Research On Arbitrary Waveform Generation And Loading Based On FPGA

With the rapid development of electronic technique in the recent decades,the demand of signal source is growing quickly in electronic devices and circuits design,optical and physics experiments,radar detection and electronic confrontation,biomedical and other fields.As one of the most powerful signal source,the AWG(Arbitrary Waveform Generator)has become a hotspot in the current electronic simulation test instrument.The AWG has a high degree user-programmable features,which can generate any shape of the waveform according to the waveform data users edited.The AWG's function has covered the mostly traditional signal source such as function signal generator.In this paper,a multi-channel,low-jitter arbitrary waveform generation system according is designed to project requirements.Different from the traditional DDS-based arbitrary waveform generator,the design draws on the TrueArb technology program,using the FPGA +multiplexer + high-speed DAC's classic architecture,which can get higher waveform fidelity and lower phase jitter.And the design combines the precision synchronization system of the research group to transmit the clock and waveform trigger signal in the form of optical data stream.The clock and trigger signal recovery by the CDR circuit at the receiving terminal,which can guarantee the low loss and low error rate of signal under long distance transmission,applicable to large area of large equipment and engineering applications.In addition,the optical data stream can fan out multiple signals,then multi-channel arbitrary waveform can achieve synchronous output by cascade multiple arbitrary waveform generators.The design uses FPGA and multiplexer for parallel and serial conversion to improve the data rate,to achieve high-speed DAC interface connection,resulting in up to 7.4Gsa/s high sampling rate.FPGA internal program written by the Flash memory after the instrument is turned on,waveform data sent by the host computer and stored in the FPGA internal storage resources,which reducing the design difficulty and external circuit wiring pressure.The 4-frequency-division clock output from the high-speed DAC is used as the working clock of the multiplexer and the 2-frequency-division clock of the multiplexer is fed back to the FPGA for phase relationship identification to obtain the synchronous clock system to ensure the timing of the whole system accurate.The AWG can communicate with the host computer through USB-to-serial data cable,and the host computer software can edit the standard waveform such as sine wave and square wave,and can transmit the waveform data file of DAT format generated by MATLAB and other software to FPGA,to control the output of any waveform.In addition,we reserved DDR3 high-capacity memory interface for the late upgrade requirements,which can achieve large waveform data storage depth.As the circuit in the design is a high-speed digital-analog circuit,the PCB design in the key design rules were analyzed,and the design of the filter application were introduced.Finally,we analys the clock quality and conduct the arbitrary waveform output experiment,and a satisfactory experimental result is obtained.The AWG chould be applied to nuclear magnetic resonance spectrometer,electrocardiogram machine and other medical equipment development and testing,which has a large practical value.In addition,the resserch in this paper provides experience and technical accumulation for the research of high sampling rate and high synchronization accuracy arbitrary waveform generator.