Generalized Continuous Wave Synthetic Aperture Radar

University of Technology Sydney. Faculty of Engineering and Information Technology.Synthetic aperture radar (SAR) suffers from several intrinsic limitations caused by the slow time sampling in azimuth. In this thesis, a generalized continuous wave synthetic aperture radar (GCW-SAR) is developed based on one-dimensional (1-D) continuous wave (CW) signalling, thus removing these limitations. GCW-SAR reconstructs a radar image originally by correlating the received one-dimensional raw data after self-interference cancellation (SIC) with predetermined location dependent reference signals. The SIC in GCW-SAR is discussed and then the system geometry and the original imaging method are proposed. To reduce the complexity, a novel piecewise constant Doppler (PCD) algorithm based on the linear approximation of the slant range, is proposed reconstructing a SAR image recursively in azimuth. Additionally, a faster and more flexible PCD implementation, called decimated PCD algorithm, is proposed, by which the image azimuth spacing can be extended further reducing the computational cost significantly. The PCD algorithm is the key technique for the GCW-SAR. This thesis presents a theoretical PCD imaging performance analysis. Firstly, the difference between conventional SAR imaging and PCD imaging is revealed. Exact ambiguity function expressions of the PCD imaging in range and azimuth are then derived respectively. An error function of the PCD imaging is further defined and shown to be a function of an image quality factor to quantify the imaging performance. The decimated PCD imaging error is also analyzed accordingly. Passive GCW-SAR system and millimeter wave GCW-SAR system with deramp-on-receive are proposed respectively. A modified PCD algorithm suited for passive GCW-SAR is proposed to remove the conventional passive SAR limitations. Using deramping technique can drastically reduce the receiving sampling rate and the millimeter wave carrier enables high azimuth resolution as well as short synthetic aperture which in turn significantly reduces the imaging computational complexity. The effects of deramp-on-receive in PCD imaging is analyzed accordingly. Finally, a real GCW-SAR experimental system is developed and the experimental results are presented. This practical system consists of four subsystems, i.e., receiver frontend subsystem, radar control subsystem, positioning control subsystem and digital imaging subsystem. The first two parts are constructed by using the AWR1843 single-chip 77-GHz FMCW radar sensor made by Texas Instruments, the third by using the linear moving platform made by FUYU Technology company, and the digital imaging is possessed by MATLAB off-line processing in a personal computer (PC). The experimental results validate the advantages of the proposed GCW-SAR system

Analog Least Mean Square Loop for Self-Interference Cancellation in Generalized Continuous Wave SAR

Generalized continuous wave synthetic aperture radar (GCW-SAR) is a promising new imaging radar system since it applies the full-duplex (FD) transmission technique to achieve continuous signaling in order to overcome several fundamental limitations of the conventional pulsed SARs. As in any FD wireless communication system, self-interference (SI) is also a key problem which can impact on the GCW-SAR system. In this paper, the analog least mean square (ALMS) loop in the radio frequency domain is adopted to cancel the SI for a GCW-SAR system with periodic chirp signaling. The average residual SI power after the ALMS loop is analyzed theoretically by a stationary analysis. It is found that the ALMS loop not only works with random signals in general FD communication systems, but also works well with the periodic signal in GCW-SAR systems. Simulation results show that over 45 dB SI cancellation can be achieved by the ALMS loop which ensures the proper operation of the GCW-SAR system

Analog Least Mean Square Loop for Self-Interference Cancellation in Generalized Continuous Wave SAR

Generalized continuous wave synthetic aperture radar (GCW-SAR) is a promising new imaging radar system since it applies the full-duplex (FD) transmission technique to achieve continuous signaling in order to overcome several fundamental limitations of the conventional pulsed SARs. As in any FD wireless communication system, self-interference (SI) is also a key problem which can impact on the GCW-SAR system. In this paper, the analog least mean square (ALMS) loop in the radio frequency domain is adopted to cancel the SI for a GCW-SAR system with periodic chirp signaling. The average residual SI power after the ALMS loop is analyzed theoretically by a stationary analysis. It is found that the ALMS loop not only works with random signals in general FD communication systems, but also works well with the periodic signal in GCW-SAR systems. Simulation results show that over 45 dB SI cancellation can be achieved by the ALMS loop which ensures the proper operation of the GCW-SAR system