Shengbo Ye

A Novel Two-Dimensional Sparse MIMO Array Topology for UWB Short-Range Imaging

In this letter, according to the two design principles of uniform distribution and less element shadowing for effective aperture, a novel two-dimensional (2-D) sparse ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna array topology is optimized and proposed for short-range high-resolution imaging. During the optimization, a “grid method” (GM) is proposed to judge the uniformity of effective aperture, and of which the maximum shadowing number (MSN) is obtained by the projection slice method. Compared to other two different arrays having the same number of transceivers, the proposed optimal array has a better control over the sidelobe level (SL) both in the interference region (IR) and non-interference region (NIR) of the simulated radiation patterns, from which the peak sidelobe levels (PSLs) of the optimal array obtained are lower than the compared ones over 2 dB. Experimental imaging results for a mannequin target also verify the outstanding imaging capability of the proposed array. Therefore, with a small number of effective elements, the proposed array topology has potential applications for high-efficiency UWB short-range imaging.

Design of a Novel Ultrawideband Digital Receiver for Pulse Ground-Penetrating Radar

A new ultrawideband-digital-sampling technology is presented. This novel sampling technology is the first to employ both the successive-approximation-register technology and the equivalent-time-sampling technology to improve the bandwidth of the receiver. Accordingly, a new low-cost and compact ultrawideband digital receiver for pulse ground-penetrating radar is designed. The merit of this receiver is that it can convert radio-frequency signal to digital signal without any analog sampling gate or analog-to-digital converter. The equivalent sampling rate of the receiver is up to 33 GHz. The measurements show that this receiver has more than 3-GHz bandwidth and nearly 100% conversion efficiency.

A novel compact UWB ground penetrating radar system

The impulse ground-penetrating radar (GPR) has a significant advantage than other radar systems, due to their high-resolution and simple system architecture. In this paper, a novel low-cost and compact impulse ultrawideband (UWB) GPR system is presented. The steep edged narrow pulse generation in the transmitter is solved with the step recovery diodes (SRD). In order to simplify the structure and improve the performance, a compact UWB antenna is employed which based on using of two smoothly shaped flares of a simple geometrical structure. Furthermore, the receiver employs a new ultra wideband digital sampling technology to realize analog-to-digital conversion instead of using commercial integrated ADC. This novel digital sampling technology is the first to employ both the successive-approximation-register technology and the equivalent-time-sampling technology to improve the sampling rate and the bandwidth of the receiver. Experimental GPR survey data obtained from different applications are presented. It is shown that the developed system has good ability for different detection applications.

Rapid Detection Methods for Asphalt Pavement Thicknesses and Defects by a Vehicle-Mounted Ground Penetrating Radar (GPR) System

The thickness estimation of the top surface layer and surface layer, as well as the detection of road defects, are of great importance to the quality conditions of asphalt pavement. Although ground penetrating radar (GPR) methods have been widely used in non-destructive detection of pavements, the thickness estimation of the thin top surface layer is still a difficult problem due to the limitations of GPR resolution and the similar permittivity of asphalt sub-layers. Besides, the detection of some road defects, including inadequate compaction and delamination at interfaces, require further practical study. In this paper, a newly-developed vehicle-mounted GPR detection system is introduced. We used a horizontal high-pass filter and a modified layer localization method to extract the underground layers. Besides, according to lab experiments and simulation analysis, we proposed theoretical methods for detecting the degree of compaction and delamination at the interface, respectively. Moreover, a field test was carried out and the estimated results showed a satisfactory accuracy of the system and methods.

An improved transient-type ice-penetrating radar

A low-cost, compact, short-pulse ice-penetrating radar (IPR) system with a center frequency of 50 MHz for sounding glacier topography is presented. The radar was developed to measure ice thickness and to image internal structures and basal conditions of glaciers and ice sheets with a maximum range of � 16 000 ns and a depth resolution better than 2.5 m. The receiver of the IPR system employs asynchronous operation mode, avoiding the need for a cable between the transmitter and receiver. A new sampling technology using a high-speed field programmable gate array, which implements a 256-trace stacking algorithm to realize the analog-to-digital conversion, both simplifies the structure of the receiver and increases the sampling efficiency. The power consumption of the whole receiver is <1.5 W, which can be supplied by a laptop computer. Test measurements were made during the 5th China Expedition to the Grove Mountains in East Antarctica. Field tests show the capability of this system to measure ice thickness up to 650 m and to define internal layers within the ice body.

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 Ultrawideband Exponentially Tapered Slot Antenna of Combined Electric-Magnetic Type

A novel exponentially tapered slot antenna with ultrawide bandwidth and small late-time ring is presented. A microstrip-to-coplanar-stripline (CPS) transition of Chebyshev multisection type is used as feeding transmission. The exponentially tapered slot, which is considered as electric-type radiator (ER), is combined with a magnetic-type radiator (MR) to achieve ultrawideband performance and small size. The MR is completed by a lumped resistor bridged between the loop arm and the transmission ground. The measured impedance bandwidth (VSWR <; 2) of optimized antenna is 0.65 ~ 5.9 GHz, which agrees well with the simulated results. The measured gain is almost 3 dBi in the whole band, and the front-to-back ratio is about 15 dB.

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.

On Sparse MIMO Planar Array Topology Optimization for UWB Near-Field High-Resolution Imaging

An optimization method for ultrawideband multiple-input-multiple-output (MIMO) planar array topology design, which can satisfy both uniformity and lower element shadowing principles, is proposed by extending our previous work. Two planar MIMO arrays, namely, the basic optimal array (BOA) and the extended optimal array (EOA) are optimized. The focusing and sidelobe-suppression properties of the BOA and the EOA are demonstrated to be superior to other two previous state-of-the-art planar MIMO arrays. The advantages of the two optimized arrays in 3-D imaging are further indicated by experimental results for different distributed targets. The validity of the proposed method is verified by the excellent performances of the BOA and the EOA.

Design and testing of a pseudo random coded GPR for deep investigation

The sounding depth is one of the most important parameters of Ground Penetrating Radar (GPR), and it is also the main limitation of GPRs applications. A pseudo random coded GPR for deep investigation is described in this paper. It could achieve a sounding depth more than 130 meters. A long Golay sequences and TGA (time-gain amplifier) technology are utilized to increase the SNR of faint echoes from deep layer underground, and enhance the sounding depth. The platform could be either a vehicle or a large airship. Field tests were carried out on Kubuqi desert located in Inner Mongolia, north-west of china, to verify the detection ability of this GPR system. The sounding results agree well with the results from the drilling and resistivity logging.