The Design And Realization Of Pulse Synthesizer Of Arbitrary Waveform Generator

As a popular test signal source,the arbitrary waveform generator(AWG)can provide many different function waveforms and modulation waveforms.It is widely used in applications that require a variety of test signals.The pulse waveform,which is one of the most important output waveforms of arbitrary waveform generator,plays an important role in the digital circuit design.According to shape,pulse waveform can be divided into rectangular pulse and non-rectangular pulse.Aimed to the problem that pulse width of rectrangular pulse can not be precisely adjusted based on direct digital frequency synthesis(DDFS)architecture,a pulse synthesizer is realized based on the hardware architecture of 1GSPS arbitrary waveform generator,which can output pulse waveform with high pulse width adjustment resolution.The main works of this thesis are as follows:1.Multiple phase delay,dynamic phase delay and IODELAY module delay,these digital pulse width adjustment methods were analyzed and compared in the thesis.In order to realize less than 100 ps pulse width adjustment resolution,a method which change the delay between pulse leading edge trigger signal and pulse trailing edge trigger signal by using the IODELAY module in the Xilinx Kintex-7 family FPGA was put forward.In order to synthesize pulse frequency with wide range and high resolution of adjustment,by means of using counters,which based on variable clock that output by arbitrary waveform synthesis was multipled by ten through phase locking loop(PLL)in the FPGA,to generate trigger signals with frequency range from 1?Hz to 20 MHz.2.The principle and methods of adjusting pulse rising time and falling time were analyzed.In order to generate pulse with wide range of rising time and falling time,especially which can be adjusted respectively,the method that based on constant current source to charge and discharge the capacitors was adopted to realize respective and accurate adjustment of rising and falling time.The method of using capacitor array circuit with the control of five capacitors was adopted to realize adjustment of rising and falling time in the range from 2.5ns to 1ms.3.The advantages and disadvantages of the methods of adjusting symmetry of triangular waveform such as digital integrator,analog integrator and direct digital frequency synthesis were analyzed.In order to generate triangular waveform with precisely adjustable symmetry,a method which calculate and change the waveform data of rising edge and falling edge in the look-up table of direct digital frequency synthesizer.The pulse width modulation with internal or external modulation source was realized by dynamically changing pulse width which was implement by configuring pulse width coarse tuning and fine tuning module on the basis of waveform data of modulation wave.The experiment results shown that pulse synthesizer can provide rectangular pulse,triangular waveform and pulse width modulation waveform.More specifically,rising and falling time of rectangular pulse can be adjusted from 2.5ns to 1ms and the resolution of pulse width was less than 100 ps,the triangular wave having 0.5% resolution of symmetry,pulse width modulation waveform having duty cycle in the range from 10% to 90%.