Research Of Differential Frequency Hopping HF Communication System Based On FPGA

Differential frequency hopping (DFH), which combines frequency hopping (FH) pattern, information modulation and demodulation into a whole, is a new communication system based on digital signal processing (DSP). Differing from conventional FH, it successfully deels with the questions such as transmission speeds, follower jamming,etc, and represents an important development direction of current high frequency (HF) communication. Sanders, an American company, put out a new kind of shortwave FH communication system named CHESS and achieve success. However, in our country, this system and technique is still at the early stage and there is still some distance to practical application.This article mainly studies differential frequency hopping (DFH) based on FPGA chip. With FPGA, it accomplishes DSP which solves the problem of parellelism and speed. The flexible configurable characteristic makes it easier for DSP to modify, test and configurable characteristic. In the design, we use software radio architecture, reduce analog link, make digital treatment closer to antenna with might and main. We build a common, standard and modular hardware flat, so as to achieve different functions of DFH with software programme, and liberate from the design based on the hardware.The article introduces the background and meaning of the study at first, elaborate implementation of frequency synthesizer and frequency identification. In frequency synthesizer, concentration is on the simulation of phase truncation error and amplitude quantization error of direct digital synthesizer (DDS), looking for best parameter and improvement based on FPGA. In frequency identification, Xilinx provides FFT IP core, and bit synchronization and frequency identification at the receiver are designed based on FFT theory. At last, printed circuit board (PCB) is made according to design on the basis of FPGA.Two common hardware description languages, Verilog and VHDL, are applied in the modular of FH pattern, direct digital frequency synthesizer, frequency identification, bit synchronization, recovery of frequency hopping pattern, chirp-z transform etc. In this way, Migration can be taken in FPGA chips from producers.