6. Correct the value for losses.
See 7.6.3 Treatment of Losses in Calibration (page 218).
7.6.2 Single-Point Direct Method for Calibration of I
o
• Signal generator output calibrated in absolute dBm
• Power meter for checking the signal generator calibration
This calibration method uses the TTY setup commands.
1. Use the power meter to check the calibration of the signal generator.
2. Turn o the radiation and connect the signal generator to the test signal injection point.
3. Raise the antenna to at least 20°, and set the azimuth to point away from any known RF
sources including the sun.
4. Select the pulse width using the Mt command.
See 5.2.5 Mt — General Trigger Setups (page 113).
5. Select the pr command and use the commands to set the following:
Plotting Received Power Spectrum...
Rx:Pri, Zoom:x1-x8, Navg:25, Start:100.01 usec (14.99 km), Span:50 usec
6. Set the signal generator to the approximate radar RF frequency with a power level
corresponding to a strong signal (30 dB above the noise), and use a CW signal (not a
pulse).
This signal should be visible as a peak in the spectrum display.
Adjust the signal generator's RF signal frequency so that it produces the precise IF
frequency (for example, IF frequency of 30 MHz).
7. Turn the signal generator
o and record the Filtered power level.
Because of large averaging, it takes several seconds for the average to stabilize.
8. Turn the signal generator on, verify that the peak is still at the IF frequency and adjust
the power level to obtain precisely 3 dB more Filtered power than was observed with
the noise only.
Allow several seconds for the averaging to stabilize after you make each amplitude
adjustment.
This is the value of I
o
, that is, the test signal power equals the noise power.
9. Correct the value for losses.
See 7.6.3 Treatment of Losses in Calibration (page 218).
Chapter 7 – Processing Algorithms
217
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