tailieunhanh - RF và mạch lạc lò vi sóng P2

Modern communication systems require radio frequency and microwave signals for the wireless transmission of information. These systems employ oscillators, mixers, ®lters, and ampli®ers to generate and process various kinds of signals. The transmitter communicates with the receiver via antennas placed on each side. Electrical noise associated with the systems and the channel affects the performance. A system designer needs to know about the channel characteristics and system noise in order to estimate the required power levels | Radio-Frequency and Microwave Communication Circuits Analysis and Design Devendra K. Misra Copyright 2001 John Wiley Sons Inc. ISBNs 0-471-41253-8 Hardback 0-471-22435-9 Electronic 2 COMMUNICATION SYSTEMS Modem communication systems require radio frequency and microwave signals for the wireless transmission of information. These systems employ oscillators mixers filters and amplifiers to generate and process various kinds of signals. The transmitter communicates with the receiver via antennas placed on each side. Electrical noise associated with the systems and the channel affects the performance. A system designer needs to know about the channel characteristics and system noise in order to estimate the required power levels. This chapter begins with an overview of microwave communication systems and the radio frequency wireless services to illustrate the applications of circuits and devices that are described in the following chapters. It also gives an idea to the reader about the placement of different building blocks in a given system. A short discussion on antennas is included to help in understanding the signal behavior when it propagates from transmitter to receiver. The Friis transmission formula and the radar range equation are important in order to understand effects of frequency range and operating power levels on the performance of a communication system. Note that radar concepts now find many other applications such as proximity or level sensing in an industrial environment. Therefore a brief discussion on Doppler radar is also included in this chapter. Noise and distortion characteristics play a significant role in analysis and design of these systems. Minimum detectable signal MDS gain compression intercept-point and the dynamic range of an amplifier or the receiver are subsequently introduced. Other concepts associated with noise and distortion characteristics are also introduced in this chapter. 9 10 COMMUNICATION SYSTEMS TERRESTRIAL .