Phasor Analysis of Bandpass Signals Background: Phasors for Monochromatic Signals 1
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- Slide 1
- Phasor Analysis of Bandpass Signals Background: Phasors for
Monochromatic Signals 1
- Slide 2
- Phasor Analysis of Bandpass Signals Narrowband Signals: Define:
2
- Slide 3
- Narrowband Signals: Continued 3
- Slide 4
- Phasor Equivalent for Narrowband 4
- Slide 5
- Transmitting Bandpass Signals through Bandpass Systems 5
- Slide 6
- Amplitude Modulation ECE460 Spring, 2012
- Slide 7
- Analog Modulation Techniques Modulation: The process by which
some characteristic of a carrier wave is varied in accordance with
an information-bearing signal Amplitude modulation 1.Amplitude
modulation (AM) 2.Double sideband-suppressed carrier (DSB-SC)
3.Single sideband (SSB) 4.Vestigial sideband (VSB) 7
- Slide 8
- Amplitude Modulation (AM) AM is formally defined as a process
in which the amplitude of the carrier wave c(t) is varied about a
mean value linearly with a message signal m(t). Message Signal:
Sinusoidal Carrier: AM Wave: 8
- Slide 9
- Amplitude Modulation 9
- Slide 10
- Frequency Domain Message signal: Band-limited to W AM wave:
Time Domain: Frequency Domain: 10
- Slide 11
- 11
- Slide 12
- Example Message signal AM Wave Time Domain: Frequency Domain:
12
- Slide 13
- Varying m 13
- Slide 14
- Envelope Detection 14
- Slide 15
- Conclusions on AM Power Channel Bandwidth Complexity 15
- Slide 16
- Double Sideband-Suppressed Carrier Modulation (DSB-SC) Message
signal: Carrier Wave: Transmit Signal: 16
- Slide 17
- Why Coherent Detection? 17 Local Oscillator Product modulator
Low-pass filter
- Slide 18
- Costas Receiver 18 Voltage Controlled Oscillator Product
modulator Low-pass filter Product modulator Low-pass filter -90
Phase Shifter Phase discriminator
- Slide 19
- Conclusions on DSB-SC Power Channel Bandwidth Complexity
19
- Slide 20
- Single Modulation (SSB) 1.Creating an SSB signal via a Hilbert
Transform 2.Filtering a DSB SC signal 20
- Slide 21
- Filtering DSB-SC signal for SSB DSB-SC Signal: Filter: 21
- Slide 22
- Find SSB Transmission Signal Message Signal: Begin by finding
22
- Slide 23
- Demodulation of an SSB signal Requires a phase coherent
demodulator like a DSB-SC demodulation Low-pass filtering leaves:
23
- Slide 24
- Conclusions on SSB Power Channel Bandwidth Complexity 24
- Slide 25
- Vestigial Sideband Modulation Compromise between DSB-SC and
SSB: Keeps a trace, or vestige, of the other sideband A portion of
the other sideband is transmitted Transmitted Signal: Received
Signal: 25
- Slide 26
- Vestigial Sideband Filter 26