Agilent Technologies N8201A Service Manual download pdf (Page 51)

100

101

Amplitude / Y Scale 2

Agilent N8201A Performance Downconverter Synthetic Instrument Module, 250 kHz to 26.5 GHz 51

Presel Center

Adjusts the centering of the preselector filter to optimize the amplitude accuracy at the

frequency of the active marker. If no marker is on when Presel Center is pressed, the

N8201A turns on the currently selected marker and does a peak search. If a marker is

already on, it should be placed on the peak of interest before pressing Presel Center.

The microwave preselector is used for frequencies from 2.85/3.05 GHz (depending on

frequency band) to 26.8 GHz. To center the preselector, you must set up and request a

Presel Center in a microwave band. (See Presel Adjust below for more details.).

The unpreselected high band Option 123 lets you bypass the preselector path. (See

“Microwave Preselector (Option 123 Only)" on page 197.)

When the preselector path is bypassed, the Presel Center and Presel Adjust keys are

unavailable (unless you are using external mixing with preselected external mixers).

For proper preselector centering, you should make sure that:

• if the marker is off, the highest peak onscreen is valid for centering and is in the range of

an active preselector,

• if the marker is on, the signal at the marker is a peak that allows centering and is in the

range of an active preselector.

Other considerations or cautions include:

• If a marker is already on, the N8201A attempts the centering at the current marker

position and no peak search is performed. (This allows you to center the preselector for

signals which are not the strongest on-screen signals.)

• The preselector path can bypassed. See “Microwave Preselector (Option 123 Only)" on

page 197. If it is bypassed, this functionality is not available.

• If the signal at the marker position is unstable the algorithm will not function properly.

An example of this would be noise or a noise-like signal like a CDMA digital

communications signal.

• There is no preselector for signals below 3.05 GHz (in band 0).

• With Input Mixer (Ext) selected (see page 186) and the Mixer Type set to Presel (see

page 194), Presel Center adjusts the frequency of the external preselector filter to

maximize the amplitude at the active marker frequency.

Key Path: AMPLITUDE / Y Scale

Dependencies/Couplings: This function is not available (grayed out) if:

• the preselector is off. (See “Microwave Preselector (Option 123 Only)" on page 197.)

• external mixing is selected and Mixer Type is unpreselected. (See page 186 and

page 194.)

• the frequency range is entirely within band 0 (0 Hz to ~3.05 GHz).

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Agilent Technologies N8201A Service Manual Page 51

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