15.247 Operation within the bands 902-928 MHz, 2400-2483.5 MHz,
and 5725-5850 MHz.
(a) Operation under the provisions of this section is limited to
frequency hopping and direct sequence spread spectrum intentional
radiators that comply with the following provisions:
(1) Frequency hopping systems shall have hopping channel carrier
frequencies separated by a minimum of 25 kHz or the 20 dB bandwidth of
the hopping channel, whichever is greater. The system shall hop to
channel frequencies that are selected at the system hopping rate from a
pseudorandomly ordered list of hopping frequencies. Each frequency must
be used equally on the average by each transmitter. The system receivers
shall have input bandwidths that match the hopping channel bandwidths of
their corresponding transmitters and shall shift frequencies in
synchronization with the transmitted signals.
(i) Frequency hopping systems operating in the 902-928 MHz band
shall use at least 50 hopping frequencies. The maximum allowed 20 dB
bandwidth of the hopping channel is 500 kHz. The average time of
occupancy on any frequency shall not be greater than 0.4 seconds within
a 20 second period.
(ii) Frequency hopping systems operating in the 2400-2483.5 MHz and
5725-5850 MHz bands shall use at least 75 hopping frequencies. The
maximum 20 dB bandwidth of the hopping channel is 1 MHz. The average
time of occupancy on any frequency shall not be greater than 0.4 seconds
within a 30 second period.
(2) For direct sequence systems, the minimum 6 dB bandwidth shall be
at least 500 kHz.
(b) The maximum peak output power of the transmitter shall not
exceed 1 Watt. If transmitting antennas of directional gain greater than
6 dBi are used, the power shall be reduced by the amount in dB that the
directional gain of the antenna exceeds 6 dBi.
(c) If any 100 kHz bandwidth outside these frequency bands, the
radio frequency power that is produced by the modulation products of the
spreading sequence, the information sequence and the carrier frequency
shall be either at least 20 dB below that in any 100 kHz bandwidth
within the band that contains the highest level of the desired power or
shall not exceed the general levels specified in Sec. 15.209(a),
whichever results in the lesser attenuation. All other emissions outside
these bands shall not exceed the general radiated emission limits
specified in Sec. 15.209(a).
(d) For direct sequence systems, the transmitted power density
averaged over any 1 second interval shall not be greater than 8 dBm in
any 3 kHz bandwidth within these bands.
(e) The processing gain of a direct sequence system shall be at
least 10 dB. The processing gain shall be determined from the ratio in dB of the signal to noise ratio with the system spreading code turned
off to the signal to noise ratio with the system spreading code turned
on, as measured at the demodulated output of the receiver.
(f) Hybrid systems that employ a combination of both direct sequence
and frequency hopping modulation techniques shall achieve a processing
gain of at least 17 dB from the combined techniques. The frequency
hopping operation of the hybrid system, with the direct sequence
operation turned off, shall have an average time of occupancy on any
frequency not to exceed 0.4 seconds within a time period in seconds
equal to the number of hopping frequencies employed multiplied by 0.4.
The direct sequence operation of the hybrid system, with the frequency
hopping operation turned off, shall comply with the power density
requirements of paragraph (d) of this section.
Note: Spread spectrum systems are sharing these bands on a
noninterference basis with systems supporting critical Government
requirements that have been allocated the usage of these bands,
secondary only to ISM equipment operated under the provisions of part 18
of this chapter. Many of these Government systems are airborne
radiolocation systems that emit a high EIRP which can cause interference
to other users.
Also, investigations of the effect of spread spectrum interference to U.
S. Government operations in the 902-928 MHz band may require a future
decrease in the power limits allowed for spread spectrum operation.
[54 FR 17714, Apr. 25, 1989, as amended at 55 FR 28762, Jul. 13, 1990]
Sec. 15.203 Antenna requirement.
An intentional radiator shall be designed to ensure that no antenna
other than that furnished by the responsible party shall be used with
the device. The use of a permanently attached antenna or of an antenna
that uses a unique coupling to the intentional radiator shall be
considered sufficient to comply with the provisions of this section. The
manufacturer may design the unit so that a broken antenna can be
replaced by the user, but the use of a standard antenna jack or
electrical connector is prohibited. This requirement does not apply to
carrier current devices or to devices operated under the provisions of
Sec. 15.211, Sec. 15.213, Sec. 15.217, Sec. 15.219, or Sec. 15.221.
Further, this requirement does not apply to intentional radiators that
must be professionally installed, such as perimeter
protection systems and some field disturbance sensors, or to other
intentional radiators which, in accordance with Sec. 15.31(d), must be
measured at the installation site. However, the installer shall be
responsible for ensuring that the proper antenna is employed so that the
limits in this part are not exceeded.
[54 FR 17714, Apr. 25, 1989, as amended at 55 FR 28762, July 13, 1990]
Sec. 15.209 Radiated emission limits; general requirements.
(a) Except as provided elsewhere in this subpart, the emissions from
an intentional radiator shall not exceed the field strength levels
specified in the following table:
------------------------------------------------------------------------ |
Measurement |
Frequency | Field strength | distance |
(MHz) | (microvolts/meter) | (meters) |
------------------------------------------------------------------------ |
0.009-0.490 | 2400/F(kHz) | 300 |
0.490-1.705 | 24000/F(kHz) | 30 |
1.705-30.0 | 30 | 30 |
30-88 | 100 ** | 3 |
88-216 | 150 ** | 3 |
216-960 | 200 ** | 3 |
Above 960 | 500 | 3 |
------------------------------------------------------------------------ |
** Except as provided in paragraph (g), fundamental emissions from
intentional radiators operating under this section shall not be
located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz or
470-806 MHz. However, operation within these frequency bands is
permItted under other sections of this part, e.g., Secs. 15.231 and
15.241.
(b) In the emission table above, the tighter limit applies at the
band edges.
(c) The level of any unwanted emissions from an intentional radiator
operating under these general provisions shall not exceed the level of
the fundamental emission. For intentional radiators which operate under
the provisions of other sections within this part and which are required
to reduce their unwanted emissions to the limits specified in this table, the limits in
this table are based on the frequency of the unwanted emission and not
the fundamental frequency. However, the level of any unwanted emissions
shall not exceed the level of the fundamental frequency.
(d) The emission limits shown in the above table are based on
measurements employing a CISPR quasi-peak detector except for the
frequency bands 9-90 kHz, 110-490 kHz and above 1000 MHz. Radiated
emission limits in these three bands are based on measurements employing
an average detector. (e) The provisions in Secs. 15.31, 15.33, and 15.35 for measuring
emissions at distances other than the distances specified in the above
table, determining the frequency range over which radiated emissions are
to be measured, and limiting peak emissions apply to all devices
operated under this part.
(f) In accordance with Sec. 15.33(a), in some cases the emissions
from an intentional radiator must be measured to beyond the tenth
harmonic of the highest fundamental frequency designed to be emitted by
the intentional radiator because of the incorporation of a digital
device. If measurements above the tenth harmonic are so required, the
radiated emissions above the tenth harmonic shall comply with the
general radiated emission limits applicable to the incorporated digital
device, as shown in Sec. 15.109 and as based on the frequency of the
emission being measured, or, except for emissions contained in the
restricted frequency bands shown in Sec. 15.205, the limit on spurious
emissions specified for the intentional radiator, whichever is the
higher limit. Emissions which must be measured above the tenth harmonic
of the highest fundamental frequency designed to be emitted by the
intentional radiator and which fall within the restricted bands shall
comply with the general radiated emission limits in Sec. 15.109 that are
applicable to the incorporated digital device.
(g) Operation in the frequency bands allocated to TV broadcast
stations:
(1) Perimeter protection systems operating under the provisions of
this section in the frequency bands allocated to TV broadcast stations,
as shown in part 73 of this chapter, shall contain their fundamental
emissions within the frequency bands 54-72 MHz and 76-88 MHz. Further,
the use of such perimeter protection systems is limited to industrial,
business and commercial applications.
(2) Biomedical telemetry devices operating under the provisions of
this section in the frequency bands allocated to TV broadcast stations,
as shown in part 73 of this chapter, shall contain their fundamental
emissions within the frequency band 512-566 MHz. Further, the marketing
and the use of biomedical telemetry devices operating under this
paragraph shall be limited to hospitals.
[54 FR 17714, Apr. 25, 1989; 54 FR 32339, Aug. 7, 1989; 55 FR 18340, May 2, 1990]
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