Power density is an increasingly important part of our technology-reliant world. It will only become more important as more technology relies on high frequencies, requiring power density as part of compliance testing. However, the high frequencies of millimeter wave devices make proving compliance more complicated than for lower frequency devices, requiring the use of power density. To learn more about the role that power density plays in RF testing for wireless devices, keep reading.

What is Power Density?

The definition of power density is “the product of an isotropic antenna’s power density and its gain, usually calculated in mW/cm2.” It measures the amount of power that can be processed in a certain space or area. When systems are described as having high power densities, they’re able to output large amounts of energy based on their volume. 

Wireless devices benefit from power density because it improves their efficiency by allowing them to process more power with less space while improving the functionality of their systems. However, power density improvements have limitations, such as in improving conduction losses, turn-on and turn-off losses, reverse-recovery losses, charge-related losses, and thermal issues.

How Power Density is Used

When high frequencies like millimeter waves are involved, the most common way to measure how much radiofrequency (RF) humans are exposed to is in terms of incident power densities, also known as the free space Poynting vector. 

Higher frequencies require larger electrical sizes for mobile terminals, which in turn requires longer testing times to determine power densities in the proximity of devices through traditional scanning. A newer approach used to determine power densities uses standard near-field measurements and processing to determine the inverse source method. Compared to other methods, this is faster and simpler, making it ideal for RF testing. It also uses near field-far field transformation to determine power densities.

Power Density Testing for Millimeter Wave Devices

But why is power density an important part of testing for millimeter wave devices? It’s used to accurately determine the compliance of a device with SAR and RF regulations. Specific absorption rate (SAR) is a measurement used to explain the amount of RF energy that is absorbed by human tissue per mass unit. However, millimeter wave frequencies complicate this testing because affected skin depth decreases with higher frequencies, making it difficult to measure SAR using traditional methods.

It’s recommended that high-frequency devices be evaluated using power density in order to express measurements per unit area for near-field RF exposure, rather than by unit mass in SAR.

When conducting testing for millimeter wave devices, the phantom used is able to approximate free-space conditions and allows devices to be evaluated not just on the antenna side of the device, but on any opposite-radiating side of the device as well. According to regulations set out in IEC/IEEE 63195, magnitudes and phases of E-field and H-field are necessary to accurately measure power density. 

Get Testing for Millimeter Wave Devices at RF Exposure Lab

Testing high-frequency devices presents new challenges that require expertise from an RF exposure lab that is always up-to-date on testing methods for new technologies.

When you’re in need of RF testing for a project, come to the experts here at RF Exposure Lab. The importance of working with an experienced, A2LA accredited testing lab can’t be overstated. Working with an experienced RF testing lab as early as possible in the manufacturing process will help you successfully get through the maze of regulations and ensure that your product is compliant.

We offer RF exposure testing services for a variety of wireless devices, such as

• Millimeter wave devices
• Near field charging devices
• Cell phones, laptops, and tablets
• Medical devices
• Modems

As well as many more devices! If you’re looking for RF exposure testing help that is provided with expertise, speed, accuracy, and integrity, contact us to learn more about our services or to get a quote.