Agilent Technologies HP 70910A Podręcznik Użytkownika Pobierz pdf (Strona 54)

54 Chapter 3

Operation

Operating Hints

Operation

Operating Hints

The following operating hints are provided for your convenience.

Preventing Erroneous Preselector Peaking or Centering During

Spur Searches

When performing spurious response tests on a device under test (DUT), the spectrum to be

measured typically contains both large and small signals. If the spurs are smaller than

−60

−65 dBc, they may be confused with the image or multiple response of the large signal.

In this type of test, activate the preselector-peak routine only on the larger signals. This

will avoid attempting to peak on small unwanted 11974 responses of the large signals

which can result in amplitude errors. Another way to avoid this potential problem is to

calculate the frequency of the image or multiple response and avoid measurements at

these precise frequencies.

The frequency of the image response can be found in Table 1-1 on page 15, and the

frequencies of the multiple responses can be found in Table 1-2 on page 19.

Listed below are the symptoms of errors caused by peaking on image or multiple

responses:

• Large amplitude errors for the large signals after peaking or centering on a suspected

small DUT spur which is actually an unwanted 11974 response,

• Preselector peak DAC numbers or Presel Adjustment frequencies consistently at or

near one extreme of range (due to peaking or centering on an image response of a large

signal),

• Random DAC numbers over a wide range when peaking is repeated (due to peaking on

a multiple response of a large signal).

DAC Number After Peaking Spectrum Analyzer

0 71000C with 70907B

255 8560 Series Portable

63 with message “Peak Not Found” displayed 8566B

Presel Adjustment Frequency After Centering Spectrum Analyzer

Frequency near

−350 Hz

Frequency 0.0 Hz “Preselector centering failed”

E4440A, E4446A, E4448A,

E4407B

1 2 ... 49 50 51 52 53 54 55 56 57 58 59 ... 153 154

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Agilent Technologies HP 70910A Podręcznik Użytkownika Strona 54