C-band Frequency-hopping Source Development

With the development of electronic technique, frequency synthesizer is the heart of all the electronic systems. It determines the performance of the electronic equipments. Along with the development of wireless communication, modern military and national defence, frequency synthesizer plays the leading role. Most countries in the world have been playing more attention on the design of higher performance frequency synthesizers with wide frequency range, low phase noise, high spurious restraining, low jumping time and high working frequency.The subject comes from the cooperation project"C-band hopping frequency synthesizer"between Chendu Sine Science and Technology Ltd. and CETC the 20tH. There are many difficulties in this project, such as low phase noise, high spurious restraining and output power fluctuation. In order to solve these problems , the PLL+Mixer hybrid frequency synthesis technology is adopted.There are two PLLs have been used. One is a digital PLL which can achieve the mainly function of hopping,the other is to get a local oscillator with much lower phase noise. Then the two sigals are upconvented together to get high working frequencies. Both of these two PLLs have low multiples (N), so low phase noise is got. At the same time AGC circuit has been used at the output section in order to reduce power fluctuation.At first, the history of the frequency synthesis technology is reviewed. Subsequently, the theory of PLL frequency synthesis technology and the most important phase noise are introduced. Then the scheme of this subject, specially in phase noise, spurious restraining and power fluctuation have been discussed. Finally, the testing results are given and analyzed in detail.