AN4126

An overview of FCC regulations

Doc ID 023299 Rev 1

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greater than 0.4 seconds within a 10 second period. The maximum allowed 20 dB

bandwidth of the hopping channel is 500 kHz.

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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).

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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.

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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.

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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.

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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:

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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.

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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.

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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