Glossary of antenna types and technical parameters - Protel Antennas - Professional Antennas for Telecomunications

How to use this glossary

This glossary explains the main antenna types and technical parameters that appear in PROTEL datasheets and technical documents. It is intended as a practical guide for engineers, system integrators, operators and infrastructure owners who work with professional antennas in transport, broadcast, mobile networks, tunnels and critical infrastructures.

Definitions are given in a general, application-oriented way, with particular attention to the use of PROTEL antennas in railway, highway and metro tunnels, along transport corridors and on professional telecommunication sites.

Main antenna types

Omnidirectional antennas

Omnidirectional antennas are designed to radiate (or receive) radio waves uniformly in the horizontal plane, creating a 360° pattern around the vertical axis. They are used when coverage is required in all directions around the antenna, for example in sites placed in the centre of an area, or along tracks and roads where many directions must be served at once. In PROTEL products, omnidirectional antennas can be used for PMR, TETRA, mobile, broadcast and measurement applications.

Ground-plane antennas

Ground-plane antennas are a class of omnidirectional antennas where a vertical radiator works above a set of radial elements that form a "ground plane". They offer a predictable vertical pattern and are often used for base stations, monitoring posts and measurement setups. PROTEL ground-plane antennas are available for fixed installations and as measurement versions with screw or quick plug-in elements.

Dipole antennas

A dipole antenna is composed of two conductive arms fed in the centre. It is a fundamental radiating element that can be used alone or combined in arrays. In PROTEL catalogues, single dipoles can be supplied as stand-alone antennas (often for VHF and UHF) or combined in stacked or phased arrays to obtain specific patterns and gains for broadcast, PMR, TETRA or DAB services.

Yagi antennas

Yagi antennas are directional arrays composed of a driven element (usually a dipole) plus one reflector and one or more directors. They provide significant gain and a narrow main lobe in a preferred direction, with reduced radiation in other directions. PROTEL yagi antennas are used for point-to-point links, corridor coverage along railways and highways, donor antennas for tunnel systems and directional sectors in many frequency bands from VHF up to microwave ranges.

Log-periodic antennas

Log-periodic antennas are broadband directional antennas composed of multiple elements of different lengths arranged along a boom. Their impedance and radiation pattern remain stable over a wide frequency range. PROTEL log-periodic antennas are used for monitoring, measurement, multi-band systems and tunnel or corridor coverage where a wide band of services must be supported with a single directional antenna.

Panel and sector antennas

Panel or sector antennas are directional antennas built as flat radiating panels. They are widely used in mobile, wireless and broadcast systems to form sectors with defined horizontal and vertical beamwidths. In PROTEL projects, panel antennas are often used for corridor coverage in tunnels and along tracks, as well as for donor and fill-in sectors on towers and masts.

Collinear antennas

Collinear antennas consist of multiple radiating sections stacked vertically and fed in phase, in order to increase gain in the horizontal plane while keeping an omnidirectional azimuth pattern. They are common in VHF and UHF PMR and broadcast applications when a higher gain omnidirectional antenna is needed.

Magnetic-mount antennas

Magnetic-mount antennas are omnidirectional or short radiators mounted on a magnetic base. They are used when the antenna must be temporarily installed on vehicles, measurement cars, metallic structures or test platforms. PROTEL magnetic antennas are particularly suitable for drive tests, interference hunting and coverage verification along railway, highway and metro lines.

Measurement antennas

Measurement antennas are designed to offer stable, repeatable behaviour over time, so that field measurements are reliable and comparable. PROTEL measurement antennas include ground-plane omnidirectional models, magnetic omnidirectional versions and directional log-periodic antennas, covering wide ranges such as 60-6000 MHz for EMC testing, spectrum monitoring and interference hunting.

Radiation pattern and beamwidth

Radiation pattern

The radiation pattern describes how an antenna radiates (or receives) energy in space. It is typically represented in one or more planes (horizontal, vertical, cuts through the main lobe) and shows the relative field strength as a function of direction. In directional antennas, the pattern has a main lobe pointing towards the desired direction and side lobes in other directions.

Horizontal and vertical beamwidth

Beamwidth is usually defined as the angular separation between the two directions where the radiated field drops to 50% of its maximum value (−3 dB points). Datasheets often specify:

• Horizontal beamwidth (H-plane): opening angle in the horizontal plane.
• Vertical beamwidth (E-plane): opening angle in the vertical plane.

In tunnel and corridor applications, horizontal and vertical beamwidths are critical to control coverage along the tunnel and to limit unwanted radiation outside the desired area.

Front-to-back ratio

The front-to-back ratio is the difference in level (usually in dB) between the maximum radiation in the forward direction and the radiation in the opposite direction. A high front-to-back ratio helps to reduce interference and unwanted coverage behind the antenna, which is especially important in corridor and tunnel systems.

Polarisation

Vertical and horizontal polarisation

Polarisation describes the orientation of the electric field vector of the radiated wave. The most common cases are:

• Vertical polarisation: electric field oriented vertically.
• Horizontal polarisation: electric field oriented horizontally.

Many PMR, TETRA, mobile and railway systems use vertical polarisation, while some broadcast and special services may use horizontal or mixed solutions.

Slant and cross polarisation

In some systems, especially mobile and multi-input multi-output (MIMO) systems, antennas use slant or cross polarisation:

• Slant polarisation: for example ±45° relative to vertical.
• Cross polarisation (X-pol): two polarisations (often ±45°) combined in the same antenna for diversity or MIMO purposes.

PROTEL antennas can be supplied in different polarisation configurations depending on project requirements, including corridor and tunnel coverage where specific polarisation is needed to match the system design.

Circular and elliptical polarisation

Some special antennas use circular or elliptical polarisation, where the electric field rotates with time. These solutions are less common in typical PROTEL projects, but may appear in particular measurement or broadcast applications.

Electrical parameters

Frequency range and operating bandwidth

The frequency range indicated in a datasheet defines the band where the antenna meets specified electrical performance (VSWR, gain, pattern). Within this range the antenna supports the services for which it has been designed, for example GSM-R, LTE, 5G NR, DAB, FM, TETRA or Wi-Fi.

Nominal impedance

The nominal impedance is the reference impedance for which the antenna is designed, typically 50 ohm in professional communication systems. Matching the antenna impedance to the feeder and equipment impedance is essential to minimise reflections and power loss.

VSWR (Voltage Standing Wave Ratio)

VSWR is a measure of how well the antenna is matched to the transmission line and system impedance. A VSWR close to 1:1 indicates very good matching. Higher values mean more reflected power. PROTEL datasheets specify a maximum VSWR over the declared frequency range.

Return loss

Return loss is another way of expressing the amount of reflected power at the antenna port, measured in dB. A higher return loss (for example −20 dB) corresponds to better matching. VSWR and return loss are directly related quantities; datasheets may specify one or both.

Gain

Antenna gain indicates how much the antenna concentrates radiated power in a given direction compared to a reference antenna. It is usually expressed in dBi (relative to an isotropic radiator) or in dBd (relative to a half-wave dipole). PROTEL datasheets state the gain values and the reference (dBi or dBd) used for each antenna family.

Max input power and power rating

Max input power indicates the highest RF power that can be continuously applied to the antenna under specified environmental conditions. It depends on mechanical construction, materials, connectors and internal design. In tunnel and corridor projects, power rating must be coordinated with combiners, filters and transmitters.

PIM (Passive Intermodulation)

Passive intermodulation (PIM) is the generation of unwanted intermodulation products due to non-linear behaviour in passive components such as antennas, connectors or cables. Low-PIM antennas are important in multi-operator and multi-carrier environments, especially in mobile, railway and tunnel systems where several high-power carriers share the same antenna or site.

Mechanical and environmental aspects

Radomes and flame-retardant fiberglass radomes

A radome is a protective cover that shields the radiating elements from weather and mechanical stress while minimally affecting the antenna pattern. PROTEL offers antennas with fiberglass radomes and flame-retardant fiberglass radomes specifically designed for railway, highway and metro tunnels and for other critical environments where fire behaviour and safety are a key requirement.

Mounting hardware and clamps

Mounting hardware (clamps, brackets, supports) allows the antenna to be fixed to masts, walls, tunnel structures or portals. Correct installation is essential to maintain the specified radiation pattern and to ensure mechanical stability under wind, vibration and other stresses. PROTEL supplies dedicated clamps and brackets for different antenna families, including solutions optimised for tunnel walls, ceilings, portals and trackside masts.

Mechanical tilt and alignment

Mechanical tilt is the physical inclination of the antenna relative to the vertical axis. It is used to adjust the vertical coverage, for example to illuminate a specific tunnel section, platform area or corridor along a railway or highway. Correct alignment (azimuth and tilt) is crucial to achieve the expected coverage and limit interference.

Wind load and mechanical robustness

Wind load is the force exerted by wind on the antenna and its mounting structure. Datasheets may provide indicative values to support mechanical design. PROTEL antennas are designed for long-term operation in harsh outdoor conditions, including high wind, ice and temperature variations, as well as demanding indoor environments such as tunnels and industrial sites.

Connectors and interface

RF connectors

The RF connector is the interface between the antenna and the feeder cable. Common types in PROTEL products include N-type connectors, 7/16 connectors and 4.3-10 connectors, in female configuration. The choice of connector depends on the frequency range, power level and system design.

Cable and feeder interface

The antenna must be connected to the system using suitable coaxial cables and accessories. Correct installation, high-quality connectors and proper weatherproofing are essential to maintain electrical performance over time, especially in outdoor, tunnel and corridor environments.

How this glossary supports PROTEL projects

Understanding antenna types and technical parameters is essential when selecting PROTEL antennas for real projects: railway and metro lines, highway and road tunnels, broadcast networks, mobile and multi-operator sites, industrial plants and critical infrastructures.

By using the same terminology as PROTEL datasheets, this glossary helps designers and end users interpret specifications correctly, compare different antenna families and choose the most suitable solution for each site, tunnel section or corridor, in combination with filters, combiners and other RF components.