§ 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 § § 15.250, 15.252,
   15.253(d), 15.255, 15.256, and 15.509 through 15.519 of this part, 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
   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;  77 FR 48102 , Aug. 13, 2012;  79 FR 12678 , Mar. 6,
   2014]

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