Lesson 13 Function Generators 电子技术专业英语教程[冯新宇主编][电子教案].pptVIP

《电子技术专业英语教程》 Lesson 13 Function Generators 《电子技术专业英语教程》冯新宇 主编 电子工业出版社 Lesson 13 Function Generators Terminology odd harmonics 奇次谐波 triangle wave 三角波 peak deviation 峰值偏差 angular frequency 角频率 sawtooth wave 锯齿波 Terminology bandlimite 带限 function generators 函数发生器 single-shot 单次激发 aliasing distortion 混淆（折叠）失真 A function generator is a piece of electronic test equipment or software used to generate electrical waveforms. These waveforms can be either repetitive, or single-shot in which case some kinds of triggering source are required (internal or external). Another type of function generator is a sub-system that provides an output proportional to some mathematical function of its input. Analog function generators usually generate a triangle waveform as the basis for all of its other outputs. The triangle is generated by repeatedly charging and discharging a capacitor from a constant current source. This produces a linearly ascending or descending voltage ramp. As the output voltage reaches upper and lower limits, the charging and discharging are reversed using a comparator, producing the linear triangle wave. By varying the current and the size of the capacitor, different frequencies may be obtained. A 50% duty cycle square wave is easily obtained by noting whether the capacitor is being charged or discharged, which is reflected in the current switching comparators output. Most function generators also contain a non-linear diode shaping circuit that can convert the triangle wave into a reasonably accurate sine wave. It does so by rounding off the hard corners of the triangle wave in a process similar to clipping in audio systems. The type of output connector from the device depends on the frequency range of the generator. A typical function generator can provide frequencies up to 20 MHz and uses a BNC connector, usually requiring a 50 ohm or 75 ohm termination. Specialized RF generators are capable of gigahertz frequencies and typically u