Hardware Design Of Frequency Hopping Synthesizer Based On DDS

Frequency hopping communication has the advantages of strong anti-interference, code division multiple access network communication capabilities, and high security, making it widely used in communications, electronic warfare and other fields. Frequency synthesizer is the core part of the frequency hopping communication system, and it directly impacts on the performance of frequency hopping systems, so it is very important to the frequency hopping synthesizer of the radio frequency.The subject mainly completes the design and implementation of the hopping frequency synthesizer system hardware, and proposed a new method of design synthesis, the simultaneous multi-frequency design program which greatly enhances the frequency synthesizer and frequency hopping rate resolution. The advantage of the new program is its strong confidentiality, and the Multi-frequency simultaneous transmission time can be shortened, resulting in confused signals and enhanced by the difficulty of deciphering.This paper introduces the basic theory and features of the spread spectrum communication, and then analyzed and compared several major technologies of the frequency of synthesis, chose a design which combines the kind of phase-locked loop technology (PLL) and direct digital frequency synthesis (DDS) program together, this scheme can make the two technologies'complement to each other. The paper gives the overall program design, and circuit design of the various parts of the overall program, including synthesis design, loop filter circuit design, chip AD9850 interface circuit design, low-pass filter design, principle of VCO and the FPGA control circuit design. Finally, the paper gives the specific design block diagram of synthesis with the new methods and completes the task of the technical requirements to be achieved. In the control of DDS circuits using FPGA technology to control, replacing the previous system controlled by the microcontroller, so that the control system is designed to be simple and reasonable and also become more flexible and convenient to use, easier for secondary development.