Global Markets: Low-Power Spread-Spectrum Transmitter Approvals

Andrew Cutler and Chris Zombolas
The option of local testing and other improvements are making
radio-frequency approvals easier worldwide.

The use of wireless devices has proliferated to an extent that microwave ovens and remote car alarms are now competing to use the part of the radio spectrum that has been their sole domain for many years. The information technology (IT) industry is leading the way with the introduction of many new products with protocols that use existing spread-spectrum technologies.

Wireless applications have the advantage that devices can be used without a physical connection between the remote device and the main server. Spread-spectrum technologies allow a single transmitter to interconnect a large number of devices with a minimum of interference. This allows greater flexibility and uses less hardware than a fixed wire network.

Bluetooth Transmitters

Leading the way in new protocols has been the introduction of Bluetooth technology. Bluetooth is a protocol that has been developed by a consortium of the larger IT players including Nokia, Microsoft, Hewlett-Packard, NEC, and Ericsson. Bluetooth technology enables many different devices to interact with each other by using a common protocol.

Progress to date has been slow, with a number of issues having to be overcome. The utilization of this technology now appears to be gaining momentum. Several manufacturers have developed specialized products that use the Bluetooth protocol, and many industry sources are predicting exponential growth in the use of wireless devices.

Most manufacturers and suppliers are aware of the electromagnetic compatibility (EMC) approval requirements for general electrical and electronic products, but the regulatory approval of wireless devices such as Bluetooth and other spread-spectrum devices is not so straightforward. In order to sell these specialized high-value products, various certifications are required by regulatory organizations.

Bluetooth Approvals

The radio-frequency (RF) characteristics of Bluetooth devices, which operate using frequency-hopping techniques, are tested in a manner similar to standard spread-spectrum devices.

All Bluetooth devices are required to exhibit identical protocol characteristics. Parameters such as dwell time, frequency range, and hopping sequences do not need to be measured every time certification is requested. For Bluetooth devices, the parameters do not change from device to device.

Before a company can legally use the Bluetooth name for a device, it must be qualified by a Bluetooth Qualification Authority. This qualification process is very involved and, as a result, is very expensive.

To make things easy for developers, Bluetooth-qualified chip sets have been produced that enable developers to use the Bluetooth protocol in wireless devices. Bluetooth devices use the 2.4–2.483-GHz ISM band. This band has been allocated for use in virtually every country in the world, but some countries such as Australia and New Zealand have additional
requirements.

United States

The Federal Communications Commission (FCC) requires that the RF parameters comply with FCC Part 15 rules, and several tests are necessary.

Bluetooth devices to be sold in the United States must be certified by FCC. The FCC certification process is relatively onerous. It should not be attempted by anyone unfamiliar with the vagaries of the FCC approval process, which can be bureaucratic, lengthy, and expensive. The business plan should not be based on a short time to market. The budget should account for FCC certification fees. The Telecommunications Certification Body (TCB) program has significantly improved the time to market and reduced many of the associated costs. In addition, FCC is playing its part, which has resulted in OET Docket 99–231. This has simplified the approvals process significantly by removing requirements such as processing gain.

Testing must be carried out by an FCC site-listed laboratory in accordance with FCC Part 15 Section 15.247. The speediest and least-expensive path to market is achieved by using a test house that is both FCC listed and accredited for FCC testing to the relevant parts of the FCC Part 15 rules. FCC and the TCBs prefer the use of laboratories that are accredited to test to the FCC Part 15 rules.

Canada

In a manner similar to that of the United States, devices to be sold in Canada must meet Industry Canada Standard RSS-102 and must be certified. In general, the FCC Part 15.247 report may be used to demonstrate compliance with the Canadian requirements.

New Zealand

Devices are required to meet either AS/NZS 4771, ETSI EN 300 328, or FCC Part 15 Section 15.247. The New Zealand Radio C-Tick and supplier identification code can be applied only if testing is carried out to AS/NZS 4771. Devices that comply with either of the other two specifications cannot be C-ticked, but they must have a New Zealand supplier ID code applied in order to be sold.

Because the New Zealand and Australian radio frameworks have not yet been harmonized (the latest estimate is mid-2004), a device with a New Zealand Radio C-Tick or a supplier ID cannot be sold automatically in Australia.

Australia

For Australia, however, the situation is rather more complex. The use of Bluetooth devices in Australia is covered by the Spread Spectrum Class License. Class licenses enable users to use a radio-transmitting device without an individual license, provided the device meets the conditions of the license. The administrative requirements are very simple compared with most other countries. The license provides virtually unimpeded access to market.

The user of the Bluetooth product must ensure that the device meets the class license requirements. The Australian Communications Authority (ACA) has not issued a mandatory standard for these devices, so an Australian Radio C-Tick cannot be applied by the manufacturer or importer.

The class license requirement for these devices is confusing in some cases. For example, when a spread-spectrum transmitter wireless LAN card is connected to a personal computer (PC), the attached PC will need to be C-ticked in accordance with the EMC Framework, but not the wireless LAN transmitter card, which is covered by the Spread Spectrum Class License device.

ACA advises that a Spread Spectrum Mandatory Standard, based upon AS/NZS 4771, will be adopted in the near the future (early 2004), at which time the C-tick must be used. Until that happens, in order to meet the ACA class license requirements, products must meet ETS 300 328 or FCC Part 15 Section 15.247.

Unfortunately, there is a slight complication in meeting these requirements. FCC Part 15 Section 15.247 has no date attached, so the version in force at the time the class license was made (May 29, 1996) must be used. ETS 300 328 is also date specific.

It is very unlikely that a supplier or user of a Bluetooth device would readily test to these older specifications, because test houses tend to test to the latest version of a specification. However, a good test house should have the earlier standards as references and should be able to list the differences between the version tested and the older version.

Investigations show that if a Bluetooth device complies with the latest version of FCC Part 15 Section 15.247 and EN 300 328, it will also meet the 1996 versions of these specifications.

An additional precaution is recommended for spread-spectrum devices other than Bluetooth. Before the product is used in Australia, it is prudent to check that the test report—which is most likely to be to the most up-to-date version—shows that the product would also meet the 1996 versions detailed above.

This is more of an issue if the product has only been tested to FCC Part 15 Section 15.247. This specification has been significantly modified since 1996, whereas ETS 300 328 has remained relatively unchanged.

ACA has updated the Spread Spectrum Devices Class License to call up FCC Part 15 Section 15.247, which was published in October 2001, and EN 300 328, which was published in December 2001.

Europe

Since the introduction of the Radio and Telecommunications Terminal Equipment (R&TTE) Directive, the administrative requirements for the certification of radio equipment are relatively easier. Certification by a regulatory agency is now no longer required. A system based upon a manufacturer's Declaration of Conformity (DoC) has been introduced. The test requirements, however, appear to be far more complex. The following list outlines the R&TTE Directive's requirements for Bluetooth devices:

Once all the required testing has been carried out, all documentation should be placed in a compliance folder, and a DoC should be completed. The CE mark is then placed on the product. Because the 2.4 GHz band has not been harmonized across the entire European Union, the "!" warning label must also be applied to the product.

EMR Requirements

Most countries now have regulations that limit the exposure of persons to RF fields from RF transmitters operated in close proximity to the human body. RF human exposure guidelines differentiate between portable and mobile devices according to their proximity to exposed persons. For portable devices used in close proximity to the human body, RF evaluation must be based on specific absorption rate (SAR) limits.

Human exposure to RF emissions from devices that are not used close to the human body can be evaluated with respect to maximum permissible exposure (MPE) limits for field strength or power density, or with respect to SAR limits, whichever is most appropriate.

When a product requires evaluation against the SAR limits, the evaluation must be performed against prescribed limits using the guidelines and procedures prescribed by the standards and regulations. In general, where a transmitter is used no closer than 20 cm to the human body, SAR measurements are not strictly necessary. Compliance may be proved with power density or field strength measurements.

EMR and SAR in Australia

As of March 1, 2003, the ACA C-tick requirements include the Radio Communications (Electromagnetic Radiation—Human Exposure) Standard 2003 and the Radiocommunications (Compliance Labelling—Electromagnetic Radiation) Notice 2003.

The new ACA standard now covers all devices that operate between 3 kHz and 300 GHz. For specified portable radiocommunications transmitters, the ACA standard mandates the EMR exposure limits from the standard published by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). It has replaced the previous ACA standard that mandated the exposure limits of AS/NZS 2772.1(Int):1998. The ARPANSA standard adopts the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommendations, which effectively increases the SAR limit from 1.6 W/kg (measured in a 1-g tissue mass) to 2.0 W/kg (measured in a 10-g tissue mass).

The ACA EMR standard 2003 now includes the most recent developments in SAR measurement and test methods and captures all RF transmitters used in close proximity to the body. It has broadened the scope to capture more handheld and portable devices such as push-to-talk radios, wireless LAN cards for laptop computers, wireless electronic funds transfer point-of-sale (EFTPOS) terminals, body-worn devices, and similar devices used within 20 cm of the body. The new SAR standard calls up EN 50361 (European SAR measurement standard) for cell phones or devices used at the ear and FCC OET65C 01-01 SAR evaluation guidelines for other devices. (Licensed transmitters are regulated under the ACA Licence Condition Determination 2003.)

In general, devices used within 2.5 cm of the body and transmitting greater than 20-mW RF power require SAR evaluation. Devices operating at more than 20 cm from the body do not require SAR evaluation but must comply with the ARPANSA reference levels. Evaluation against the reference levels involves measurements with a conventional field strength meter or a power density meter.

The ACA Labelling Notice requires Australian manufacturers and importers of transmitters covered by the ACA standard to assess their transmitters for compliance with the ACA standard and label their products (C-tick, A-tick, or RCM) to indicate compliance. A DoC must be completed and a technical description of the device must be kept in the compliance folder. Labeling rules are virtually identical to the ACA C-tick requirements under the EMC regulations. (The ACA EMR standard and labeling notices can be downloaded from the ACA Web site at http://www.aca.gov.au/standards_compliance.htm)

Bluetooth devices generally operate with powers up to 100 mW and are used by nonaware users. Bluetooth devices operate continuously, and, as long as the device is intended for use at a distance greater than 20 cm from any part of the body of the user, no EMR or SAR testing or evaluation is need. Such devices are said to meet the nonevaluation criteria and do not need testing to prove EMR compliance. All that is necessary is for the device to be C-ticked, a technical description be maintained, and a DoC be signed. It should be noted that such devices are not exempt from compliance.

If, however, the device exceeds 20 mW and is used within 2.5 cm of the body (e.g., a handheld or body-worn device) or is a device used in close proximity to the head (e.g., a mobile phone), SAR testing is needed. A compliance folder must be established, and it must include the technical description, the test report from a laboratory accredited for SAR testing, and a signed DoC. The C-tick must then be applied prior to marketing (refer to ACA rules for the use of the C-tick).

U.S. and European RF Exposure Requirements

In the United States and in Europe, spread-spectrum transmitters must comply with broadly based requirements for human exposure. Similar assessments and evaluation criteria apply, and all RF transmitters should be assessed against the relevant exposure standards in order to establish the exact administrative requirements and whether EMR or SAR testing is applicable.

In the United States, compliance with the FCC human exposure limits must be established either by SAR measurement or by assessment against the MPE limits. Refer to FCC OET65C 01-01 for further details on measurements and SAR evaluations.

In Europe, for devices used at the ear, compliance with the human exposure limits may be established by SAR testing to the limits of EN 50360 using SAR test method EN 50361. Low-power devices may be deemed to comply with the SAR limits without testing or measurements by establishing compliance with EN 50371. If the device meets the criteria specified by EN 50371, further SAR or MPE evaluation is not necessary; however, the product must still comply.

Conclusion

The regulatory approval of RF transmitting devices has been greatly simplified in recent years, especially in Australia and New Zealand. In Europe, the applicable standards have increased in number and complexity. However, the manufacturer or supplier now has the option of local testing, without the onerous process of submitting a product to government test laboratories. A planned testing and approval program using an appropriately accredited local test house allows a rapid time to market with great savings.

Andrew Cutler is the general manager of EMC Technologies (NZ) Ltd. based in Auckland, New Zealand. Chris Zombolas is technical director. The EMC Technologies group provides accredited testing of radio products, including FCC, Australian, and New Zealand EMC, EMR, SAR, and electrical safety standards. Cutler can be reached at aucklab@ihug.co.nz. Zombolas can be reached at chris@emctech.com.au.