AN4126 STMICROELECTRONICS | Alldatasheet
Document overview
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Technical content
Datasheet sections
- 1 An overview of FCC regulations
- 2 Application circuit
- 3 Transmitter parameter
- 3.1.2 Carrier frequency separation
- 3.1.3 Number of hopping channels
- 3.1.4 Frequency hopping systems peak output power
- 3.1.5 Frequency hopping systems 100 kHz bandwidth of band edges conducted
- 3.1.6 Spurious RF conducted emission
- 3.2.1 Signal bandwidth
- 3.2.2 Digital modulation schemes peak output power
- 3.2.3 Power spectral density
- 3.2.4 Digital modulation schemes 100 kHz bandwidth of band edges conducted
- 3.2.5 Spurious RF conducted emission
- 3.3.1 Peak output power
- 3.3.2 Conducted harmonics and other harmonics emissions
- 4 Receiver parameter
- 5 Reference
- 6 Revision history
August 2012 Doc ID 023299 Rev 1 1/28 AN4126 Application note Using the SPIRIT1 transceiver under FCC title 47 part 15 in the 902 - 928 MHz band By Placido De Vita Introduction The SPIRIT1 is a very low power RF transceiver, intended for RF wireless applications in the sub-1 GHz band. It is designed to operate in both the license-free ISM and SRD frequency bands at 169, 315, 433, 868 and 915 MHz. This application note outlines the expected performance when using the SPIRIT1 under FCC title 47 part 15 [ 2] in the 902 to 928 MHz band. There are no specific requirements in this band, no specific use and no channel spacing are defined. For details on the regulatory limits in the 902 - 928 MHz frequency band, please, refer to the FCC title 47 part 15 regulations [ 2]. These can be downloaded from www.scc-ares-races.org/FCCpartstitles.html.
An overview of FCC regulations AN4126 4/28 Doc ID 023299 Rev 1
1 An overview of FCC regulations
Low power, non-licensed devices operating in the 902 - 928 MHz band can be found everywhere, in toys, wireless security systems, wireless telemetry or wireless automatic meter reading, and so on. The FCC is the USA body responsible for implementation rules to limit the potential for interference to licensed operations by low power, non-licensed transmitters. These rules are documented in part 15 of title 47 of the FCC. For operation in the 902 - 928 MHz band, a low power, non-licensed device must meet one of the following sub-parts of the regulation:
- Part 15.243: operation is restricted for devices to use radio frequency energy to measure the characteristic of a material. Voice communication or other data transmission is not permitted.
- Part 15.245: operation is limited to devices operating as field disturbance sensors, excluding perimeter protection systems.
- Part 15.247: devices that operate to this part are limited to frequency hopping and digitally modulated schemes.
- Part 15.249: this sub-part does not enforce restrictions on either modulation scheme or the end application. The SPIRIT1 is designed to meet the 15.247 and 15.249 sub-parts, so this document continues with a description and measurement results of these two parts. 1.1 Part 15.247 Devices that operate to FCC part 15.247 are limited to frequency hopping and digitally modulated schemes. To be compliant with the frequency hopping system, the device or system must meet the following requirements:
- Frequency hopping systems must have hopping channel carrier frequencies separated by a minimum of 25 kHz or 20 dB bandwidth of the hopping channel, whichever is greater.
- The system must hop to channel frequencies that are selected at the system hopping rate from a pseudo randomly ordered list of hopping frequencies. Each frequency must be used equally on the average by each transmitter.
- If the 20 dB bandwidth of the hopping channel is less than 250 kHz, the system must use at least 50 hopping frequencies and the average time of occupancy on any frequency must not be greater than 0.4 seconds within a 20 second period; if the 20 dB bandwidth of the channel is 250 kHz or greater, the system must use at least 25 hopping frequencies and the average time of occupancy on any frequency must not be
AN4126 An overview of FCC regulations Doc ID 023299 Rev 1 5/28 greater than 0.4 seconds within a 10 second period. The maximum allowed 20 dB bandwidth of the hopping channel is 500 kHz.
- For systems employing at least 50 channels, the maximum peak conducted output power output is +30 dBm (1 W). For systems that employ less than 50 channels, but at least 25 channels, the maximum output power is +24 dBm (0.25 W).
- In any 100 kHz bandwidth outside the frequency band of operation, the power must be at least 20 dB below that in the 100 kHz bandwidth within the band that contains the highest level of the desired power.
- Radiated harmonic and spurious emissions which fall within the restricted bands, as defined in FCC part 15.205, must comply with the radiated emission limits specified in FCC part 15.209.
- To be compliant with the digital modulation scheme the devices or systems must meet the following requirement: the minimum 6 dB bandwidth of the signal must be at least 500 kHz.
- The maximum permitted peak conducted output power is + 30 dBm (1 W). However, the power spectral density conducted from the intentional radiator to the antenna must not be greater than 8 dBm in any 3 kHz band during any time interval of continuous transmission.
- In any 100 kHz bandwidth outside the frequency band of operation, the power must be at least 20 dB below that in the 100 kHz bandwidth within the band that contains the highest level of the desired power.
- Radiated harmonic and spurious emissions which fall within the restricted bands, as defined in FCC part 15.205, must comply with the radiated emission limits specified in FCC part 15.209. 1.2 Part 15.249 As opposed to part 15.247, FCC part 15.249 in the 902 - 928 MHz bandwidth does not enforce restrictions on either the modulation scheme or the end application. To be compliant with part 15.249, the device or system must meet the following requirements:
- The maximum permitted field strength is 50 mV/m. Since the field strength limits are specified at a distance of 3m from the radiating source, this equates to a conducted power of about -1 dBm measured at the antenna port.
- The maximum permitted field strength of harmonic components is 500 µV/m. This equates, at a 3 m distance, to a conducted power level of about -41 dBm measured at the antenna port.
- Radiated emission other than harmonics must be attenuated by at least 50 dB below the level of the fundamental or to the general radiated emission limits in the 15.209 section, whichever has the lesser attenuation. Sub-part 15.31 duty cycle correction applies to pulse modulated transmitters and where an average limit for carrier or spurious field strength is specified. 1.3 Parts 15.205 and 15.209 As already described in the previous paragraphs, radiated harmonics and spurious emissions of devices that comply with part 15.247 which fall within the restricted bands, as
bandwidth within the band that contains the highest level of the desired power. the 15.209 section, whichever has the lesser attenuation. 15.205, and the radiated and conducted emission limits are defined in part 15.209. Table 1. Restricted bands defined in part 15.205
Table 2. Radiated and conducted emission limits defined in part 15.209
2 Application circuit
Figure 2) by two header 5x2 connectors (J6 and J7). correct functionality and verify the ETSI standard request. (PA) and balun network for the receiver. switch. This daughterboard is designed to show the SPIRIT1 functionality in this condition. Figure 1. SPIRIT1 application daughterboard
Figure 2. SPIRIT1 application daughterboard plugged on the motherboard
Figure 3. Daughterboard schematic
3 Transmitter parameter
instrument, and the display set to peak hold. span must be set two or three times higher than the 20 dB measured bandwidth. Figure 4. The three different cases have a 20 dB bandwidth lower Figure 4. 20 dB channel bandwidth measurement
3.1.2 Carrier frequency separation
minimum of 25 kHz or the 20 dB bandwidth of the hopping channel, whichever is greater. separation, this parameter can be measured on either an unmodulated or modulated signal. Figure 5. If separate measurement must be made for each mode. Figure 5. Minimum carrier frequency separation measurement
3.1.3 Number of hopping channels
the spectrum is set to 100 kHz, the VBW (video bandwidth) is set equal to the RBW. part 15.247 frequency hopping systems.
Figure 6. Full band hopping channels measurement
3.1.4 Frequency hopping sys tems peak output power
channels and 24 dBm (0.25 W) for the 25 hopping channels. must be used to reach the maximum output power.
Figure 7. Peak output power measurement
3.1.5 Frequency hopping systems 10 0 kHz bandwidth of band edges
comply with the radiated emission limits specified in part 15.209. the SPIRIT1 usable for FCC part 15.247.
Figure 8. 902 MHz band edge conducted emission measurement Figure 9. 928 MHz band edge conducted emission measurement
902 MHz band edge
928 MHz band edge
3.1.6 Spurious RF conducted emission
which is the frequency range of measurement. Figure 10. Spurious conducted em ission below 1 GHz measurement
Figure 11. Spurious conducted emission above 1 GHz measurement
3.2.1 Signal bandwidth
must be set wide enough to capture the entire modulation envelope. the digital modulation schemes as defined in FCC part 15.247.
Figure 12. 6 dB bandwidth measurement
3.2.2 Digital modu lation schemes peak output power
can be used to reach the maximum output power. used to reach the maximum output power.
Figure 13. Peak output power measurement
3.2.3 Power spectral density
signal level should not exceed +8 dBm. Figure 14. The SPIRIT1 meets the power spectral density requirement with large margin.
Figure 14. Power spectral density measurement
3.2.4 Digital modulation schemes 100 kHz bandwidth of band edges
comply with the radiated emission limits specified in part 15.209.
928 MHz with a data rate of 500 kbps, a frequency deviation of 250 kHz and a 2-FSK
the SPIRIT1 usable for the FCC part 15.247 digital modulation scheme.
Figure 15. 902 MHz band edge conducted emission measurement Figure 16. 928 MHz band edge conducted emission measurement
3.2.5 Spurious RF conducted emission
fully complies with the conducted spurious emission requirements. Figure 17. Spurious conducted em ission below 1 GHz measurement
Figure 18. Spurious conducted emission above 1 GHz measurement
3.3.1 Peak output power
There are no particular requirements regarding the maximum permitted peak output power. modulation scheme or the end application.
Figure 19. Peak output power at -1 dBm measurement
3.3.2 Conducted harmonics a nd other harmonics emissions
harmonic is 9.28 GHz which is the frequency range of measurement. Figure 20 and 21 the harmonics and other harmonics conducted emissions are shown. maximum level, the spurious level is -43 dBm, so the specification is met.
4 Receiver parameter
No specific requirements are defined for FCC compliance of the receiver in the US FCC title 47 part 15 [2] in the 902 to 928 MHz band. No measurements were done for the receiver.
5 Reference
- SPIRIT1 datasheet 2. FCC title 47 part 15: “Radio frequency devices”
6 Revision history
Table 3. Document revision history 02-Aug-2012 1 Initial release.