Research And Implementation Of Vector RF Signal Source Output Circuit

The rapid development of technology has brought great convenience to people’s lives and has derived from many high-tech electronic products. With the continuous advancement of electronic technology, communication technology, computer technology, more and more requirements of electronic measuring instrument have been put forward. Vector RF Signal Source which is one of the most basic and important instrument in the field of electronic measurement, has got rapid development in recent years. This paper studies the research and realization of large range and high accuracy Vector RF Signal Source output circuit.This paper introduces the basic concept and principle of Automatic Level Control. Automatic Level Control can stabilize RF signal power, achieve a variety of modulation, change the output state, shielding the environmental impact and so on. But at present,the output RF vector scheme has three obvious defects: First, the dynamic range of output power is not wide enough, the dynamic range of the system output usually between-70 dBm — +7dBm,especially for the high frequency RF signal, this defect is more obvious; Secondly, There is a big flaw in the realization of analog modulation. Mainly for the modulation depth is shallow, low velocity modulation, the modulation effect is poor. Third, the calibration method is complex.The main calibration mode is manual calibration, single-point calibration, this way will bring great workload and more errors.Directly affects The performance index of Vector RF Signal Source.Therefore, in order to solve the three problems above. Based on the laboratory Vector RF Signal Source, this project has done a lot of research in the overall design and the specific circuit implementation.Finally, put forward the solutions. First of all, Through theoretical analysis and experimental simulation,we assigned output dynamic range indicators and overcomes the defects of small output dynamic range.System output can be achieved-100 dBm — +10d Bm;Secondly, through data and theoretical analysis, design a "feedforward- feedback" structure.This structure solved the problem of analog modulation, and the depth of modulation can be reached more than 90%, the rate of modulation can be 300 KHz. Finally, depend on software, FPGA and standard instrument, an automatic calibration scheme based on linear fitting model is designed. Through the early construction of the table, single-point calibration frequency, "Frequency- Power" calibration, the program realize a full band dynamic range of power calibration. Greatly reducing the manual workload, improve the calibration precision and accuracy, optimizing the output index of Vector RF Signal Source.