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Chapter 2

Radio Frequency Fundamentals. Chapter 2. Outline. Define a Radio Frequency Signal Define and Describe the Following RF Characteristics Define and Describe the Following RF Behaviors. What Is an RF (Radio Frequency) Signal?.

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Chapter 2

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  1. Radio Frequency Fundamentals Chapter 2

  2. Outline • Define a Radio Frequency Signal • Define and Describe the Following RF Characteristics • Define and Describe the Following RF Behaviors

  3. What Is an RF (Radio Frequency) Signal? • RF signal starts out as an electrical alternating current (AC) signal • The shape and form of the AC signal – defined as the waveform – is what is known as a sine wave

  4. Radio Frequency Characteristics • In every RF signal exists characteristic that are defined by the laws of physics: • Polarity • Wavelength • Frequency • Amplitude • Phase

  5. Radio Frequency Characteristics • Polarity • The waves consist of two component fields: the electrical (E-field) and the H-field, which is magnetic.

  6. Radio Frequency Characteristics • Wavelength

  7. Radio Frequency Characteristics • Frequency • 1 hertz (Hz) = 1 cycle per second • 1 kilohertz (KHz) = 1,000 cycles per second • 1 megahertz (MHz) = 1,000,000 (million) cycles per second • 1 gigahertz (GHz) = 1,000,000,000 (billion) cycles per second • 2.4 GHz WLAN radio cards, the RF signal is oscillating 2.4 billion times per second!

  8. Radio Frequency Characteristics • Amplitude

  9. Radio Frequency Characteristics • Phase

  10. RF Behaviors • Wave Propagation • The way in which the RF waves move – known as wave propagation – can vary drastically depending on the materials in the signal’s path

  11. RF Behaviors • Absorption

  12. RF Behaviors • Reflection

  13. RF Behaviors • Scattering

  14. RF Behaviors • Refraction

  15. RF Behaviors • Diffraction

  16. RF Behaviors • Loss (Attenuation) • Loss, also known as attenuation, is best described as the decrease of amplitude or signal strength

  17. RF Behaviors • Free Space Path Loss • Due to the laws of physics, an electromagnetic signal will attenuate as it travels despite the lack of attenuation caused by obstructions, absorption, reflections, diffractions, and so on. • Free space path loss is the loss of signal strength caused by the natural broadening of the waves, often referred to beam divergence.

  18. RF Behaviors • Multipath • Multipath is a propagation phenomenon that results in two or more paths of a signal arriving at a receiving antenna at the same time or within nanoseconds of each other.

  19. RF Behaviors • Gain (Amplification) • Gain, also known as amplification , can best be described as the increase of amplitude or signal strength • Active gain is usually caused by the use of an amplifier on the wire that connects the transceiver to the antenna. The amplifier is usually bidirectional, meaning that it increases the AC voltage both inbound and outbound. Active gain devices require the use of an external power source. • Passive gain is accomplished by focusing the RF signal with the use of an antenna. Antennas are passive devices that do not require an external power source. Instead, the internal workings of an antenna focus the signal more powerfully in one direction than another.

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