# 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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