The Development Of The Fm Noise Source

With the development of modern digital technology and the Very Large Scale Integration electronic circuit (VLSI), the method of digital waveform synthesis is widely used in radar systems now. The waveform generation using digital system is of strict coherence, repetitiveness, high stability and programmable capability, which can also easily realize the waveform parameter's agility and generate arbitrary complicated waveforms in order to meet the urgent requirement for interference and anti-interference ability of radars under modern electronic warfare environments. The Direct Digital Synthesis (DDS) technology is widely used in civil and military affairs.To disorder enemies'radar detecting signal, noise jamming is used to interfering radar set. In this thesis, a Broad Band signal generator based on noise frequency modulation for radar is studied. Gauss white noise that produced by analog circuit is used to be as modulating signal, through signal amplifier circuit, A/D conversion, change to Gaussian random sequence. Then this random sequence and the input operation code of center frequency are processing and as a frequency tune word (FTW). To come into being the FM signal noise by direct digital synthesis(DDS) technology. Through the removal of the spectrum (by change center frequency operation code) can be achieved by different frequency interference signals, Finally FM noise signal after amplify, then the output FM noise signal through band-pass filter.In the beginning of the paper, introducing the FM signal noise and the overall design based on the theory, including the theory of noise, digital PLL frequency synthesizer and the principle of direct digital frequency synthesis (DDS), the principle of modulation of DDS, features of DDS. In succession, details of the hardware design signal generator circuit, including the key chip AD9224 (ADC), LMX2531 (PLL+VCO), AD9858 (DDS) and the principle of circuit parts. Then on the design of signal generator control, gave a brief control chip (FPGA), a detailed presentation on the internal FPGA logic of the function, including some of the control logic and circuit simulation results. Finally, introducing problems should pay attention to in the PCB design, debugging and test results. The test results completely meet the technical indicators system requirements.