Đang chuẩn bị liên kết để tải về tài liệu:
Lò vi sóng RF và hệ thống không dây P5

Receiver System Parameters A receiver picks up the modulated carrier signal from its antenna. The carrier signal is downconverted, and the modulating signal (information) is recovered. Figure 5.1 shows a diagram of typical radio receivers using a double-conversion scheme. The receiver consists of a monopole antenna, an RF amplifier, a synthesizer for LO signals, an audio amplifier, and various mixers, IF amplifiers, and filters. | RF and Microwave Wireless Systems. Kai Chang Copyright 2000 John Wiley Sons Inc. ISBNs 0-471-35199-7 Hardback 0-471-22432-4 Electronic CHAPTER FIVE Receiver System Parameters 5.1 TYPICAL RECEIVERS A receiver picks up the modulated carrier signal from its antenna. The carrier signal is downconverted and the modulating signal information is recovered. Figure 5.1 shows a diagram of typical radio receivers using a double-conversion scheme. The receiver consists of a monopole antenna an RF amplifier a synthesizer for LO signals an audio amplifier and various mixers IF amplifiers and filters. The input signal to the receiver is in the frequency range of 20-470 MHz the output signal is an audio signal from 0 to 8 kHz. A detector and a variable attenuator are used for automatic gain control AGC . The received signal is first downconverted to the first IF frequency of 515 MHz. After amplification the first IF frequency is further downconverted to 10.7 MHz which is the second IF frequency. The frequency synthesizer generates a tunable and stable LO signal in the frequency range of 535985 MHz to the first mixer. It also provides the LO signal of 525.7 MHz to the second mixer. Other receiver examples are shown in Fig. 5.2. Figure 5.2a shows a simplified transceiver block diagram for wireless communications. A T R switch is used to separate the transmitting and receiving signals. A synthesizer is employed as the LO to the upconverter and downconverter. Figure 5.2b is a mobile phone transceiver transmitter and receiver 1 . The transceiver consists of a transmitter and a receiver separated by a filter diplexer duplexer . The receiver has a low noise RF amplifier a mixer an IF amplifier after the mixer bandpass filters before and after the mixer and a demodulator. A frequency synthesizer is used to generate the LO signal to the mixer. Most components shown in Figs. 5.1 and 5.2 have been described in Chapters 3 and 4. This chapter will discuss the system parameters of the receiver.