Research On Wireless Channel Reconstruction Of Multi-probe Anechoic Chamber In MIMO OTA Setup

With the development of MIMO communication technology, MIMO devices have been widely used in the world, the overall performance test for MIMO device is becoming more and more important. MIMO OTA test method can well test the performance of the MIMO equipment, and it has attracted the great interests of industry and academia. Currently, the industry and the academia are committed to research the MEMO OTA test methods, and try to develop the MIMO OTA test method standards.Among the three existing MIMO OTA test methods, the multi-probe anechoic chamber based method has been accepted by many scientific research institutions, equipment manufacturers and operators because of its accurate simulation of the propagation environment of the real wireless channel.However, the existed three-dimensional multi-probe anechoic chamber based method is not perfect, there still some points which could be improved in the following areas: (1) the three-dimensional probe configuration is too complex, and there is still no clear standard; (2)When the reconstruction of the wireless channel is performed by using the pre-fading synthesis technique, the computational algorithm of probe weighting has some shortcomings, and sometimes the optimal probe weights can't be obtained; (3) When the reconstruction of the wireless channel is performed by using the pre-fading synthesis technique, the sampling method has some shortcomings. It can not cover all of the test area when sampling the test area. It has bad influence on the reconstruction accuracy of the wireless channel.This paper mainly focuses on the above three issues, the specific content includes the following three points:(1) A new three-dimensional probe configuration scheme is proposed.All probes are distributed over three rings. The specific position of each probe is decided by the chamber size and the probe ring angle. And the effects of different channel models, different test area sizes, different chamber sizes and different probe ring angles on the reconstruction accuracy of the wireless channel are studied. Finally, it can be concluded that for a given channel model, when the size of the device to be tested is determined, the specific chamber size and probe ring angle can be got to achieve the highest wireless channel reconstruction accuracy.(2) When using the pre-fading synthesis technique to reconstruct the wireless channel, we propose using the simulated annealing algorithm to solve the complex weight of the probe, instead of the proxy convex optimization algorithm. Thus we can get the global optimum solution instead of the local optimum.(3) An improved sampling method is proposed. For the original symmetrical sampling method, we only take points on the sphere of the test area. On the basis of the symmetrical sampling method, we take points inside of the test area, all of the test area can be included. The spatial properties of the global spherical test area are taken into consideration, and reconstruction accuracy of the wireless channel will be improved.