Design Of The Modulation Quality Test System For CMMB Signal

With the development of communication technology and the popularity of mobile terminals, mobile TV has become a hot research subject in recent years. CMMB is an independently developed mobile multimedia broadcasting standard, with completely independent intellectual property rights of China. The CMMB is a mobile TV service integrated by mobile multimedia and TV media, having a holonomic technology system which can meet people’s needs of listening to the broadcast and watching TV at any time. However, since the ground transmission environment is complex, CMMB is always interfered by white Gaussian noise, multipath fading and other interference in the transmission process which is inconvenient for people to watch mobile TV. In order to scientifically evaluate the anti-jamming ability of CMMB system, the modulation quality of the system needs to be tested comprehensively.Therefore, this paper proposed a modulation quality testing system for CMMB signal and the main contributions of this paper are as follows.Firstly, this paper introduces the principle of CMMB, OFDM transmitter system and the modulation quality testing system, as well as the main testing parameters of CMMB signal modulation quality test system. Secondly, this paper makes a study of the key algorithms:synchronization and channel estimation, which is vital to the testing accuracy of the modulation quality. In addition, this paper also optimizes the algorithms of the synchronous speed estimation and accuracy estimation of channel. The new algorithm eliminates the edge phenomenon of channel estimation. On this basis, this paper describes the design scheme of the modulation quality testing system for CMMB signal, including the overall design scheme of the system, the hardware connection scheme, the software architecture, and the introduction of the realization method of each module of the testing software.Finally, this paper chooses Agilent N5182A vector signal generator, Agilent 81104A pulse signal generator and Agilent vector N9030A signal analyzer as the experimental equipment, and the realization of the CMMB signal modulation quality test verifies the correctness of the test system.