Agilent Technologies E8247C PSG CW - Manual (Page 86)

76 Chapter 3
Optimizing Performance
Adjusting Reference Oscillator Bandwidth (Option UNR)
Adjusting Reference Oscillator Bandwidth (Option UNR)
The reference oscillator bandwidth (sometimes referred to as loop bandwidth) in signal generators with
Option UNR (improved close-in phase noise) is adjustable in fixed steps for either an internal or external
10 MHz frequency reference. The reference bandwidth can be set to 25, 55, 125, 300, or 650 Hz; models
without option UNR have a fixed reference oscillator bandwidth of about 15 Hz.
The reference oscillator bandwidth is the frequency below which the PSG derives its reference directly from
the internal or external frequency reference. Above this frequency, stability and phase noise are governed by
the synthesizer hardware within the PSG.
To optimize the overall phase noise performance of the signal generator for your particular application,
make this adjustment depending on your confidence in the stability and phase noise of the external or
internal reference versus the synthesizer hardware for various frequency offsets from the carrier.
To Select the Reference Oscillator Bandwidth
When using the internal timebase reference:
1. Press
Utility
>
Instrument Adjustments
>
Reference Oscillator Adjustment
>
Internal Ref Bandwidth
.
2. Select the desired bandwidth.
When using an external timebase reference:
1. Press
Utility
>
Instrument Adjustments
>
Reference Oscillator Adjustment
>
External Ref Bandwidth
.
2. Select the desired bandwidth.
To Restore Factory Default Settings:
Internal Timebase: 125 Hz
External Timebase: 25 Hz
Press
Utility
>
Instrument Adjustments
>
Reference Oscillator Adjustment
>
Restore Factory Defaults
.