Antenna Test Range Basics and Types

This page covers antenna range basics and mentions antenna range types, which include near field and far field antenna test ranges. It also describes their functions, applications and benefits. As we know, an antenna is a device used as an electromagnetic (EM) transformer. It is used to send and receive EM Waves to/from the air.

Antenna measurements

Following are the parameters that need to be evaluated for an RF antenna:

• Input Impedance
• Frequency range
• Polarization
• Directivity
• Gain
• Radiation Efficiency
• Radiation Pattern

An antenna test range is required to test and measure the above-mentioned antenna parameters. The selection of an antenna test range depends on the following parameters:

• RF Antenna specifications as listed above
• Mechanical specifications of the antenna (e.g., size, volume, weight)
• Accuracy of antenna measurement to be done

Perfect antenna measurement depends on monitoring and controlling the following parameters, in addition to selecting the right antenna range as per need:

• Incident field phase variation
• Incident field amplitude variation
• Interference due to reflections

An antenna test range used for radiation pattern measurement consists of the following subsystems:

• Positioning and control: The AUT (Antenna Under Test) is installed on a positioner and tested in receiving mode. It is rotated using a control unit, and the pattern measurement is captured.
• Receiver: This is other equipment used for capturing the RF signal and used to vary different axes for measurement.
• Signal source: This is used to provide an RF signal for the remote AUT. It is fixed on the ground floor.
• Recording and processing: A positioner placed at the test antenna side is used for this purpose.

Antenna Range Types

Following are the types of antenna ranges:

• Outdoor far-field antenna range
• Indoor far-field test antenna range
• Compact antenna test range
• Near-field antenna range

Near-field Antenna Range

The figure-1 depicts a near-field antenna range. The distance or range from the antenna up to 2*D^2/λ is known as the near-field distance. Here, D is the aperture diameter of the AUT (Antenna Under Test), and λ is the operating wavelength.

These antenna test ranges are usually used to test antennas indoors in a small space. It uses a small RF probe on one side and the AUT on the other side. The distance or separation between the two is about 4 to 10 wavelengths long.

Either the RF probe is scanned and the AUT is kept fixed, or the AUT is moved and the RF probe is kept fixed during measurement. During the measurement, both amplitude and phase information are collected at discrete points as determined.

Based on the scanning method, there are three types of near-field methods: planar, cylindrical, and spherical.

Compact Antenna Test Range

The figure-2 depicts a compact antenna test range. This is a supplement to the traditional far-field antenna range. The testing carried out in the far-field can also be done in a compact antenna test range.

The advantage of such a test range is that testing is done in an indoor anechoic chamber. This avoids all weather and security-related concerns while testing. One can also avoid interference generated by other sources with the use of a shielding chamber. This facility is very convenient for R & D engineers due to its compact size.

Indoor Far-field Antenna Test Range

The figure-3 depicts an indoor far-field antenna test range. The distance or range from the antenna above 2*D^2/λ is known as the far-field range or distance. An anechoic chamber is used here.

There are three main entities in this antenna range: a receiver front end, a signal source, and a positioner. The Antenna Under Test (AUT) is located on the positioner. Polarization control is available with the source antenna.

A control room is connected to both ends of the antenna range using cables or links. As all the equipment is located indoors and an anechoic chamber is used, the test facility is known as an indoor far-field range.

Outdoor Far-field Antenna Range

The figure-4 depicts an outdoor far-field antenna range. The test system consists of a test antenna with a receiver front end and positioner, a source antenna, and an outdoor enclosure.

The outdoor enclosure protects the setup from weather and temperature effects. The receiver portion is remotely controlled using a control console. Both sides are fixed on a tower or supporting structure opposite each other.

Benefits of Antenna Range

An antenna range is a controlled testing environment used to measure and evaluate the performance of antennas. Following are some of the advantages of antenna range types.

1. Provides precise measurements of antenna parameters such as gain, radiation pattern, beamwidth and efficiency.
2. Helps in designing antennas for improved signal strength, reduced interference, and better network coverage.
3. Identifies and corrects issues like sidelobe interference and polarization mismatches to enhance overall system performance.
4. Helps manufacturers meet regulatory requirements (such as FCC, ETSI, and IEEE) before commercial deployment.
5. Suitable for Different Testing Environments which include anechoic chambers, open-field ranges and compact ranges, catering to diverse testing needs.

Applications

• Supports Aerospace and Defense Applications Ensures reliable communication for satellites, military radars, and aircraft by testing antenna capabilities in controlled conditions.
• Enables 5G and IoT Antenna Development Assists in testing and optimizing antennas for emerging technologies such as 5G, IoT, and mmWave communication.
• Facilitates R&D and Innovation Provides a dedicated environment for engineers and researchers to develop and validate new antenna designs efficiently.

Conclusion

Antenna range testing is crucial for ensuring the efficiency, reliability, and regulatory compliance of antenna systems. By providing precise performance measurements and reducing interference, antenna ranges contribute to the development of high quality antennas for modern communication networks. As technology evolves, these testing facilities will continue to be instrumental in enhancing connectivity and innovation across various industries.