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Questions and Answers
Digital modulation involves transmitting digitally modulated analog signals called ______ between points in a communication system.
Digital modulation involves transmitting digitally modulated analog signals called ______ between points in a communication system.
carriers
Traditional analog modulation systems such as AM, FM, and PM are being replaced by digital modulation systems due to their advantages in processing and ______.
Traditional analog modulation systems such as AM, FM, and PM are being replaced by digital modulation systems due to their advantages in processing and ______.
noise immunity
Digital transmission systems require a physical medium such as wire, cable, or ______ between the transmitter and receiver.
Digital transmission systems require a physical medium such as wire, cable, or ______ between the transmitter and receiver.
fiber optic cable
In Amplitude Shift Keying (ASK), the ______ of the carrier is varied in proportion to the information signal.
In Amplitude Shift Keying (ASK), the ______ of the carrier is varied in proportion to the information signal.
Frequency Shift Keying (FSK) varies the ______ of the carrier proportional to the information signal.
Frequency Shift Keying (FSK) varies the ______ of the carrier proportional to the information signal.
Both the amplitude and phase are varied in ______, which is a form of digital modulation.
Both the amplitude and phase are varied in ______, which is a form of digital modulation.
Digital microwave communications systems are one of the four common applications of ______.
Digital microwave communications systems are one of the four common applications of ______.
The precoder in a transmitter converts data levels and encodes incoming data into ______ that modulate an analog carrier.
The precoder in a transmitter converts data levels and encodes incoming data into ______ that modulate an analog carrier.
The transmitter begins with input data that is pre-processed by a ______.
The transmitter begins with input data that is pre-processed by a ______.
Information capacity is often expressed as a ______ rate.
Information capacity is often expressed as a ______ rate.
Hartley's law relates information capacity, bandwidth, and ______ time.
Hartley's law relates information capacity, bandwidth, and ______ time.
The signal at the receiver is filtered and then applied to a ______ and decoder circuit.
The signal at the receiver is filtered and then applied to a ______ and decoder circuit.
Critical components for the demodulation process include clock and carrier ______ circuits.
Critical components for the demodulation process include clock and carrier ______ circuits.
Flashcards
Digital Modulation
Digital Modulation
The process of transmitting digitally modulated analog signals (carriers) between points in a communication system.
Digital Radio
Digital Radio
A type of digital communication that uses high-frequency analog carriers modulated by low-frequency digital signals, allowing information to travel through the Earth's atmosphere.
Amplitude Shift Keying (ASK)
Amplitude Shift Keying (ASK)
The process of changing the amplitude of a carrier signal in proportion to the information signal.
Frequency Shift Keying (FSK)
Frequency Shift Keying (FSK)
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Phase Shift Keying (PSK)
Phase Shift Keying (PSK)
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Quadrature Amplitude Modulation (QAM)
Quadrature Amplitude Modulation (QAM)
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Precoder
Precoder
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Carrier Shaping
Carrier Shaping
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Information Theory
Information Theory
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Information Capacity
Information Capacity
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Bit (binary digit)
Bit (binary digit)
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Bit Rate
Bit Rate
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Hartley's Law
Hartley's Law
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Study Notes
Digital Modulation
- Electronic communications involves transmission, reception, and processing of information using electronic circuits.
- Information is defined as communicated knowledge or intelligence between points.
- Digital modulation transmits digitally modulated analog signals (carriers) in communication systems.
- Digital modulation is sometimes called digital radio because digitally modulated signals can travel through the atmosphere, enabling wireless communication.
- Traditional analog systems (AM, FM, PM) are being replaced by digital systems, offering advantages like ease of processing, multiplexing, and noise immunity.
- Digital communication has different meanings for various people. In this context, it includes high-frequency analog carriers modulated by low-frequency digital signals (digital radio) and digital pulse transmission systems.
- Digital transmission systems need a physical link (cable, wire, fiber optic) between transmitter and receiver. The link can be a metallic cable, optical fiber, or a combination of both, or it could be free space.
- Digital modulation differentiates from analog modulation in the nature of the modulating signal. Analog modulation systems use analog signals, whereas digital systems use digital signals.
- Digital signals can be computer-generated data or digitally encoded analog signals.
- Different forms of digital modulation include:
- Amplitude Shift Keying (ASK): Varying the amplitude of the carrier proportional to the information signal.
- Frequency Shift Keying (FSK): Varying the frequency of the carrier proportional to the information signal.
- Phase Shift Keying (PSK): Varying the phase of the carrier proportional to the information signal.
- Quadrature Amplitude Modulation (QAM): Varying both the amplitude and phase of the carrier proportionally to the information signal.
Applications of Digital Modulation
- Digital modulation suits various applications, including:
- Low-speed voice-band data communication modems (e.g., personal computers).
- High-speed data transmission systems (e.g., broadband DSL).
- Digital microwave and satellite communication systems.
- Cellular telephone systems (e.g., PCS).
- Cable and wireless systems.
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