Anritsu S331C - Manual (Page 46)

InstaCal Module Verification
Verifying the InstaCal module before any line sweeping measurements is critical to the
measured data. InstaCal module verification identifies any failures in the module due to cir-
cuitry damage or failure of the control circuitry. This test does not attempt to characterize
the InstaCal module, which is performed at the factory or the service center.
The performance of the InstaCal module can be verified by the Termination method or the
Offset method. The termination method is the preferred method in the field, and is similar
to testing a bad load against a known good load.
Termination Method
The Termination method compares a precision load against the InstaCal Module and pro-
vides a baseline for other field measurements. A precision load provides better than 42 dB
directivity.
Step 1. Set the frequency according to the device under test (cellular, PCS, GSM).
Step 2. Press the MODE key and select
FREQ-RETURN LOSS mode.
Step 3. Connect the InstaCal module to the Site Master RF OUT port and calibrate the
Site Master using the InstaCal module (page 3-6).
Step 4. Remove the InstaCal module from the RF OUT port and connect the precision
load to the RF OUT port.
Step 5. Measure the return loss of the precision load. The level should be less than 35
dB across the calibrated frequency range.
Step 6. Press the MARKER key and set the M1 marker to
MARKER TO PEAK. The
M1 value should be less than 35 dB return loss.
Step 7. Press SAVE DISPLAY (page 3-8) name the trace, and press ENTER .
Offset Method
An alternative to the termination method is to measure the return loss of a 20 dB offset.
This is similar to measuring an antenna that has been specified to have a 20 dB return loss
across the frequency of operation. A 20 dB offset provides a 20 dB return loss across a very
wide frequency range. Measuring the return loss with the 20 dB offset will provide a rela-
tively flat response across the operating frequency range of the Site Master models (S113C,
S114C, S331C, and S332C).
Step 1. Set the frequency according to the device under test (cellular, PCS, GSM).
Step 2. Press the MODE key and select
FREQ-RETURN LOSS mode.
Step 3. Connect the InstaCal module to the Site Master RF OUT port and calibrate the
Site Master using the InstaCal module (page 3-6).
Step 4. Remove the InstaCal module from the RF OUT port and connect the 20 dB Off-
set to the RF OUT port.
Step 5. Measure the return loss of the 20 dB Offset. The level should be 20 dB,
±2 dB
across the calibrated frequency range.
Step 6. Press the MARKER key and set the M1 marker to
MARKER TO PEAK. The
M1 value should be approximately 20 dB return loss.
Step 7. Press SAVE DISPLAY (page 3-8) name the trace, and press ENTER .
3-5
Chapter 3 Getting Started