CHl S T A R T 5 7 0 ps

S T O P 2 . 5 0 5 ns

pg682d

Figure 6-73. Response Resolution

While increasing the frequency span increases the response resolution, keep the following points in mind:

w The time domain response noise floor is directly related to the frequency domain data noise floor. Because of this, if the frequency domain data points are taken at or below the measurement noise floor, the time domain measurement noise floor is degraded.

w The time domain measurement is an average of the response over the frequency range of the measurement. If the frequency domain data is measured out-of-band, the time domain measurement is also the out-of-band response.

You may (with these limitations in mind) choose to use a frequency span that is wider than the test device bandwidth to achieve better resolution.

Range resolution. Time domain range resolution is defined as the ability to locate a single response in time. If only one response is present, range resolution is a measure of how closely you can pinpoint the peak of that response. The range resolution is equal to the digital resolution of the display, which is the time domain span divided by the number of points on the display. lb get the maximum range resolution, center the response on the display and reduce the time domain span. The range resolution is always much liner than the response resolution (see Figure 6-74).

CHl

COC

Sll

me

 

1 mU/REF 4

mU1:

7 . 4 2 1 5

mU

14

 

 

/

 

 

1.321

ns

 

 

 

 

 

1

 

 

MARIER

1

 

 

\

 

 

1

. 3

2 1

ns

 

 

 

 

396.03 m TI

/I

1x1

I

 

I I\I I I

I I I I

I I I I I I \I

CHI S T A R T 1078 ns

S T O P I.505 ns

pg683d

Figure 6-74. Range Resolution of a Single Discontinuity

6-140 ApplicationandOperationConcepts

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HP 8753E manual I I