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 PUBLIC  NOTICE  Federal  Communications  Commission  445  Twelfth  St.,  S.  W. 
 Washington,  D.  C.  20554 
 DA:  04-  3946  Released:  December  17,  2004 
 OET  Clarifies  Equipment  Authorization  Policy  for  Measurement  of  Broadband  Emissions 
 Part  15  of  the  FCC  Rules  provides  for  the  operation  of  low  power  communication  devices  without  an  individual  license  (e.  g.,  intrusion  detectors,  pulsed  water  tank  level  gauges,  etc.),  subject  to  certain 
 requirements.  Some  of  these  devices  use  extremely  narrow  pulses  to  generate  wideband  emissions,  which  are  measured  to  determine  compliance  with  the  rules.  These  measurements  are  typically  performed  with 
 a  receiver  or  spectrum  analyzer.  Depending  on  a  number  of  factors  (e.  g.,  resolution  bandwidth,  pulse-width,  etc.),  the  spectrum  analyzer  may  not  always  display  the  true  peak  value  of  the  measured  emission. 
 This  effect,  called  “pulse  desensitization,”  relates  to  the  capabilities  of  the  measuring  instrument.  For  the  measurement  and  reporting  of  the  true  peak  of  pulsed  emissions,  it  may  be  necessary  to  apply  a  “pulse 
 desensitization  correction  factor”  (PDCF)  to  the  measured  value,  pursuant  to  47  CFR  15.35(  a). 
 It  has  come  to  our  attention  that  some  test  laboratories  and  manufacturers  are  either  not  aware  of,  or  are  not  applying  the  PDCF  when  required.  Test  laboratories  and  manufacturers  of  devices  using  pulse 
 emissions  are  reminded  to  include  in  the  test  report  the  true  peak  level  of  the  emission  when  the  limit  is  specified  in  terms  of  a  peak  emission,  which  may  necessitate  the  use  of  a  PDCF.  (Note:  PDCF  is  not 
 required  when  measuring  Ultra-  Wide  Band  (UWB)  systems  because  the  FCC  Rules  specify  a  different  measurement  procedure  for  determining  compliance  with  the  UWB  Rules.) 


 Information  about  pulse  desensitization  is  available  in  a  book  entitled  “Spectrum  and  Network  Measurements,”  297  Pages,  Robert  A.  Witte,  and  Publisher:  Noble  Publishing,  2001,  originally 
 published:  1993  by  Prentice-  Hall.  Another  good  explanation  of  pulse  desensitization  and  source  for  determining  the  PDCF  was  the  Hewlett  Packard  Application  Note,  150-  2,  entitled:  “Spectral  Analysis  – 
 Pulse  RF,”  November,  1971.  Unfortunately,  this  application  note  is  no  longer  published. 
 To  fill  the  void  of  an  adequate  measurement  procedure  for  PDCF,  we  understand  that  the  Accredited  Standards  Committee  on  Electromagnetic  Compatibility,  C63,  is  planning  to  include  information  about 
 the  application  of  PDCF  in  a  future  edition  of  ANSI  C63.4,  “American  National  Standard  for  Methods  of  Measurement  of  Radio-  Noise  Emissions  from  Low-  voltage  Electrical  and  Electronic  Equipment  in  the 
 Range  of  9  kHz  to  40  GHz.”  ANSI  C63.4  is  the  procedure  used  by  the  FCC  in  determining  compliance  to  many  devices  subject  to  Part  15  of  the  FCC  Rules. 


 In  the  meantime,  questions  about  this  public  notice  or  about  the  measurement  of  true  peak  emissions  should  be  referred  to  Art  Wall  (301-  362-  3023),  Art.  Wall@  fcc.  gov  or  William  Hurst  (301-  362-  3031), 
 William.  Hurst@  fcc.  gov  . 
 --  FCC  -- 


 News  media  information  202  /  418-  0500  Fax-  On-  Demand  202  /  418-  2830 
 Internet:  http://  www.  fcc.  gov  ftp.  fcc.  gov 
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