Xiaobing Sun

A high accuracy mono-station UWB positioning system

A unique way to determine the position of an UWB tag relative to a single UWB base station is proposed in this paper. The system is made possible by applying the mono-pulse angle measurement concept of the conventional mono-pulse radar to the UWB system to find the direction of the tag. Together with the range measurement based on the time-of-flight of the UWB pulses, a mono-station UWB positioning system can be built. Low data rate communication function can also be included into the system. A prototype system based on above ideas is implemented. The performance of the system is tested and shows that the STD for the angle estimation is smaller than 1.0deg and for the range estimation is smaller than 2cm. Therefore it is a high accuracy positioning system. Compared with other UWB positioning systems, in that generally more than 3 reference points with known positions are needed, the proposed one need only a single reference. The system is of the simplest configuration and is very easy to be used and very quick in deployment. The possible application of the system to home robot is also described.

A Digital Watermarking Technique Based on ICA Image Features

A novel digital watermarking technique based on ICA image features is proposed in this paper. This new watermarking technique is provided for both high-quality visual imperceptibility and robust & effective watermark detection. An adaptive-transform approach is employed in this technique, which is different from the conventional DCT or Wavelet transformations. The learned image-adaptive ICA features with localized, oriented and band-pass characters represent similar properties exhibited by the primary and secondary visual cortexes in human vision system (HVS). It enables a powerful masking effect to hide extra information into images with very little visual changes to human eyes. The embedding and detection of watermarks on ICA coefficients whose distribution is super-Gaussian in nature are found to be effective and robust even when only a classical spread-spectrum method is used. Additionally, the adaptive watermarking on suitable images and image regions is achieved implicitly owing to the merit that the ICA bases are automatically learnt from images. The experiments of the blind image watermarking system demonstrate its advantages on good image quality and robustness under various attacks such as image compression, geometric distortion and noises, in comparison with some conventional methods.

UWB Circular Monopole Ominidirectional Antenna with a Slot for Radiation Pattern Improvement

An ultra wideband (UWB) circular monopole antenna consisting of a ground plane, a radiating element and a feed member is proposed in this paper. The radiating element comprises a simple circular metal patch, with a slot on one side of the patch. This slot can decrease the gain variation in the y-z plane of the radiation pattern and increase the impedance bandwidth. The whole size of the antenna is 30 x 30 x 0.813 mm3. The measured -10 dB impedance bandwidth of the circular monopole antenna is from 2.3 GHz to 6.1 GHz. The gain variation is less than or around 15 dB in the y-z plane and below 7 dB in the x-z plane over the operating bandwidth.

High Quality Directional Audio System

Highly directional audible sound can be reproduced by the nonlinear interaction of finite amplitude AM ultrasound waves in the air. Due to the nonlinear process, however, the reproduced audible sound does not quite match the level of the traditional speaker in sound quality. There are mainly two reasons for this, namely, high harmonic and non-harmonic distortions and -12 dB/oct dependence for the low frequency response. In this paper, new methods for improving the sound quality are proposed and verified. Furthermore, a technique of forming desirable sound beam shapes is also discussed.

UWB Reference-Free Self-Positioning with Electrical Scanning Directional Antenna

An Ultra-Wideband (UWB) self-positioning system and its architecture are presented. It consists of a pulse-based transceiver for ranging from the surrounding objects, an electrical scanning antenna for direction detection, and baseband positioning algorithms. Self-positioning can be performed by using the ranging and direction information based on reflected signals in a room environment. It can also determine its own position in the presence of some blocking objects by employing the so-called multi-layer reflection algorithm. This reference-free self-positioning system operated in an office meeting room is shown to be capable of achieving 30 cm positioning accuracy with the 70% bound.

Data hiding method for broadcasting system

A novel method of hiding data into multimedia contents by using watermarking technology is described in this paper. This method can be used for analog images, digital raw images, JPEG and other compressed images and has advantages over the existing data hiding methods in terms of less distortion to original multimedia contents, robustness against noise attacks, and efficient data embedding/detection. By modifying the summed value of selected DCT coefficients and making the quantization adaptive to the DCT amplitudes and other parameters, the data hiding method is found to be robust against signal distortions in broadcasting system due to noise, contrast and luminance change, pixel shift, and multi-path interference.