Antenna coupler

p0001The invention relates to an antenna for testing of transmitters and / or receivers, especially mobile phones or devices that operate on the Blue Tooth standard.

p0002From DE 197 32 639 C1 an antenna coupler for testing mobile phones is known. In the known antenna a receiving element for a mobile telephone is mounted on a circuit board. On the circuit board a rod antenna is constructed in stripline technology, which acts in particular as a dipole antenna. An essential property of the antenna coupler is the coupling factor, which indicates the ratio of received power with respect to the total power radiated. Since the known arrangement is extremely sensitive to changes in position of the antenna of the mobile phone, the coupling factor for each fixed to the receiving element type mobile phone is different.

p0003The US 5,777,585 is based on an antenna coupler, a first external antenna terminal and a second external antenna connection on a conductive plate which suppresses unnecessary radiation from power. The antenna coupler reduces the power loss in transmission and has a long life and good operability on. It comprises an electromagnetic coupling element which consists of a conductor which is not connected with a first antenna in terms of DC components in contact. Further, the coupling member contacts a ground conductor in terms of DC components, wherein the power transmitted by the first antenna and the received power is transmitted to the electromagnetic coupling element out. The first and the second external antenna connector comprise an electrical circuit in their housings, which couples the antenna of a portable radio terminal having an external antenna electromagnetically. The external antenna connectors are not in contact in terms of dc components with the radio portable terminal, if this is fixed. The US 5,777,585 discloses an antenna according to the preamble of independent claim 1.

p0004The object of the invention is therefore to provide an antenna coupler that is insensitive to changes in position of the antenna of the transmitter and / or receiver and is adopting a common coupling factor for testing various transmitters and / or receivers.

p0005The object is achieved by an antenna having the features of claim 1. Advantageous developments of the invention are specified in the subclaims.

p0006According to the invention the antenna element is formed as a spatially substantially closed loop. Characterized the magnetic component is detected in addition to the electrical component of the radiated field from the mobile telephone. Conversely, the transmission is improved to the mobile phone. The term mobile phone is treated here and hereinafter as a possible application. Instead of the mobile phone, the invention is also suitable for any other transmitter and / or receiver, z. B. those which operate according to the blue-tooth principle. Characterized the coupling factor of the antenna coupler according to the invention is largely independent of the precise positioning of the mobile telephone relative to the antenna element. Therefore, a mobile phone can be tested, in which at least from the outside, the exact position of the antenna is not known without special adjustments to the spatial orientation and position are required.

p0007It is advantageous that the loop is arranged substantially in a plane which is orientated parallel to a reflector plate. Thus, the up / down ratio of the antenna coupler is decisively improved.

p0008It is furthermore advantageous in that a further embodied as a spatially substantially closed loop antenna element is provided, which is formed so arranged that the feed point of another antenna element opposite the feed point of the one antenna element shifted by 90 ° at least substantially. This allows the antenna via the receive antenna and a transmit simultaneously on the other antenna, where maximum phase decoupling is achieved in order to avoid mutual interference.

p0009The invention will be explained in more detail with reference to the drawing. In the drawings:<dl id="dl0001"><dt>Fig. 1</dt><dd>a first example for better understanding of an antenna coupler in a top view;</dd><dt>FIG. 2</dt><dd>a section along the cutting line designated in Fig 1 by II. </dd><dt>Fig. 3</dt><dd>a schematic view of the antenna element together with a measurement arrangement according to the first example for better understanding of a Autennenkopplers</dd><dt>Fig. 4</dt><dd>a schematic view of two antenna elements according to a first embodiment;</dd><dt>Fig. 5</dt><dd>a schematic representation of two antenna elements according to a second embodiment of the invention; and</dd><dt>Fig. 6</dt><dd>building a crossover that can be switched between two antenna elements and a measuring arrangement according to the second embodiment of the invention.</dd></dl>

p0010Fig. 1 shows an antenna 1 according to a first example for better understanding the invention in a plan view. The antenna 1 is used for testing a mobile telephone 2. For this purpose, the mobile phone 2 is positioned by means of a fixed to a reflector plate 3 receiving element 4 of the antenna coupler via an antenna element. 5 By the receiving element 4 a defined position is predetermined and prevents a displacement of the mobile phone 2 during the measurements carried out. For secure attachment of the mobile phone 2, the receiving element 4 this particular several locking elements 6 comprises.

p0011The antenna 7 of the mobile phone 2, which is shown in the interior of the mobile phone 2 as a broken line, is arranged by the attachment of the antenna element above the fifth Since the exact position of the antenna 7 from the outside can not be assessed readily, also exactly centered arrangement of the antenna 7 via the antenna element 5 is difficult, that is, only by a complex balance, possible. This is particularly the situation when the mobile phones 2 are used, in which the antenna 7 is completely housed within the casing 8 of the mobile phone 2nd It is awkward when for various mobile phones 2 spatially precise adjustment must be carried out since then, the receiving element 4 would be displaced. The present invention avoids the foregoing problems by reducing the coupling factor between the antenna element 5 and the antenna 7 is largely to the antenna element 5 independently from the precise geometric arrangement of the antenna 7 of the mobile phone 2 relative.

p0012The antenna element 5 has an interrupted in the Fig. 1 illustrated inner conductor 9 and a surrounding the inner conductor 5 outer conductor 10, the outer conductor 10 shields the inner conductor 9. a dielectric may be provided between the two conductors 9, 10th Preferably, the outer conductor surrounds the inner conductor 10 9 peripherally in the form of a cylinder jacket-shaped shield. The antenna element 5 is formed as a spatially substantially closed loop, wherein the a feed point 11 and the one end 12 of the antenna element 5 is a smallest possible distance between. At the end 12 of the antenna element 5 of the inner conductor 9 is led out of the outer conductor 10th The lead-out inner conductor 9 11 is guided in the region of the feeding point 13 on the outer conductor 10 to make electrical contact between the two. The region 13 is preferably located near the feed point 11th

p0013The antenna element 5 is arranged in a plane 14, which is shown in FIG. 2. These include,. As Teflon are existing holders 15 used that hold the antenna element 5 with respect to the feeding point 11th

p0014Since the designed as a closed loop antenna element 5 measures both oriented in the y-direction electric component and the perpendicular to the plane 14 oriented magnetic component of the from the antenna 7 radiated electric field, there is a high degree of independence in the x- and y-direction at the positioning of the mobile phone 2 and the antenna 7 of the mobile phone 2. This also applies to transmission from the antenna element 5 to the antenna 7 of the mobile phone. 2

p0015The extent of in FIG. 1 annularly arranged antenna element 5 substantially corresponds to the mean wavelength λ, which is emitted or received by the antenna element 5 in order to achieve an advantageous emission and reception characteristics. By mounting the antenna element 5 on the embodied as a reflector reflector plate 3 also gives an excellent forward / reverse ratio. The arrangement consists of four dipoles, the half loop a first λ / 2 dipole and the half loop relative to the feeding a second λ / 2 dipole is at the entry point and two additional λ / 2 dipoles by the reflector plate 3 virtually be mirrored.

p0016The section taken along the line designated in Fig. 1 with II shown in FIG. 2, also, the height H, in which the antenna element 5 is arranged above the reflector plate 3 be removed. Here, the height H is equal to one eighth of the wavelength λ to which the antenna element 5 is tuned. For a center frequency of 2.45 GHz, this results in a developed length of the antenna element 5 of approximately 12 cm and a height H of about 1.5 cm.

p0017By reaching homogeneous field behavior in the z direction and a z. B. is therefore structurally related height variation of the antenna 7 for the coupling factor achieved largely without influence.

p0018Fig. 3 shows an antenna with a measuring arrangement in a schematic diagram of the first example. The bent to a substantially closed annular loop antenna element 5 has the outer conductor 10 and the inner conductor 9, between which a dielectric 16 is provided. At the end 12 of the antenna element 5, the inner conductor 9 on the feed point 11 closest portion 17 of the outer conductor 10 is guided, to establish electrical contact therebetween. Via the connecting piece 18, the antenna element 5 is connected to a measuring instrument 19, wherein the connecting piece 18, as shown in FIG. 2, the antenna element 5 is supported in the region of the feeding point 11 relative to the reflector plate 3.

p0019Fig. 4 shows the basic structure of a first embodiment of the invention. Matching elements are identified in this and in all other characters with matching reference numerals, whereby a repeated description is unnecessary.

p0020According to the first embodiment, a first antenna element 5, it is provided that the antenna element 5 of the first example corresponds. In addition, a second antenna element 25 is provided, which in principle has the same construction as the first antenna element fifth The second antenna element 25 therefore has an outer conductor 26, an inner conductor 27 and an open end 28th Accordingly, the antenna element 5, the inner conductor 27 is guided to the outer conductor 26 in the region of the feeding point 29 of the antenna element 25 for making electrical contact. In addition, a connector 30 is provided, which support the antenna element 25 along with two retainers, not shown, corresponding to the supports 15, on a common reflector plate 3rd

p0021In the first embodiment of the invention, the antenna element 25 apart from the polarization approximately is intended to have the same radiation pattern as the antenna element. 5 For reasons of space, the antenna element 25 is however arranged inside the antenna element 5, so that its unwound length is shorter than that of the antenna element. 5 In order nevertheless to achieve a good emission characteristic of the two antenna elements 5, 25, can be prepared starting from a central wavelength of the antenna element 5 has a slightly larger circumference and the antenna element 25 have a somewhat smaller circumference, so that there is an acceptable compromise in terms of voting. On the other hand, the antenna element 25 can be also formed the same as the antenna element 5, the latter being then in the z-direction (see Fig. 2) above or to be arranged below the other element. To maintain the up / down ratio, which is achieved through the reflector plate 3, it is advantageous if the arrangement of the two antenna elements 5, 25 something takes place above and below the height H = λ /. 8

p0022The feed point 29 of the further antenna element 25 is offset from the feed point 11 of the antenna element 5 by 90 °, so that a maximum decoupling between the two antennas is achieved with regard to receiving and transmitting simultaneously. If both Antnennenelemente be 5, 25 is used as a transmitting antenna or as receiving antenna can be adjusted using this arrangement also achieved in that a at an arbitrary angle to the x- and y-axis standing antenna of the mobile phone at least relative to one of the antenna elements 5, 25 a good coupling factor has.

p0023FIG. 5 shows a second embodiment in which the antenna element 5 and a further antenna element 35 are provided. The antenna element 5 is constructed as the antenna elements 5 of the first and second embodiments. The further antenna element 35 corresponds in terms of its fundamental structure is also the antenna element 5, that has an outer conductor 36, an inner conductor 37, the lead-out of the inner conductor 37 from the end 38 and the corresponding connection to the outer conductor 36 in the region of the feeding point 39 and a connecting piece 40 on. The developed length of the antenna element 35, however, is only about half the unwound length of the antenna element 5, so that it is tuned for transmission on the double center frequency. With the antenna element 35, therefore, the next higher mode of the transmission signal can be received or sent. The connecting pieces 18 and 40 of the two antenna elements 5, 35 are rotated by 180 ° to each other. By the two antenna elements 5, 35 according to the third embodiment, a wide-band transmission is achieved by means of the antenna coupler first

p0024For the connection of the two antenna elements 5, 35 by means of the connecting pieces 18, 40 with the measuring instrument 19, a crossover network is needed, which is connected between the antenna elements 5, 35 and the measuring device 19th

p0025Such a crossover is shown in Fig. 6. To simplify the presentation, which provided for the Freuqenzweiche 50 components in FIG. 6 are designated by specific values. This is, however, merely illustrative of the preferred embodiment and does not limit the invention also in terms of the achieved frequency separation there. The crossover 50 has a connection point 51, a connection point 52 for a lower frequency branch and a connection point 53 for an upper frequency branch. The connection point 51 is connected to a node 54 which is connected to ground 55 via a capacitor C4 and a coil L4. About the coil L1 of the node 54 is connected to the node 56th The node 56 is placed over the coil L3 and the capacitor C5 to ground, to lock the upper frequency range that lies on the side of the connection point 53. In addition, the node 56 is connected via the coil L2 to the connection point 52nd

p0026The node 54 is connected to the node 58 via capacitor C2. The node 58 is connected through the coil L5 and the capacitor C3 to ground 59, to lock the lower frequency range which is transmitted through the connection point 52. The node 58 is also connected via capacitor C1 to the terminal point 53rd

p0027Preferably, the values ​​of the devices according to the third embodiment: C1 = 6.8 pF, C2 = 1.5 pF, C3 = 6.8 pF, C4 = 0.8 pF, C5 = 3.9 pF, L1 = 10 nH , L2 = 3.9 nH, L3 = 1 nH, L4 = 12 nH and L5 = 3.9 nH. With these values, a frequency allocation of 0.8 GHz to 1 GHz in the low frequency branch, which is transmitted via the connection point 52, and 1.7 GHz to 2 GHz in the high frequency branch, which is transmitted via the connection point 53, is reached.

p0028In the context of the invention, other values ​​for the components and / or a different frequency allocation are possible.

p0029In the described embodiments, the inner conductor 9 of the respective antenna element for forming an open antenna is guided to the the feed point lying electrically closest portion of the outer conductor. In the present invention, the inner conductor may, however, also be recirculated directly to the outer conductor surrounding it. The inner conductor of the respective antenna element is then passed to the portion of the outer conductor, the inner conductor is the spatially closest.

p0030The invention is not limited to the embodiments described. Particularly suited to the antenna for testing of any transmitters and / or receivers or transmitting and / or receiving devices, a preferred application in the testing of mobile phones (mobile phones) is. In the embodiments described, the mobile phone 2 is placed on a support surface 20 of the receiving element 4 of the antenna coupler first The support surface 20 can be formed as a housing upper side, it is not absolutely necessary to additionally provide a receiving element 4 for fixedly holding the mobile telephone 2, since the reaching coupling factor is substantially independent of displacements in the y and x-direction. It is more advantageous, however, nevertheless, provide a defined position of the mobile phone 2 by the above-receiving element. 4 The housing z. B. of metal and in the other regions to avoid reflections from a non-conductive material is preferably only in the area of ​​the reflector plate conductively possibly run in the side regions with an absorbent coating.