Zhenghuan Xia

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.

Design of modulated m-sequence ultrawideband radar for life detection

In life detection with ultrawideband (UWB) radar, the high signal-to-noise ratio (SNR) is very important for good performance. In this paper, the m-sequence with a carrier is applied to life detection, and SNR can be improved by pulse compression and linear average. The hybrid sampling technique is used to improve the sampling resolution and reduce the cost. The peak-to-sidelobel ratio after pulse compression would be degraded when the delay resolution of the delay line drifts in different temperature, thus the actual delay resolution of the delay line should be measured before hybrid sampling. Experiments show that the proposed modulated m-sequence UWB radar has good detection performance.

A novel handheld pseudo random coded UWB radar for human sensing applications

A novel handheld pseudo random coded ultra-wideband (UWB) radar for human sensing applications is presented in this paper. In order to reduce the size of the radar and obtain good penetrability, the center frequency of the m-sequence is assigned to about 1.1GHz. The peak voltage of the m-sequence is 4.5Vpp, while the length of the m-sequence can be chosen to obtain different signal-to-noise ratio (SNR). The digital transmitter, the dual-channel receiver and the clock synchronization are discussed in detail. The experimental results show that the proposed handheld pseudo random UWB radar has good detection performance for human sensing applications in complex environment.

Non-destructive survey of pavement layer thicknesses with ground penetrating radar

In pavement survey engineering, ground penetrating radar (GPR) is an effective and non-destructive survey method, compared with traditional core drilling method. Dielectric constant and layer thickness can be acquired from inversion analysis of the GPR signals. In this paper, metal reflection method and a layer picking algorithm called trace correlation are combined to estimate pavement layer thickness rapidly and efficiently. Highway testing shows this survey approach gives small errors, and meets the pavement survey requirements.

Design of wireless automatic synchronization for the low-frequency coded ground penetrating radar

Low-frequency coded ground penetrating radar (GPR) with a pair of wire dipole antennas has some advantages for deep detection. Due to the large distance between the two antennas, the synchronization design is a major challenge of implementing the GPR system. This paper proposes a simple and stable wireless automatic synchronization method based on our developed GPR system, which does not need any synchronization chips or modules and reduces the cost of the hardware system. The transmitter omits the synchronization preamble and pseudorandom binary sequence (PRBS) at an appropriate time interval, while receiver automatically estimates the synchronization time and receives the returned signal from the underground targets. All the processes are performed in a single FPGA. The performance of the proposed synchronization method is validated with experiment.

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.