A carrier frequency is a base electromagnetic wave that is modulated to transmit information in telecommunications and broadcasting systems.

Carrier Frequency

A carrier frequency is a fundamental electromagnetic wave used as the foundation for transmitting information in radio communication and telecommunications systems. It serves as the "vehicle" that carries modulated signals from transmitter to receiver.

Basic Principles

The carrier wave typically has these key characteristics:

Constant amplitude
Fixed frequency
Continuous sinusoidal waveform
Higher frequency than the information signal

When information needs to be transmitted, it is superimposed onto this carrier wave through a process called modulation. This creates variations in either the:

Amplitude (AM - Amplitude Modulation)
Frequency (FM - Frequency Modulation)
Phase (PM - Phase Modulation)

Applications

Broadcasting

AM radio: Carrier frequencies between 535-1605 kHz
FM radio: Carrier frequencies between 88-108 MHz
Television: Various bands from VHF to UHF

Telecommunications

Mobile phones use multiple carrier frequencies
Satellite communication systems
Digital broadcasting systems

Selection Criteria

Several factors influence carrier frequency selection:

Required transmission distance
Available bandwidth
Signal propagation characteristics
Regulatory requirements
Interference considerations

Technical Considerations

The carrier frequency must be significantly higher than the frequency of the information signal to ensure effective signal processing. This relationship is known as the modulation index.

Advantages of Higher Frequencies

Greater bandwidth capacity
Smaller antenna requirements
Better noise immunity

Disadvantages of Higher Frequencies

More expensive equipment
Greater signal attenuation
Line-of-sight limitations

Modern Developments

Contemporary systems often employ multiple carrier frequencies through techniques like:

These advanced approaches enable more efficient spectrum usage and improved communication reliability.