1. Overview Calibration Exciter Receiver Oscillators
High-Powered Amplifier
Calibration

2. Calibration: Requirements
Able to retrieve calibrated reflectivity (Phase A)
Transmitted power
Receiver gain
System noise floor
Must be extendable to retrieve calibrated polarimetric variables (Phase B)
Must accommodate pulse compression (Phase B)
Measurement of the transmitted pulse desirable

3. Calibration: Requirements
Absolute Calibration
Laboratory measurements using noise and signal sources to measure gain and dynamic range of the receiver
Ground corner reflector for periodic reflectivity calibration
Other techniques in flight, e.g. sea surface (Li, 2003)
Dynamic Calibration
Transmitted signal continuously switched into the receiver during operation while the radar is “blind”
Blue sky noise measurement possible periodically during aircraft turns, etc.

4. Calibration Network: Dynamic Calibration
Transmitted signal is coupled into the into the receiver through a well-calibrated path, GCAL
Reflectivity can be calculated from the ratio of and
PEIKA
GTX
PRX
GCAL
GREC1
PADC
GREC2

5. Calibration Network: Dynamic Calibration
Therefore, need to know GCAL, GREC1, and GTX
Need to temperature stabilize front-end electronics
Move calibration coupler to after T/R circulator to minimize GTX
GTX
GCAL
GREC1

6. Calibration Network: Isolation
T/R isolation required between calibration channel signal, and transmit signal reflected from the antenna
Given antenna return loss of −14 dB, and maximum linear-range input signal to the LNA of −30 dBm, dB of isolation is required between transmit and receive (5 latching circulators at 25 dB/circulator) to achieve > 0.1 dB amplitude distortion on calibration signal
114 dB isolation