Research On Double-multiple Frequency Testing Technology And Application

Since the nonlinearity behavior of Radio Frequency(RF) system possibly causes electromagnetic compatibility(EMC) problem, how to measure and analyze EMC problem of RF system accurately has become a hot research under the compulsory execution of National and International EMC Regulations. For the platform installed with many pieces of frequency applied equipment is with complex electromagnetic environment and rich signal frequency components, the intermodulation interference produced by nonlinearity effect between transmitter and receiver systems becomes one of the main sources of EMC problem. Nonlinearity characteristic is a major cause of EMC problem existed in electronic system and it is difficult to measure and predict, thus, the testing and analysis to the nonlinearity characteristic of EMC are taken as the key and difficult points of EMC analysis and evaluation. How to avoid the external interference, and analyze the nonlinearity characteristic of Device Under Test(DUT) rapidly and accurately will be studied and shown in this paper.In this paper, a new double frequency testing system(DFTS) is studied and designed for nonlinearity measurement, which would be used for testing nonlinearity and EMC of devices and receiver system. Compared with the dual tone and multi tone testing in the past, double frequency testing technique is quite different, it could detect and identify all the signal channels and interference paths, in that, its basic idea is to inject several controllable signals to DUT, measure its response, treat and analyze its EMC characteristic by those signals.. A large number of studies on the nonlinearity characteristic of devices and systems have been done as the support of this paper, including its main work and innovations being summarized as follows:(1) This paper studies the cause and influence of nonlinearity existed in present devices and systems, shows the current research at home and abroad, researches the method to test nonlinearity characteristic by its on site quick measurement and analysis, as well as identifies the significance of this research and the specific follow up to be done.(2) This paper raises double frequency testing(DFT) method for the nonlinearity characteristic testing based on system level, which achieves the quick test of devices and whole system. DFTS is a system, which combines test and analysis in one. The system software is designed and developed based on the idea of "virtual instruments", under the control of standard monitoring bus, it could form a complete testing system with the hardware which meets the design indexes.(3) This paper also raises DFT algorithm based on signal transmission channel frequency equation. Firstly, select and treat the number of the harmonics of the system, the harmonic of the LO signal, the IF frequency and other parameters according to the system signal transmission channel frequency equation; after that, scan and integrate the frequency on the basis of coefficient; finally, draw 3D images to obtain the system nonlinearity characteristic according to the output power which accords with the intermediate frequency. This algorithm greatly reduces the scanning time, improves the scanning accuracy, meets the requirements for nonlinearity testing on site and makes it more practical.(4) DFTS designed in this paper has been applied for devices and system and rapidly got the intermodulation, cross modulation and other parameters that completely indicate the nonlinearity behavior of system. The test experience shows that DFTS could rapidly measure and analyze the nonlinearity characteristics of devices and systems. Complete the application of frequency assignment by using DFT in this paper.