EE 551/451, Fall, 2006 Communication Systems

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## EE 551/451, Fall, 2006 Communication Systems

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**EE 551/451, Fall, 2006Communication Systems**Zhu Han Department of Electrical and Computer Engineering Class 6 Sep. 7th, 2006**Homework1**EE 541/451 Fall 2006**Homework1**• Remote Sensing Mentor Engineering CTA Communications NovaSol Analytical Spectral • Local company Smarter Process Incorporated • Others Telecommunication systems Sony Motorola Aeroflex Broadcom Global Communications Fujitsu Rohde & Schwarz Gilat Satellite Networks EE 541/451 Fall 2006**Homework2**Dear all, Some students asked a question how to plot the response of the filter. Here are some codes that might be useful z=zeros(10000,1); % generate the delta function. z(5000)=1; % notice it starts from half, so that it is a delay version. %otherwise it is a unit function times a delta function. y=filter(Hd,z); %Hd is the filter parameters psd(y,10000,22050); %size of samples=10000, fs=22050. Also, if window such as humming window is added, the fluctuation in the stop-band can be removed. This is because the input z is not infinite long and window can reduce the finite length effect. Let me know if you have any questions. Best regards, Zhu Han EE 541/451 Fall 2006**Carrier Recover Error**• DSB: e(t)=2m(t)cos(wct)cos((wc+ w)t+) e(t)=m(t) cos((w)t+) • Phase error: if fixed, attenuation. If not, shortwave radio • Frequency error: catastrophic beating effect • SSB, only frequency changes, f<30Hz. • Donald Duck Effect • Crystal oscillator, atoms oscillator, GPS, … • Pilot: a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes. EE 541/451 Fall 2006**Phase-Locked Loop**• Can be a whole course. The most important part of receiver. • Definition: a closed-loop feedback control system that generates and outputs a signal in relation to the frequency and phase of an input ("reference") signal • A phase-locked 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. EE 541/451 Fall 2006**Voltage Controlled Oscillator (VCO)**• W(t)=wc+ce0(t), where wc is the free-running frequency • Example EE 541/451 Fall 2006**Ideal Model**• Model • Si=Acos(wct+1(t)), Sv=Avcos(wct+c(t)) • Sp=0.5AAv[sin(2wct+1+c)+sin(1-c)] • So=0.5AAvsin(1-c)=AAv(1-c) • Capture Range and Lock Range LPF VCO EE 541/451 Fall 2006**Carrier Acquisition in DSB-SC**• Signal Squaring method • Book page 187 • Costas Loop • SSB-SC not working EE 541/451 Fall 2006**PLL Applications**• Clock recovery: no pilot • Deskewing: circuit design • Clock generation: Direct Digital Synthesis • Spread spectrum: • Jitter Noise Reduction • Clock distribution EE 541/451 Fall 2006**Homework and Lab Demo**• 4.5.1 • 4.6.1 • Graduate student 4.5.5 EE 541/451 Fall 2006**Project One**• Nine channels from 100KHz. Each channel has 10KHz. • Filter design to get the desired band and transmit without interferencing other band (nine bandpass filters, passband 4K, stopband 5K) • Voice bandwidth 4KHz, your voice with length of 3 seconds • A=1; 50% AM, transmitter receiver in different files • Sample frequency for modulated data 400KHz, for baseband 22050Hz. • Both coherent and envelop decoders (not necessary RC). • Graduate student, SSB USB. Hilbert Transceivers • Ranking methods at class • Add all signals together, if others can hear you, you have one point EE 541/451 Fall 2006**Questions?**EE 541/451 Fall 2006