Design And Implementation Of A VHF Radio Frequency Synthesizer

Military communication technology is developing rapidly, the ability to resist interference and high speed data is the key to the future information war. Frequency hopping communication technology has excellent anti disturbance performance and multi access network capacity, as the core of the communication technology, frequency synthesizer determines the performance of entire VHF frequency hopping radio system.This paper introduces and analyses the overall technical scheme of high speed data transmission in VHF frequency hopping radio. The radio channel scheme adopts the super heterodyne structure to realize the upper and lower frequency conversion of the analog channel, and uses the DSP technology to realize the digital IF, while using the frequency hopping system to realize anti-interference. On the basis of the scheme and performance requirements of the radio station, this thesis analyzes the theory of frequency hopping and frequency synthesizer, and compares the advantages and disadvantages of three frequency synthesizer schemes.According to the channel requirements of the station, the design requirements of the two local oscillators are proposed. The first local oscillator is a frequency variable frequency hopping frequency source, using fractional PLL scheme. In this scheme, the integrated circuit LMX2485 is chosen as the core phase locked loop chip. Using dual path controlled voltage controlled oscillator, the contradiction between the phase noise and the lock time is balanced, and the performance index of the system is achieved. The second local oscillator produce a fixed frequency, the integrated circuit ADF4110 is chosen as the core phase locked loop to achieve. In the frequency synthesizer module, the two local oscillator registers are controlled by a control circuit. The control circuit selects FPGA as the hardware platform, the SPANTAN-3E series chip XC3S100 E which is produced by the Xilinx Inc as the core chip, AD45DB011 as the peripheral memory, through the hardware and software of the unified coordination, realize the design of frequency synthesizer.Finally, the auxiliary circuit of the frequency synthesizer, such as the power interface circuit is introduced. At the same time, the reasonable layout of the printed board, and take the space shield, optimize the electromagnetic compatibility of the module and the radio system, and meet the performance index of the radio system.