What's the best way to measure an antenna's radiation pattern?

During my career, I've designed and worked on far-field antenna ranges. Setting up a far-field range is straightforward, assuming you have the budget for the required equipment and access to the space. One of the most critical aspects of assuring accurate pattern measurements with a far-field range is to minimize reflections on the range. There are methods to measure the reflections by measuring variations in signal field strength to ensure a uniform plane wave. It is critical to make these measurements and then make any needed range modifications, such as the addition of diffraction fences, where necessary.

Measuring an antenna's radiation pattern involves: 1. Environment: Use an anechoic chamber or open space to avoid reflections. 2. Equipment: Employ a network or spectrum analyzer, a rotator, and a reference antenna. 3. Setup: Place antennas at a distance to ensure far-field conditions. 4. Measurement: Rotate the antenna to record radiation at various angles. Perform a frequency sweep if needed. 5. Data Analysis: Analyze measurements to plot the radiation pattern, showing signal strength variation with direction. 6. Environmental Factors: Account for temperature and humidity. 7. Repeat for Accuracy: Conduct multiple measurements and average results for precision.

Si la distancia entre puntos va a depender de la topografía del terreno para que sea una línea de vista óptima y la se?al no sufra ninguna distorsión

That's a broad question. Depends on antenna type, range, frequency/wavelength, power on TX end, and sensitivity on the RX end. But the setups will need signal generator(s). spectrum analyzer, no budget constraints, vector analyzer, various mixers, waveguides, audio meter, power meter, PIM analyzer (maybe), near and far field probes, and ferrites of various geometry. Technically it is extremely complex and should not be tried at home!

Types of Near-Field Scanning: There are three primary types of near-field scanning techniques: Planar Scanning: The probe moves in a planar pattern, suitable for antennas with a relatively flat radiation pattern. Cylindrical Scanning: The probe moves in a cylindrical pattern around the AUT, ideal for antennas with elongated radiation patterns. Spherical Scanning: The probe moves in a spherical pattern, covering all possible angles around the AUT, which is the most comprehensive.

You can also do this manually and have the antenna connected to its transmitter as it will be on the field. Ensure that the signal being transmitted is consistent. Have a receiver and either move the receiver around the antenna or rotate the antenna. Be careful about possible reflections.

To measure an antenna's radiation pattern, the most common and effective method is to use an anechoic chamber and a network analyzer

Getting a true reading of all the parameters. This is often the case when only 1 or 2 KPIs are tested. Today's devices are used in the mobile industry because they can test not only power, receive levels, but also talk back and throughput along with dropped data rates. That's been an issue for some time where people only look at RF coverage and not actual data throughput in that coverage. It can be a challenge, btu the more data you have the better off you are.

To measure an antenna's radiation pattern effectively, a setup with two antennas is essential—one being the antenna under test (AUT), and the other a secondary antenna. The process involves rotating the receiving antenna stand in 10° steps from 0 to 360 degrees, noting the power readings. After completing a full rotation, the antenna returns to 0°. This procedure is then repeated for the radiation pattern in another plane (E-plane) by rotating both the transmitting (Tx) and receiving (Rx) antennas by 90°. The received power is meticulously recorded at each position, allowing for the accurate determination of the test antenna's radiation pattern magnitude.

When the antenna is designed to be integrated within a larger system, it is valuable to make sure any parts within close proximity of the antenna is present during the testing or the performances will probably be very different. This includes metal parts, batteries, wiring, screws, PCB... but also any plastics or covers. The materials dimensions should be close to the final design and be prepared with final surface finishes such as paint or coating. (some paint colors might contain ferrous materials for instances).

The biggest issue is the availability of an anechoic chamber, which will be costly especially for lower frequencies. Measurement on a flat field is possible, ideally with no metallic objects or other structures around. Do note that the type of ground and distance to ground will affect the radiation pattern.

To measure an antenna's radiation pattern, the most common and effective method is to use an anechoic chamber and a network analyzer. Anechoic Chamber: This is a room designed to completely absorb reflections of electromagnetic waves. It's used to simulate a free-space environment where external signals and reflections are minimized. Positioning the Antenna: The antenna under test (AUT) is placed on a non-reflective mount or stand. It's important that the mount doesn't interfere with the antenna's radiation pattern. Network Analyzer: This device is used to measure the transmitted and received signals. It can provide data on various parameters like return loss, VSWR (Voltage Standing Wave Ratio), and gain.

If someone wants to use an off the shelf system then you can use MegiQ Antenna RMS, this includes both software and measurement setup, you do not require and anechoic chamber, although as far as I can recall this is limited to 600 MHz to 6 GHz, for higher frequencies there are solution from Kyocera