Giga-tronics Series 12000A, Руководство по эксплуатации

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Performance Verification
Publication 31231, Rev. J, October 2003 4-23
4.5 Calibration (Series 12500A/12700A Native)
Use Section 4.3 for calibration data pertaining to all three models. Use this section for native specific
data belonging to the 125XXA/127XXA models. Refer to the Series 12000A Microwave Synthesizers
Service Manual for detailed calibration instructions (P/N 31232).
4.5.1 Frequency Modulation Calibration
The calibration of the Frequency Modulation function is accomplished by using a known external
source (the 1 Vdc supply) to measure various gains within the FM system. For this test, it is
recommended that the external power source be connected to the FM input with a series resistor of
approximately 500
Ω
. This will provide about a 10:1 voltage divider (the FM input is 50
Ω
). Measure
the voltage at the input connector with a digital voltmeter and set it to 1.00 V. For those parts of the test
requiring a zero volt input, simply remove the connection to the FM input connector and the internal
50
Ω
pull-down resistor will establish zero volts.
The FM calibration is divided into two parts, the low band and the high band. In the low band, the
DDS portion may be directly calibrated since the DDS provides a fixed frequency increment for every
accumulator set point bit increment. This allows calculating the multiplication coefficient for
converting FM-ADC bits to DDS bits. Once the DDS is calibrated, it provides a precise shift in the loop
control voltage. This voltage is null’ed using an internal voltage previously calibrated by the 1 Vdc
source. The gains and offsets required to produce the null become the calibration factors for the high
band.
4.5.2 Amplitude Modulation Calibration
The calibration of the Amplitude Modulation function is accomplished by using a known external
source (the 1 V and 6 V supply) to measure various gains within the AM system. For this test, it is
recommended that the external power source be connected to the AM input with a series resistor of
approximately 600
Ω
for 1 volt and 600
Ω
for 6 volts. This will provide about a 10:1 or 2:1 voltage
divider (the AM input is 600
Ω
). Measure the voltage at the input connector with a digital voltmeter
and set it to 1.00 V or 6.00 V as prompted. For those parts of the test requiring a zero volt input, simply
remove the connection to the AM input connector and the internal 600
Ω
pull-down resistor will
establish zero volts.
Since the Amplitude Modulation system is dc coupled, the application of the accurate 1 Vdc source
allows the instrument computer to set the gain calibration to produce an appropriate shift in carrier
power. Once this calibration has been done, application of a modulating signal will produce the proper
depth.
Calibration (Series 12500A/12700A)
Model
124XXA
125XXA/
127XXA
4.5.1 - Frequency Modulation Calibration N/A
√
4.5.2 - Amplitude Modulation Calibration N/A
√
4.5.3 - Mode Related Calibrations N/A
√