Reseach On Ka Band Frequency Synthesizer Technology

Frequency source is the heart of radar, communication and other electronic systems, and it has important significance in guidance, radio astronomy, clinical medicine and other fields. The performance of frequency source has a direct impact on the index of the electronic system[1]. In this paper, a high performance frequency synthesis technology of Ka band, low phase noise, low spurious, frequency agility, small step and small size is studied.First of all, this paper describes the basic theory of frequency synthesis technology, analyzes the pros and cons of various techniques, combined with the index requirements of the article, and after the initial calculation of indicators, we determine the framework of DDS drives PLL.Then, based on the basic framework of DDS drives PLL, the specific design of the program is carried out. The final signal require for the Ka band, in order to reduce the design difficulty, firstly we achieve the signal output of the X band, and then, after 3 times, we achieve the final output of Ka band. In order to solve the requirement of low phase noise, the VCO output through a down-conversion then be divided by N, which can greatly reduce the value of the frequency division ratio, so that the purpose of reducing the phase noise is achieved. In order to solve the low spurious requirement, the output frequency and bandwidth of DDS should be reduced as much as possible. In this paper, firstly a fixed local oscillator, frequency division ratio N variable method is achieved, test found that certain frequency points can not be locked; and then a fixed frequency ratio N but the local oscillator switching is achieved. Finally we found that the latter can solve the problem that some frequency points can not be locked.Finally, combine all the modules we get the final test results of the system: the Ka band output frequency is 34~36GHz; phase noise is better than-90 d Bc/Hz@1KHz; the spurious suppression is better than-60 d Bc; the frequency resolution is better than 53Hz; the frequency hopping time is better than 7 microsec(33.9GHz jump to 36GHz), all meet the requirements.