Components of RF Communications

Robert J. Ditzig
WiFiFundamentals

Transmitter

Responsible for determining and generating an AC signal that oscillates on the frequency (2.4 GHz, 5 GHz or 6 GHz) of the operating radio wave. This is done by using a modulation technique to encode the data into the signal. This modulated AC signal now becomes a carrier signal, containing (or carrying) the data to be transmitted through an (cable) to the antenna. The transmitter is also tasked with ascertaining the initial transmission's amplitude, commonly known as its power level. Greater wave amplitude corresponds to increased wave power and a greater reception distance. Transmitter power levels are are determined by local authorities, (e.g. FCC in US).

Antenna

Provides two functions in a communication system:

  1. When connected to the transmitter, it collects the AC signal that it receives from the transmitter and directs, or radiates, the RF waves away from the antenna in a pattern specific to the antenna type.
  2. When connected to the receiver, the antenna takes the RF waves that it receives through the air and directs the AC signal to the receiver. The receiver converts the AC signal to bits and bytes.

The RF transmission of an antenna is usually compared or referenced to as an isotropic radiator. An isotropic radiator is a point source that radiates signal equally in all directions.

Two ways to increase the power output from an antenna:

  • Generate more power at the transmitter
  • Direct, or focus, the RF signal that is radiating from the antenna

Receiver

Is the final component in the wireless medium, it takes the carrier signal received from the antenna and translates the modulated signal into 1s and 0s and then passes them on to the computer. The receiver has the difficult task of dealing with a weaker signal than generated, due to loss, interference, multipath and other RF sources.

Intentional radiator (IR)

Defined by FCC (CFR) part 15 as “a device that intentionally generates and emits radio frequency energy by radiation or induction.” The IR includes all the components from the transmitter to the antenna, excluding the antenna itself, the power output of the IR is the sum of these components. The IR is generally measured in milliwatts (mW) at the last point before the antenna attaches.

Equivalent isotropically radiated power (EIRP)

Is the highest RF signal strength that is transmitted from a particular antenna. It represents the total power output of the antenna, taking into account both the power supplied to the antenna and the antenna gain in a given direction relative to an isotropic antenna. EIRP is an important measurement in wireless communication systems as it determines the effective range and coverage of the antenna. It is regulated by regulatory bodies, such as the FCC, to ensure that the transmitted power does not exceed certain limits.