Automatic Target Recognition (ATR) is the task of automatically detecting and classifying targets. Recognition using Synthetic Aperture Radar (SAR) images is interesting because SAR images can be acquired at night and under any weather conditions, whereas optical sensors operating in the visible band do not have this capability. Existing SAR ATR algorithms have mostly been evaluated using the MSTAR dataset.1 The problem with the MSTAR is that some of the proposed ATR methods have shown good classification performance even when targets were hidden,2 suggesting the presence of a bias in the dataset. Evaluations of SAR ATR techniques are currently challenging due to the lack of publicly available data in the SAR domain. In this paper, we present a high resolution SAR dataset consisting of images of a set of ground military target models taken at various aspect angles, The dataset can be used for a fair evaluation and comparison of SAR ATR algorithms. We applied the Inverse Synthetic Aperture Radar (ISAR) technique to echoes from targets rotating on a turntable and illuminated with a stepped frequency waveform. The targets in the database consist of four variants of two 1.7m-long models of T-64 and T-72 tanks. The gun, the turret position and the depression angle are varied to form 26 different sequences of images. The emitted signal spanned the frequency range from 13 GHz to 18 GHz to achieve a bandwidth of 5 GHz sampled with 4001 frequency points. The resolution obtained with respect to the size of the model targets is comparable to typical values obtained using SAR airborne systems. Single polarized images (Horizontal-Horizontal) are generated using the backprojection algorithm.3 A total of 1480 images are produced using a 20° integration angle. The images in the dataset are organized in a suggested training and testing set to facilitate a standard evaluation of SAR ATR algorithms.
Electronically steered antenna quality mainly relies on the accurate periodicity of the radiating element positions. Very
thin antenna with non-rigid structures will permit the implementation of disruptive mechanical designs and provide
better tactical deployment and permit implementation on non-dedicated platforms. To maintain planar antenna
performances, we propose to dynamically cope with distortions with an innovative method. In this presentation, we will
report on an innovative real-time and embedded measurement technique in harsh environment based on an optical
polarization sensor coupled with an adapted mechanical model, designed in order to maintain a sufficient calibration of
the antenna during its operational use.
We present a new coherent optical Beamformer for the receive mode based on a Dual Frequency Laser and Spatial Light Modulation matrixes. This coherent architecture, described and detailed by different building blocks, allows a full reconfiguration of the beam thanks to the SLM matrixes and a first down conversion due to the conjoint use of a heterodyne source and an external modulator.
We show that diode-pumped solid-state lasers can generate tunable high-purity microwave signals. In the case of a single-axis cavity containing an adjustable linear phase anisotropy, orthogonal linear eigenstates oscillate with a continuously tunable frequency difference. The maximum beat frequency is fixed by the laser cavity length and can reach a few tens of GHz. In order to reach the THz range, insertion of a double refraction crystal inside the laser cavity creates a two-axis laser that allows one to choose independently the frequencies of the two eigenstates. In this case the maximum beat frequency is fixed by the active medium gain bandwidth which is of a few THz for an Er:Yb:glass active medium. We show that doubling the two frequencies emitted by such a two-axis laser at 1.55 mum yields a source of tunable cw THz beat notes suitable for photomixing in GaAs-based THz emitters. Moreover, the beat notes generated by diode-pumped solid-state lasers can be phase-locked to microwave local oscillators. In particular, we show that a single-axis Er:Yb:glass laser provides a beat note continuously tunable from 0 to 20 GHz with a 170 muHz line width. The phase noise of such a source is measured to be lower than -130 dBc/Hz at 100 kHz offset from the carrier.
We report a novel straightforward theoretical analysis and improved high frequency experimental performance of a new type resonant photodetector. A large detection volume is provided by a synchronous drift of photogenerated carriers with a moving interference pattern in a photoconductor. It appears to be suitable for optical generation of microwave signals at high power levels. Performances as a function of applied electric field, photocarrier lifetime, fringe period, and optical power level are analyzed. Experimental results using a GaAs photoconductive layer are presented at frequency f equals 1.6 GHz.
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