基于声卡的虚拟信号发生器的设计外文翻译(编辑修改稿)

基于声卡的虚拟信号发生器的设计外文翻译(编辑修改稿)内容摘要：

ive form in IEEE Std. 1057 [1]. Nowadays, the new, about to be accepted standards IEEE Std. 1241 [2] and DYNAD [3] are ing with some new ideas and test procedures described in more detail. Moreover, many researchers have contributed with lots of ideas and approaches to solve AD and DA converter test problems. Probably the widest survey of those ideas was made in [4]. Comparing the standards, IEEE Std. 1057—―Standard for digitising waveform recorders‖—is the closest to the task of sound card testing. However, this standard covers mostly the static and quasistatic tests methods based mainly on the histogram testing and there is a deficiency of procedure and data processing details on testing and determining the dynamic parameters of ADC especially in the frequency domain. The histogram based methods are generally not very convenient for sound card characterisation because of the AC coupling on signal input of the cards (Fig. 1). Fullsize image (9K) Fig. 1. Typical function block diagram of analogue and digital circuits for signal recorder part in sound cards. View Within Article Both oning standards are more focused on testing standalone ADCs but they contain much more specific details on execution and evaluation of some dynamic tests. Particularly, the DYNAD draft contains very detailed descriptions of data processing for estimation of the ADC dynamic parameters in the spectral domain. These facts, as well as many similarities in testing ADCs and digitising waveform recorders, led to the decision to apply many procedures referred in DYNAD and in IEEE Std. 1241 for evaluation of ADC dynamic parameters on PC sound card testing in the role of waveform recorder. 本科毕业设计（论文）外文翻译 15 Testing waveform recorders in the form of PC plugin boards have some specifics. The interior of PC is generally illic it for a precise digitalisation of an input signal. The test methods developed and suggested, as well as some achieved test results for multifunction industrial plugin boards in various circumstances, have been published in [5, 6 and 7]. The authors preferred the dynamic test methods based on FFT spectrum or sinusoidal curve fit with determining effective number of bits (ENOB) versus test frequency as the main quality characterisation parameter of the tested board. In the software area, two universal versions of VI test software have been developed and published—one in LabVIEW [9] and another in Matlab [8]. Both versions of software have very general assignations—they process data from any measurement recorded in a file and they do not contain any data acquisition part. 3. Sound card as a waveform recorder Sound cards are generally dedicated to recording and playing sound signals. This results in a restriction of input and output frequencies span, usually to the frequency bandwidth from 20 Hz to 20 kHz, which prevents application of the static test methods and leads to the application of the dynamic test methods using the sinusoidal input test signal. The typical function block diagram of sound blaster input recording channels is shown in Fig. 1 ( [10 and 11] and others). The analoguetodigital conversion usually employs sigma–delta converters that can work in at least two precision modes—8 and 16 bits. Data can be coded into a few nonlinear and linear formats. The linear format (PCM), which is the most suitable format for the performance test, was chosen in the developed testing procedure. A variety of optional sampling frequencies depending on the sound card model—at least 8, 11, and kHz—are monly offered. The stability and, eventually, a frequency shift of these frequencies are not usually explicitly indicated in sound card manuals. Digitising input may be switched by an analogue multiplexer. A microphone input and a less sensitive linein (aux) input are builtin for linking external analogue signal sources. Sound cards are probably most often used in PCs with operational systems (OS) Windows 9x/NT/20xx/ME/XP. Any sound application under Windows can use some of the three levels of Win32 API multimedia class of functions for controlling and data transferring to/from any Windowspatible sound card: • the highest MCIWnd window class, • the middle MCI deviceindependent interface, • the lowlevel audio interface, which is used by applications that need the finest possible control over audio devices. 4. Test software and setup characteristics The general setup needed for performance testing sound blaster recording part is very simple (Fig. 2). It consists only of a precise test signal generator and a mon PC with the sound card to be tested in a PC chassis. The ultra low distortion generator DS360 by Stanford Research Systems with 20 bits DAC and THD better than 100 dB was used in the testing setup. The sound cards were tested in various new (ATX) and old (AT) PC chassis with different motherboards and in a few notebooks. 本科毕业设计（论文）外文翻译 16 Fullsize image (3K) Fig. 2. Setup for sound card testing. View Within Article This setup must be integrated with a convenient software, which must control the sound blaster to be tested, collect and process the recorded data, as well as present and archive the results. The current generalpurpose software [8 and 9] does not contain any part of data collecting and they enable only data processing. A possible additional distortion in the recorded data, which can be caused by using a thirdparty, unknown in detail recording software acquiring data from a sound card in a nonlinear format, led to the decision to develop a new special VI software. The software was created with the intention of maximal prehensiveness at sound card testing. It was fully integrated with its lowlevel data recording subroutines and it can be installed as an executable file。