ECEN5533 Modern Communications Theory Lecture #91 February 2016 Dr. George Scheets n Read 5.6 n Problems 5.14 – 5.16 n Exam #1, 10 February

ECEN5533 Modern Communications Theory Lecture #103 February 2016 Dr. George Scheets n Read n Skim Design #1 n Problems 5.17, 18, & 21 n Corrected Quizzes due 5 February n Exam #1, 10 February

ECEN5533 Modern Communications Theory Lecture #115 February 2016 Dr. George Scheets n Problems: Exam #1 (2012 – 2014) n Corrected Quizzes due Today n Exam #1, 10 February n Design #1 due 19 February

Model for a Active Device S in & N in GS in & G(N in + N ai ) G N amp = kT amp W n + + G > 1

Model for a Passive Device S in & N in GS in & G(N in + N ai ) G N amp = kT passive W n + + G < 1 T passive = (L-1)T physical

Noise Figure n F = SNR in /SNR out u WARNING! Use with caution. If input noise changes, F will change. u WARNING! Use with caution. If input noise changes, F will change. n F = 1 + T amp /T in u T in = 290 o K (default)

System Noise (Actual) Noise Striking Antenna = N o W Thermal = kT surroundings 1000*10 9 = k*290*1000*10 9 = 4.00 n watts Much of this noise doesn't exit system. Blocked by system filters. kT ant W N = ??? System Cable + Amp Noise exiting Antenna that will exit the System = kT ant 6*10 6 = 12.42* watts Noise Antenna "Sees" = Noise exiting antenna = N o W Antenna ≈ kT ant 1000*10 9 = 2.07 n watts (T antenna = 150 Kelvin)

System Noise (Simplified Model) System Cable + Amp Noise Actually Exiting Antenna = Noise Antenna "Sees" ≠ Noise Exiting Antenna that will exit the System = kT ant W N = 12.42* watts Antenna Power Gain = 1 Signal Power in = Signal Power out This is the model we use. We don't worry about noise that won't make the output.

SNR Considering all the noise Noise Seen by Antenna = N o W Antenna = kT ant 1000*10 9 = 2.07 n watts Signal Power Picked Up by Antenna = watts System Cable + Amp SNR at "input" of antenna = /(4*10 -9 ) = SNR at output of antenna = /(2.07*10 -9 ) = SNR at System Output = 43.63

SNR Considering Noise Hitting Antenna That Can Reach the Output Noise seen by Antenna TCRO = N o W N = kT ant 6*10 6 = femto watts Signal Power Picked Up by Antenna = watts System Cable + Amp SNR at output of antenna = SNR at System Output = This is the noise we're worried about.

SNR of Actual System Improves Filtering... Removes noise power outside signal BW Lets the signal power through System Cable + Amp SNR at Antenna Input = SNR at Antenna Output = SNR at System Output = 43.67

SNR of Model Worsens Only considers input noise that is in the signal BW & can reach the output. Cable & electronics dump in more noise. System Cable + Amp SNR at antenna output = SNR at System Output = 43.67

Tracking Noise Power 1/2 ∑ 10 8 ∑ Cable Amp 12.42( ) 24.01( ) 36.43( ) 18.22( ) 96.29( ) 114.5( ) 114.5(10 -7 ) Output SNR = dB

Low Noise Amps

Tracking Noise Power 10 8 ∑ 1/2 ∑ Amp Cable 12.42( ) 96.29( ) 108.7( ) 108.7(10 -7 ) 24.01( ) 108.7(10 -7 ) 54.35(10 -7 ) Output SNR = dB

Design #1: Analog Satellite Relay n Specify Uplink & Downlink u Antenna Size u Ground Power Out u Satellite Power Gain etc. n "Bent Pipe" Configuration u Uplinked signal is amplified and broadcast back down u Advantage: Maximum Flexibility u Disadvantage: If Digital, Regen Outperforms

Noise Satellite & Earth Station antennas both pick up noise. Images from & wikipedia Design #1: Analog GEOS Relay Noise

There is noise in transmitted signal. Can ignore. Images from & wikipedia Design #1: Analog GEOS Relay Signal

Treat transmitter as noise free. Images from & wikipedia Design #1: Analog GEOS Relay Signal Noise

Pr at satellite may be similar in size to antenna noise. Images from & wikipedia Design #1: Analog GEOS Relay Signal Noise

Relayed Signal is not noise free. Track it! Sees Sat Power G, Transmit Ant. G, etc. Images from & wikipedia Design #1: Analog GEOS Relay Signal Noise

Design #1: Analog GEOS Relay Signal Noise ! Caution ! Check output SNR with Margin = 0 and your design Margin.

Use a Spread Sheet!!! n Can use again (with mods) on Design 2 n Tie in costs to design choices u Can see how changes affect cost n Get a system (any system) that works u Output power > 0.4 watt & SNR > 33 dB u Anything over the minimum is Margin!!! F System delivers 35 dB SNR? Increase Margin by 2 dB n Adjust parameters to reduce Costs u Get some of those extra credit points!

Grading n Real World RFP: u 1 team gets full credit u Everyone else gets a zero n Partial credit u Awarded on Quizzes & Tests u NOT AWARDED ON DESIGN PROJECTS! n Real world designs don't get partial credit u Either Work or They Don't n Double check your work!!! Use a spreadsheet

Multipath

Multipath (20 m antenna height)

Multipath (10 m antenna height)

Urban Ray Tracing

Effect of Ionosphere (f < 35 MHz) Line of Sight & Ground Wave

Ionosphere Multipath

"Cue Ball" Earth

Using Earth Contours

RF Link Equations... n are accurate for Line of Sight Far Field No Multipath n give a useful average for Line of Sight Far Field Multipath

RF Link Equations... n can give ball park results for No Line of Sight Far Field Multipath if path loss is increased n Radio Horizon is 4/3 Optical Horizon

Analog to Digital Conversion) Part 1... Sampler analog input x(t) discrete time output x s (t) transmitter side

Sampling n Ideal Sampler u Minimum Sampling Frequency > 2 * W abs n Real World Realizable Sampler u Unable to build brick wall filters u Must sample about 10% faster than 2*W abs n Output is discrete time u But contains info to reconstruct original n Voltage is still Continuous u Infinite Precision → Infinite # of bits/sample

Analog to Digital Conversion) Part 2... Sampler analog input x(t) discrete time signal x s (t) transmitter side Source Coder bit stream

Analog to Digital Conversion) Part 2... Analog Low Pass Filter estimate of analog input discrete time signal estimate receiver side Decoder bit stream