年ITU亚太地区监测业务培训-教材-.pptVIP

Presented for Pre-address Principles of radio transmitters and receivers Dr Ding JiaXin Engineer of Radio Monitoring Division State Radio Monitoring Center dingjiaxin@srrc.org.cn +8610 Radio Monitoring and Spectrum Management Training (China,23-31,May,2005) Contents: Position of oscillator: Function of oscillator: Generate a periodic output Provide stable and accurate frequencies for mixer Classification of oscillators: Feedback oscillator Negative resistance oscillator Principle of feedback oscillator: Barkhausen’s criteria The loop gain must be equal to unity The total phase shift around the loop must be equal to zero Frequency selective network: Oscillator characteristics: Accuracy Stability Definition of accuracy: fx: actual frequency f0: nominal frequency Stability of oscillator: The ability to remain at a fixed frequency Long-term Short-term Phase noise: Output spectrum of oscillator： Effect of phase noise (I): On the transmitting path Effect of phase noise (II): On the receiving path Single side-band phase noise: Describe frequency stability in frequency domain PSSB: noise power in unit bandwidth Pc: carrier power Unit: dBc/Hz Example: Typical value of SSB phase noise: =10KHz typical value: -80~-110 dBc/Hz Summary: Function of oscillator Classification of oscillator Principle of feedback oscillator Characteristics of oscillator Phase noise SSB phase noise Contents: Modulation Demodulation: General considerations Basic concepts Classification Analog modulation Digital modulation Modulation Demodulation: General considerations Basic concepts Classification Analog modulation Digital modulation Where is modulator ? Where is demodulator ? What is modulation? Why convert ? For antenna design easy For frequency multiplex For efficiently transmit Modulation Up-conversion (I): Modulation Baseband = IF Linear or nonlinear conversion Up-conversion IF = RF Linear conversion Mo