Radio Electronics

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Antennas

The antenna is a key component of any equipment that uses radio or is an electrical device that emits and/or receives radio waves. It is typically used with a radio transmitter or a radio receiver. A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing.

In transmission, the radio transmitter supplies an oscillating radio frequency electric current to the antenna's terminals, and the antenna radiates the energy from the current as radio waves.

In reception, the antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.[1]

Antenna Parameters

Gain

The gain is the ratio of the power gain in a particular direction relative to that of an ideal isotropic antenna.

Isotropic Antenna

The isotropic antenna is an ideal, theoretical antenna that radiates the same amount of power in all directions, in a 3D space. This theoretical type of antenna is used as a reference for measuring the gain.

Front-to-back Ratio

Front to back radio describes the ratio between the peak gain in the front of the antenna to the 180° gain behind the antenna.

Beamwidth

Beamwidth is the defined angle between the half power (-3 dB) points to the main lobe of radiation in a circular pattern; measured in degrees.

Antenna Types

For Coverage

The antennas used for ensuring coverage are of two types:

  • omnidirectional (omni)
  • sector

Omni antennas radiate power uniformly in all directions. The power drops with the elevation angle above or below the plane, reaching zero on the antenna's vertical axis.

Sector antennas radiate power on a particular sector of a circle. The antenna radiates a horizontal beam, shaped as a fan. These antennas have different designs, covering either 60°, 90° and 120° portions of a circle's circumference.

Omni vs 3sector.png

Note: All things being equal – antenna size, power level, operating frequencies – a 120° sector antenna will have 5 dB more gain than an omni antenna, yet the coverage area will be about the same in both antenna types.

For Backhaul

Backhaul antennas are used for increasing the capacity and the quality of service in a wireless network.

Amplifiers

An amplifier is an electronic device meant to increase a signal's power.

There are two main types of amplifiers that are essential in radio communications:

  • RF power amplifiers
  • Low-noise amplifier

The RF power amplifier (PA) has the role of boosting the power of a high frequency, high power signal.

Power amplifiers are used to increase voice and data signals that are sent or received through an antenna. PAs can be distinguished between themselves by three characteristics:

  • the operating range of frequencies
  • the gain they can achieve
  • the maximum output power they can deliver without distortion

To increase their efficiency, they must accomplish a number of conditions: to have a high output power compression, optimal head dissipation, good gain and good return loss on the input and output.

A low-noise amplifier (LNA) has the role of increasing very weak signals received by an antenna. It is typically installed very close to the antenna to be more efficient.

Duplexers

The duplexer is an electronic device meant to allow both the receiver and the transmitter to use the same antenna.

It does so by isolating the receiver from the transmitter.

A duplexer has a number of characteristics:

  • the range of frequencies on both its transmit and receive sides
  • the degree of isolation of the uplink and downlink
  • the amount of power going through it

Duplexers have two main roles: to eliminate any sideband noise coming from the transmitter on the receiving frequency and to attenuate the transmitter carrier, thus preventing the receiver to overload.

Tower Mounted Booster

A tower mounted booster (TMB) is a type of equipment used when deploying a network, meant to extend the signal coverage. A TMB will increase the downlink signal with its RF power amplifier and will boost the uplink signal with its low-noise amplifier.

Tower mounted boosters are installed right under the antenna to increase both the receiver sensitivity and the transmit power and prevent cable losses.

Tower Mounted Amplifier

A tower mounted amplifier (TMA) is a LNA mounted as close as possible to the antenna in mobile mast installations, and is meant to extend the signal coverage.

Tower mounted amplifiers increase the uplink sensitivity, improving the coverage and leading to the mobile to use less power when transmitting.

Software-Defined Radio

Software-defined radio is the "radio in which some or all the physical layer functions are software defined", according to a definition of the Wireless Innovation Forum in collaboration with Institute of Electrical and Electronic Engineers P1900.1 group[2]

To be more exact, it is the type of radio that implements as software components that are usually found as hardware: filters, modulators, demodulators, mixers etc. The implementation is done on a computer or an embedded system.

SDR was initially employed in the military, but it has become the most used technology in the radio communications field.

A basic SDR implementation is comprised of a computer, equipped with a type of analog-to-digital converter, as a sound card, and an RF front end.[3] Ultimately, this system produces a radio able to tune into different frequencies and receive and transmit a multitude of radio protocols via its software alone.

Through SDR, some of a typical radio's functions are implemented in easy to modify programmable processing technologies, such as: FPGAs, DSPs, SoCs etc.

Radio technology exists in a variety of common use objects such as: mobile phones, TVs, cars, computers etc. Before SDR it was difficult and expensive to bring modifications to traditional radio hardware. In the SDR era, modifications are done by simply performing software upgrading to wireless devices.

Basic Radio Design

Below is a simplified basic radio design diagram containing a digital radio transceiver, a control processor, a power amplifier, a low-noise amplifier, a duplexer and an antenna.

Basic radio design.png

Notes

  1. Wikipedia contributors. "Antenna (radio)". Wikipedia, The Free Encyclopedia; 2014 Mar 09, 10:39 UTC [cited 2014 Mar 20]. Available from: http://en.wikipedia.org/wiki/Antenna_%28radio%29
  2. The Wireless Innovation Forum. "What is Software Defined Radio?"; [cited 2014 Jul 07]. Available from: http://www.wirelessinnovation.org/Introduction_to_SDR
  3. Wikipedia contributors. "Software-defined radio". Wikipedia, The Free Encyclopedia; 2014 Jun 27, 00:07 UTC [cited 2014 Jul 07]. Available from: http://en.wikipedia.org/wiki/Software-defined_radio