Sec.  15.35   Measurement detector functions and bandwidths.

   

   The conducted and radiated emission limits shown in this part are
   based on the following, unless otherwise specified elsewhere in this
   part:

   (a) On any frequency or frequencies below or equal to 1000 MHz, the
   limits shown are based on measuring equipment employing a CISPR
   quasi-peak detector function and related measurement bandwidths,
   unless otherwise specified. The specifications for the measuring
   instrument using the CISPR quasi-peak detector can be found in
   Publication 16 of the International Special Committee on Radio
   Interference (CISPR) of the International Electrotechnical Commission.
   As an alternative to CISPR quasi-peak measurements, the responsible
   party, at its option, may demonstrate compliance with the emission
   limits using measuring equipment employing a peak detector function,
   properly adjusted for such factors as pulse desensitization, as long
   as the same bandwidths as indicated for CISPR quasi-peak measurements
   are employed.

   Note: For pulse modulated devices with a pulse-repetition frequency of
   20 Hz or less and for which CISPR quasi-peak measurements are
   specified, compliance with the regulations shall be demonstrated using
   measuring equipment employing a peak detector function, properly
   adjusted for such factors as pulse desensitization, using the same
   measurement bandwidths that are indicated for CISPR quasi-peak
   measurements.

   (b) Unless otherwise specified, on any frequency or frequencies above
   1000 MHz, the radiated emission limits are based on the use of
   measurement instrumentation employing an average detector function.
   Unless otherwise specified, measurements above 1000 MHz shall be
   performed using a minimum resolution bandwidth of 1 MHz. When average
   radiated emission measurements are specified in this part, including
   average emission measurements below 1000 MHz, there also is a limit on
   the peak level of the radio frequency emissions. Unless otherwise
   specified, e.g., see Sec. Sec. 15.250, 15.252, 15.255, and 15.509-15.519, the
   limit on peak radio frequency emissions is 20 dB above the maximum
   permitted average emission limit applicable to the equipment under
   test. This peak limit applies to the total peak emission level
   radiated by the device, e.g., the total peak power level. Note that
   the use of a pulse desensitization correction factor may be needed to
   determine the total peak emission level. The instruction manual or
   application note for the measurement instrument should be consulted
   for determining pulse desensitization factors, as necessary.

   (c) Unless otherwise specified, e.g. Sec. 15.255(b), when the radiated
   emission limits are expressed in terms of the average value of the
   emission, and pulsed operation is employed, the measurement field
   strength shall be determined by averaging over one complete pulse
   train, including blanking intervals, as long as the pulse train does
   not exceed 0.1 seconds. As an alternative (provided the transmitter
   operates for longer than 0.1 seconds) or in cases where the pulse
   train exceeds 0.1 seconds, the measured field strength shall be
   determined from the average absolute voltage during a 0.1 second
   interval during which the field strength is at its maximum value. The
   exact method of calculating the average field strength shall be
   submitted with any application for certification or shall be retained
   in the measurement data file for equipment subject to notification or
   verification.

   [ 54 FR 17714 , Apr. 25, 1989, as amended at  56 FR 13083 , Mar. 29, 1991;
    61 FR 14502 , Apr. 2, 1996;  63 FR 42279 , Aug. 7, 1998;  67 FR 34855 , May
   16, 2002;  70 FR 6773 , Feb. 9, 2005]