ECOMMS Lecture - users.rowan.edu

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Electrical Communications Systems ECE.09.331 Spring 2008 Lecture 14a April 29, 2008 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring08/ecomms/ S. Mandayam/ ECOMMS/ECE Dept./Rowan University Plan Broadcast Transmitters and Receivers AM Broadcast Transmitter

Class-C Amp Collector Modulator TRF Receiver Superheterodyne Receiver S. Mandayam/ ECOMMS/ECE Dept./Rowan University ECOMMS: Topics E le c tr ic a l C o m m u n ic a tio n S y s te m s S i g n a ls D is c r e te S y s te m s C o n tin u o u s A n a lo g P r o b a b ility P o w e r & E n e r g y S i g n a ls AM S w itc h in g M o d u la to r

E n v e lo p D e te c to r In fo r m a tio n C o n tin u o u s F o u r ie r T r a n s fo rm D S B -S C P ro d u c t M o d u la to r C o h e r e n t D e te c to r C o s ta s L o o p E n tro p y D is c r e te F o u r ie r T r a n s fo rm SSB W e a v e r 's M e th o d P h a s in g M e th o d F re q u e n c y M e th o d C h a n n e l C a p a c ity B a s e b a n d a n d B a n d p a s s S i g n a ls F re q u e n c y & P h a s e M o d u la tio n

N a rr o w b a n d /W id e b a n d V C O & S lo p e D e te c to r PLL D ig ita l D ig ita l C o m m T r a n s c e iv e r B aseband CO DEC B andpass M O DEM S o u r c e E n c o d in g H u ffm a n c o d e s ASK PSK FSK E rr o r-c o n tro l E n c o d in g H a m m in g C o d e s BPSK

S a m p lin g PAM Q PSK Q u a n tiz a tio n PCM M -a ry P S K L in e E n c o d in g Q AM C o m p le x E n v e lo p e G a u s s ia n N o is e & S N R T im e D iv is io n M u x T 1 (D S 1 ) S ta n d a rd s R a n d o m V a r ia b le s N o is e C a lc u la tio n s P a c k e t S w itc h in g E th e rn e t

IS O 7 -L a y e r P r o to c o l S. Mandayam/ ECOMMS/ECE Dept./Rowan University AM Broadcast Transmitter Temp. Stabilized Crystal Oscillator Audio Input Buffer Amplifier Class-C Modulated Power Amp. Stage Class-C Modulated Power Amp. Stage

Impedance Matching Network Demodulator + - Audio Amplifier Modulator Driver Amplifier S. Mandayam/ ECOMMS/ECE Dept./Rowan University Amplifier Classification ic

ic Class A ic t t Class AB Class B t

t ic Class C S. Mandayam/ ECOMMS/ECE Dept./Rowan University BJT Collector Modulator Output Characteristics Circuit S. Mandayam/ ECOMMS/ECE Dept./Rowan University BJT Collector Modulator Operation Circuit S. Mandayam/ ECOMMS/ECE Dept./Rowan University

AM Receiver Purpose Demodulate received signal Requirements Carrier frequency tuning Filtering Amplification S. Mandayam/ ECOMMS/ECE Dept./Rowan University Tuning Circuits Series Tuned Circuit I + C r V L - S. Mandayam/ ECOMMS/ECE Dept./Rowan University

Series Tuned Circuit function [f,A]=resonance(f0,Q) %ECOMMS Spring 08 Class Demo %S. Mandayam, ECE Dept., Rowan University %To illustrate series resonance and Q-factor close all; %defining frequency axis f=f0-f0/2:0.1:f0+f0/2; %calculating relative response y=(f/f0)-(f0./f); A=20*log10(1./(1+(y*Q).^2).^0.5); plot(f-f0,A);grid on; xlabel('Shift from resonant frequency in Hz'); ylabel('Relative Response in dB'); title('Series Tuning Circuit'); S. Mandayam/ ECOMMS/ECE Dept./Rowan University Tuning Circuits Parallel Tuned Circuit I +

r V C L - Active Tuned Circuits? S. Mandayam/ ECOMMS/ECE Dept./Rowan University Tuned Radio Frequency (TRF) Receiver Active Tuning Circuit Detector Circuit Local Oscillator Bandpass Filter

Baseband Audio Amp S. Mandayam/ ECOMMS/ECE Dept./Rowan University Heterodyning All Incoming Frequencies Heterodyning (Upconversion/ Downconversion) Fixed Intermediate Frequency Subsequent Processing (common) S. Mandayam/ ECOMMS/ECE Dept./Rowan University Superheterodyne Receiver

fRF or fc RF Amplifier H1(f) Mixer fIF IF Amplifier H2(f) fIF fm Detector Local fLO Oscillator Common

tuning Downconversion Upconversion fIF = |fRF - fLO| fIF = fRF + fLO Audio Amp fm S. Mandayam/ ECOMMS/ECE Dept./Rowan University Summary