Administrative Stuff Lecture 2: Transceivers and...
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1 Amin Arbabian Jan M. Rabaey Lecture 2: Transceivers and Signal Modulation EE142 – Fall 2010 Introduction Aug. 30 th , 2010 2 Administrative Stuff HW 1 posted, due September 7 th , 5pm – Not as long as it looks, but start early! Lab sessions have started Siva’s OH (481 Cory Hall)- This week only: – Tuesday 10-11 am – Wednesday 2:30-3:30pm My OH: Tu 1-2pm, Th 2:30-3:30pm, 550 Cory Hall – Or by appointment (arbabian@eecs) Lecture notes available before each lecture – Will also have in-class notes uploaded after lectures – Most lecture material from Professor Niknejad 3 Modulation Involves two waveforms: – Modulating signal – Carrier wave (or just carrier) Alters the carrier wave with properties of the modulating waveform. The carrier carries the information. Reversible (Demodulation) Generally a CW carrier is modulated (also have pulse modulation) 4 Why Modulate? Ease of radiation – Antenna size ~ ଵ ி௨௬ ⁄ Overcome HW limitations – Fractional BW Frequency assignment Multiplexing Reduced noise and interference – Trade BW for SNR (e.g. early FM) 5 AM Modulation- Can’t get simpler than this! In AM modulation – ൌ ܣ 1 ݔ ݐcos ݐൌ ܣሺݐሻ cos ݐ– ܣሺݐሻ is the Envelope of the signal Spectrum of the signal – ൌ ଵ ଶ ܣ⁄ െ െ ଵ ଶ ܣ⁄ ߜെ ߜ 6 Time-Domain Waveform Modulation Index: ൌ ሺ௧ሻ ሺ௧ሻ ሺ௧ሻ ାሺ௧ሻ Carrier added to the signal (1+x(t)), is this efficient? What are the benefits? Overmodulated Signal From Clarke, Hess
Transcript of Administrative Stuff Lecture 2: Transceivers and...
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Amin ArbabianJan M. Rabaey
Lecture 2:Transceivers and Signal Modulation
EE142 – Fall 2010Introduction
Aug. 30th, 2010
2
Administrative Stuff
HW 1 posted, due September 7th, 5pm
– Not as long as it looks, but start early!
Lab sessions have started
Siva’s OH (481 Cory Hall)- This week only:
– Tuesday 10-11 am
– Wednesday 2:30-3:30pm
My OH: Tu 1-2pm, Th 2:30-3:30pm, 550 Cory Hall– Or by appointment (arbabian@eecs)
Lecture notes available before each lecture
– Will also have in-class notes uploaded after lectures
– Most lecture material from Professor Niknejad
3
Modulation
Involves two waveforms:– Modulating signal
– Carrier wave (or just carrier)
Alters the carrier wave with properties of the modulating waveform. The carrier carries the information.
Reversible (Demodulation)
Generally a CW carrier is modulated (also have pulse modulation)
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Why Modulate?
Ease of radiation– Antenna size ~ ⁄
Overcome HW limitations– Fractional BW
Frequency assignment
Multiplexing
Reduced noise and interference– Trade BW for SNR (e.g. early FM)
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AM Modulation- Can’t get simpler than this!
In AM modulation– 1 cos
cos– is the Envelope of the signal
Spectrum of the signal– ⁄⁄
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Time-Domain Waveform
Modulation Index:
Carrier added to the signal (1+x(t)), is this efficient? What are the benefits?
Overmodulated Signal
From Clarke, Hess
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Demodulation
Envelope Detector:
From Clarke, Hess
RC too large: Failure-to-Follow distortion
What if RC is too small?
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Other Amplitude Modulation Schemes
DSB Modulation: Removing the carrier tone:
– cos cos– Improves the power efficiency on transmitter
SSB: Removing one of the side-bands
– Improving the Spectral Efficiency
– Poor low frequency response
VSB: One sideband plus a trace of the other
– For practical transmission of signals with significant low frequency content (e.g. video)
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Phase/Frequency Modulation (“Exponential Modulation”)
“Linear” modulation schemes:– Modulated spectrum
translation of signal spectrum
– BW 2
In exponential modulation these will change. We have also an opportunity to trade BW for signal to noise ratio (Quality).
AM
FM
PM
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FM/PM Modulation
FM Modulation≡ .
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2
PM Modulation≡ ∆.
∆.
From: Communication Systems by Carlson
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Special Case: Narrowband FM Approximation
From: Communication Systems by Carlson 12
Simple FM Transmitter/Receiver
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Using Digital Signaling
On-Off Keying (OOK)
Binary-Shift Keying (BPSK)
Frequency-Shift Keying (FSK)
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A Modern Receiver
Digitize Signals
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A Superheterodyne Transmitter
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Received Signal Strength
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Impedance Matching
If we have a source with certain ‘internal’ impedance, what are the conditions for extracting the maximum power?
What is the maximum “available” power from the source?
Do we always need to match the impedances?
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Receiver Selectivity: Filtering
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Filtering in Receivers
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Transmitter Spectrum
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Frequency Synthesis
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Key EE142 TOPICS
Linear Time Invariant Circuits
Noise
Distortion
Linear Time Varying Circuits
Oscillator
Power Amplifiers
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Wideband and High-Frequency Amplifiers:Linear Time-Invariant Circuits (LTI)
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Noise
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Distortion
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Linear-Time Varying Circuits (LTV)
