The Design Of Pseudo-random Signal Generating And Acquisition Equipment

2nseries of pseudo-random signal has been used as signal source for frequency domainelectrical prospecting. Compared with the frequency observation system using square wave asthe field source, it has the advantages of high efficiency, high accuracy, portable instrument,rich observational parameters and so on. In my graduation project, by writing VHDL hardwaredescription language program, the CPLD will generate pseudo random double-frequency wave,pseudo random triple-frequency wave, pseudo random five-frequency wave. The signalfrequency is adjustable between0.1Hz and10Hz.My graduation project are including two parts: the first part including as follows, CPLDgenerating signal, controlling the dead time of signal to generate circuit, opt coupler isolating,driving circuit, H-Bridge Power circuit, isolating power and work power circuit. Also, therequired wave by VHDL state machine producing in VHDL language has been supplied, aswell as the programming and timing simulation in Quartus Ⅱ which is a simulation software.The operating principle like this: after joining the dead zone, the pseudo-random signal will gothrough the isolating opt coupler and driving circuit, and then the four MOSEET pipes inH-Bridge Power circuit will make break; the final power of the output signals will be suppliedby the bus power of H-Bridge.The second part introduces a pseudo-random based on single chip microcomputer controlsignal acquisition and processing circuit design. The system based on the AT89S52SCM,consist of pseudo-random simulation signal circuit, A/D transform circuit and display module.Signal circuit produced three frequency pseudo-random signal and output voltage value to A/Dtransform circuit, with single-chip microcomputer controlling A/D transform circuit to realize4N times sampling, and sampling process as three part, using a digital orthogonal detectionalgorithm, the three main frequencies obtained respectively amplitude and frequency of relativephase, and in LCD display simultaneously on handling result. By test, the system can work witha high and the processing speed is fast. In the low frequency signal detection and equipmentproduction, this system can be widely applied because it has the performance that can shortenthe development cycle. Therefore, the system has the high availability.