Ikuo Arai

Signal Processing of Ground Penetrating Radar Using Spectral Estimation Techniques to Estimate the Position of Buried Targets

Super-resolution is very important for the signal processing of GPR (ground penetration radar) to resolve closely buried targets. However, it is not easy to get high resolution as GPR signals are very weak and enveloped by the noise. The MUSIC (multiple signal classification) algorithm, which is well known for its super-resolution capacity, has been implemented for signal and image processing of GPR. In addition, conventional spectral estimation technique, FFT (fast Fourier transform), has also been implemented for high-precision receiving signal level. In this paper, we propose CPM (combined processing method), which combines time domain response of MUSIC algorithm and conventional IFFT (inverse fast Fourier transform) to obtain a super-resolution and high-precision signal level. In order to support the proposal, detailed simulation was performed analyzing SNR (signal-to-noise ratio). Moreover, a field experiment at a research field and a laboratory experiment at the University of Electro-Communications, Tokyo, were also performed for thorough investigation and supported the proposed method. All the simulation and experimental results are presented.

Super-resolution imaging for point reflectors near transmitting and receiving array

This paper presents subsurface imaging techniques using the well-known MUSIC algorithm to localize point reflectors in cross-borehole radar arrangements. Radar signals received by a spatial array have to be decorrelated, in general, as a preprocessing step when the MUSIC algorithm is implemented. Since most of the decorrelation techniques are based on planar wave incidence model, it is difficult to apply the decorrelation technique for signals from radar targets in the near field of the array. In this paper, we introduce a decorrelation technique with transmitting and receiving array for targets near the array and apply the MUSIC algorithm for estimating the two dimensional position of the point targets in crosshole tomographic measurement. Further, an expanded version of the algorithm to eliminate the direct wave is also derived. Simulation results show that this method offers much higher resolution and accuracy than the conventional diffraction stack method. The paper also discusses the relationship between the SNR ratio and the minimum target separation to be resolved.

A novel apparatus for non-contact measurement of heart rate variability: a system to prevent secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, in monitoring sepsis or in predicting multiple organ dysfunction syndrome.

Abstract Background. The impaired balance of the low-frequency/high-frequency ratio obtained from spectral components of RR intervals can be a diagnostic test for sepsis. In addition, it is known that a reduction of heart rate variability (HRV) is useful in identifying septic patients at risk of the development of multiple organ dysfunction syndrome (MODS). We have reported a non-contact method using a microwave radar to monitor the heart and respiratory rates of a healthy person placed inside an isolator or of experimental animals exposed to toxic materials. Apparatus design and testing. With the purpose of preventing secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, we designed a novel apparatus for non-contact measurement of HRV using a 1215 MHz microwave radar, a high-pass filter, and a personal computer. The microwave radar monitors only the small reflected waves from the subjects chest wall, which are modulated by the cardiac and respiratory motion. The high-pass filter enhances the cardiac signal and attenuates the respiratory signal. In a human trial, RR intervals derived from the non-contact apparatus significantly correlated with those derived from ECG (r=0.98, P<0.0001). The non-contact apparatus showed a similar power spectrum of RR intervals to that of ECG. Conclusions. Our non-contact HRV measurement apparatus appears promising for future pre-hospital monitoring of septic patients or for predicting MODS patients, inside isolators or in the field for mass casualties under biochemical hazard circumstances.

High resolution image reconstruction by GPR using MUSIC and SAR processing method for landmine detection

Landmine detection is a difficult and very sensitive task as it may cost a human life even with a slight mistake or misdetection. In addition, the invention of non-metallic landmines made the scenario much more complicated and difficult. Various landmine detection techniques have been proposed, such as a metal detector, an electromagnetic induction (EMI), and so on. However, the probability of false alarm is very high in such techniques, which is considered as a sever problem. In this paper, ground penetrating radar, which has the capability to detect the non metal and the plastic mines, has been proposed to detect landmines. In addition, super resolution technique MUSIC algorithm and SAR (Synthetic Aperture Radar) has been implemented for the signal processing and image reconstruction of a GPR signal.

Signal processing of ground penetrating radar using super resolution technique

Ground penetrating radar (GPR) using electromagnetic pulse requires high resolution due to its narrow bandwidth nature. The rising requirement for high resolution lead to specific demands for improved prediction methods, all requiring many aspects to be examined. The application of the super resolution method MUSIC (multiple signal classification) algorithm and FFT (fast Fourier transform) are examined. The combined processing method (CPM) of the time domain response of MUSIC and IFFT (inverse fast Fourier transform) is proposed for signal processing of GPR for the first time. Simulation and experimental results show that CPM has both higher resolution and higher receiving signal level than other conventional signal processing methods.

Small prospecting radar system

It is required that the locations of underground installations are made clear on the viewpoint of safety. It is very important to sufficiently investigate the position (for example, depth, horizontal position) of the pipes before the piping work is carried out. However, it is not easy to get the accurate information on the ordinary matter. Because of the size of underground prospecting system and crowded traffic problem, we often could not bring any useful equipment. Thus, the purpose of the present investigation is to miniaturize such system. And we experimentally produced a small prospecting system which could probe underground installations which were near range. The design of the small circuit with high frequency and the small antenna were mainly examined. As a result, it is shown that the object buried in the ground which is ahead at a distance of 50 cm can be prospected with high resolution.

Archaeological survey using pulse compression subsurface radar

A pulse compression subsurface radar using a chirp signal has been developed and evaluated by experimental survey at an archaeological site. This subsurface radar shows the superior ability to detect buried objects by weaker transmitting power than that of a conventional subsurface radar. Although several types of subsurface radars are now used to probe buried objects, it is sometimes difficult to use them for archaeological surveys. This is because echoes from targets such as tombs, ruins, and old mounds are sometimes very weak owing to their smallness and electromagnetic properties, which are very similar to the surrounding soils. In contrast, a pulse compression radar using a chirp signal has the ability to detect a very weak signal masked by noise, with very high resolution. We have applied this technique to a subsurface radar for archaeological survey and assembled an experimental system of a chirp subsurface radar using a delay correlator for pulse compression. This system has been successfully tested at an archaeological site called ‘The remains of Tajiri’ (Komochi, Gunma prefecture, Japan): a mounded tomb buried in the pumice layer has been clearly detected by this system. Copyright

High speed processing method to improve the resolution for subsurface radar

A synthetic aperture method is one effective processing method to improve the horizontal resolution in a subsurface radar. Especially, a pattern matching method, which is a kind of synthetic aperture method, seems to be able to high-speed process by use of the fast Fourier transform. As a result of application to real data, such as a cavity survey and the detection of steel rods in concrete, it was found that a pattern matching method was very effective in improving the horizontal resolution and less processing time was required in comparison with a conventional synthetic aperture method.<<ETX>>

Application possibilities of super-resolution technique for GPR imaging

ABSTRACT Improvement of resolution is the challenging issue in Ground Penetrating Radar (GPR) and that is greatly desired to increase in order to get the clear imaging of very closely buried targets. GPR has been approved as very successful technology for various kinds of investigations & detection of buried targets. In this paper, the application possibility of super resolution technique MUSIC (Multiple Signal Classification) algorithm is examined because of its superior results. Moreover, the conventional FFT (Fast Fourier Transform) has been utilized to get higher precision receiving signal level. Combined Processing Method (CPM) oftime domain response of MUSIC and IFFT (Inverse FFT) has been proposed for the first time to get high resolution and high precision receiving signal level. Simulation and experiment result show that the proposed method has high resolution and high precision receiving signal level than other conventional signal processing approach. Key words: Subsurface radar, FFT, MUSIC Algorithm, Super Resolution

Development of an Array Antenna Landmine Detection Radar System

We have developed an anti-personnel landmine detection radar system which uses an impulse signal of pulse-width 150 ps. We were able to reduce detection time by using an array of wideband spiral antennas of diameter 9 cm, with five transmitter antennas facing six receiver antennas. The resulting device is able to detect landmines in a 50 × 50 cm area in approximately two minutes. We were also able to produce an accurate image of the shape of the underground target by applying super-resolution signal processing (MUSIC processing) to the pulse signal.