Research Of Program-Controlled Intelligent Function Generator

In the recent years, all kinds of program-controlled instruments and automation testing systems that are configured by common instrument interfaces of IEEE-488 standard have come forth continually. The GPIB interface of IEEE-488 standard can connect all kinds of instruments to make up an automation testing system. This interface is an interface for a system or an instrument to exchange and transfer information with outside environment. This topic (program-controlled intelligent function generator) adopts this common interface technology (GPIB), which can be acted as different function module and connect each other via passive bus cable by means of building block.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. It introduces advanced digital signal disposal theory into signal synthesize domain, and its appearance provides new resolve methods for improve signals' stability of frequency. This technology is of good traits: fast frequency conversion, high resolution, low phase noise and so on.This paper firstly introduces the background, study significance and principal of GPIB interface and DDS technology, and then provides the debugging process in detail. The process adopts two schemes early or later. The first one is that its hardware is on the basis of the ES1400 GPIB interface card of ISA bus;the software control part is completed under the environment of ES BASIC. The second one isthat its hardware is on the basis of PCI-GPIB card (82350) of Agilent Company;the software control part is completed under the environment of Labview. In the second scheme, 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 Virtual Instrument Software Architecture-VISA is adopted to call bottom drive program of PCI-GPIB, and this architecture can connect different standard's I/O instruments . This instrument's control commands can pluralize SCPI, and 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.This function generator can produce these two sine and square signals, is of 20MHz bandwidth, and its frequency resolution is lHz. Besides it is as an independent instrument, because this generator is of GPIB interface, and can conveniently be controlled by computer remotely, it is likely to be connected in automation testing system.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. Its high performance is realized at low cost and it has wide application future.