FCC Testing Requirements – Unintentional Radiators

FCC CFR 47 Part 15 Subsection B
Test Requirements for Unintentional Radiators

In 1975 the FCC published new regulations as part of CFR 47 to protect radio and TV broadcast services. The new rules published as Part 15 covered a huge range of electronic devices. Control of conducted and radiated emissions were now required for all equipment that does not generate RF energy as part of its intended operation.

Over the intervening years leading up to today the FCC have added more and more subparts to address the continuing development of electronics systems. The CFR 47 part 15 rules were rewritten in 1989 as a consolidation exercise, becoming effective in 1992, and today’s FCC part 15 rules contain 8 subparts, subpart A to subpart H;

Subpart A – General (15.1 thru 15.38)

Subpart B – Unintentional Radiators (15.101 thru 15.124)

Subpart C – Intentional Radiators (15.201 thru 15.257)

Subpart D – Unlicensed Personal Communications Service Devices (15.301 thru 15.323)

Subpart E – Unlicensed National Information Infrastructure Devices (15.401 thru 15.407)

Subpart F – Ultra Wideband Operation (15.501 thru 15.525)

Subpart G – Access Broadband Over Power Line (15.601 thru 15.615)

Subpart H – Television Band Devices (15.701 thru 15.717)

Subpart A – General

Subpart A contains specific details that must be adhered with in order to ensure compliance. One of the very important rules (15.1) has the definitions for the common terms used in the compliance requirements. A sample of the definitions include;

? Digital device: “An unintentional radiator…that generates and uses timing signals or pulses with a frequency > 9 kHz, and uses digital techniques.” This applies to personal computers, peripherals, and other equipment using clocks and logic circuitry.

? Class A digital device: “A digital device marketed for use in a commercial, industrial, or business environment and not intended for use by the general public or in the home.”

? Class B digital device: “A digital device marketed for use in the home, although it could be used elsewhere.” Examples include calculators and personal computers.

? Incidental radiator: “A device that generates RF energy during the course of its operation but is not designed to do so intentionally, for example, DC motors and mechanical light switches.” (There are no specific technical requirements in Part 15 governing incidental radiators, other than the general one that they not cause interference. The EU, in contrast, imposes emissions standards for many incidental radiators.)

? Intentional radiator: “A device that intentionally generates and emits RF energy by radiation or induction.” If the RF energy performs work, it is a Part 18 device.

? Peripheral device: “An input/output unit of a system that feeds data into and/or receives data from the CPU of a digital device.” Peripherals to a digital device include the following:

o any external device connected to the digital device;

o any device internal to the digital device and connecting to an external device via wire or cable; and

o any plug-in circuit board, either internal or external, that increases the operating speed of the digital device. Examples of peripheral devices include printers, external (but not internal) floppy disk drives and other data-storage devices, video monitors and driver boards, and keyboards. CPU boards are not considered peripheral devices.

? RF energy: “Electromagnetic energy at any frequency in the radio spectrum between 9 kHz and 3000 GHz.” (Part 15 regulations cover up to only 231 GHz, if it’s any consolation.)

? Unintentional radiator: “A device that intentionally generates RF energy for use within the device…but which is not intended to emit RF energy by radiation or conduction.” Receivers and digital devices are examples of unintentional radiators.

Subpart A requires that a wide range of requirements are met in addition to the specific technical requirements for each of the devices covered in Part 15.

Labeling and user information are contained in 15.19 and 15.21.

Actual measurement standards are detailed in 15.31 thru 15.37, referring to the test standards and test methodology (ANSI C63.4 for unintentional Radiators) and directing manufacturers to the specific part of the Part 15 rules that must be satisfied (The technical requirements).

Unlike the European Union (EU) requirements, immunity is not a mandatory. A very broad statement in 15.17 advises manufacturers to design equipment so as to reduce the susceptibility for receiving harmful interference.

Subpart B – Unintentional Radiators

An extremely wide range of equipments that contain electronic circuitry with clocks and logic circuits are covered in this subpart. Anything from personal computers, PC peripherals, Television receivers, are examples of typical equipment that fall within the scope of this subpart.

Because of the nature of potential interfering signals that can be generated from the different devices, the applicable compliance route is determined in section 15.101. Various terms are used to describe the equipment authorization required;

Verficiation – is a procedure where the manufacturer makes measurements or takes the necessary steps to insure that the equipment complies with the appropriate technical standards. Submittal of a sample unit or representative data to the commission demonstrating compliance is not required unless specifically requested by the commission.

Declaration of Conformity – is a procedure where the responsible party makes measurements or takes other necessary steps to ensure that the equipment complies with the appropriate technical standards. Submittal of a sample unit or representative data to the commission demonstrating compliance is not required unless specifically requested by the commission.

Certification – is an equipment authorization issued by the commission based on representations and test data submitted by the applicant.

Of course not ALL equipment is covered by the scope of the FCC rules, Section 15.103 list the exemptions;

1. are used solely in any transportation vehicle such as a car or an airplane;

2. are used solely as an electronic control or power system by a public utility or in an industrial plant;

3. are used solely as industrial, commercial, or medical test equipment;

4. are used solely in a domestic or commercial appliance;

5. are used as specialized medical devices under the direction or supervision of a licensed healthcare practitioner;

6. have a power consumption of 6 nW or less; or

7. use or generate a frequency less than 1.705 MHz and are never connected to the AC line.

8. a joystick controller, mouse, or similar device that is used with a digital device but itself contains non-digital circuitry. Such devices are, for these purposes, regarded as passive add-ons.

Section 15.105 details instructions to the user that must be included in instruction manuals for Class A and Class B digital devices.

The Class A statement cautions that operation of the device in a residential area is likely to cause harmful interference

The Class B statement offers suggestions for minimizing interference to radio or TV receivers.

Measurement Limits are defined in sections 15.107 and section 15.109

Two levels of radiated and conducted emissions limits for unintentional radiators are specified in Subpart B, as they pertain to;

1) Class A digital devices

2) everything else. Products such as receivers and TV interface devices, because they are not Class A digital devices, must meet the lower Class B limits

F-Squared Laboratories is a full service product conformity assessment organization founded in 1992. We have three testing facilities strategically located in Maryland, North Carolina and Ohio. ?Our mission is to strive for total client satisfaction while maintaining the highest level of quality and integrity. ?We are accredited by the American Association for Laboratory Accreditation (A2LA). ?We are able to provide a variety of services, including testing/certification of products for the FCC, Industry Canada, European CE, Australian Communication Authority (ACA), North American/Canadian) Visit our website at: http://www.F2Labs.com

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