Teruyuki Hara

Doppler Frequency Tolerant Synthetic Bandwidth Radar

Synthetic Bandwidth Radar (SBR) is one of the pulse radar which can obtain high range resolution. SBR has an advantage in that range resolution is not restricted by receiver bandwidth and/or sampling frequency of A/D converter. However, in the case of targets with non-zero relative velocity, accuracy of the measured range by SBR is getting worse because of Doppler frequency. In this paper, we propose a novel Doppler frequency tolerant SBR and show the effectiveness of the proposed SBR by computer simulation.

Image-Based Target Detection and Radial Velocity Estimation Methods for Multichannel SAR-GMTI

In order to enhance the performance of spaceborne synthetic aperture radar–ground moving target indication (SAR-GMTI) systems, multichannel systems with large and preferably nonuniform baselines are required. In this paper, SAR-GMTI algorithms for multichannel SAR systems, which we call multichannel displaced phase center antenna (DPCA), multichannel along track interferometry (ATI), and multichannel DPCA-ATI, are presented. Multichannel DPCA is a deterministic algorithm for clutter and azimuth ambiguity suppression. It successfully suppresses not only uniform azimuth ambiguities but also nonuniform isolated ones, since it does not require uniform clutter covariance assumption as adaptive algorithms do. Multichannel ATI and multichannel DPCA-ATI are the algorithms for target radial velocity estimation. Both of them reduce the target radial velocity ambiguities, which arise with the long baseline systems, by exploiting the multiple receive channel signals. And multichannel DPCA-ATI further achieves robust performance to clutter influence by suppressing the clutter and the azimuth ambiguity in advance. The performances of the proposed algorithms are shown through airborne Ku-band three-channel SAR experiments. It is shown that the multichannel DPCA suppresses strong azimuth ambiguity up to more than 20 dB, and the accuracy of the radial velocity estimation of the multichannel DPCA-ATI is on the order of 0.1 m/s. Furthermore, statistical performance analysis is presented to discuss the potential performance on the spaceborne system.

Derivation of monopulse angle accuracy for phased array radar to achieve Cramer-Rao lower bound

Derivation of monopulse angle accuracy for phased array radar to achieve Cramer-Rao lower bound is presented in this paper. Antenna element positions originating from antenna center are used for difference beam taper in this monopulse angle estimation. For uniform linear array, the accuracy is 1.16 times higher than conventional monopulse method. In other words, SNR can be reduced by 1.3 dB to achieve required angle accuracy. Suboptimal difference beamforming taper for the subarray-based digital beamforming radar is also derived.

Radar video generated from Synthetic Aperture Radar image

Synthetic Aperture Radar (SAR) can take a fine radar image without relation to sunshine condition. Recently, video generated from SAR is discussed. The radar video offers the practical understanding of the target motion without the added implement. The radar video is often generated from raw data in spotlight mode. In contrast, we propose the radar video generated from SAR image. The proposed scheme provides a low complexity and the freedom of the observation mode. In the paper, we show the process of the proposed scheme and indicate the snapshot image of radar video made of our air-borne stripmap SAR data or Advanced Land Observing Satellite-2 data. The images show possibility of the radar video with stripmap mode or space-borne SAR.

Coherent integration with null constraint on clutter spectrum for pulse Doppler radar

In this paper, the null constrained coherent integration (NCCI) is proposed to improve detectability of the slow moving or maneuvering target for pulse Doppler radar. The projection matrix for clutter mitigation is predetermined based on clutter spectrum shape and the required clutter attenuation. In the real time processing, received clutter is mitigated by applying the projection matrix, then a target signal is coherently integrated by DFT or FFT. The process without adaptive processing relaxes the computational complexity and burden compared to the optimum Doppler filter. By computer simulation, the proposed method shows higher magnitude response around zero Doppler and wider flatten magnitude response in the passband compared with MTI followed by coherent integration.

A display method allocating SAR image and ATI phase map to value and saturation, respectively

Synthetic Aperture Radar (SAR) can take a fine radar image without relation to sunshine condition, so it is important to propose the display method that fulfills a users demand. SAR provides some information with high-level process. To confirm both SAR image and the results of the high-level process simultaneously, the color display is effective. However, conventional method has the restriction of color combination. In this context, we proposed the display method focusing the saturation. The proposed method superimposed the phase map of along track interferometry, which is one of the high-level processes, on SAR image with good visibility. In this paper, we discuss the effect of the proposed display method, explain its formularization, and demonstrate the effect by airborne SAR data.

Angle measurement method for two targets within antenna beam width using two receivers

Monopulse angle measurement methods are often utilized to measure a target angle. However, this method cannot measure a correct angle for multiple targets which cannot be distinguished by range, Doppler frequency and beam width. A method to simultaneously measure azimuths and elevations for only two targets was proposed, which requires a low computational load compared with other methods. However, the conventional method requires four receivers, therefore it is difficult to utilize it when there is a hard ware limitation. In this paper, we propose a method to measure azimuths and elevations for two targets using two receivers and time division system. We also show a verification of the proposed method by a numerical simulation and experimentation, though measured angles are restricted to azimuths or elevations. The results show that two targets angles can be measured by our proposed method using two receivers.