Siyang Cao

Scaling function waveform for effective side-lobe suppression in radar signal

Scaling function of generic wavelet is proposed to be the radar waveform of a radar signal. Its shows significant advantage on conventional linear frequency modulated (LFM) or chirp radar waveform in side-lobe compression. To increase the bandwidth of the radar waveform, we further propose a new radar waveform named chirp-Z, which is composed of wavelet packets. The generation of the chirp-Z signal is introduced, and the signal is compared with the chirp radar pulse with the same duration and same bandwidth chirp. The result demonstrates that chirp-Z signal has much better side-lobe suppression than the conventional chirp signal. Furthermore, due to the composition of wavelet packets in the chirp-Z signal, subband adaptation in both amplitude and phase adjustment becomes flexible in responding to the variation of environments. The latter enables powerful cognitive radar.

Wavelet-Based Waveform for Effective Sidelobe Suppression in Radar Signal

A new radar waveform based on wavelets is proposed. The waveform shows significant advantages over conventional linear frequency modulated (LFM) and Costas waveforms for effective sidelobe suppression. Another benefit comes from the wavelet packets, each of which occupies a subband in the frequency domain. Subband adaptation of the waveform in both magnitude and phase becomes flexible, responding to varying target and environmental conditions. The latter facilitates the development of powerful cognitive radars.

A Wavelet-Packet-Based Radar Waveform for High Resolution in Range and Velocity Detection

In this paper, a new radar waveform based on wavelet packets is proposed. This waveform shows significant advantages over conventional linear frequency modulated waveforms for range and velocity detections of moving targets. The proposed waveform can decouple its envelope and carrier for range and velocity estimations, respectively, because of which the Doppler spread term can be totally removed when estimating velocity and the Doppler effect ignored when estimating range. This way, the proposed waveform produces higher resolution in range or velocity detection. The proposed waveform can be applied to the synthetic aperture radar for improved performance.

Portable millimeter wave 3D imaging radar

The paper aims to build a new, portable, and affordable millimeter wave imaging radar. The proposed radar uses rotation movement and applies inverse Radon transform to resolve a 2D image of each range bin. Consequently, 3D imaging can be realized by the radar system. Its resolution is comparable to light-based imaging sensors, such as cameras and LIDAR - light detection and ranging. Because of using a single transceiver element, the new radar imaging system is compact, low cost, and portable. It can be used for detection, security and surveillance systems.

3D Imaging Millimeter Wave Circular Synthetic Aperture Radar

In this paper, a new millimeter wave 3D imaging radar is proposed. The user just needs to move the radar along a circular track, and high resolution 3D imaging can be generated. The proposed radar uses the movement of itself to synthesize a large aperture in both the azimuth and elevation directions. It can utilize inverse Radon transform to resolve 3D imaging. To improve the sensing result, the compressed sensing approach is further investigated. The simulation and experimental result further illustrated the design. Because a single transceiver circuit is needed, a light, affordable and high resolution 3D mmWave imaging radar is illustrated in the paper.

From RGBD image to hologram

We propose an approach to produce computer generated holograms (CGH) from RGBD data. Being able to produce CGH from RGBD images simplifies the recording process and results in more realistic reconstruction. A multilayer wavefront recording plane method is described for fast wave propagation, and it is completed with a two-step occlusion culling process to preserve the self-occlusion effect. The approach is evaluated on RGBD images of real world 3D scene and the the reconstructed images from the CGH demonstrate the effectiveness of the proposed approach.

From image pair to a computer generated hologram for a real-world scene.

We propose an approach to produce computer generated holograms (CGHs) from image pairs of a real-world scene. The ratio of the three-dimensional (3D) physical size of the object is computed from the image pair to provide the correct depth cue. A multilayer wavefront recording plane method completed with a two-stage occlusion culling process is carried out for wave propagation. Multiple holograms can be generated by propagating the wave toward the desired angles, to cover the circular views that are wider than the viewing angle restricted by the wavelength and pitch size of a single hologram. The impact of the imperfect depth information extracted from the image pair on CGH is examined. The approach is evaluated extensively on image pairs of real-world 3D scenes, and the results demonstrate that the circular-view CGH can be produced from a pair of stereo images using the proposed approach.

From phased array to holographic radar

A new radar system named holographic radar is proposed in this paper. The new radar records the transmission pattern of the electromagnetic wave instead of the directed amplitude and phase information from individual target, which is utilized by the traditional electronic scanning radar. The recorded pattern can then be studied for target detection or for radar imaging. The advantages of the new radar system are multi-folds: a. the receiver elements do not need to be synchronized in sampling, b. radar system can resolve the ranges of interested targets using a single frequency waveform instead of a wide bandwidth signal, and c. the single frequency waveform reduces the complexity of the microwave circuits which build up the radar system.

Compressed sensing for portable millimeter wave 3D imaging radar

In our previous paper, a 3D imaging radar system is proposed. To further improve the sensing efficiency and imaging quality, compressed sensing approach to recover 3D imaging is studied in this paper. Based on the raw radar of the proposed system, we discussed the sensing basis and constructed representation basis. The simulation and experiment results show that the compressed sensing approach can achieve a high quality 3D imaging.

Two viewing angles for holographies in radar and light

In this work, a new topic, which is to synthesize (recover) the holograms between two or more recorded holograms with a large angle discrepancy, is presented. The technique aims at enlarging view angle, speeding up the recording process by reducing sensing points, and increasing resolution in holographic radar and light. Our method to tackle the problem is proposed. We analyze the problem in both single target and multiple targets cases. Given recorded magnitudes at receiving elements, nearby magnitudes of virtual receiving elements can be approximated. The accuracy of the approximation is also evaluated.