Spring 2012 Signals and Systems Chapter SS-8 Communication Systems ShoushuiWei SDU-BME Sep08 Dec08 Figures and images used in these lecture notes are adopted from Signals & Systems by Alan V. Oppenheim and Alan S. Willsky, 1997 Introduction SDUBME-SS8-Comm-2 2 2 3 1.5 1 0.5 1.5 1 0.5 2 1 0 0 0-0.5-1 -1.5-0.5-1 -1.5-1 -2-2 0 5 10 15 20 25 30-2 0 5 10 15 20 25 30-3 0 5 10 15 20 25 30 2 3 3 1.5 1 0.5 0 2 1 0 2 1 0-0.5-1 -1.5-2 0 5 10 15 20 25 30-1 -2-3 0 5 10 15 20 25 30-1 -2-3 0 5 10 15 20 25 30 2 3 3 1.5 1 0.5 0 2 1 0 2 1 0-0.5-1 -1.5-2 0 5 10 15 20 25 30-1 -2-3 0 5 10 15 20 25 30-1 -2-3 0 5 10 15 20 25 30
Introduction SDUBME-SS8-Comm-3 Modulation & Demodulation: M:Embedding an information-bearing signal into a second signal D:Extracting the information-bearing signal Methods: > Amplitude Modulation (AM) > Frequency Modulation (FM) Multiplexing & Demultiplexing: Simultaneous transmission of more than one signal with overlapping spectra over the same channel Methods: > Time-Division Multiplexing (TDM) > Frequency-Division Multiplexing (FDM) Outline SDUBME-SS8-Comm-4 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-5 Signal Frequency Characteristics: 200 4K 100M 300M 40G 300G 2.4G Voice Signals f (Hz) Communication Satellite Microwave Link 802.11 & Bluetooth Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-6 AM with a Complex Exponential Carrier:
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-7 AM with a Complex Exponential Carrier: Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-8 AM with a Complex Exponential Carrier:
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-9 AM with Sinusoidal Carriers: Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-10 AM with a Sinusoidal Carrier:
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation AM with a Sinusoidal Carrier: SDUBME-SS8-Comm-11 Complex Exponential & Sinusoidal Amplitude Modulation SDUBME-SS8-Comm-12 Overlapping of AM with a Sinusoidal Carrier:
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-13 Not Synchronized in Phase: Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Not Synchronized in Phase: SDUBME-SS8-Comm-14
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-15 Asynchronous Demodulation: In audio transmission over a RF channel > w M : 15-20 Hz > w c /2π: 500kHz 2 MHz Envelope Detector: Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Asynchronous Demodulation: SDUBME-SS8-Comm-16
Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation SDUBME-SS8-Comm-17 Synchronous & Asynchronous Demodulation: Outline SDUBME-SS8-Comm-18 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation
Frequency-Division Multiplexing (FDM) SDUBME-SS8-Comm-19 FDM Using Sinusoidal AM: Frequency-Division Multiplexing (FDM) SDUBME-SS8-Comm-20 Demultiplexing and Demodulation:
Allocation of Frequencies in the RF Spectrum SDUBME-SS8-Comm-21 Feng-Li Lian 2004 Signals & Systems NTU-EE Outline SDUBME-SS8-Comm-22 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation
Single-Sideband Sinusoidal Amplitude Modulation SDUBME-SS8-Comm-23 SSB Modulation: Single-Sideband Sinusoidal Amplitude Modulation SDUBME-SS8-Comm-24 Retain Upper Sidebands Using Ideal Highpass Filter
Single-Sideband Sinusoidal Amplitude Modulation SDUBME-SS8-Comm-25 Retain Lower Sidebands Using Phase-Shift Network Retain Upper Sidebands Outline SDUBME-SS8-Comm-26 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation
Amplitude Modulation with a Pulse-Train Carrier SDUBME-SS8-Comm-27 Modulation of a Pulse-Train Carrier: Amplitude Modulation with a Pulse-Train Carrier SDUBME-SS8-Comm-28 Time-Division Multiplexing (TDM):
Outline SDUBME-SS8-Comm-29 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation Pulse-Amplitude Modulation SDUBME-SS8-Comm-30 Pulse-Amplitude Modulated Signals: TDM-PAM:
Pulse-Amplitude Modulation SDUBME-SS8-Comm-31 Intersymbol Interference in PAM Systems: Pulse-Amplitude Modulation SDUBME-SS8-Comm-32 Avoiding Intersymbol Interference in PAM Systems:
Pulse-Amplitude Modulation SDUBME-SS8-Comm-33 General Form of Band-Limited Pulses with Time-Domain Zero-Crossing at kt 1, k Z: Outline SDUBME-SS8-Comm-34 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation
Sinusoidal Frequency Modulation SDUBME-SS8-Comm-35 Frequency Modulation (FM): The modulating signals is used to control the frequency of a sinusoidal carrier With sinusoidal AM, the peak amplitude of the envelope of the carrier is directly dependent on the amplitude of the modulating signal x(t), which can have a large dynamic range. With FM, the envelope of the carrier is constant An FM transmitter can always operate at peak power and amplitude variations introduced over a transmission channel due to additive disturbances or fading can be eliminated at the receiver FM generally requires greater bandwidth than does sinusoidal AM Sinusoidal Frequency Modulation SDUBME-SS8-Comm-36 Angle Modulation: Phase Modulation: Use the modulating signal x(t) to vary the phase θ c Frequency Modulation: Use the modulating signal x(t) to vary the derivative of the angle
Sinusoidal Frequency Modulation SDUBME-SS8-Comm-37 Phase & Frequency Modulation: Sinusoidal Frequency Modulation SDUBME-SS8-Comm-38 Instantaneous Frequency: If y(t) is truly sinusoidal: Phase Modulation: Frequency Modulation:
Sinusoidal Frequency Modulation SDUBME-SS8-Comm-39 Narrowband FM: Frequency Modulation with Instantaneous Frequency: Sinusoidal Frequency Modulation SDUBME-SS8-Comm-40 Narrowband FM: Modulation Index for FM: Which m is small narrowband FM
Sinusoidal Frequency Modulation SDUBME-SS8-Comm-41 Narrowband FM: When m is sufficiently small (<< π/2) Sinusoidal Frequency Modulation SDUBME-SS8-Comm-42 Narrowband FM: Approximate spectrum for narrowband FM Narrowband FM AM-Double Sideband/with carrier
Sinusoidal Frequency Modulation SDUBME-SS8-Comm-43 Wideband FM: When m is large Periodic signals with fundamental frequency ω m Sinusoidal Frequency Modulation SDUBME-SS8-Comm-44 Magnitude of Spectrum of Wideband FM:
Sinusoidal Frequency Modulation SDUBME-SS8-Comm-45 Periodic Square-Wave Modulating Signal: Sinusoidal Frequency Modulation SDUBME-SS8-Comm-46
Outline SDUBME-SS8-Comm-47 Complex Exponential & Sinusoidal Amplitude Modulation & Demodulation Frequency-Division Multiplexing Single-Sideband Sinusoidal Amplitude Modulation Amplitude Modulation with a Pulse-Train Carrier Pulse-Amplitude Modulation Sinusoidal Frequency Modulation Discrete-Time Modulation Discrete-Time Modulation SDUBME-SS8-Comm-48 DT Sinusoidal AM:
Discrete-Time Modulation SDUBME-SS8-Comm-49 Transmodulation or Transmultiplexing: TDM to FDM