler input, the input signal is forwarded to the second coupler output in decoupling mode, and the first coupler output is isolated.

[0046] According to a further embodiment, the antenna arrangement further comprises a control device configured to selectively control the DPDT switch, the first switching device, and / or the second switching device. The control device is thus capable of switching the coupler circuit into the different operating modes, i.e., coupling mode, decoupling mode, or partial coupling mode. In particular, the control device can automatically adapt the operating mode of the coupler circuit depending on a reception result of the antenna, i.e., switch from a linear polarization to a circular or elliptical polarization and vice versa. Furthermore, the control device can control the respective switching devices depending on the amplitude of the input signal.For example, with a high input signal amplitude, it may be advantageous to operate the coupler circuit in coupling mode, as the splitting of the input signal and the associated loss of transmission power are acceptable in order to reach a larger number of potential receivers of the antenna's transmission signal. Conversely, with a low input signal amplitude, it may be advantageous to operate the coupler circuit in decoupling mode to achieve a higher transmission power of the antenna's transmission signal.

[0047] Another aspect of the invention relates to a coupler circuit comprising: a first coupler input connected to a first node; a second coupler input connected to a second node; a first coupler output connected to a third node; and a second coupler output connected to a fourth node, wherein the first and third nodes are electrically coupled to one another via a first line, wherein the second and fourth nodes are electrically coupled to one another via a third line, wherein the first and second nodes are electrically coupled via a second line by means of a first switching device, wherein the third and fourth nodes are electrically coupled via a fourth line by means of a second switching device.

[0048] Another aspect of the invention relates to a method for receiving and transmitting electromagnetic waves of different polarization, which comprises: a high-frequency input signal is applied to a coupler circuit according to one of the preceding embodiments, a polarized electromagnetic wave is emitted from an antenna connected to the coupler circuit, wherein the type of polarization of the electromagnetic wave is changed by switching the first and / or second switching device of the coupler circuit.

[0049] A further aspect of the invention relates to an RFID reader (RFID for Radio Frequency Identification) comprising an antenna arrangement of the type explained herein. The RFID reader comprises an evaluation unit that sends readout signals in the form of input signals to the signal input of the antenna arrangement in order to send radio signals to RFID tags, wherein the evaluation unit is designed to evaluate signals emitted by RFID tags and received via the antenna arrangement.

[0050] The statements regarding the antenna arrangement apply to the coupler circuit, the RFID reader, and the method accordingly. This applies in particular to embodiments and advantages.

[0051] Different embodiments of the invention are described below with reference to the drawings. They show: Figs. 1A and 1B show a coupler circuit in a coupling mode and a decoupling mode; Fig. 2 shows a coupler circuit according to a further embodiment; Fig. 3 shows a coupler circuit according to a further embodiment; Fig. 4 shows a coupler circuit according to a further embodiment; and Fig. 5 shows an antenna arrangement with a coupler circuit.

[0052] Fig. 1A und 1B show a coupler circuit 12 for use in an antenna arrangement 80 (not shown) for receiving and transmitting electromagnetic waves of different polarization, wherein the coupler circuit 12 is in Fig. 1A in pairing mode and in Fig. 1B operated in decoupling mode.

[0053] The coupler circuit 12 comprises a first coupler input 24 connected to a first node 16, a second coupler input 26 connected to a second node 18, a first coupler output 28 connected to a third node 20, and a second coupler output 30 connected to a fourth node 22. The first and third nodes 16, 20 are further electrically coupled to one another via a first line 32, with the second and fourth nodes 18, 22 being electrically coupled to one another via a third line 36. Furthermore, the first and second nodes 18, 20 are electrically coupled via a second line 34 by means of a first SPDT switch 40, with the third and fourth nodes 20, 22 being electrically coupled via a fourth line 38 by means of a second SPDT switch 42.

[0054] Each line has a respective impedance 46, 48, 50, 52, wherein the impedances 46, 50 of the first line 32 and the third line 36 are equal and each assume an impedance value of Z 1 . Furthermore, the impedances 48, 52 of the second line 34 and the fourth line 38 are equal and each assume an impedance value of Z 2 . The relationship Z 1 = 0.707*Z 2 applies to the impedances Z 1 and Z 2 . This dimensioning of the impedances ensures that the amplitude of the two output signals of the coupler outputs 28, 30 are essentially equal.

[0055] Each line 32, 34, 36, 38 further has an electrical length that indicates the phase shift of the transmitted signal caused by the line. In the present case, the electrical length 54, 58 of the first and third lines 32, 36 each corresponds to an electrical length L1, which corresponds to a phase shift of 90°. Furthermore, the electrical length 56, 60 of the second and fourth lines 34, 38 each corresponds to an electrical length L2, wherein the electrical length L2 and the electrical length LS of the first and second SPDT switches 40, 42 are dimensioned such that the electrical length L 2S = L2 + LS corresponds to a phase shift of 90°.

[0056] As shown in Figures 1A and 1B, the SPDT switch 40 is disposed at an end of the second line 34 closer to the first line 32 in close proximity to the first node 16, and the second of the SPDT switches 42 is disposed at an end of the fourth line 38 closer to the third line 36 in close proximity to the fourth node 22.

[0057] In pairing mode, which is Fig. 1A As shown, the SPDT switches 40, 42 are in a coupling state, ie the SPDT switches 40, 42 are closed, and connect the first and second nodes 16, 18 via the second line 34 and the third and fourth nodes 20, 22 via the fourth line 38. When an input signal 44 is applied to the first or second coupler input 24, 26, the input signal 44 is thus divided, so that an output signal is present at each of the first and second coupler outputs 28, 30, which output signal has a reduced signal power compared to the input signal 44.

[0058] In the following, it is assumed that the input signal 44 is applied to the first coupler input 24, wherein in the event that the input signal 44 is applied to the second coupler input 26, the operation of the coupler circuit 12 applies in a corresponding manner.

[0059] The input signal 44 present at the first coupler input 24 is passed from the first node 16 via the first line 32 to the third node 20 and thus to the first coupler output 28, wherein the output signal of the first coupler input 24 is phase-shifted by 90° with respect to the input signal 44 and is reduced in amplitude.

[0060] Secondly, the input signal 44 present at the first coupler input 24 is routed to the second coupler output 30 via two different paths 43, 45. The input signal 44 is routed to the second coupler output 30 via a first path 43, namely from the first node 16 via the second line 34 to the second node 18 and from the second node 18 via the third line 36 to the fourth node 22, and via a second path 45, namely from the first node 16 via the first line 32 to the third node 20 and from the third node 20 via the fourth line 38 to the fourth node 22. The signal transmitted via the first path 43 and the signal transmitted via the second path 45 are phase-shifted by 180° with respect to the input signal 44 and by 90° with respect to the output signal of the first coupler output 28 at the fourth node 22, respectively, and their amplitude is reduced.The signal transmitted via the first path 43 and the signal transmitted via the second path 45 are combined and added at the fourth node 22, so that the addition of the two signals is present as an output signal at the second coupler output 30.

[0061] The output signal of the second coupler output 30 also has a phase shift of 180° relative to the input signal 44 or 90° relative to the output signal of the first coupler output 28. Furthermore, the amplitude of the output signal of the second coupler output 30 corresponds to the amplitude of the output signal of the first coupler output 28.

[0062] The output signals of the first and second coupler outputs 28, 30 can then be used in the coupling mode to be fed into the patch antenna 64 via feed points 92, 94, 96, 98 of a patch antenna 64 (not shown) in order to generate and transmit a circularly or elliptically polarized RF wave.

[0063] In decoupling mode, which is Fig. 1B As shown, the SPDT switches 40, 42 are in a decoupling state, i.e. the SPDT switches 40, 42 are open, so that an electrical connection between the first and second nodes 16, 18 via the second line 34 and between the third and fourth nodes 20, 22 via the fourth line 38 is interrupted. When an input signal 44 is applied to the first or second coupler input 24, 26, the input signal 44 is therefore no longer split, but is passed from the first node 16 via the first line 32 to the third node 20 and thus to the first coupler output 28, wherein the output signal of the first coupler input 28 is 90° out of phase with the input signal 44 and reduced in amplitude. The second coupler output 30 is thus isolated, i.e. no output signal is output via the second coupler output 30.

[0064] The output signal of the first coupler output 28 can be used in the decoupling mode to be fed into the patch antenna 64 via feed points 92, 94, 96, 98 of the patch antenna 64 (not shown) in order to generate and transmit a linearly polarized RF wave.

[0065] Fig. 2 bis 4 show further embodiments of the coupler circuit 12, wherein the coupler circuit 12 is shown only in coupling mode for the sake of simplicity.

[0066] Fig. 2 shows a coupler circuit 12 which differs from the coupler circuit 12 of the Fig. 1A in that the SPDT switches 40, 42 in Fig. 2 along the second line 34 or the fourth line 38 more centrally than in Fig. 1A are arranged. The first SPDT switch 40 is arranged between a first subline 66 of the second line 34 and a second subline 68 of the second line 34, and the second SPDT switch 42 is arranged between a first subline 70 of the fourth line 38 and a second subline 72 of the fourth line 38.

[0067] Fig. 3 shows a coupler circuit 12 which differs from the coupler circuit 12 of the Fig. 2 differs in that the first and second SPDT switches 40, 42 in the decoupling state connect the first sub-line 66, 70 of the second and fourth lines 34, 38, respectively, to a ground line 74 which is connected to ground, wherein an impedance 76 of the ground line 74 has an impedance value ZM.

[0068] Fig. 4 shows a coupler circuit 12 which differs from the coupler circuit 12 of the Fig. 2 differs in that the first and second SPDT switches 40, 42 in the decoupling state connect the first sub-line 66, 70 of the second and fourth lines 34, 38, respectively, to an additional open-ended line 78.

[0069] The additional line element of the Fig. 3 and 4 , ie the ground line 74 and the additional line with open end 78, can optimize the transmission attenuation, ie the isolation of the second coupler output 30, in the decoupling mode, since mismatches of the coupler circuit can be compensated for thereby.

[0070] Fig. 5 shows an antenna arrangement 80, in particular an RFID antenna arrangement, with a coupler circuit 12 for receiving and transmitting RF waves of different polarization. The antenna arrangement 80 comprises a signal input 82 with a high-frequency input signal 44, wherein the signal input 82 is connected to a DPDT switch 84, which couples the signal input 82 to a first coupler input 24 of the coupler circuit 12 and connects a second coupler input 26 of the coupler circuit 12 to ground. Alternatively, the DPDT switch 84 can switch the signal input 82 to the second coupler input 26 and connect the first coupler input 24 to ground, whereby, for example, the polarization angle and / or the polarization direction of the RF wave can be changed, i.e., depending on the switch position of the DPDT switch 84.

[0071] The Fig. 5 The coupler circuit 12 shown corresponds to the coupler circuit 12 of the Fig. 1A or 1B. As already described above, the coupler circuit 12 can be operated in coupling mode or decoupling mode. In Fig. 5 the coupler circuit 12 is operated in coupling mode, so that at the first coupler output 28 an output signal is output to a first antenna coupler 85, which divides the output signal of the first coupler output 28 and feeds the divided signals via respective feed lines 80 to a first feed point 92 and a third feed point 96 opposite the first feed point 92. Furthermore, at the second coupler output 30 an output signal is output to a second antenna coupler 86, which divides the output signal of the second coupler output 30 and feeds the divided signals via respective feed lines 90 to a second feed point 94 and a fourth feed point 98 opposite the second feed point 94. The phase offset between the output signal of the first coupler output 28 and the output signal of the second coupler output 30 corresponds to 90°, while the amplitudes of the two signals are essentially the same.In particular, the feed lines 88 of the first and third feed points 92, 96 are offset by 90° to the feed lines 90 of the second and fourth feed points 94, 98, whereby the resulting RF wave is circularly or elliptically polarized.

[0072] When the coupler circuit 12 is operated in the decoupling mode, the input signal 44 is not split, but is passed from the first node 16 via the first line 32 to the third node 20 and to the first coupler output 28. The second coupler output 30 is then isolated, i.e., no output signal is output via the second coupler output 30. The output signal of the first coupler output 28 is output, as in the coupling mode, to the first antenna coupler 85, which splits the output signal of the first coupler output 28 and feeds the split signals to the first feed point 92 and the third feed point 96 via the respective feed lines 88. No signals are fed in via the second and fourth feed points 94, 98, so that the resulting RF wave is linearly polarized. Bezugszeichenliste

[0073] 12 Coupler circuit 14 Antenna arrangement 16 First node 18 Second node 20 Third node 22 Fourth node 24 First coupler input 26 Second coupler input 28 First coupler output 30 Second coupler output 32 First line 34 Second line 36 Third line 38 Fourth line 40 First SPDT switch 42 Second SPDT switch 43 First path 44 Input signal 45 Second path 46 Impedance of the first line 48 Impedance of the second line 50 Impedance of the third line 52 Impedance of the fourth line 54 Electrical length of the first line 56 Electrical length of the second line 58 Electrical length of the third line 60 Electrical length of the fourth line 64 Patch antenna 66 First subline of the second line 68 Second subline of the second line 70 First subline of the fourth line 72Second sub-line of the fourth line 74Ground line 76Impedance of the ground line 78Additional open-ended line 79Impedance of the additional open-ended line 80Antenna arrangement82 Signal input 84 DPDT switch 85 First antenna coupler 86 Second antenna coupler 88, 90 Feed lines 92 First feed point 94 Second feed point 96 Third feed point 98 Fourth feed point

Claims

1. An antenna arrangement (80), in particular an RFID antenna arrangement, for receiving and transmitting electromagnetic waves of different polarization, comprising: an antenna having at least two feed points (92, 94, 96, 98) arranged at a distance from one another, the antenna being designed to emit a polarized electromagnetic wave; a signal input (82) for a high-frequency input signal (44); a coupler circuit (12) coupled to the signal input (82), which coupler circuit comprises: a first coupler input (24) connected to a first node (16); a second coupler input (26) connected to a second node (18); a first coupler output (28) connected to a third node (20);and a second coupler output (30) connected to a fourth node (22), wherein the first and third nodes (16, 20) are electrically coupled to one another via a first line (32), wherein the second and fourth nodes (18, 22) are electrically coupled to one another via a third line (36), wherein the first and second nodes (16, 18) are electrically coupled via a second line (34) by means of a first switching device, wherein the third and fourth nodes (20, 22) are electrically coupled via a fourth line (38) by means of a second switching device, wherein the signal input (82) is coupled to the first coupler input (24) or to the second coupler input (26), wherein the first and second coupler outputs (28, 30) are each connected to one or more feed points (92, 94, 96, 98) of the antenna.

2. Antenna arrangement (80) according to claim 1, wherein the coupler circuit (12) is operable in a decoupling mode and in a coupling mode, wherein the coupler circuit (12) is designed in the decoupling mode such that the first and second switching devices are operated in a decoupling state, such that the signal input (82) is only connected to the first or second coupler output (30), wherein the antenna is designed in the decoupling mode to emit a linearly polarized electromagnetic wave, wherein the coupler circuit (12) is designed in a coupling mode such that the first and / or second switching devices are operated in a coupling state, such that the signal input (82) is connected to the first and second coupler output (30), wherein the antenna is designed in the coupling mode to emit a circularly polarized or elliptically polarized electromagnetic wave.

3. Antenna arrangement (80) according to one of the preceding claims, wherein an electrical length (54) of the first line (32) substantially corresponds to an electrical length (58) of the third line (36), wherein the electrical length (54, 58) of the first and / or third line (36) each corresponds to an electrical length L1, an electrical length (56) of the second line (34) substantially corresponds to an electrical length (60) of the fourth line (38), wherein the electrical length (56, 60) of the second and / or fourth line (38) each corresponds to an electrical length L2, wherein an electrical length of the first switching device substantially corresponds to an electrical length of the second switching device, wherein the electrical length of the first and second switching devices each corresponds to an electrical length L S where a length defined by the electrical lengths L2 and L S jointly caused phase shift L 2Sessentially corresponds to an odd integer multiple of 90°.

4. Antenna arrangement (80) according to one of the preceding claims, wherein the first and third lines (32, 36) each have a first impedance, wherein the second and fourth lines (34, 38) each have a second impedance, wherein the first impedance and the second impedance are selected such that output signals of substantially the same amplitude are output at the first coupler output (28) and at the second coupler output (30).

5. Antenna arrangement (80) according to claim 2, wherein the coupler circuit (12) is operable in a partial coupling mode in which the first switching device is operated in the coupling state and the second switching device is operated in the decoupling state or vice versa, wherein the antenna is configured to emit an elliptically polarized electromagnetic wave in the partial coupling mode.

6. Antenna arrangement (80) according to one of the preceding claims, wherein the first switching device is arranged at an end of the second line (34) closer to the first line (32) and the second switching device is arranged at an end of the fourth line (38) closer to the third line (36) or the first switching device is arranged at an end of the second line (34) closer to the third line (36) and the second switching device is arranged at an end of the fourth line (38) closer to the first line (32).

7. Antenna arrangement (80) according to one of the preceding claims, wherein the first switching device is arranged between a first sub-line (66) of the second line (34) and a second sub-line (68) of the second line (34) and / or wherein the second switching device is arranged between a first sub-line (70) of the fourth line (38) and a second sub-line (72) of the fourth line (38).

8. Antenna arrangement (80) according to claim 7, wherein the first and / or second switching device is configured in the decoupling state to connect the respective first or second sub-line (66, 68, 70, 72) to a ground line (74).

9. Antenna arrangement (80) according to claim 7, wherein the first and / or second switching device in the decoupling state is designed to connect the respective first or second sub-line (66, 68, 70, 72) to an additional open-ended line (78).

10. Antenna arrangement (80) according to one of the preceding claims, wherein the lines comprise microstrip lines, coplanar lines, stripline lines, waveguides and / or coaxial lines.

11. Antenna arrangement (80) according to one of the preceding claims, wherein the first and / or second switching device each comprise an SPDT semiconductor switch (40, 42), a mechanical switching relay or a PIN diode.

12. Antenna arrangement (80) according to one of the preceding claims, wherein the coupler inputs (24, 26) are connected to a DPDT switch (84) which is designed to couple the signal input (82) to the first coupler input (24) or the second coupler input (26) and to short-circuit the respective other coupler input (26, 24) to ground.

13. The antenna assembly (80) of claim 12, further comprising a control device configured to selectively control the DPDT switch (84), the first switching device, and / or the second switching device.

14. A coupler circuit (12), comprising: a first coupler input (24) connected to a first node (16); a second coupler input (26) connected to a second node (18); a first coupler output (28) connected to a third node (20); and a second coupler output (30) connected to a fourth node (22), wherein the first and third nodes (16, 20) are electrically coupled to one another via a first line (32), wherein the second and fourth nodes (18, 22) are electrically coupled to one another via a third line (36), wherein the first and second nodes (16, 18) are electrically coupled via a second line (34) by means of a first switching device, wherein the third and fourth nodes (20, 22) are electrically coupled via a fourth line (38) by means of a second switching device.

15. A method for transmitting electromagnetic waves of different polarization, comprising: applying a high-frequency input signal (44) to a coupler circuit (12) according to claim 14, transmitting a polarized electromagnetic wave from an antenna connected to the coupler circuit (12), wherein the type of polarization of the electromagnetic wave is changed by switching the first and / or second switching device of the coupler circuit (12).

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