FCC Part 30 MMWave Signal Booster Case Study

By Senior RF Test Engineer Greg C.

An example of how to get a new product to market that doesn’t have existing regulatory rules.

Target Audience: OEMs of new devices, CTOs, Founders of Startups, Technical or Product Leads, Design Engineers, Compliance Managers, Hardware Managers, Project Managers. 

This article describes the process for working with the manufacturer and the FCC to determine the test and filing requirements for a new technology that does not have published FCC rules or guidance.

A manufacturer contacted Compliance Testing (CT) to assist them in certifying a signal booster operating at 28 GHz. The equipment was designed to receive 5G NR (New Radio) signals, boost the signal level and re-transmit the signals at 28 GHz.

On the surface this seemed like a fairly straight forward task, except for the fact that there were no approved rules for signal boosters operating in the newly defined Part 30 CFR (Code of Federal Regulations) which governs the frequency range that the manufacturer designed their equipment for. At the same time the manufacturer approached CT, the FCC released test guidance for Part 30 transmitters. This was good news, except that the guidance did not cover signal boosters. Therefore another path to FCC certification was required. What next? How can we get this OEM device to market?

The first step in the process was collecting enough information on the equipment in order to send an inquiry to the FCC thru the FCC process known as a KDB inquiry (Knowledge Database Inquiry). Compliance Testing worked with the manufacturer to collect the required information, and submitted a detailed KDB inquiry ASAP.

The FCC initially responded that signal boosters could not be certified under Part 30 and had no other resolution at that time. This, of course, was not the answer that our OEM wanted. Pressure was building to find the right approach, as the manufacturer was getting anxious to get their product certified and out on the market.

After a few months of follow up, the FCC contacted Compliance Testing and stated that they were reconsidering their position and requested that Compliance Testing submit a test plan for approval. CT utilized previous knowledge & experience working in the group that earlier developed the signal booster rules that the FCC put into force in 2014, and thus created and submited the requested test plan to the FCC. The FCC approved the test plan and provided a list of additional requirements for the compliance lab to follow in order to obtain approval. 

One of those requirements was almost a show stopper as it required CT to have Part 30 listed on the Scope of Accreditaion. Since Part 30 was a newly defined rule section, the compliance lab did not have Part 30 listed on the Scope of Accreditation. Adding a new rule section to a compliance lab’s scope requires an indepenent audit by an accreditation body to determine the capability and competency of the lab and staff to perform the required testing.

Part of the test requirements for testing a a 28 GHz device requires emission testing to be performed up to the 5^th harmonic or 110 GHz, which requires specialized test equipment in order to measure frequencies above 100 GHz. The additional equipment: external mixers, low noise pre-amplifiers and standard gain horn antennas that are used for mmWave testing also required the test lab to verify the equipment is working properly before using it for final compliance measurements.

Verifying this equipment requires test signals in the frequency range of 40 – 110 GHz. This is performed using a microwave signal generator from 12 – 18 GHz and a mmWave source module to multiply the frequency range up to 40 – 110 GHz. This signal is then used to verify operation of the external mixers and pre-amplifiers before they are used for the final compliance measurements.

Additional signal requirements for Part 30 mmWave testing is generating a 5G NR test signal at 28 GHz with 500 MHz BW, and 2 signals at 28 GHz with 100 MHz BW for OOBE ( Out of Band Emissions). The test equipment available to generate these test signals is very limited with only 1 or 2 choices currently on the market.

When performing radiated emission tests on mmWave equipment thare are a few additional challenges. As the frequency range increases so does the noise floor of the EMI receiver. Along with the increased noise floor level is the additional problem that the external mixer conversion loss and test cable insertion loss increases with frequency and contributes to the increased noise floor level. In order to counteract this increased mixer conversion and cable insertion loss a low noise pre-amp is added to the test set-up. The test engineer is required to record the raw emissions data and add all the correction factors in a spreadsheet to determine the final level of the emission.

After the compliance lab has completed all the required testing as defined in the test plan previously approved by the FCC, the final step is to submit the test report and documentation package to a TCB (Telecommunications Certification Body) for review. Part 30 is listed on the FCC KDB 388624 Pre-Approval Guidance (PAG) list which requires the TCB to submit a PAG so the FCC can approve the product for certification. This slows the issuance of the FCC Grant by the TCB while the FCC reviews the PAG for final approval. 

With the PAG approved by the FCC and the documentation package and test report approved by the TCB, the TCB issues a Grant of Certification and the manufacturer is allowed to market their product. 

Compliance Testing was able to successfully support the manufacturer through the entire process – FCC communication to accept the product type, test plan development, testing, PAG, and TCB Grant Issuance. 

Designing a new product for market? CT always recommends that you determine your product meet regulatory compliance rules before it enters production versus after. In order to save delays to market & unexpected expense, ask an engineer here today or call 1 (866) 311-3268.

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