Here at RF Exposure Lab, the KDB inquiry is a topic we’re often asked for clarification about. Although they’re not always required, KDB inquiries are not uncommon in the world of SAR testing. However, this is a fairly complicated subject that lacks sufficient explanation, so we’ve decided to take some time to explain the KDB inquiry process and how it affects manufacturers of wireless devices. 

What is SAR Testing?

Because KDB inquiries are connected to SAR testing, we need to explain what SAR testing is before getting into the details of a KDB inquiry.

SAR testing is conducted using models of the human head and body that are filled with liquid to mimic how radiofrequency (RF) is absorbed by your body’s tissues. Using these models, wireless devices are tested in ways that simulate how users would typically hold these devices. As they are being tested in various positions, the devices are operated at their highest power level in all the frequency bands in which they operate.

A good example of this would be a cell phone, which will be tested in multiple positions to imitate the way they are held by users, such as up to the side of the head. While the cell phone is placed in different positions, a robotic probe measures the electric field at specific locations within the head and torso model.

The data collected is then submitted to the FCC to prove that the device conforms to the FCC’s RF exposure guidelines. When a device is approved by the FCC it means that the data has proven that the device will not expose users to RF exposure levels that are higher than what FCC guidelines allow.

The Details of a KDB Inquiry

First of all, KDB stands for Knowledge Database. A KDB inquiry, or Knowledge Database inquiry, provides further information about testing devices that are subject to FCC rules. 

When attempting to prove compliance with FCC SAR guidelines, it’s required to use the methods specified in the FCC rules. For example, if the device you manufacture is a Part 15 device, you will be required to use the measurement methods set out in that section of the FCC rules.

However, other measurement procedures have been found acceptable by the FCC, such as those in accordance with Section 2.947, and may be used. In cases in which differing measurement procedures may be acceptable, a KDB inquiry may be necessary.

The FCC Office of Engineering and Technology (OET) published authorization procedures and measurement guidance in the form of Knowledge Database (KDB) publications. This guidance is meant to assist manufacturers and testing labs in efforts to follow FCC requirements. These publications do not constitute rules.

There are two types of KDB inquiry: public access and TCB access only. Public access inquiries typically request or provide FCC interpretation or clarification of rules and usually aren’t specific to a particular FCCID, filing, or device. KDBs can be the result of questions submitted in the form of an inquiry by a SAR compliance lab to get further guidance on how to test a specific device. 

What is the TCB Council?

The TCB Council is the Telecommunication Certification Body Council. This council is an accredited organization that has the authority to issue Grants of Certification stating compliance with FCC SAR regulations.  RF Exposure Lab is an associate member of the TCB Council.

Although TCBs have FCC authorization to certify wireless devices, some authorization functions still require oversight by the FCC, such as the new 6 GHz band for WiFi. Section 2.964 describes Pre-Approval Guidance (PAG) procedures for determining SAR compliance of devices for which FCC regulations are not completely developed. PAG procedures also allow authorization approval processes for applications that may not have existing FCC guidance. 

There are three classes of applications for which equipment authorization will be subject to PAG review.

• Devices subject to special conditions where authorization procedures require approval by the FCC before approval by a TCB.
• Devices that require pre-approval testing by the FCC through a sample submission before they can be approved by a TCB.
• Devices that have new or unique installation issues that are subject to FCC review before they can be approved by a TCB. 

When a KDB Inquiry is Necessary

In most cases, manufacturers or SAR testing labs are not required to submit a KDB inquiry before submitting an equipment authorization application to a TCB.  In other cases, published guidance may not be directly applicable to a specific device. In this case, the manufacturer or testing lab may need to seek further guidance from the FCC. When this is necessary, the manufacturer or testing lab will need to do the following before they can submit an equipment authorization application to a TCB:

• Submit a KDB inquiry that requests FCC guidance for the test methods and measurements that will be used to evaluate the device.
• Submission of separate KDB inquiries for different issues that require additional guidance.
• Continue the dialogue with the FCC through the KDB inquiry until all issues have been clarified and resolved.
• Once testing is complete, the application can be submitted to the TCB with the following information:
  • The KDB inquiry tracking number for each guidance given by the FCC.
  • A complete copy of each KDB inquiry correspondence.
  • Copies of all relevant attachments associated with each KDB inquiry.
  • A description of how the device meets the guidelines outlined in each KDB inquiry.
  • Documentation of how this guidance applies to the specific case and to the device that requires authorization.
• The application may still need to have PAG approval from the FCC prior to the TCB issuing the grant.

RF Exposure Lab is Here to Help!

As you can see, when a wireless device requires a KDB inquiry, the process can be very long and complicated. While manufacturers may be able to attempt to go through with this themselves, steps and requirements could easily be missed, prolonging the process of authorization. This could also lead to devices failing to be approved for public use. Working with an experienced SAR testing lab like RF Exposure Lab will help you successfully navigate the maze of a KDB inquiry and TCB approval, and ensure that your product is compliant.

At RF Exposure Lab, we go above and beyond to ensure our clients understand what testing is required for their products. Through our unique expertise and commitment to our clients, we guarantee accurate testing and results.

We offer testing services for a variety of wireless devices such as cell phones, wireless modems, laptops, tablets, modems, medical products, and much more. If you’re looking for SAR testing help provided with speed, accuracy, expertise, and integrity, contact us to get a quote for our services.