Instrument Error Model for Internal Calibration

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Kurzfassung

Two key requirements for a modern space-borne Synthetic Aperture Radar (SAR) are a high azimuth resolution and a wide swath. This can be achieved by using SAR instruments with multiple digital channels. Differences between the channels lead to a reduced performance due to the degraded antenna pattern. To account for that the system has to be calibrated. In this paper we focus on the internal instrument calibration. The internal calibration concept suggested here allows for a simultaneous calibration during SAR transmit and receive operation. For the receive calibration, a single tone calibration signal, the CalTone, is sequentially coupled to the echo signal path. The transmit calibration is done by first characterizing the receiver (Radio Frequency Unit (RFU) and Digital Beam-forming Unit (DBU)) with a CalTone and then couple a part of the transmitted signal to the receiver. We created a mathematical model and a simulation tool to estimate the errors in such a calibration system and aid in the system design. The frequency of the signal can be varied to account for frequency dependencies. We show results with a calibration signals outside the SAR echo signal spectrum and with a varying frequency over time. We then introduce an improved method to estimate the drift and make a prediction. Further, the simulation tool allows for an analysis of the estimation errors.

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• Instrument Error Model for Internal Calibration. (deposited 20 Dez 2019 17:26) [Gegenwärtig angezeigt]