Xijing Jing

A Novel Method for Respiration-Like Clutter Cancellation in Life Detection by Dual-Frequency IR-UWB Radar

Detection of trapped survivors under collapsed buildings using impulse-radio ultra-wideband (IR-UWB) radar has become an important research topic. However, due to the jitter or drift of the radar, clutter reflected from walls or rubble is similar to the human respiratory response in some scenarios. Thus, it becomes difficult to determine the presence or absence of the survivor under ruins. In this paper, a novel dual-frequency IR-UWB radar with low center frequencies is developed and a method based on adaptive clutter cancellation is proposed to eliminate the respiration-like clutter. Experiments are carried out in both through-wall and simulated rubble cases, and the results shows that the proposed method outperforms the common method, which is based on linear-trend subtraction with single-frequency IR-UWB radar in removing the respiration-like clutter and improves the radar performance in life detection.

Human-Target Detection and Surrounding Structure Estimation Under a Simulated Rubble via UWB Radar

The presence of a human target and the surrounding rubble structure are both important information in postdisaster rescue. In this letter, we study the signal-processing algorithm for detecting a human target in radar echo data. Furthermore, a solution is proposed to estimate the surrounding structure-the distance between the human target and the top wall of the cavity where the human target is trapped. In the latter procedure, the human position estimated before is used as a prior knowledge. In order to verify the feasibility of the proposed method, experiments are carried out with a human subject lying under the simulated rubble structure. The results show prospects of the proposed method.

A NEW METHOD FOR NON-LINE-OF-SIGHT VITAL SIGN MONITORING BASED ON DEVELOPED ADAPTIVE LINE ENHANCER USING LOW CENTRE FREQUENCY UWB RADAR

The physiological parameters monitoring of human target are considered to be a meaningful and challenging task in non-lineof-sight (NLOS) scenes such as rescue of trapped survivors in postdisaster. In this paper, a new method based on developed adaptive line enhancer (DALE) is proposed to monitor vital signs via ultra-wideband (UWB) radar with centre frequency of 400MHz. The validity of this new method is proved by means of two experiments with different positions of human target. The good results demonstrate that this new method can be used for vital sign monitoring including respiration and heartbeat through the obstacle. Furthermore, the motion responses due to respiration and heartbeat in different body positions are also discussed.

A Novel Radar Sensor for the Non-Contact Detection of Speech Signals

Different speech detection sensors have been developed over the years but they are limited by the loss of high frequency speech energy, and have restricted non-contact detection due to the lack of penetrability. This paper proposes a novel millimeter microwave radar sensor to detect speech signals. The utilization of a high operating frequency and a superheterodyne receiver contributes to the high sensitivity of the radar sensor for small sound vibrations. In addition, the penetrability of microwaves allows the novel sensor to detect speech signals through nonmetal barriers. Results show that the novel sensor can detect high frequency speech energies and that the speech quality is comparable to traditional microphone speech. Moreover, the novel sensor can detect speech signals through a nonmetal material of a certain thickness between the sensor and the subject. Thus, the novel speech sensor expands traditional speech detection techniques and provides an exciting alternative for broader application prospects.

A NEW KIND OF NON-ACOUSTIC SPEECH ACQUISITION METHOD BASED ON MILLIMETER WAVERADAR

Air is not the only medium that can spread and can be used to detect speech. In our previous paper, another valuable medium | millimeter wave (MMW) was introduced to develop a new kind of speech acquisition technique (6). Because of the special features of the MMW radar, this speech acquisition method may provide some exciting possibilities for a wide range of applications. In the proposed study, we have designed a new kind of speech acquisition radar system. The super-heterodyne receiver was used in the new system so that to mitigate the severe DC ofiset problem and the associated 1=f noise at baseband. Furthermore, in order to decrease the harmonic noise, electro-circuit noise, and ambient noise which were combined in the MMW detected speech, an adaptive wavelet packet entropy algorithm is also proposed in this study, which incorporates the wavelet packet entropy based voice/unvoiced radar speech adaptive detection method and the human ear perception properties in a wavelet packet time- scale adaptation speech enhancement process. The performance of the proposed method is evaluated objectively by signal-to-noise ratio and subjectively by mean-opinion-score. The results conflrm that the proposed method ofiers improved efiects over other traditional speech enhancement methods for MMW radar speech.

Multi-target human sensing via UWB bio-radar based on multiple antennas

Being capable of sensing human through obstacles, bio-radar is promising in many applications like healthcare, public securities, emergency rescue and so on. In these applications, the presence of human and the human count are among the most important issues that are concerned by people. At present plenty of studies deal with the former issue but theres no study dealing with the latter one. To this end, a framework of determining the count of human targets using ultra-wideband (UWB) bio-radar was presented in this paper. It was developed based on multiple antennas and correlation processing of sensed respiration among the data channels. In the experiment, the UWB bio-radar could distinguish among the cases of no target, single target, two targets and three targets present behind a brick wall and determine the target count with no priori information. On this basis, multi-target estimation and localization can be further realized.

Characterization and Identification of IR-UWB Respiratory-Motion Response of Trapped Victims

Impulse-radio ultrawideband (IR-UWB) radar is a popular research topic in the field of post-earthquake search and rescue. By lowering center frequency, it can penetrate through earthquake rubble to detect trapped victims mainly by identifying their respiratory-motion response. Thus, low-center-frequency IR-UWB respiratory-motion response is characterized for the first time in this paper. On this basis, a novel constant false alarm rate (CFAR) algorithm that automatically identifies the response is developed. The IR-UWB respiratory-motion response has range extension and interrelation characteristics. With these characteristics, the algorithm can effectively improve the estimation accuracy of clutter energy in CFAR detection. The characteristics and the algorithm performance are verified by experiment results, which show not only great promise in practice but also significance for future research of IR-UWB radar for detection of trapped victims.

A 94-GHz Millimeter-Wave Sensor for Speech Signal Acquisition

High frequency millimeter-wave (MMW) radar-like sensors enable the detection of speech signals. This novel non-acoustic speech detection method has some special advantages not offered by traditional microphones, such as preventing strong-acoustic interference, high directional sensitivity with penetration, and long detection distance. A 94-GHz MMW radar sensor was employed in this study to test its speech acquisition ability. A 34-GHz zero intermediate frequency radar, a 34-GHz superheterodyne radar, and a microphone were also used for comparison purposes. A short-time phase-spectrum-compensation algorithm was used to enhance the detected speech. The results reveal that the 94-GHz radar sensor showed the highest sensitivity and obtained the highest speech quality subjective measurement score. This result suggests that the MMW radar sensor has better performance than a traditional microphone in terms of speech detection for detection distances longer than 1 m. As a substitute for the traditional speech acquisition method, this novel speech acquisition method demonstrates a large potential for many speech related applications.

A Novel Method for Speech Acquisition and Enhancement by 94 GHz Millimeter-Wave Sensor

In order to improve the speech acquisition ability of a non-contact method, a 94 GHz millimeter wave (MMW) radar sensor was employed to detect speech signals. This novel non-contact speech acquisition method was shown to have high directional sensitivity, and to be immune to strong acoustical disturbance. However, MMW radar speech is often degraded by combined sources of noise, which mainly include harmonic, electrical circuit and channel noise. In this paper, an algorithm combining empirical mode decomposition (EMD) and mutual information entropy (MIE) was proposed for enhancing the perceptibility and intelligibility of radar speech. Firstly, the radar speech signal was adaptively decomposed into oscillatory components called intrinsic mode functions (IMFs) by EMD. Secondly, MIE was used to determine the number of reconstructive components, and then an adaptive threshold was employed to remove the noise from the radar speech. The experimental results show that human speech can be effectively acquired by a 94 GHz MMW radar sensor when the detection distance is 20 m. Moreover, the noise of the radar speech is greatly suppressed and the speech sounds become more pleasant to human listeners after being enhanced by the proposed algorithm, suggesting that this novel speech acquisition and enhancement method will provide a promising alternative for various applications associated with speech detection.

THE ENHANCEMENT OF MILLIMETER WAVE CONDUCT SPEECH BASED ON PERCEPTUAL WEIGHTING

A new non-air conduct speech detecting method is introduced in this paper by means of millimeter wave (MMW) radar. Due to its special attribute, this method may provide some exciting possibility of wide applications. However, the resulting speech is of less intelligible and poor audibility since the present of the combined and colored additive noise. This paper, therefore, investigates the problem of the MMW radar speech enhancement by taking into account the frequency-domain masking properties of the human auditory system and reduces the perceptual effect of the residual noise. Considering the particular characteristics of MMW speech, the perceptual weighting technique is developed and incorporated into the traditional spectral subtraction algorithm to shape the residual noise and make it inaudible. The results from both acoustic and listening evaluation suggest that the background noise can be reduced efficiently while the distortion of MMW radar speech remains acceptable, the enhanced speech also sounds more pleasant to human listeners, suggesting that the proposed algorithm achieved a better performances of noise reduction over other subtractive-type algorithms.