Research Of The Wide-band Frequency Agile Signal Synthesis Technique

Frequency synthesis technique is the key technique of modern electronic systems, determines the performance of system to a large extent. With the development of digital communications, radar, information warfare, electronic countermeasure and other techniques, hopping-frequency signal is widely used in the current anti-jamming communication systems. Due to the constantly changing carrier frequency, the hopping-frequency signal makes decoding and interference difficult to implement, and then has the advantages of high security and anti-jamming. As a measurement instrument, the frequency agile synthesizer, namely the fast hopping-frequency signal generator, plays an important role in the field of radar, communication and electronic countermeasure, etc.In this thesis, under the background of modern anti-jamming communications, based on the project of a wide range of hopping-frequency and complex modulation signal synthesis technique , the main research work of frequency agile signal synthesis technique is generating the signals with the functions of both frequency hopping signal and traditional analog modulation, thereby provides various simulation signals for modern anti-jamming communications.The direct synthesis (DS) method, direct digital synthesis (DDS) method, digital phase-locked loop (PLL) method and mixed method are commonly used in the frequency agile synthesis. According to the rquirements of indicators, this design chooses the direct digital synthesis (DDS) method, which has the advantages of high-speed frequency switching and fine resolution. For better spectrum purity, finer frequency accuracy, faster frequency hopping speed and higher reliability, this design uses FPGA (Field Programmable Gate Array) to generate high-speed digital control signal and command DDS synthesizing frequency agile signal. The frequency switching time of the DDS output hopping-frequency signal can be achieved ns level. Using the ISE9.1 software design FPGA internal logic circuit, FPGA generates the high-speed and flexible digital signal to control the frequency, phase, amplitude of DDS output signal,so that achieve high-speed frequency hopping with different hopping sequences, as well as FM,? M, AM analog modulation.Experimental results show that, the wide range frequency agile signal, which is the output of this design, with the bandwidth of 300MHz, frequency swithing time better than 64ns, and frequency resolution less than 1Hz. Compared with the state-of-the-art, obviously, this design has the evident advantages of frequency hopping rate and bandwidth. As the hopping sequence,rate and duty cycle of the hopping-frequency signal can be real-time control, this design has great practical value.The carrier frequency and modulation rate,which are the major parameters of the output FM, ? M, AM analog modulated signals, are easily setted and changed. Because the modulation range is wide and extendable, this design has reference value. Consequently, this frequency synthesis technique that has the functions of both broadband frequency agile and multiple analog modulation , has great research value and market prospects.