信号发生原理.ppt

Signal Generators for analog and digital modulation Signal Generators Agenda Signal generator applications Signal generator applications Signal Generators - Categories of Quality Important Frequency Bands for Communication 9kHz to 1GHz Civil EMS measurements 3MHz to 30MHz HF band (e.g. CB radio, world wide communication, airborne communication) 89 MHz to 108 MHz FM sound broadcasting 30 MHz to 300 MHz VHF (e.g. avionics, television) 890 MHz to 960 MHz GSM 900 1.71 GHz to 1.88 GHz GSM 1800 300 MHz to 3 GHz UHF (e.g. PCN, PCS, DECT, L-band, spread spectrum appl.) 1.9 GHz to 2.2 GHz UMTS ISM bands Wireless LANs2.4 and 5 GHz Signal Generator Block Diagram PLL, Block Diagram PLL - Synthesizer DDS Synthesizer DDS Synthesizer YIG Oscillator for Microwave Generators Microwave Generator Level Intermodulation products I Intermodulation products depend on: Output level RF frequency Isolation between the two signal generators Bandwith of the ALC (auto level control) loop of each generator ALC On/Off function ??? the advantage of RS generators Intermodulation products II ALC On/Off measurement results (e.g. SME) Intermodulation Measurements Applications for analog modulations Analog Modulation Spectral Purity Harmonics /Subharmonics SSB Phase Noise Phase Noise Simple Model for Phase Noise Effect of Frequency Multiplication Effect of Signal Mixing Phase Noise in PLL′s Phase Noise in PLL′s, Estimating Phase Noise Example: SMIQ (optimum PLL bandwidth) Example: SMY (narrow PLL bandwidth) Receiver Measurements/Sensitivity Receiver Measurements/Selectivity Revceiver Measurements/Selectivity Revceiver Measurements/Selectivity Revceiver Measurements/Selectivity Revceiver Measurements/Selectivity Revceiver Measurements/Selectivity Receivers must be able to suppress interfering co channel signals, i.e. signals which are received at the same frequency as the useful signals. Two signal generators are used, one with a signal l