The innovative spaceborne Earth observation mission LuTan-1 (LT-1) deploys advanced full polarimetric L-band synthetic aperture radar (SAR) to obtain high-precision, multidimensional ground feature information. As the quad-pol SAR system, LT-1 suffers from strong ambiguities that degrade the quality of the observation products. Antenna pattern synthesis algorithm can suppress the range ambiguities without the increase of the azimuth ambiguities and the system complexity and therefore has great potential to improve the overall ambiguity performance of the quad-pol SAR system. However, the previous research on this kind of method is generally limited to specific situations and lacks of the analysis of actual measurement results. Based on the application requirements of LT-1, this article proposes a novel pattern synthesis algorithm that suppresses the range ambiguities via sequential convex optimizations. In simulation and comparison, the proposed algorithm effectively suppresses the strong co-polarized range ambiguities and shows the flexibility, efficiency, and stability that are significantly better than the previous algorithms. What is more, the analysis of practical performance loss is performed based on the measurement result of the LT-1 antenna, and the practicality and validity of the algorithm are strongly verified. 

Pattern Synthesis Algorithm for Range Ambiguity Suppression in the LT-1 Mission via Sequential Convex Optimizations

MIMO stands for Multiple Input Multiple Output. This technology was introduced first by an expert from Bell Laboratories in 1984. With MIMO technology, a receiver or a transmitter uses more than one antenna; the goal is to make the reflected signal as the main signal amplifier so it does not frustrate each other. MIMO also have the drawback, that is the interval of time which caused a slight delay when sending a signal to the antenna, although the signal itself faster delivery. This time interval is due to the process by which the system must split the signal to follow the number of antennas owned by MIMO devices of more than one. In the system, not just use a MIMO antenna but using two or more of (plural) both at the transmitter and receiver. By using multiple antennas that results in better performance, it can be compared to the single input single output system (SISO) . The results of this study can be used as recommendations for improving the effectiveness of service and excellence services and mobile data communications. The method used in this study was adapted from the frame of information systems research methodology that starts from the stage of concept exploration, analysis, collection and analysis of data and drawing conclusions. The results of the study showed that the more antennas the capacity of the system will be greater.

Multiple Input Multiple Output

A 2-D massively parallel, high throughput, systolic array for a spatio-temporal wave-digital filter (WDF) architecture is proposed. RF receive mode aperture beam personalities are achieved using 2-D fan filters with dynamically steerable passband directions and fan angles. The wave-digital realization results in low sensitivity of the far-field beam to errors in filter coefficients due to fixed-point effects in the digital arithmetic hardware. A fixed-point design of the systolic-array architecture that eliminates overflow errors is described. The architecture is implemented in FPGA-prototype form and tested using MATLAB Simulink with Xilinx EDA tools. The verified digital design is ported to CMOS standard-cell technology to obtain the area and power costs as well as the operational frequency. The 45 nm CMOS synthesis, placement, and routing show overflow free maximum frequency of operation of 131.02 MHz for 1-passband fan filter and an estimated power consumption of 450.30 mW at DC supply voltage 1.1 V indicating potential applications in the VHF range.

Systolic array architecture for steerable multibeam VHF wave-digital RF apertures

An improved nonlinear chirp scaling (NLCS) algorithm for dechirped missile-borne synthetic aperture radar was proposed. The key step is to use an improved NLCS operation to equalize azimuth frequency modulation rate after linear range walk correction, secondary range compression, and range compression. By adopting a higher-order approximation, the image has better accuracy and less distortion. Validity of the algorithm is demonstrated using simulated and real datasets. Moreover, the whole procedure only consists of fast Fourier transform and complex multiplication, which means easier implementation and higher efficiency.

Improved nonlinear chirp scaling algorithm for dechirped missile-borne synthetic aperture radar

The evaluation of the ambiguous signal level, the Ambiguity-to-Signal Ratio (ASR), plays a key role in the Synthetic Aperture Radar (SAR) design and performance prediction. In conventional SAR acquisition scenarios, the computation of the ASR is based on the evaluation of the range and azimuth ambiguous contributes. Though appealing for its simplicity, this approach could be inaccurate in case of complex SAR acquisition geometries. In this paper we focus on the ASR performance of the SAOCOM-CS system in large baseline bistatic (LBB) configuration, extending a previous performance analysis by investigating the effect of cross-ambiguities on the achievable ASR performance.

SAR Cross-Ambiguities in SAOCOM-CS Large Baseline Bistatic Configuration

A method is proposed to optimize the radiation pattern of a planar array in order to maximize the signal-to-ambiguity-ratio for a squinted synthetic aperture radar (SAR) observation geometry The optimal beamformer is the generalized eigenvector associated with a pair of matrices that depends on observation geometry and the Earth reflectivity model The proposed approach is valid for any array configuration This enables adaptivity to surface background and T/R module failures, thus increasing system robustness

Optimal Beamforming for Range-Doppler Ambiguity Minimization in Squinted SAR

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Optimal Beamforming for Range-Doppler Ambiguity Minimization in Squinted SAR