Basics of Radio Frequency (RF) and Wireless Communication Systems

Radio frequency (RF) is any frequency within the electromagnetic spectrum associated with radio-wave propagation. When an RF current (input signal) is supplied to an antenna, an electromagnetic field is created that is then able to propagate through the space.

RF field propagation technology is used in many wireless technologies like:

1. Remote Sensing:

• Telemetry
• Tracking
• Weather forecast

2. Personal Communication Systems:

-Bluetooth

-Wireless LAN

-Wireless local loop

-Wireless application protocol

3. Fixed and mobile satellite

4. Microwave RF System

The Emerging Wireless technology

RF is similar to wireless and high-frequency signals however, RF has frequencies ranging from a few kHz to roughly 1 GHz. This range extends to 300 GHz by considering microwave frequencies as radio frequency.

Many wireless devices make use of RF fields, e.g. satellite communication systems, cordless and cellular telephone, radio and television broadcast stations, all operate in the RF spectrum. Some wireless devices operate infrared (IR) or visible light frequencies, whose electromagnetic wavelengths are shorter than those of RF fields.

You can also read: Microwave tubes

Wireless Communication

Wireless communication maybe defined as the transfer of information over a distance without the use of electrical conductors or wires. The distance for wireless communication maybe small or large depending on the distance of communication e.g. a television remote requires a short distance whereas radio communications requires a longer distance and maybe thousands of kilometres long.

Wide bandwidths, large signal dynamics and high carrier frequencies are applied in wireless communication system in order to fulfil the demand for high data rates.

High frequencies are always desired in RF based wireless communication because high frequencies include efficiency in propagation, immunity to some forms of noise and impairments as well as the size of the antennae required. The height of the antennae is determined on the basis of the wavelength of the signal and is usually selected as one fourth of the wavelength of the signal.

During transmission of the signal, there are always some losses due to spreading of the RF energy as it propagates through the free space. This space loss can be represented as:

Where,

Pt is the power of transmitter antenna

Pr is the power of receiving antenna

R is the distance between the antennas

The main reasons of using high frequencies in communication systems is to reduce the antenna size, increase efficiency in propagation and improve the signal-to-noise ratio.

According to this formula:

As the frequency and wavelength are inversely proportional, we require high frequencies to reduce the antenna size.