High resolution mono- and bistatic SAR imaging by using a novel modular Radar transmitter and multi-channel receiver system

• Applicant: Dr.-Ing. Holger Nies
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2014 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 254415837

• Final Report Year: 2022

Final Report Abstract

The main goal of this project was to theoretically and experimentally investigate the use of noise as a radar waveform and compare it to deterministic waveforms. After evaluating the correlation effects of the stochastic waveform, it was found that due to self­interference after correlation ­ which is normally done by a matched filter ­ weak targets are masked by strong targets. Therefore, although a matched filter optimizes the signal­to­noise ratio for a single target, it does not provide an optimal result for a scene. The analysis of different deconvolution filters has shown that the Least­Mean­Squares method can achieve an optimal reconstruction of the scene. There is a linear relationship between the signal­to­ noise performance and the SNR of the scene estimation. The same optimal result can be obtained with the optimized FIR filter. With the Wiener deconvolution filter, a very good but not optimal result is obtained after only one iteration. To complete the bistatic HITCHHIKER receiver system, an experimental transmitter system was built, and several experiments were successfully conducted. Through these experiments, the pulse com­ pression techniques considered in this work could be tested. Weak targets, e.g., small moving targets such as cars, were not detectable in the range Doppler domain when a matched filter was used. On­ ly by applying the developed deconvolution filters and reconstruction algorithms was detection and tracking of the target possible. However, the Wiener filter required the least processing time and is therefore recommended for range compression of noise signal pulses. The receiver system ­ consisting of four identical superheterodyne receivers ­ was further develo­ ped into a measurement instrument through extensive calibrations in this project. By modeling the TerraSAR­X transmit system, it has become possible to describe the synchronization between the transmitter and the GPS­synchronous HITCHHIKER receiver by the relative frequency deviation of the transmit oscillator. Furthermore, the transmit pulse can now be taken from a model as an alter­ native to the measurement in the reference channel. For the case of a stationary component and a moving component with linear trajectory, the trans­ formation between radar and ground coordinates was analytically investigated and two approaches for processing in the frequency domain were derived. By using a transponder, the range error of the bistatic measurement using a satellite and our receiving system could be estimated with less than 10 cm in the absolute difference range after focusing considering the troposphere.

Publications

• “First HITCHHIKER Noise Radar Imaging Experiment”. In: EUSAR, Juni 2014, S. 794–797
  Simon Reuter, Florian Behner, Holger Nies und Otmar Loffeld
  
• “Synchronization and Prepro­ cessing of Hybrid Bistatic SAR Data in the HITCHHIKER Experiment”. In: EUSAR 2014
  Florian Behner, Simon Reuter, Holger Nies und Otmar Loffeld
  
• “A Multi Channel Antenna Setup for Trajectory Estimation of Moving Targets for ISAR Imaging Using Time Difference of Arrival with the HITCHHIKER Noise”. In: Proceedings of EUSAR, Juni 2016
  Simon Reuter, Florian Behner, Holger Nies und Otmar Loffeld
  
• “High Resolution Bistatic Experiments using TerraSAR­X Staring Spotlight Mode and the Very High Resolution SAR Mode of the Fraunhofer FHR PAMIR System”. In: Proceedings of EUSAR, Juni 2016
  Florian Behner, Simon Reuter, Holger Nies und Otmar Loffeld
  
• “Synchronization and Processing in the HITCHHIKER Bistatic SAR Experiment”. In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Volume: 9 Issue: 3 (2016), S. 1028–1035
  Florian Behner, Simon Reuter, Holger Nies und Otmar Loffeld
  
• “Compact Ground­Based Interferometric Synthetic Aperture Radar: Short­Range Structural Monitoring”. In: IEEE Signal Processing Magazine 36.4 (2019), S. 42–52
  Andrei Anghel u. a.
  
• “Characterization of the PAZ X­Band SAR Using the HITCHHIKER Ground Receiver”. In: IEEE Geoscience and Remote Sensing Letters (2021), S. 1–5
  Florian Behner u. a.