The Hardware Design Of Arbitrary-function Waveform Generator

Arbitrary Function Generator(AFG)is a flexible broadband signal generator that could generate multiple waveforms and has multiple functions.It is widely used in many testing and verification areas.Frequency agility,multiple modulation functions,wideband pulse generation and precisely adjustable pulse parameters are characteristics of AFG.This thesis focuses on the above characteristics,and have deeply researched the AFG waveform synthesis scheme,signal conditioning method and hardware implementation structure.The main research contents of this paper include:1.Implement frequency agile signals and arbitrary signal synthesis.Take the DDFS-based,and multi-channel parallel waveform generation structure as standard waveform and arbitrary basic waveform generation structure.An arbitrary waveform generation method is designed to reduce signal distortion that caused by the loss of waveform information.Implement 1?Hz to 500 MHz sine waveform and 1mHz to 120 MHz arbitrary waveform generation;2.Implement multiple modulations and functions.Analyze the modulation parameters and classify all modulation functions into amplitude modulation,frequency control,and phase control according to the modulation calculation characteristics.Amplitude modulation,frequency modulation,and phase modulation of two arbitrary waveforms are realized by digital modulation module.A variety of modulations and functions such as frequency shift keying(FSK),pulse width modulation,frequency sweeping,and bursting are realized.Especially for the problem of modulation depth greater than 100% in amplitude modulation,combined with theoretical analysis to introduce the depth adjustment factor,design the amplitude modulation unit with modulation depth up to 120%;3.Implement wideband pulse synthesis and precise adjustment of pulse width.Pulse was divided into high-speed and low-speed parts.The low-speed part of the pulse is synthesized by digital integration from 1?Hz to 1kHz.High-speed pulse synthesis was realized by edge trigger signal delay comparison,finally generated 1 kHz to 120 MHz pulses.The pulse width was controlled by delay fine-tuning unit and delay coarse-tuning unit with high precision,and the step of pulse width up to 10 ps.4.A wide range of linear adjustment of the pulse edge is implemented.For the digital mode adjustment pulse edge resolution is not well.And when take the analog method,the range of pulse edge adjustment the is limited.Combined with digital integration and analog mode to achieve pulse edge adjustment.The low-speed pulse edge is adjustable from 1ms to 625 s by digital integration module.A high-speed pulse edge conditioning unit is designed based on the capacitor group constant current charge and discharge edge adjustment circuit structure.Finally,the edge conditioning effect of 2.5ns to 1ms pulse is realized.The system test results show that AFG can generate multi-waveform generation,complete a variety of signal modulations,and have many functions such as frequency sweeping and burst.Sine and pulse frequency errors are not more than 0.3ppm and 0.25ppm;Output 1MHz sine signal to noise ratio is-76.01dBc;Pulse edge control error does not exceed 6.04%;Signal amplitudes are controllable in the range of 50 mV to 5V(peak to peak),sine and pulse amplitude errors do not exceed ±(1%×|Setings| +5mV(Vpp))and(2%×|Setings| +5mV(Vpp)).The amplitude control accuracy is 0.1mV.Overall,this AFG is equivalent to the Tektronix AFG3252 level.