Design Of C-band Vector Signal Generator

Benefiting from the characteristics of high transmission rate and high channel utilization, the vector signals have been widely used in modern communication. The vector signal generator meeting the demands of users to research vector signals, modern communication technologies and channel. Researching the c-band vector signal generator is significant for the ground microwave communication, satellite communication, digital TV and medical field. Traditional vector signal generator is expensive, difficult to achieve and lacks of scalability. In this paper, the c-band vector signal generator is designed and manufactured, whicn has the characteristics of low cost, strong expandability and easy implementation. Paper’s main contents are as follows:First of all, the domestic and international researching status of modern vector signal generator is analysed, and the major direction is determined. The theories and generation methods of vector signals are compared. The feature of several kinds of transmitters is pointed out.Second, the implementation scheme of vector signal generator is proposed after analyzing and comparing among three kinds of. The system is divided into upper computer, digital module and radio frequency (RF) module. Upper computer, based on LabVIEW and MATLAB, includes the components of baseband signal generator, constellation mapping and shaping filter. Baseband signals are interpolated and modulated to intermediate frequency (IF) signals by quadrature digital up converter in digital module. RF module converts IF signals to RF signals through superheterodyne transmitter. The upper computer exchanges data with digital module through the high speed digital I/O device, and the digital module transmits signals to RF module through coaxial cable.Then, the system is modeled and simulated in MATLAB to verify the correctness of the design.Finally, the vector signal generator is made. Every module and the whole system are tested, and the test results are analyzed. Test results show that the carrier frequency of output signal is 8.0125GHz, the highest transmission rate reaches 6.5M Symbol/s, and all indicators meets the requirements.Ac-band vector signal generator based on software radio is designed and completed in this thesis. It has the feature of modular, software, and digital, and it is programmable and extendable. It can be used as a vector signal source, carrier frequency from 20MHz-300MHz, or be applied to the research of 8GHz communication system and channel. This paper promotes the application of vector signal generator.