Research Of DDS Function Generator With LAN Interface

LXI (LAN—based extensions for Instrumentation) is a new instrument interface criterion, which is established by Agilent Corporation and VXI Science and Technology Corporation in PALOALTO of Cal, on sept.2004. Based on the famous Ethernet technology, LXI extends the languages, commands and protocols, constitutes a new modularization instrument interface standard of auto-testing system.Following the world instrument interface technology's development, I select the program-controlled instrument with LAN interface, which is the hardware of LXI, as my research's emphasis.At same time this program-controlled intelligent function generator is on basis of direct digital synthesize technology (DDS), and this technology is a breakthrough in the domain of frequency synthesize technology with the development of computer, digital integration circuit and micro-electronically technology. Advanced digital signal disposal theory was introduced into signal synthesize domain, and new resolves for improving signals' stability of frequency is provided. This technology takes advantage of fast frequency conversion, high resolution, low phase noise and so on.This paper firstly introduces the background, study significance and principal of web testing &controlling systems and DDS technology, and then provides the debugging process in detail. The NI instrument board adopts powerful graphical language (G language) to program, and programming is convenient, the interface of human machine is visual, friendly; the instrument adopts the technique of parsing the SCPI (Standard Commands for Programmable Instruments) commands to make of instrument's interface channels. This SCPI is an instrument command language based on ASCII, because every instrument manufacturer must abide by this standard, the compatibility and performance of easy to use between instrument and system are ensured; Besides it is as an independent instrument, because this generator is of LAN interface, and can conveniently be controlled by computer remotely, it is likely to be connected in auto-testing system. This function generator can produce these four sine and square and triangle and saw tooth signals, is of 40MHz bandwidth, and its frequency resolution is 1Hz.From above all, from the theory used and function realized in this design, it is concluded that this function generator can enter into remote-control state and local-control state easily, it is easy to be betterment, and it has wide application future. It is preparative for the research of Programmed-controlled Intelligent instrument Embedded LXI Interface.