Fundamentals of Waves, Signals, and Electromagnetic Spectrum

Understanding Waves and Signals

Fundamentals of Wave Propagation

A wave is a disturbance in movement, propagating from one point to another.

Mechanical waves are waves that propagate through a material medium.

Electromagnetic radiation is a combination of oscillating electric and magnetic fields, which propagate through space, carrying energy from one place to another. It spreads in a vacuum or space.

Key Signal and Wave Terminology

• Amplitude: The maximum displacement from the equilibrium position.
• Channel: The means by which information is transmitted.
• Decibel: A unit for measuring the relative intensity of a signal, such as power, voltage, etc.
• Frequency: Represents the number of complete cycles per unit time of an electrical signal. Measured in Hertz (Hz).
• Modulation: A process that uses a baseband signal to change any parameter of a higher-frequency carrier signal.
• Amplitude Modulation (AM): In this type of modulation, the parameter varied is the carrier amplitude.
• Frequency Modulation (FM): In this type of modulation, the parameter varied is the carrier frequency.
• Phase Modulation (PM): In this type of modulation, the parameter varied is the carrier phase.
• Period: The time required for a complete cycle of an electrical signal or event.
• Signal: Any event that implies certain information.
• Carrier Signal: A sinusoidal, high-frequency signal whose parameters (amplitude, frequency, phase) are usually varied in proportion to the baseband signal.
• Baseband Signal: The electrical signal obtained directly from the source of the message (without any modulation).
• Analog Signal: A signal whose waveform is continuous.
• Digital Signal: A signal whose waveform is discrete.
• Transducer: A device that converts one form of energy into an electrical signal.
• Wavelength: The length in meters between two consecutive crests or troughs of an electrical signal.

The Electromagnetic Spectrum

The electromagnetic spectrum is a range of waves, from those with longer wavelengths, such as radio waves, to those with shorter wavelengths, such as gamma rays.

Electromagnetic Frequency Bands

• VLF (Very Low Frequency): 10 kHz - 30 kHz — Long-range Radio
• LF (Low Frequency): 30 kHz - 300 kHz — Radio Navigation
• MF (Medium Frequency): 300 kHz - 3 MHz — Medium Wave Radio
• HF (High Frequency): 3 MHz - 30 MHz — Shortwave Radio
• VHF (Very High Frequency): 30 MHz - 300 MHz — Television, Radio
• UHF (Ultra High Frequency): 300 MHz - 3 GHz — Television, Radar
• SHF (Super High Frequency): 3 GHz - 30 GHz — Radar
• EHF (Extremely High Frequency): 30 GHz - 300 GHz — Radar

Signal Impairments and Characteristics

• Attenuation: A gradual decrease in the amplitude of a signal, or a reduction in its amplitude as it passes through a circuit or channel, often due to resistance, leaks, etc.
• Noise: Any unwanted power that contaminates the desired signal (e.g., thermal noise, electrical noise, interference, distortion).
• Interference: Any natural or artificial (man-made) disturbance in the reception of a signal, caused by unwanted signals.
• Signal-to-Noise Ratio (SNR): The ratio of desired signal power to noise power at a specific point and under specific conditions.