Modern wireless equipment relies on a high level of performance of the antenna to ensure constant communications, precise data transmission, and general durability of the equipment. Since products are incorporating Bluetooth, WiFi, GPS, 5G modules and many RF systems in compact formulations, engineers must still make sure that the antennas are effective and are not emitting unnecessary noise. In this regard, the EMC tester is an essential tool in the evaluation and validation of the antenna behaviour in the case of radiated emission test.
As radiated emissions have a direct influence on the quality of wireless and compliance with the regulations, it is worthwhile to know how, what, and how are measured when evaluating antenna behavior.

Understanding Radiated Emissions

Radiated emissions are due to inadvertent electronic circuit electromagnetic emissions. The noise level radiated by a device is emitted when there is a device operating, switching power, logic and high frequency oscillator, and communication modules. Antennas in their turn may unwillingly work as effective emitters of this noise. The even PCB traces, cables or mechanical structures can act as antennas at particular frequencies and enhance unwanted emissions.
Here the radiated emission test comes into play. It measures electromagnetic energy emitted by the device being tested and makes a check to ensure that the emissions do not exceed the legal permissible limit stipulated under some standard like CISPR, FCC Part 15, and IEC 61000. These limits help in keeping other electronic products off the interference and in a way that the product will not affect the neighboring communication systems.
Antennas are considered as both communication and possible pathways of the radiation of noise and so it is important to assess their performance when subjected to the emission tests. EMC tester is the key tool that assists engineers to detect, interpret and fix issues which arise as a result of antenna behavior.

How an EMC Tester Supports Antenna Performance Analysis

EMC tester reads and records the electromagnetic energy emitted by a device. When validating the antennas, the tester monitors the peaks of the frequencies, makes a comparison of the readings with the regulation and gives highlighted frequencies where the antenna performance will also cause high noise.

Precise Measurement of Emission Peaks

The antenna structures are known to resonate with certain frequencies. These peaks are accurately measured on the EMC tester and the engineers can locate which frequencies are contributing towards the level of emission and also study the contribution made by the antenna to the level of emission.

Evaluation of Polarization and Orientation

Due to the varying radiation of the antennas in relation to the orientation, the device will have to be rotated and experimented on both vertical and horizontal polarity. These orientations are recorded by the EMC tester and are used to identify which antenna forms the source of an increase in the peaks.

Support for Standardized Measurement Bandwidths

The standards of compliance outline rigid bandwidth measures of radiated tests. These bandwidths are followed by professional EMC testers and in the process, antenna radiation patterns and unwanted emissions are measured under appropriate conditions. This assists the engineers in having confidence in the data in analyzing problems with the antennas.
The LISUN equipment commonly comes with automated scanning, recording of data, and frequency marking features in laboratories. ECU testers are used as a part of an emission analysis system when linked to calibrated antennas, turntables, and LISUN automation software. This enables engineers to correlate directly the patterns of the antennas and the results of the emissions.

Importance of Antenna Evaluation During Radiated Emission Testing

The antennas are not merely the receiving and transmitting parts. They are capable of accidental internal digital noise. Their size, shape, orientation, and position have a great impact on the level of emission. E.g. minimal variations in antenna alignment or the structure of a ground plane can give emission peaks at harmonic frequencies within sensitive regulatory bands.
Radiated emission test detects these problems in the initial stages of certification. In case there is a noise emitted by the antenna, the EMC tester will show high peaks at set frequencies which are not supposed to be there. Corrective measures can then be made by the engineers like ground plane redesign, shielding, modifying RF circuits, or filtering of the connected circuitry.
When antennas are included in small devices, e.g., smartphones or IoT modules, there is always a risk that there are several components with common ground and power structures. EMC testers assist in separating desired transmission and unwanted radiation and it is easier to analyze the actual behavior of an antenna.

Key Measurements Performed with EMC Testers

In radiated emissions test, there are a number of measurements which are critical to understand the behavior of the antennas. Each testing offers valuable clues on the movement of noise and the response of antenna designs as well as the minimization of emissions.

Frequency Range Scanning

The EMC tester imaging has a large frequency range, typically 30 MHz to several gigahertz. During this scan, the peaks that are associated with the antenna resonance or internal switching noise can be seen. These readings help engineers where to make improvements on the design.

Harmonic and Subharmonic Identification

Antenna structures can accidentally increase the second, third or higher order of internal oscillators. Determination of these harmonics is significant to equipment with switching power sources of high frequency or devices with high-speed data communications.

Correlation With Antenna Gain

High gain antennas may unwillingly release additional unwanted noise. EMC testers assist in correlations between the antenna gain properties with the emission peaks that gives an engineer a more in-depth view of the effect of performance on the compliance of antennas.

Common Causes of Antenna Related Radiated Emission Failures

There are a number of design problems that may result in the radiations of noise through antennas when performing EMC assessments. Others are improper design of ground plane, inadequate control of return path, excessive PCB trace radiator, inadequate shielding of noisy circuits and asymmetrical antenna feedlines.
Internal cables that are long like those found in a device can act as antennas and raise the chances of failing to pass a radiated emission test. Noise may also be radiated at antennas that are too near switching power supplies or high-speed digital circuits. Only an EMC tester can be used to diagnose these problems properly measuring noise distribution across the frequency spectrum.
Failure due to harmonics caused by microcontrollers, oscillators and RF modules is also faced by engineers. When these harmonics are at the resonant frequencies of the antenna the emissions are magnified. The EMC tester assists in eliminating these interactions and indicates the necessity of changing the structure of the antenna.

Strategies to Improve Antenna Compliance Using EMC Testers

Before analysis of test results analyses, engineers adopt various measures to specify the reduction of antenna related emissions. Optimization of ground plane geometry is one of the most effective. Zero and symmetric ground planes allow the unwanted radiations of feedlines and signal paths to be minimized.
Interference can be minimized by adding shields to the components that are noisy or with conductive enclosures. The amount of noise that reaches the antenna can also be reduced using filtering circuits, ferrites and chokes.
In certain cases, emission problems are solved by adjusting the position of the antenna or by tuning. Peak emissions can be reduced by small adjustments of antenna length, antenna placement or matching networks. The EMC tester is used to substantiate these changes through providing real time feedback to test cycles.

Conclusion

In a radiated emission test, the EMC tester is critical in testing the performance of antennas. With high accuracy measurements of emissions, finding resonance related noise, and comparing the behavior of antennas with the regulatory limits, the tester assists engineers in developing stable and standard wireless products. With the increased complexity and integration of antennas the capability to analyze- interpret pattern of emission using the aid of professional equipment like the one provided by LISUN is becoming more important. Knowing the skill of using EMC testers also guarantees that the design of an antenna is carried out as per international standards and the electronic appliances used in carrying out its functions do not cause unwanted interference.

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