Shengwei Meng

Application of Equivalent-Time Sampling Combined with Real-Time Sampling in UWB Through-Wall Imaging Radar

Experiments show that ultra-wideband (UWB) through-wall imaging radar enables good penetration capabilities operating in the frequency range 0.3GHz to 3GHz. According to Shannon sampling theorem, signal acquisition unit only be able to acquire a signal with at least 6GS/s sampling frequency utilizing real-time sampling electronics. It is difficult to find such A/D converter chip in practice. Taking it into account that ultra-wideband through-wall imaging radar transmits signal repeatedly, this paper proposes a method of applying equivalent-time sampling combined with real-time sampling in UWB radar to acquire the echo signal. An ultra-wideband through-wall imaging radar which embeds a PC104 as its main control unit and a FPGA as its timing controller is developed based on this method. The application shows that the ultra-wideband signal can be sampled and recovered with the use of this method.

A simple strategy for moving target imaging via an experimental UWB through-wall radar

In this paper, a simple and effective procedure for through-wall moving target imaging is introduced and discussed via the UWB-SP radar. The modified Kirchhoff migration algorithm is selected as the imaging method to validate the effectiveness of the proposed detection procedure. Considering that the motion of the target behind wall is irregular and unknown, the model of the target with the “go-stop” motion is adopted in the procedure. Based on this model, a proper background removal strategy without complicated operations is introduced to extract the “go-stop” target signal. As the original imaging results obtained from the modified Kirchhoff migration imaging method are dissatisfactory, an effective imaging processing step is given out.

Study on a Novel UWB Linear Array Human Respiration Model and Detection Method

A novel ultra-wideband (UWB) linear array human respiration model and detection method is proposed to obtain vital sign feature (VSF) including azimuth, range, and respiration frequency. As the azimuth of the human being cannot be estimated by a single receiving channel, the new method generates new B-scans for different scanning angles. When the azimuth angle is determined by the azimuth estimation method, the corresponding new B-scans can be processed to obtain the range and respiration frequency. The new method not only estimates the azimuth angle of the human being, but also detects multiple respiration motions from the new B-scans instead of the traditional B-scans. Meanwhile, the implementation steps of the new method are fully illustrated both in free-space and rubble situation. Four free-space simulations are performed and prove the necessity of the new method using the UWB linear array. The results verify its capability for the azimuth estimation and the multiple VSFs detection. In addition, the scene with one person trapped in rubble is simulated to validate the new method for the rubble case with unknown permittivity. Furthermore, a practical experimental validation is performed in an artificial ruin to show the effectiveness of the proposed method.

Through-Wall Shape Estimation Based on UWB-SP Radar

This letter presents a new method for localizing and identifying a target through walls with known wall parameters. A time-delay difference curve (TDDC) is utilized in this method for target localization and identification. The characteristic of the TDDC can be applied to estimate the incident angle and offset the influences in propagation path and propagation time delay brought from the wall. This letter analyzes the method and gives out the theoretical TDDC. Extensive simulations and experiments show the effectiveness of the proposed method.

Data acquisition system of ultra-wide band life detection radar based on PC104 and FPGA

A data acquisition system to acquire and record the output signal of a pulse generator is described. The system was built around Xilinx FPGA interfaced to an embedded computer via the PC104 bus. The system dynamically adjusts parameters (such as time window, sampling interval, pulse repetition frequency, etc.) to satisfy performance requirements of ultra-wide band life detection radar. The system can provide a minimum sampling interval of 5ps.

Tracking and imaging algorithm of walking human bodies for ultra wideband radar

The Ultra WideBand(UWB) Radar used for detecting human bodies is a promising technique in many fields such as urban-warfare, counter-terrorism and calamity rescue scenarios. Conventional UWB imaging algorithm can not meet the demand in the capability of targets recognition and calculation efficiency. The SEABED Algorithm based on the reversible Boundary Scattering Transform (BST) can be used to fast reconstruct target shape, but its application is restricted because antenna are scanned to collect data, which is impractical for systems of detecting moving targets. In this paper, walking motion was used to replace antenna scanning by assuming a system model, and a novel algorithm based on SEABED for UWB radar systems is proposed. Simulation results show that the proposed algorithm features simple hardware requirement, low calculation, and high imaging precision, and it can also estimate the velocity, image and track walking human bodies.

An FPGA-Integrated time-to-digital converter based on a ring oscillator for programmable delay line resolution measurement

We describe the architecture of a time-to-digital converter (TDC), specially intended to measure the delay resolution of a programmable delay line (PDL). The configuration, which consists of a ring oscillator, a frequency divider (FD), and a period measurement circuit (PMC), is implemented in a field programmable gate array (FPGA) device. The ring oscillator realized in loop containing a PDL and a look-up table (LUT) generates periodic oscillatory pulses. The FD amplifies the oscillatory period from nanosecond range to microsecond range. The time-to-digital conversion is based on counting the number of clock cycles between two consecutive pulses of the FD by the PMC. Experiments have been conducted to verify the performance of the TDC. The achieved relative errors for four PDLs are within 0.50%–1.21% and the TDC has an equivalent resolution of about 0.4 ps.

Implementation of the UWB Radar with Two Transmitting and Four Receiving Channels Based on FPGA

Hardware design methods for MIMO (Multiple-input multiple output) UWB (Ultra wideband) radar are presented. The MIMO-UWB radar system mainly consists of two transmitting antennas, four receiving antennas, two impulse generator, sample-and-hold, AD converter, and data acquisition subsystem base on FPGA. All these modules are designed and realized. Additionally, the designed system supports four equivalent time sampling channels with 50GS/s sample rate. Finally, we proved the feasibility of the designed system through closed-loop testing.

A new method of through wall moving target detection and imaging using UWB-SP radar

This paper proposes a new algorithm to obtain the target shape imaging and track it synchronously using triangle localization method and the difference of time delay in the application of through wall imaging (TWI). The proposed algorithm based on a system model built in the near field can effectively estimate the velocity and track of moving target with the imaging result. Simulation results show that the effect of the wall can be removed visibly and the purpose of the imaging and tracking of moving target can be realized well.

The detection and localization of targets in 2D or 3D scene using ultra-wideband short-pulse through-the-wall radar

This paper presents the simulations of TWRI (through the wall radar imaging) in 2D and 3D scene and discusses the finite beamwidth processing to reduce the high calculation of the back-projection algorithm. The 2D and 3D scene are reconstructed to display the performance of the TWRI system using analysis, numerical simulations and real data collected from Through-the-Wall Radar (TWR). At the end of this paper, a novel approach is proposed to locate the position of the target accurately using the Ultra-Wideband Short-Pulse (UWB-SP) Radar.