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Analog system modulation
This is a mind map about analog system modulation. The main contents include: anti-noise performance of linear modulation systems, modulation methods, functions and purposes, and definitions.
Edited at 2024-10-28 23:46:26- Fortpflanzungssystem
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Analog system modulation
- Fortpflanzungssystem
Diese Vorlage zeigt die Struktur und Funktion des Fortpflanzungssystems in Form einer Mind Map. Es führt die verschiedenen Komponenten der internen und externen Genitalien ein und sortiert das Wissen eindeutig aus, um Ihnen dabei zu helfen, mit den wichtigsten Wissenspunkten vertraut zu werden.
- Interpretation und Zusammenfassung des Beziehungsfeldes E-Book
Dies ist eine Mind Map über die Interpretation und Zusammenfassung des Beziehungsfeldes E-Book, des Hauptinhalts: Überblick über die Essenzinterpretation und Übersicht über das Feld E-Book. "Relationship Field" bezieht sich auf das komplexe zwischenmenschliche Netzwerk, in dem ein Individuum andere durch spezifische Verhaltensweisen und Einstellungen beeinflusst.
- Buchhaltungsbücher und Buchhaltungsunterlagen
Dies ist eine Mind Map über Buchhaltungsbücher und Buchhaltungsunterlagen.
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Analog system modulation
definition
Modulation is a process definition of converting a signal form into a form suitable for transmission in a channel.
baseband modulation
carrier modulation
Function and purpose
Improve emission efficiency
Improve channel utilization
Improve system anti-interference ability
Modulation method
Linear modulation (amplitude modulation)
Common amplitude modulation
AM, double sideband, single sideband, vestigial sideband
Amplitude Modulation (AM)
Spectrum
Carrier component, upper sideband, lower sideband
bandwidth
Twice the bandwidth of the baseband signal
total power
Carrier power
Does not carry information
sideband power
related to modulated signals
Modulation efficiency
The maximum value is 1/3
advantage
System structure is simple and low price
application
radio broadcast
double sideband modulation
Modulation efficiency
100%
Bandwidth is twice the bandwidth of the baseband signal
The envelope of the DSB signal is no longer consistent with the change pattern of the modulated signal, and simple envelope detection cannot be used to recover the modulated signal.
Using coherent demodulation, also known as synchronous detection
advantage
Saves carrier power
single sideband modulation
It is formed by filtering out one sideband of the double sideband signal.
Generation method
filter method
First generate a double-sideband signal, and then pass it through a sideband filter to filter out unwanted edges. bring
difficulty
Making sideband filters
The smaller the normalized value of the transition band relative to the carrier frequency, the more difficult it is to implement the sideband filter.
phase shift method
Using a phase shift network, the carrier and modulated signals are appropriately phase shifted so that one of the sidebands is canceled out during the synthesis process.
difficulty
Fabrication of Broadband Phase Shift Network
Using coherent demodulation, also known as synchronous detection
advantage
Save transmit power
The bandwidth is equal to the baseband signal bandwidth
vestigial sideband modulation
demodulation
coherent demodulation
Implemented by multiplying the carrier with the multiplication method
Suitable for demodulation of all linearly modulated signals
Incoherent demodulation (envelope detection)
composition
Half-wave or full-wave rectifiers and low-pass filters
Advantages
Simple, no need for carrier synchronization
For modulated signals that suppress the carrier, the insertion carrier envelope detection method can be used
Requirements: The amplitude of the inserted carrier wave should be much larger than the amplitude of the signal. It is also required that the inserted carrier wave and the modulated carrier wave have the same frequency and phase.
Nonlinear modulation (angle modulation)
Common angle modulation
Frequency modulation (FM), phase modulation (PM)
The difference between angle modulation and amplitude modulation is that the spectrum of the modulated signal is no longer a linear shift of the original modulated signal, but a nonlinear transformation of the spectrum, which will produce new frequency components that are different from the spectrum shift, so it is also called nonlinear modulation.
phase modulation
Refers to the linear change of the instantaneous phase with the modulation signal.
Frequency modulation
Refers to the instantaneous frequency offset that changes proportionally with the modulation signal
The relationship between FM and PM
If the modulated signal is first differentiated and then frequency modulated, the phase modulated wave will be obtained. This method is called indirect phase modulation.
If the modulated signal is first integrated and then phase modulated, the result is an FM wave. This method is called indirect FM.
Noise immunity performance of linear modulation systems
The system gain of the DSB modulation system is 2, that is to say, the demodulator of the DSB signal improves the signal-to-noise ratio by a factor of 1
The system gain of the SSB modulation system is 1, but the anti-noise performance of SSB is the same as that of DSB, and the transmission bandwidth of SSB is only 1/2 of DSB
The anti-noise performance of VSB is approximately the same as that of the SSB modulation system.
AM anti-noise
Large signal-to-noise ratio situation
Small signal-to-noise ratio situation