Overview Calibration Exciter Receiver Oscillators High-Powered Amplifier Calibration

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

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.

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

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

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, 114.1 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