| Measurement lays the foundation of science. Spectrum analyzer, as a general and important signal frequency measurement instrument, has been widely applied in military and civilian fields. According to statistics, imports constitute 95% of the internal requirements for the advanced instruments by 2013. With respect to spectrum analyzer, certain domestic manufactures have developed their own-brands, but they only occupy part of the low-end market. Besides, the innovation of domestic products is continuously constrained by the restrictions of hardware platform, long development cycle, high cost of design and other factors. Along with the rapid development of software radio technology, its openness, flexibility and reconfigurability promote the technological innovation in modern spectrum analyzer, and meanwhile offer domestic spectrum analyzer a new development opportunity. The application of software radio not only reduces the input costs and difficulty in product development, but also makes the reconfigurable instruments become a trend.This paper mainly studies the technology of signal spectrum analysis and presents a type of hybrid analog-digital spectrum analyzer rooted in our homegrown software radio platform. The work in this paper is organized as follows.Firstly, a signal spectrum analysis scheme is demonstrated. By studying the basic principles and key technologies of spectrum analyzer, we design the new spectrum analysis scheme by utilizing multi-rate signal processing and discrete spectrum analysis and correction technologies, which involves the properties of hardware platform and the demands of practical project. For the sake of achieving the high frequency resolution, efficient decimation filters and FFT techniques are introduced to the digital intermediate frequency system. In addition, the Hanning window is employed to reduce the spectrum leakage. Besides, the ratio correction and energy centrobaric correction methods are used to reduce the spectrum analysis errors. Moreover, each sub-module is expanded with the detailed design ideas, the algorithm analysis and the processing flow. And the simulation link is built, with which relevant simulations and analyses for the algorithms are also conducted.Secondly, the detailed realization of the proposed scheme is explored. In accordance with the scheme features and hardware properties, we have further discussed the complete implementation of the digital intermediate frequency system on the FPGA. In addition, optimal implementation structures of the key modules are explored. At the same time, each sub-module is expanded with the logical structures and key implementation points. Furthermore, we have developed the host-computer software for the spectrum analyzer, with which the dynamic configuration of spectrum parameters and visualization display of analysis results are realized.Thirdly, this paper presents the availability of the proposed spectrum analysis scheme in system-level. On the basis of the software radio platform and relevant equipment, detailed functional tests are conducted to the digital intermediate frequency system and the host-computer software. We also represent concrete hardware tests and analyses to the key properties for the signal spectrum analysis system, which verifies the rationality and feasibility of the implementation scheme.The results show that this paper has realized a hybrid spectrum analyzer rooted in the software radio platform. It can function well within signals of the frequency range from 1MHz to 4GHz and the bandwidth of 30 MHz, which is capable to fulfill the adjustable analysis within the frequency resolution from 5Hz to 60 kHz. Furthermore, the design pattern of modularization and parameterization are applied to the studied system, and the dynamic host-computer software is developed. In the end, the whole system can be controllable, adjustable and reconfigurable, which provides a reference for the further exploration of modern spectrum analyzer. |
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