CN118381568A - Arbitrary field simulation framework for air interface test of integrated multi-antenna system - Google Patents
Arbitrary field simulation framework for air interface test of integrated multi-antenna system Download PDFInfo
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- 239000011159 matrix material Substances 0.000 claims abstract description 17
- 230000005540 biological transmission Effects 0.000 claims abstract description 7
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- 238000005457 optimization Methods 0.000 description 4
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Abstract
The invention discloses an arbitrary field simulation framework for air interface test of an integrated multi-antenna system, relates to the technical field of air interface test, and aims to calibrate a transmission matrix between a probe antenna and an antenna port of a Device Under Test (DUT), and only use a small amount of probe antennas to generate high-quality arbitrary plane waves under the conditions of miniaturization and no noise elimination. The actual DUT antenna is bypassed in the measurement, only as an interface for OTA testing.
Description
Technical Field
The invention relates to the technical field of air interface testing, in particular to an arbitrary field simulation framework for air interface testing of an integrated multi-antenna system.
Background
Radio testing of commercial products such as base stations and user equipment is performed primarily through cable connections, with Radio Frequency (RF) connectors and passive antennas on the DUT. The test signals generated by the test instrument are guided to the respective antenna ports through the RF cable to measure the indexes, and the method has high fidelity and does not cross-talk with other antenna ports. However, due to the integrated design of the transceiver front-end and antenna in 5G and future communication systems, conventional RF ports are no longer suitable and cannot be connected to test instruments by cables. Thus, air interface testing, which uses radio as an interface between a test instrument and a DUT, has become a standard test solution.
Measuring the performance of a multi-antenna system under certain propagation scenarios is very important, where plane waves are essential for characterizing antenna radiation and radio frequency transceiver performance, such as antenna radiation patterns, antenna array calibration, antenna array transmission metrics and receiver metrics. Plane waves, however, are typically limited to the line-of-sight direction between the DUT and the probe antenna. It is necessary for the multi-antenna system to test under certain arbitrary signal and air interference conditions, which can be achieved by the principle of occasion-forming, i.e. to assign optimized complex weights to a sufficient number of probe antennas. However, measurement devices, including probe antennas, feed networks, RF anechoic chambers, and suitable measurement ranges, generally require extremely high costs, and no solution for simulating any test signal at each antenna port on a DUT with low cost, miniaturized measurement devices is currently available.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects of the prior art and providing an arbitrary field simulation framework for air interface test of an integrated multi-antenna system, which simulates equivalent fields of antenna ports of a DUT in the air interface test and realizes the simulation of arbitrary test signals of respective antenna ports on the DUT in a low-cost and miniaturized arrangement.
The invention adopts the following technical scheme for solving the technical problems:
According to the invention, an arbitrary field simulation framework for air interface test of an integrated multi-antenna system is provided, which is used for calibrating a transmission matrix between a probe antenna and a DUT antenna of a device to be tested, and comprises a measurement system, wherein the measurement system comprises K probe antennas and N DUT antennas,
The received signal vector r N×1 at the N DUT antennas is calculated as:
rN×1＝AN×KGK×NpN×1
where N is the number of DUT antennas, For an N x 1 complex set, A N×K is the transmission matrix of K probe antennas to N DUT antennas,Is an NxK complex set, G K×N is a calibration matrix,P N×1 is the equivalent target field vector at the DUT antenna port to be emulated,
As a further optimization scheme of the arbitrary field simulation framework for the air interface test of the integrated multi-antenna system, A N×K is directly measured through an on-off scheme.
As a further optimization scheme of the arbitrary field simulation framework for the air interface test of the integrated multi-antenna system,Satisfying a N×KGK×N≈IN×N,IN×N as the identity matrix.
As a further optimization scheme of an arbitrary field simulation framework for the air interface test of the integrated multi-antenna system, the selection of p N×1 is as follows:
The DUT antenna array includes a DUT antenna configuration and an antenna pattern, wherein,
If the DUT antenna array is known, incorporating the known DUT antenna pattern into p N×1;
If the DUT antenna array is unknown, using the synthetic DUT antenna, incorporating the synthetic DUT antenna pattern into p N×1;
The actual measured antenna is bypassed and only acts as a port to send and receive test signals in any field simulator.
As a further optimization scheme of the arbitrary field simulation framework for the air interface test of the integrated multi-antenna system, the number of probe antennas is not smaller than the number of DUT antenna ports.
Compared with the prior art, the technical scheme provided by the invention has the following technical effects:
(1) The invention can simulate any propagation field of the DUT with any antenna configuration;
(2) Due to the compact antenna configuration, the cost of the measurement setup of the proposed method is quite small;
(3) Measurements can be made in an open office scenario, with a sound deadening chamber not being necessary.
Drawings
FIG. 1 is a diagram of an arbitrary field simulator framework of an embodiment of the present invention.
FIG. 2 is a schematic diagram of a measurement system according to an embodiment of the invention; wherein, (a) is a plane wave impinging at an arbitrary angle of arrival, (b) is a spherical wave impinging at an arbitrary point source, and (c) is a spatially non-stationary case.
Fig. 3 is a schematic diagram of a measurement scheme of an embodiment of the present invention.
FIG. 4 is a schematic diagram of measurement results in a measurement scenario according to an embodiment of the present invention; wherein (a), (b), (c), (d) are measured signal values at four DUT antenna ports when the angle of incidence of the plane wave is 5 °, 15 °,25 ° and 50 °, respectively.
FIG. 5 is a schematic diagram of measurement results under a second measurement scenario according to an embodiment of the present invention; wherein, (a) is the measurement result at the incident angle of 5 DEG, at the time of the 3 rd DUT unit failure, and (b) is the measurement result at the incident angle of 25 DEG, at the time of the 2 nd DUT unit failure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
The invention provides an arbitrary field simulation framework for air interface test of an integrated multi-antenna system, which is based on the following principle:
Assuming a measurement system consisting of a DUT with N antenna ports and K probe antennas, the receive field vector r N×1 at the DUT antenna ports is calculated as:
rN×1＝AN×KGK×NpN×1 (1)
Wherein, Is the received signal vector at the N antenna ports,The transmission matrix, K probe antenna ports to N DUT antenna ports, is affected by the probe antennas, DUT antennas and multipath propagation channels between the probe array and DUT antenna array. A N×K cannot be directly calculated or simulated due to unknown propagation environments and DUT antenna patterns. The MIMO vector may be measured directly by an "on-off" method.For calibration matrix, a N×KGK×N≈IN×N,IN×N should be satisfied as an identity matrix. Therefore, K should be not less than N, and if A N×K is known, G N×K can be obtained by pseudo-inverse operation.Is the equivalent target field vector at the DUT antenna port to be emulated. If the DUT antenna array (i.e., DUT antenna configuration and antenna pattern) is known, it can be incorporated into the equivalent target field vector. In practice, if the DUT antenna array is not known, a synthetic DUT antenna may be used in equation (1), i.e., the DUT antenna array employed may be different from the physical DUT antenna. In the proposed solution of the invention, the physical antenna under test is bypassed and only the test signals in the proposed framework are sent and received as an interface.
For any of the proposed field simulators, any field received at the DUT antenna port can be generated, including factors such as the propagation conditions required and the DUT antenna configuration. The number of probe antennas should not be less than the number of ports on the DUT. The DUT antenna pattern is bypassed during testing and the DUT antenna is used only as an interface to receive and transmit test signals. If the DUT antenna pattern is known, it is combined with the target field vector. Transfer matrixOnce determined, it should remain unchanged during the test. Because the solution provided by the invention does not need a sound damping chamber, a small measuring range can be realized, and the system cost is greatly reduced. The inverse operation of the transfer matrix A N×K is required if the transfer matrixBeing irreversible, more probe antennas should be used to improve the conditions of the matrix, looking for a N×K with better conditions.
As shown in fig. 1, the embodiment of the invention discloses an arbitrary field simulation framework for air interface test of an integrated multi-antenna system, and three cases are shown in fig. 2:
(1) In fig. 2 (a), a Uniform Linear Array (ULA) of plane waves and DUTs with arbitrary impinging AoA is depicted. The equivalent field vector p N×1 can be expressed as:
Where g n is the complex radiation pattern of the nth DUT antenna, d is the ULA cell spacing and θ is the collision AoA.
(2) In fig. 2 (b), the spherical wavefield of the ULA is derived from a point source, and the equivalent field vector p N×1 can also be designed based on the point source geometry and DUT array configuration.
(3) In fig. 2 (c), a spatially non-stationary field is illustrated, and an attenuation factor is introduced to represent the spatially non-stationary effect in the target field vector p N×1.
The measurement system adopted in this embodiment includes:
(1) Vector Network Analyzer (VNA) with continuous wave tone at 3.55GHz excitation;
(2) As OTA probe array and DUT antenna array 21 x 8 patch antenna Uniform Linear Arrays (ULA) were used. The measurement range was 10.5cm, the ULA element spacing was 0.5λ and the frequency was 3.55GHz. Two ULA's are placed face-to-face in the measurement. This embodiment selects only four intermediate antenna elements for two ULA's due to the lack of sufficient programmable phase shifters and attenuators. The measurement range is 10.5cm far less than the far field distance of the quaternary ULA (i.e., 38cm at 3.55 GHz);
(3) A four-way radio frequency power divider is arranged at the OTA probe side and comprises four digital phase shifters and four attenuators for generating equivalent target field response vectors for DUT elements;
The measurement scheme employed in this embodiment is shown in fig. 3, where the reconstructed fields at the four DUT antenna ports are measured directly by the VNA. In this embodiment, the four radio frequency paths (amplitude and phase) associated with the probe antenna are first recorded and calibrated to ensure that non-uniformities between the radio frequency links are eliminated with the aid of programmable phase shifters and attenuators. The transfer matrix a is then measured directly with the VNA in the "on-off" mode.
In the present embodiment, two measurement scenarios are employed:
(1) Plane waves strike the ULA at angles of incidence of 5 °, 15 °, 25 °, and 50 °. Assuming a DUT as a ULA consisting of four isotropic antennas spaced 0.5λ apart, the DUT antennas can be of any configuration that does not need to match the physical DUT used in the measurement.
(2) Plane waves strike the ULA at angles of incidence of 5 ° and 25 °. A ULA consisting of 4 isotropic antennas with a spacing of 0.5λ and one faulty unit was used as DUT (5 ° for the 3 rd DUT unit and 25 ° for the 2 nd DUT unit). The "faulty element" is modeled in an equivalent target field, and all connections in the physical setup are sound.
For measurement scenario 1, complex field measurements (amplitude and phase) of four DUT antenna ports under the effect of plane waves at different angles of impingement are shown in fig. 4, where (a), (b), (c) (d) in fig. 4 are measured signal values at the four DUT antenna ports when the angle of incidence of the plane wave is 5 °, 15 °, 25 ° and 50 °, respectively. The amplitude and the phase can reach good consistency under all the measured impact angles, the deviation of the simulation field and the target field is maximum +/-0.75 dB and +/-1.5 degrees at the impact angle of 5 degrees, the deviation is maximum +/-0.8 dB and +/-6 degrees at the impact angle of 15 degrees, the deviation is maximum +/-0.7 dB and +/-6 degrees at the impact angle of 25 degrees, and the deviation is maximum +/-0.25 dB and +/-2.5 degrees at the impact angle of 50 degrees. The measured phase and power of the first DUT unit are normalized to target values, respectively. The measurements clearly show that plane waves at arbitrary angles can be accurately reproduced at the DUT port. Uncertainty of the programmable shifters and attenuators, quantization errors of the implementation equivalent field vectors, and non-idealities in the measurement environment may lead to bias.
For measurement scenario 2, as shown in fig. 5, (a) in fig. 5 is the measurement result at the incident angle of 5 °, the 3 rd DUT unit is failed, and (b) in fig. 5 is the measurement result at the incident angle of 25 °, the 2 nd DUT unit is failed, any DUT configuration with the same number of DUT receiving ports and DUT unit patterns can be modeled and implemented by any of the proposed field simulators. The amplitude and phase deviation of the simulation field and the target field are respectively the amplitude +/-0.9 dB and the phase +/-0.25 DEG when the collision angle is 5 DEG, and the amplitude deviation +/-0.15 dB and the phase deviation +/-1 DEG when the collision angle is 25 deg. For a faulty element scenario, more than 25dB of "isolation" can be implemented to simulate a faulty antenna element in both cases (i.e. "DUT element 3 off" and "DUT element 2 off"). In practice, isolation is substantially limited by the antenna coupling between DUT elements. The phase deviation of the failed element is large because the power of the failed element is too weak.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the scope of the present invention.
Claims (5)
1. An arbitrary field simulation framework for air interface testing of an integrated multi-antenna system for calibrating a transmission matrix between a probe antenna and a DUT antenna of a device under test, comprising a measurement system comprising K probe antennas and N DUT antennas, wherein,
The received signal vector r N×1 at the N DUT antennas is calculated as:
rN×1＝AN×KGK×NpN×1
where N is the number of DUT antennas, For an N x 1 complex set, A N×K is the transmission matrix of K probe antennas to N DUT antennas,For the nxk complex set G K×N as the calibration matrix,P N×1 is the equivalent target field vector at the DUT antenna port to be emulated,
2. An arbitrary field simulation framework for air interface testing of an integrated multi-antenna system according to claim 1, wherein a N×K is measured directly by an on-off scheme.
3. An arbitrary field simulation framework for air interface testing of an integrated multi-antenna system as defined in claim 1 wherein,Satisfying a N×KGK×N≈IN×N,IN×N as the identity matrix.
4. An arbitrary field simulation framework for air interface testing of an integrated multi-antenna system as defined in claim 1, wherein p N×1 is selected as follows:
The DUT antenna array includes a DUT antenna configuration and an antenna pattern, wherein,
If the DUT antenna array is known, incorporating the known DUT antenna pattern into p N×1;
If the DUT antenna array is unknown, using the synthetic DUT antenna, incorporating the synthetic DUT antenna pattern into p N×1;
The actual measured antenna is bypassed and only acts as a port to send and receive test signals in any field simulator.
5. An arbitrary field simulation framework for air interface testing of an integrated multi-antenna system as claimed in claim 1 wherein the number of probe antennas is not less than the number of DUT antenna ports.
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