operation were being used, the required offset would be entered as follows:
8501A:
[MENU] (3) [F1]
8502A:
[MENU] (3) [F1] (ch A) or [F2] (ch B).
10.
Enter the value of the offset in dB, followed by the dB Units key:
[30.2] [dB]
The PPM will now be reading CW power, and the display will look something like:
A: +35.26 dBm
*FREQ=10.78 GHz CW
☛
NOTE: +35.26 dBm represents the power at the input of the attenuator which is connected
to the detector input. The actual power at the detector input would be +35.26 - 30.2 =
+5.06 dBm.
11.
Select the number of samples to be taken to arrive at an average reading (default is 4 readings).
Press [MENU] (2) [F1].
12.
Enter the desired number followed by pressing any Units key. The number of samples that can be
taken to arrive at an average can be between 1 and 999. For power levels below -30 dBm, it is
recommended that more than 100 samples be taken to reduce noise effects.
13.
To change the displayed power reading from dBm to milliwatts or vice versa, press [MENU] (4) [F3].
2.8.5
Peak Power Measurement
Method 1: Peak Mode via Graph Autoscale
There are several methods that can be used to make Peak Power measurements with the system. The
easiest method is to use the Autoscaling function in the Graph Mode. The Autoscaling function only
operates on pulses greater than the selected trigger level. Complex pulse shapes such as double pulses
cannot always be successfully autoscaled. Methods for these situations will be covered later.
After the pulse to be measured has been successfully autoscaled, it is only necessary to press [PEAK] and
the system will read the power at the center point of the pulse. The readout will be displayed in large
alphanumeric characters. For the following procedure, assume that either a single channel Model 8501A
is being used or just channel A or channel B of the dual channel 8502A.
Autoscaling Procedure - Internal Trigger
1.
Connect the detector(s) to the PPM and allow it to warm up for 30 minutes. Then conduct the
Self-Cal procedure as described in Section 2.7.
2.
When Self-Cal has completed, connect the channel A (or B) detector input to a pulsed signal
greater than -10 dBm (the default trigger level). Press [GRAPH] to select the Graph Mode, and
then press it again to start the Autoscaling function.
When the Autoscaling function is initiated the PPM will change to internal triggering off of the
displayed channel. Then it will attempt to automatically select the correct Window Delay time
and Reference Power which will center the pulse on the display. The Start Delay will be set to
zero. If the signal at the detector RF input is less than the trigger level (or there is no pulse
present at the input), then the system will not trigger and the following display will appear:
Operation
Manual No. 20790, Rev C, November 1998
2-19
Содержание 8501A
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