The Key Modules Study And Implement Of ISM Band Receiver

With the rapid development of wireless communication technology, the index of the RF receiver, which serves as the front end of entire wireless communication system, determines the capability of the whole system. So, the study on RF receiver has an important practical value.In this thesis, the scheme of RF receiver is realized through the superheterodyne twice frequency transformation. Then several modules of which consists the receiver are discussed respectively. The reassure background of the receiver, the task of the research subject and the research of this thesis is introduced in chapter 1. Chapter 2 first introduces the matching circuit of low noise amplifier, analyzes the stability, power gain and noise figure of low noise amplifier and discusses the working state and common bias circuit of transistor. Besides, the specifications and design method of coupled microstrip band pass filter is introduced at the end of this chapter. Chapter 3 first introduces synthesizer technology systematically, and then makes an analysis of the basic principle of direct digital frequency synthesizer and phase locked loop. The efficiency of transistor working on class C state is derived and the scheme of local oscillator is proposed. Last the indicators of mixer and the realizing means are introduced. In chapter 4, a S-band low noise amplifier is designed and simulated based on Advanced Design System. An experimental low noise amplifier circuit is realized through traditional PCB process. The result shows that the low noise amplifier within 2.4GHz central frequency, 100MHz operation bandwidth, noise figure less than 1dB, power gain more than 28dB, the flatness of power gain less than 1dB and the input/output VSWR less than 2:1, the measured results of the low noise amplifier are basically compatible with that of the simulation. Then the coupled microstrip band pass filter is designed, fabricated and measured. In chapter 5, a 30MHz signal is realized with the integrated DDS chip, and then the local oscillator with 120MHz output is realized through four frequency multiplier. In the end, a mixer circuit is realized by integrated circuit and the measureed results are given at last.Chapter 6 summarizes the design work of RF receiver and discusses the future research prospects.