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Unformatted text preview: ECE 4371, Fall, 2009 Zhu Han Department of Electrical and Computer Engineering Class 5 Sep. 8 th , 2007 PhaseLocked Loop PhaseLocked Loop Can be a whole course. The most important part of receiver. Definition: a closedloop feedback control system that generates and outputs a signal in relation to the frequency and phase of an input ("reference") signal A phaselocked loop circuit responds both to the frequency and phase of the input signals, automatically raising or lowering the frequency of a controlled oscillator until it is matched to the reference in both frequency and phase. Ideal Model Ideal Model Model Si=Acos(w c t+ 1 (t)), Sv=A v cos(w c t+ c (t)) Sp=0.5AA v [sin(2w c t+ 1 + c )+sin( 1 c )] So=0.5AA v sin( 1 c )=AA v ( 1 c ) Capture Range and Lock Range LPF VCO Type of waves Type of waves GPS Orbits GPS Orbits FM Basics FM Basics VHF (30M300M) highfidelity broadcast Wideband FM, (FM TV), narrow band FM (twoway radio) 1933 FM and angle modulation proposed by Armstrong, but success by 1949. Digital: Frequency Shift Key (FSK), Phase Shift Key (BPSK, QPSK, 8PSK,) AM/FM: Transverse wave/Longitudinal wave Angle Modulation vs. AM Angle Modulation vs. AM Summarize: properties of amplitude modulation Amplitude modulation is linear just move to new frequency band, spectrum shape does not change. No new frequencies generated. Spectrum: S(f) is a translated version of M(f) Bandwidth 2W Properties of angle modulation They are nonlinear spectrum shape does change, new frequencies generated. S(f) is not just a translated version of M(f) Bandwidth is usually much larger than 2W Angle Modulation Pro/Con Application Angle Modulation Pro/Con Application Why need angle modulation? Better noise reduction Improved system fidelity Disadvantages Low bandwidth efficiency Complex implementations Applications FM radio broadcast TV sound signal Twoway mobile radio Cellular radio Microwave and satellite communications Instantaneous Frequency Instantaneous Frequency [ ] ( ) cos ( ) , where :carrier amplitude, ( ) :angle (phase) c i c i s t A t A t = ( ) 1 ( ) 2 i i d t f t dt = Angle modulation has two forms...
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This note was uploaded on 01/20/2012 for the course EE 301 taught by Professor Ahmetçakar during the Spring '11 term at Gazi Üniversitesi.
 Spring '11
 ahmetçakar

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