§  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 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
   instrumentation using the CISPR quasi-peak detector can be found in
   ANSI C63.4-2014, clause 4 (incorporated by reference, see § 15.38). 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 as long at
   the same bandwidth as indicated for CISPR quasi-peak measurements are
   employed.

   (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 § § 15.250, 15.252, 15.253(d), 15.255, 15.256, and
   15.509 through 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., § § 15.255(b), and 15.256(l)(5),
   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 Supplier's
   Declaration of Conformity.

   [ 82 FR 50832 , Nov. 2, 2017]