通信电路实训论文..doc

桂林电子科技大学课程设计（论文）报告用纸 摘　　要 随着现代社会的快速发展，人们对电子产品的要求越来越高，因而电子产品无论从制作上还是从销售上都要求很高。小功率调幅发射机常用于通信系统和其它无线电系统中，特别是在中短波广播通信的领域里更是得到了广泛应用。原因是调幅发射机实现调幅简便，调制所占的频带窄，并且与之对应的调幅接收设备简单，所以调幅发射机广泛地应用于广播发射。发射机的主要任务是完成有用的低频信号到高频载波的调制，将其变为在某一中心频率上具有一定带宽、适合通过天线发射的电磁波。 高频部分一般包括主振荡器、缓冲放大、倍频器、中间放大、功放推动级与末级功放。主振器的作用是产生频率稳定的载波。为了提高频率稳定性，主振级往往采用石英晶体振荡器，并在它后面加上缓冲级，以削弱后级对主振器的影响。在以前应用最广泛的是调频接收机，随着科学技术的发展，出现了超外差式调频接收机。低频部分包括话筒、低频电压放大级、低频功率放大级与末级低频功率放大级。低频信号通过逐级放大，在末级功放处获得所需的功率电平，以便对高频末级功率放大器进行调制。 关键词：高频功率放大器、振荡器、调频发射机、功率放大器 Abstract With the rapid development of modern society, people to the electronic product of the increasingly high demand, so the electronic products in terms of production or sales is demanding. Low power AM transmitter is often used in communication systems and other radio systems, especially in the medium - and short-wave radio communication field is more widely applied. The reason is simple to achieve amplitude modulation AM transmitter, occupies a narrow frequency band, and the corresponding amplitude modulation receiver has the advantages of simple equipment, so am transmitter is widely used in radio transmitter. The transmitter s main task is to complete the useful signal of low frequency to high frequency modulated carrier, to turn it into a center frequency at a certain bandwidth, suitable for electromagnetic waves emitted by the antenna. The high frequency portion generally include a master oscillator, a buffer amplifier, multiplier, intermediate amplifier, power amplifier driver stage and the final power amplifier. The main isolator effect is generated by a frequency stabilized carrier. In order to improve the frequency stability, vibration level often uses the quartz crystal oscillator, and behind it with buffer, to weaken the back stage on the main isolator effect. In the past the most widely used is the FM receiver, with the development of science and technology, appeared the superheterodyne FM receiver. The low frequency part comp