Study And Fabrication Of Fast Hopping Frequency Synthesizer

Frequency source is a very important portion in wireless hopping communication. The output of frequency synthesizer directly affects the communication quality of the hopping communication system. This design is to design a frequency source with high hopping wideband and low noise based on engineering requirement. Phase-locked loop (PLL) frequency synthesis is a well-developed frequency synthesis technology. It has better spurious rejection performance advantages, but it has weakness on frequency conversion speed and frequency resolution. The DDS technology has been attracted popular attention for its excellent performance on frequency conversion speed, frequency resolution and low phase noise, but with its narrow output bandwidth and low quality of spurious suppression due to its all-digital structure.The paper takes the advantage of the PLL and DDS together, using the PLL and DDS mixing outside method to design a hopping frequency synthesizer. The PLL output the fixed frequency with low noise, and the DDS use parallel FPGA configuration having fast frequency switching speed and frequency resolution. After mixing with PLL, the frequency switching time of the frequency synthesis system is completely decided by DDS, and the system can produce fast hopping frequency output, which can improve the frequency-hopping system security, anti-jamming and anti-interception capability. As the PLL output frequency is high, afer mixing with DDS, the system can have a high output frequency.In this paper, we analysis and simulate the key parameters of the frequency synthesizer, including the phase noise, spurious suppression, frequency resolution, frequency switching time. To get a lower level of spur, well design of filters were required. In the paper the author used the real S parameter to simulate these filters, and the effect of this method was satisfying. We have described the function of the main device using in the frequency synthesize and design the schematic of the main device and system configuration of process steps. At the same time we compare the performance of various frequency hopping sequences, and then selected and designed the appropriate frequency hopping sequence into frequency hopping pattern. Finally, by the demonstration and simulation of the system, this system solution can meet the system requirements of the indicators.