METHODS AND APPARATUSES FOR TESTING WIRELESS COMMUNICATION TO VEHICLES

Abstract

An apparatus for measuring over-the-air (OTA) wireless communication performance in an automotive application of a device under test arranged on or in a vehicle. The apparatus includes a chamber and a platform for supporting the vehicle within the chamber. The platform is a rotatable platform that can rotate the vehicle, and the floor is inwardly reflective, and optionally covered with a top layer to resemble asphalt or other road covers. In one embodiment, the chamber is a reverberation chamber, simulating a multi-path environment, and preferably a rich isotropic multipath (RIMP) environment. In another embodiment, the chamber has inwardly absorbing walls, simulating a random-LOS environment.

Claims

1. An apparatus for measuring over-the-air (OTA) wireless communication performance in an automotive application of a device under test arranged on or in a vehicle, comprising: a chamber defining an internal cavity therein, and a platform for supporting the vehicle, wherein the chamber is a random-LOS chamber, having inwardly absorbing walls, and wherein the chamber is adapted to enclose the platform, wherein the platform is a rotatable platform that can rotate the vehicle, and wherein the floor of the chamber is inwardly reflective, and optionally covered with a top layer to resemble asphalt or other road covers, and further comprising at least one linear array antenna within the chamber.

2. The apparatus of claim 1, wherein the platform has means to allow the vehicle to be measured with the wheels rolling and the engine working.

3. The apparatus of claim 1, wherein the platform is arranged to be rotatable 360° continuously or intermittently during measurement.

4. (canceled)

5. (canceled)

6. (canceled)

7. (canceled)

8. (canceled)

9. (canceled)

10. (canceled)

11. The apparatus of claim 1, wherein the random-LOS chamber has absorbers on all walls, rendering the walls absorbing to electromagnetic waves, thereby simulating a random-LOS environment, at least one chamber antenna arranged in the cavity; and a measuring instrument connected to the device under test and the chamber antenna, for measuring the transmission between them.

12. The apparatus of claim 1, wherein the internal chamber formed in the chamber is completely shielded, having reflecting material behind the absorbers, such as metal, on all walls and floor and ceiling, and absorbers being provided on all or most walls and ceiling, but not on the floor.

13. The apparatus of claim 1, wherein at least one chamber antenna arranged in the chamber is a vertical linear array antenna.

14. The apparatus of claim 13, wherein the vertical linear array antenna is dual-polarized, and arranged in one corner of the chamber or along a wall of the chamber.

15. The apparatus of claim 13, further comprising a branched distribution network connecting the vertical linear array antenna to a base station emulator.

16. The apparatus of claim 13, wherein the linear array antenna is tiltable to assume different tilt angles in the elevation plane.

17. The apparatus of claim 1, wherein at least one chamber antenna arranged in the chamber is a pill-box style antenna, comprising two parallel plates, a curved reflecting wall between the two plates, and an elongated aperture opposite to the curved wall.

18. The apparatus of claim 1, wherein the height of the internal cavity is in the range of H+0.5 m and H+3 m, where H is the height of the highest vehicle on which the chamber is intended to measure.

19. The apparatus of claim 1, wherein the length and width of the internal cavity are both in the range of L+1.5 m and L+4 m, where L is the length of the longest vehicle on which the chamber is intended to measure.

20. The apparatus of claim 1, wherein it is adapted to measure at least one of the following communication performance parameters: total radiated power (TRP), total isotropic sensitivity (TIS), throughput, antenna efficiency, average fading sensitivity and diversity and MIMO gain.

21. (canceled)

22. The apparatus of claim 1, wherein at least one of the linear array antennas comprises several linear array sections arranged on top of each other.

23. The apparatus of claim 22, wherein the several linear array sections are arranged in a straight disposition.

24. The apparatus of claim 22, wherein the several linear array sections are arranged in a curved disposition, extending from the base in a direction towards the platform, and preferably extending at least partly over the platform.

25. The apparatus of claim 22, wherein two or more linear array antennas are provided, said linear array antennas being located on one side of the platform and combined by a distribution network of cables and power dividers.

26. The apparatus of claim 22, further comprising a distribution network for feeding the linear array.

27. The apparatus of claim 26, wherein the several linear array sections are arranged in a curved disposition, extending from the base in a direction towards the platform, and preferably extending at least partly over the platform, and wherein the distribution network comprises fixed delay lines compensation for the non-straight extension of the linear array, preferably in such a way that the voltage received at the end of the distribution network is representative of a far-field radiation pattern of the antenna when the platform rotates.

28. The apparatus of claim 22, wherein the linear array antennas are being tilted to assume different angles forward toward the platform, thereby providing different elevation angles of the far field.

29. The apparatus of claim 22, wherein linear array antennas are connected to the same port on a base station emulator or channel emulator via a distribution network with cables and power dividers between them.

30. The apparatus of claim 22, wherein at least two linear array antennas are provided, the linear array antennas being located at one side of the platform.

31. The apparatus of claim 22, wherein at least two linear array antennas are provided, the linear array antennas being distributed around the platform, and preferably being evenly distributed around the platform.

32. A method for measuring over-the-air (OTA) wireless communication performance in an automotive application of a device under test arranged on or in a vehicle, comprising: providing a chamber defining an internal cavity therein, wherein the chamber is a random-LOS chamber, having inwardly absorbing walls, and wherein the floor of the chamber is inwardly reflective, and optionally covered with a top layer to resemble asphalt or other road covers, and further comprising at least one linear array antenna within the chamber; arranging the vehicle within the internal cavity; and measuring over-the-air wireless communication performance while horizontally rotating the vehicle intermittently or continuously during the measuring.

33. The method of claim 32, further comprising operating the vehicle so that the wheels are rolling and the engine is working during said measuring.

34. The method of claim 32, wherein the vehicle is rotated over 360° during measurement.

35. (canceled)

36. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] For exemplifying purposes, the invention will be described in closer detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:

[0062] FIG. 1 is a perspective side view showing the interior of a reverberation chamber apparatus in accordance with one embodiment of the present invention;

[0063] FIG. 2 is a perspective side view showing the interior of a random-LOS chamber apparatus in accordance with another embodiment of the present invention;

[0064] FIG. 3 is a schematic illustration of an exemplary antenna and distribution arrangement to be used in the apparatus of FIG. 2;

[0065] FIG. 4 is an alternative embodiment of an antenna useable in the apparatus of FIG. 2;

[0066] FIG. 5 is another alternative embodiment of an antenna useable in the apparatus of FIG. 2;

[0067] FIG. 6a-6c are top views, schematically illustrating various embodiments in which several linear array antennas are distributed around the platform, at on one or several side(s) of the vehicle/platform; and

[0068] FIG. 7a-7c schematically illustrate various arrangements of a linear array antenna comprising multiple sections.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0069] In the following detailed description, preferred embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of e present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known constructions or functions are not described in detail, so as not to obscure the present invention.

[0070] In a first embodiment, as illustrated in FIG. 1, the apparatus comprises a reverberation chamber (RC). The reverberation chamber 1 has walls of an inwardly reflective material, rendering the walls reflective to electromagnetic waves, thereby emulating a multi-path environment, and preferably a rich isotropic multipath (RIMP) environment. Thus, the internal chamber formed in the chamber is preferably completely shielded, having reflecting material, such as metal, on all walls and floor and ceiling. The floor of the chamber is inwardly reflective, but optionally covered with a top layer to resemble asphalt or other road covers.

[0071] Further, a rotatable platform 2 is provided within the chamber, and enclosed within the internal cavity. The platform is arranged to support and rotate a vehicle 3 on it, such as a car, a bus or any other type of vehicle. A device under test (DUT) is arranged in or on the vehicle. The device under test can e.g. be a communication device arranged within the car, and having an exteriorly mounted antenna. However, it may also be a communication device having an integrated antenna and being operated within the car, such as a mobile phone, a tablet PC, a computer or the like being operated within the car.

[0072] The rotatable platform is preferably capable of rotating the vehicle completely, i.e. 360°. The rotation may be controlled by a control PC, in same way as for the per se known platform stirring used in U.S. Pat. Nos. 7,444,264, 7,286,961 and WO 12/171562, so that rotation can be performed intermittently or continuously during measurement. Preferably, the platform also has means to allow the vehicle to be measured with the wheels rolling and the engine working. To this end, the platform may e.g. comprise rotatable rollers on which the wheels are supported. The chamber may be intended for measurements of cars only, but may also be for measurement on busses, as well as other types of vehicles. By rotation of the vehicle during measurement, either intermittently or continuously, it has been found that a very efficient stirring of the mode distribution is obtained within the chamber. Thus, there is in most cases no need for any additional mode stirrers, even though such additional mode stirrers may optionally be provided.

[0073] Further, at least one chamber antenna 4 is provided within internal cavity of the chamber, preferably at fixed position(s). For example, the antenna may be arranged on one or several of the walls of the internal cavity. The antenna may be an electric monopole, a helical antenna, a microstrip antenna or similar small antennas. For example, the antennas may be of any of the types disclosed in the above-discussed U.S. Pat. Nos. 7,444,264 and 7,286,961.

[0074] In a preferred embodiment, the antenna is of the type having orthogonal faces, similar to the one disclosed in WO 12/171562. In such an embodiment, the antenna(s) is arranged on an antenna holder comprising three surfaces of a reflective material, wherein the surfaces extend in planes which are orthogonal in relation to each other and each surface facing away from the other surfaces. These chamber antennas correspond to the so-called wall antennas in the previous U.S. Pat. Nos. 7,444,264 and 7,286,961, but are no longer required to be fixed to the walls, but rather fixed to an antenna holder located somewhere inside the chamber away from any wall. In another preferred alternative, the antenna is a multi-port butterfly antenna, e.g. similar to the one discussed in PCT/SE2013/051130. Using such or similar antennas provides a very useful polarization stirring, and also enables e.g. MIMO measurements. Preferably, the chamber antenna(s) is/are placed at a distance from the side walls, floor and roof of the chamber. Preferably this distance exceeds ½ wavelength from each wall, floor and roof of the chamber, of the frequency used for testing.

[0075] The apparatus may further comprise a shield 5, arranged to prevent a direct line-of-sight between a chamber antenna and the device under test, the shield preferably being of metal. The shield may e.g. be configured and arranged in a way similar to the shield discussed in WO 12/171562. Preferably, the shield is dimensioned so that direct coupling between the chamber antenna(s) and the device under test is strongly reduced, and at the same time, the shield does only insignificantly reduce the multimode distribution within the chamber. Still further, the shield preferably has a non-linear extension in the width direction, and preferably a curved or angled extension, whereby the shield partly surrounds the chamber antenna(s). The shield is preferably arranged at a distance from the chamber antenna(s), said distance corresponding to at least ½ wavelength used for testing.

[0076] A measuring instrument 6 is connected wirelessly to the device under test and via cables to the chamber antenna, for measuring the transmission between them, and thereby to measure one or several parameters related to the communication performance of the device under test. The measuring instrument may be arranged externally from the internal cavity, and connected to the internal cavity by means of a cable. The measurement instrument preferably comprises analyzing means, e.g. realized by dedicated software on a personal computer or the like, and can e.g. comprise a commercially available measuring instrument, such as a network analyzer or spectrum analyzer or similar, for determining the transmitted power between the antennas. Additionally or alternatively, the measuring instrument may comprise a base station emulator.

[0077] In another embodiment, illustrated in FIG. 2, the chamber is a random-LOS chamber 1′, having inwardly absorbing walls. The random-LOS chamber is essentially the same as in the previously discussed RC chamber, but this chamber has absorbers on the walls, as seen in FIG. 2. This chamber can be made approximately equally small as the RC chamber, or only to a small extent larger. The random-LOS chamber has absorbers on most, and preferably all walls, rendering the walls absorbing to electromagnetic waves, thereby simulating a random-LOS environment. The internal chamber formed in the chamber is preferably completely shielded, having reflecting material, such as metal, on all walls and floor and ceiling, and having absorbers being provided on all or most walls and ceiling, but not on the floor. The floor is preferably of metal (or conductive), but the metal can be covered with something to resemble a top layer of asphalt or other road covers.

[0078] The Random-LOS chamber is to a large extent similar to or the same as in the previously discussed RC chamber, and e.g. has a rotatable platform 2 for supporting a vehicle 3, being structured and operated in the same way as discussed above in relation to the RC chamber embodiment.

[0079] Further, a chamber antenna/measurement antenna 4′ is preferably arranged in the chamber, and is preferably arranged as a vertical linear array antenna. The vertical linear array antenna may be dual-polarized, or there may be two orthogonally polarized linear arrays located side-by-side, and e.g. arranged in one corner of the chamber or along a wall of the chamber. The vertical linear array comprises a plurality of antenna elements 4a, equidistantly arranged in a linear direction.

[0080] As best seen in FIG. 3, the apparatus further preferably comprises two branched distribution networks 7 connecting the vertical linear array elements for each polarization to each of two ports of the measuring instrument, here shown as a base station emulator 6a, and a controller 6b, such as a PC. The branched distribution/combination network preferably comprises a number of branched connections, separating the output/input from the base station emulator 6a into a number of equally fed inputs/outputs connected to the antenna elements 4a. In the illustrated example, the branched distribution/combination network has a first branched connection, separating the line into two, two second branched connections, separating the two lines into four, and four third branched connections, separating the four lines into eight. However, other branching arrangements, e.g. using branching into three, using more or fewer layers of branched connections, etc. are feasible. Such a fixed distribution arrangement is very efficient to provide a simple interface between the linear array and the base station emulator, and is also very cost-efficient.

[0081] The linear array 4′ preferably comprises a plurality of wideband array elements. The far field radiation pattern in the direction of the linear arrays is to a good approximation given by the common output of the elements of the array. Different far field directions in azimuth plane may be obtained by rotating the car. Further, the linear array may be tiltable to assume different tilt angles, in the elevation plane. For example, the linear array may be tiltable to assume angles in the range of 60°-90° in relation to the horizontal/floor plane, or in the range 70°-90°. The normal, untilted position would be 90 degrees, and less than 90° tilt corresponds to the linear array being tilted forward in the direction of the car. The height of the linear array may also be changed in order to find the best height for measuring the far field PoD. This optimum height will depend on the location of the antennas of the wireless device on the vehicle, and the height of the vehicle. The optimum height can be found by simulation as part of the detailed design of the measurement facility.

[0082] Alternatively, a pill-box style antenna 8 can be used. Such an antenna, as is schematically shown in FIGS. 4 and 5. This antenna preferably comprises two parallel plates 81, 82, preferably of metal, forming a cavity there between, and an elongated aperture 87 formed between the parallel plates 81, 82. A curved reflector 83 is arranged opposite the elongate aperture 87. The curved reflector is preferably arranged as a part of a cylindrical wall, and having the form of a parabolic arc. A feeding or reception device 84, such as a dipole antenna, a feed horn or the like, may be arranged to emit radiation towards the curved reflector, and/or receive radiation reflected by said curved reflector. The feeding or reception device may also be provided in the form of a rectangular waveguide or the like, debouching into the cavity formed between the parallel plates. The feeding or reception device is preferably located at the focal point of the parabolic reflective wall.

[0083] The elongated aperture may be arranged between the parallel plates, and be emitting radiation in a main direction essentially parallel to the plates, as is shown in FIG. 4. However, alternatively, the elongated aperture 87′ may be arranged in one of the side walls, or in an extension of one of the side walls, and consequently be emitting radiation in a main direction being essentially perpendicular to the this plate. Such an embodiment is illustrated in FIG. 5. A slanted additional wall 86 may further be provided to reflect radiation into and/or out of the cavity through the aperture. The antenna solution of FIG. 5 can be arranged more easily, and with less space requirement, than the antenna solution of FIG. 4. Any part of the exterior of the antenna, apart from the elongated aperture, exposed to the interior of the chamber is preferably covered with absorbent material.

[0084] The elongated aperture is preferably rectangular, and preferably of essentially the same overall dimensions, orientation and position in the chamber as the previously discussed linear array. The parallel plate waveguide preferably excites the aperture with a constant phase. To this end, the spacing between the two parallel plates is preferably less than a half wavelength. The elongate aperture may further be provided with longitudinal corrugations or grooves along its sides, preferably one or two on each side, in order to direct its radiation pattern towards the vehicle.

[0085] The dimensions of the reverberation chamber discussed above in relation to FIG. 1 can be held very limited, compared to conventional anechoic chambers for automotive applications, and the same. Further, the dimensions of the random-LOS chamber, discussed in relation to FIG. 2, can be equally small, or only slightly greater. The dimensions may be as low as only 1 m separation from the vehicle in all directions, i.e. the height of the largest vehicle for which the chamber is intended+1 m in the height direction, and the length of the largest vehicle for which the chamber is intended+2 m in the width and length direction. This is illustrated by the schematic arrows in FIGS. 1 and 2.

[0086] The above-discussed linear array antenna is particularly suited for the random LOS chamber, but may also be used in other types of chambers.

[0087] The chamber may be provided with more than one linear array antenna, or columns of linear array antennas. Such embodiments are illustrated in FIGS. 6a-6c. In these embodiments four linear array antennas 4′ are provided. However, two or three linear array antennas may be used instead, or more than four, such as five or six, or even more. The linear array antennas are preferably located on one side of the platform 2, as in the embodiments of FIGS. 6a and 6b. In the embodiment of FIG. 6a, the antennas are arranged along one side of the chamber (shown in dashed lines). In the embodiment, of FIG. 6b, the antennas are arranged along an arc or semicircle, extending along a part of the platform. However, the antennas may also be distributed evenly around the platform, as in the embodiment of FIG. 6c.

[0088] At least one of the linear array antennas may further be tilted to assume a different angle forward toward the platform than the other(s), thereby providing different elevation angles of the far field.

[0089] Further, the linear array antennas are preferably connected to one base station emulator or channel emulators by using a distribution network of cables and power dividers, but they can also be connected to different ones or to different ports on a common channel emulator, and in this case they are preferably distributed around the platform and individually calibrated.

[0090] Still further, the linear array antennas may be located at different azimuth angles around the platform.

[0091] Regardless of whether one or several linear array antennas are used, the linear array antenna(s) may advantageously comprise several sections. Various embodiments of such arrangements are illustrated in FIGS. 7a-7c, where FIG. 7a illustrates an embodiment having three sections arranged in a straight disposition atop of each other. FIG. 7b illustrates an embodiment in which the linear array assumes a curved disposition, where the sections are sequentially tilted towards the platform, thereby assuming a curved disposition. FIG. 7c illustrates another curved disposition, where the linear array antenna assumes the shape of an arc. Even though these examples show three sections, more or fewer sections may also be used.

[0092] To feed the different sections in the curved disposition, the distribution network preferably comprises fixed delay lines compensation for the non-straight extension of the linear array, preferably in such a way that the voltage received at the end of the distribution network is representative of a far-field radiation pattern of the antenna when embedded on the platform.

[0093] For calibration, a reference antenna (not shown) may further be provided in the chambers. The calibration for the tests in RC is done with the vehicle in the chambers, and the calibration antenna can e.g. be located on the roof of the car, or beside the car on the platform. The location of the reference antenna in the random-LOS case is preferably such that there is no blockage caused by the car, and is preferably done without the presence of the car. The calibration is done when the platform is rotated continuously or stepwise.

[0094] The invention has now been described with reference to specific embodiments. However, several variations of the communication system are feasible. For example, the chamber is preferably, out of practical reasons, of a rectangular shape. However, other shapes, which are easy to realize, may also be used, such as vertical walls with flat floor and ceiling and with a horizontal cross-section that forms a circle, ellipse or polygon. Further, the communication between the device under test and the chamber antenna/measurement antenna may be in either or both directions. Accordingly, each antenna may be arranged for either transmitting or receiving, or both. Further, even though the reverberation chamber and the random-LOS chamber have been described as two different chambers, it may also be possible to combine these chambers into one, e.g. by use of dismountable absorbing elements to cover the walls and ceiling when the chamber is to be used as a random-LOS chamber, and to be dismounted when the chamber is to be used as a reverberation chamber. Still further, the various features discussed in the foregoing may be combined in various ways. The embodiment of the random-LOS case describes a linear array antenna with a distribution/combination network. It is envisioned that this distribution network also may be realized digitally, by having DA/AD converters and transmitting/receiving amplifiers connected to each port of the linear array. Then, the amplitude and phase can be controlled digitally, so that the mechanical tilt of the linear array will be unnecessary. Such and other obvious modifications must be considered to be within the scope of the present invention, as it is defined by the appended claims. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word “comprising” does not exclude the presence of other elements or steps than those listed in the claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. Further, a single unit may perform the functions of several means recited in the claims.