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Pulse Emission Measurements Part 15

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					         Pulse
Emission Measurements
        Part 15

              Tom Phillips
      Technical Research Branch

 Federal Communications Commission
 Office of Engineering and Technology
           Laboratory Division
                    Pulse train




                        T
                            100 ms




                            100 ms


April 5 - 6, 2011                 TCB Workshop   2
                    15.35(c)
                    – Average pulsed signal over one complete
                      pulse train or 100 ms time frame if pulse train
                      exceeds 100 ms
                    – Maximum average in 100 ms
                    – Calculate duty cycle for pulse train or 100 ms
                    – Duty cycle = (t1 + t2 + t3+…tn)/T
                      where tn = pulse width, T = pulse train length
                      or 100 ms
                    – Average = pulse amplitude x duty cycle


April 5 - 6, 2011                TCB Workshop                      3
                                       5 ms 0 dBm Pulse, 20 ms Period
                                      0 Span, 10 kHz RBW, Single Sweep

                 20



                  0



                 -20



                 -40
Amplitude dBm




                 -60



                 -80



                -100



                -120



                -140
                       0   10   20   30       40        50       60      70   80   90   100
                                                     Time ms


            April 5 - 6, 2011                 TCB Workshop                              4
                    15.35(b)
                    – Total peak emission limit 20 dB
                      above average emission limit
                    – Unless otherwise specified
                      e.g. 15.250, 15.252, 15.255 & 15.509-15.519
                      not including 15.209
                    – Pulse Desensitization Correction Factor
                      (PDCF) may be needed
                       • Wideband pulses




April 5 - 6, 2011               TCB Workshop                    5
                    PW


                    A




                    T


                         Periodic Square Pulse


April 5 - 6, 2011              TCB Workshop      6
                                                      PW
                                                  A            = Avg
                                                      T




                                                                       Freq
                                       0
                       1                                  1
                       PW                  1              PW
                                           T
                                        = PRF


                    Frequency Spectrum of Periodic Square Pulse

April 5 - 6, 2011                  TCB Workshop                         7
                                      40 usec 0 dBm Pulse, 400 usec Period
                                                  100 Hz RBW

                  0

                                                                  PRF = 2.5 kHz
                 -20



                 -40
Amplitude dBm




                 -60



                 -80



                -100



                -120


                                                              BW = 50 kHz
                -140
                       -60      -40      -20              0                       20   40   60
                                                       Freq kHz


            April 5 - 6, 2011                   TCB Workshop                                8
                                       40 usec 0 dBm Pulse, 400 usec Period
                                        0 Span, 1 MHz RBW, Single Sweep

                 20



                  0



                 -20



                 -40
Amplitude dBm




                 -60



                 -80



                -100



                -120



                -140
                       0   100   200   300      400       500       600       700   800   900   1000
                                                       Time usec


            April 5 - 6, 2011                    TCB Workshop                                   9
                                      40 usec 0 dBm Pulse, 400 usec Period
                                                  1 kHz RBW

                 0


                -10
                                                                   PRF = 2.5 kHz

                -20


                -30
Amplitude dBm




                -40


                -50


                -60


                -70

                                                              BW = 50 kHz
                -80


                -90
                   -60          -40     -20               0                   20   40    60
                                                       Freq kHz


            April 5 - 6, 2011                   TCB Workshop                            10
                                      40 usec 0 dBm Pulse, 400 usec Period
                                                  10 kHz RBW

                  0




                 -20




                 -40
Amplitude dBm




                 -60




                 -80




                -100




                -120
                       -60      -40      -20              0                  20   40    60
                                                       Freq kHz


            April 5 - 6, 2011                   TCB Workshop                           11
                                      40 usec 0 dBm Pulse, 400 usec Period
                                                  1MHz RBW

                 20

                                               40                        400 usec

                  0



                 -20
Amplitude dBm




                 -40



                 -60



                 -80



                -100

                                                    Sweep time = 1 ms

                -120
                       -60      -40      -20               0                 20     40    60
                                                       Freq kHz


            April 5 - 6, 2011                   TCB Workshop                             12
                                            1 nsec 0dBm Pulse, 1000 nsec Period
                                                      RBW = 100 kHz

                  0


                 -20
                                                                     PRF = 1 MHz
                 -40


                 -60


                 -80
Amplitude dBm




                -100


                -120


                -140


                -160

                                                                     BW = 2 GHz
                -180


                -200
                       -2       -1.5   -1         -0.5           0                 0.5   1   1.5        2
                                                              Freq GHz


            April 5 - 6, 2011                            TCB Workshop                              13
                           Pulse Desensitization
                          Correction Factor PDCF
                    Line spectrum
                    –   RBW < PRF
                    –   PDCF = PW/T
                    –   PDCFdB = 20 Log PW/T
                    –   Pulse amplitude = center line amp – PDCFdB
                    Pulse spectrum
                    – RBW > PRF
                    – PDCFdB = 20 Log PW * RBWimp



April 5 - 6, 2011                TCB Workshop                   14
                                              1 nsec 0dBm Pulse, 1000 nsec Period
                                                        RBW = 100 kHz

                  0


                 -20


                 -40
                                            PRF = 1 MHz                            Amp = A PW
                                                                                           T
                 -60
Amplitude dBm




                 -80


                -100


                -120


                -140


                -160


                -180
                       -20      -15   -10                 -5           0       5                10   15    20
                                                                    Freq MHz


            April 5 - 6, 2011                                  TCB Workshop                               15
                            Common Errors

                    Assuming peak detector yields peak pulse
                    amplitude
                    Confusing average detector with time
                    average of pulsed signal
                    Comparing peak pulse amplitude to
                    average value rather than average limit
                    Applying averaging of 15.35(c) to peak
                    pulse amplitude of 15.35(b)


April 5 - 6, 2011             TCB Workshop               16
                                References

                    Agilent Application Note 150-2
                    ANSI C63.10, Annex C
                    Public Notice DA: 04-3946
                    – http://hraunfoss.fcc.gov/edocs_public/attachma
                      tch/DA-04-3946A1.pdf




April 5 - 6, 2011               TCB Workshop                    17
                    Thanks!
                    Thanks!

April 5 - 6, 2011   TCB Workshop   18

				
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