Manual - 8500A Series Peak Power Meter - Giga-tronics

Series 8500A Peak Power Meters
2.8 Measurement Procedures
2.8.1 Frequency Correction, Cal Factor, and dB Offset
The Frequency Correction and Offset functions enhance measurement accuracy, and compensate for
detector amplitude and frequency response variations as well as devices residual to the test setup.
Frequency correction is selected in Menu-3. Three methods of frequency correction are available and will
be described in detail in this section. These are:
• PROM Table — User Supplied Frequency (default mode).
• PROM Table — External Frequency Input (uses the V α F output of the sweeper)
• User Supplied Calibration Factor — (allows direct entry in dB)
To select the desired mode, press [MENU] (3) [F3].
Then select F1, F2, or F3 respectively, for items a, b, or c. This will determine the functioning of the
FREQ key of the instrument.
Whenever a mode is selected that uses the PROM table in the detector assembly for frequency correction,
the PPM will interpolate between the discrete amplitude correction points stored in the detector PROM.
This allows entry of frequencies other than those stored in the PROM, and reduces the need for operator
interpretation and manual correction of power readings.
All of the information stored in the PROM of the detector currently in use can be reviewed by accessing
Menu-10 and pressing [F2] for channel A, and/or [F3] for channel B.
2.8.2 PROM Frequency Correction
User-Supplied Frequency
This is the User-Supplied Frequency mode. It is the default mode of the instrument. Factory measured
frequency correction data is stored in a PROM inside the detector housing, thus eliminating the need for
you to refer to a frequency correction chart and then make manual adjustments to the system for each
discrete frequency point. The PROM data is used by the PPM to correct for all of the detector’s
amplitude variations across its entire frequency range. When the system is first turned on, the PROM data
stored in the detector is transferred to the main memory of the PPM.
To select the PROM Table - User Supplied Frequency mode, press [MENU] (3) [F3] [F1].
The display will then prompt for the frequency of operation to be entered. The default frequency is
1 GHz, the same as that of the Calibrator. Press any Units key to complete the entry.
After selecting the PROM Table - User Supplied Frequency mode, use of the FREQ key allows entry of
the carrier frequency and gives the microprocessor the ability to correct any detector frequency response
deviations.
External Frequency
The purpose of the PROM Table - External Frequency input function is to allow entry of the operating
frequency by means of an externally applied voltage. The voltage level will be proportional to the
frequency, and will be used by the PPM to correct power readings for detector frequency response.
When this function is active, the RF frequency of a sweep generator or signal source can be changed and
the PPM will convert the analog voltage input (through the rear panel FREQ Input connection) to a
digital representation of the frequency. The PPM’s microprocessor uses this information to correct power
readings according to the frequency correction table stored in the detector’s PROM.
2-16 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009