Simulation And Design Of WCDMA/TD-SCDMA/WLAN Combiner For Basestation Application

At present,with the deployment of the TD-SCDMA technology,China has got into the special stage in which the third-generation mobile communications(3G) is transiting the second-generation mobile communications(2G).The existence of many communications systems has become inevitable.In the case of reducing the cost of the mobile communication network construction,Multi-compatibility is the most effective way of achieving this transition.In the systems of multi-network sharing the base station antenna,Multi-frequency combiner which is used to separate and synthesize the signals is the key to realize multi-compatible.For such consideration,microwave combiner for TD-SCDMA /WCDMA /WLAN basestation will be designed,simulated and tuned.Firstly,the design theory of microwave filter is introduced,because a multi-frequency combiner is composed of two or more microwave filters.Generalized chebyshev theory and the synthesis procedure are presented.Different optimization methods,such as rotation, Newton-Raphson are utilized to simplify the coupling matrix for some common microwave filter structures.Through the optimization process,the coupling coefficents are gained to be used in the filter emulation.Secondly,the design of the WCDMA/TD-SCDMA/WLAN combiner is introduced.Since there is only 30MHz bandwidth between the WCDMA uplink band and TD-SCDMA band,the required 60dB isolation is not to be achieved.So the cross-coupling structure is adopted to get additonal zero in order to achieve the interband isolation.The combiner is designed and optimized by using Ansoft HFSS and designer,and after several times of optimization,the interference between different channels has been largely reduced.This combiner was tested by China Electronic Product Reliability and Environment Testing Research Institute,and it measured up to a given standard.Finally,the tuning efficiency always constrains the filter and combiner production.In this case,a rapid manual tuning technology based on the refection group-delay is adopted in order to improve the tuning efficiency.In addition,the computer-aided tuning system of this combiner had been designed to guide the no-skilled worker to achieve the tuning job.