José M. García-Rubia

Analysis of Moving Human Micro-Doppler Signature in Forest Environments

Automatic detection of human motion is important for security and surveillance applications. Compared to other sensors, radar sensors present advantages for human motion detection and identiflcation because of their all-weather and day-and-night capabilities, as well as the fact that they detect targets at a long range. This is particularly advantageous in the case of remote and highly cluttered radar scenes. The objective of this paper is to investigate human motion in highly cluttered forest medium to observe the characteristics of the received Doppler signature from the scene. For this purpose we attempt to develop an accurate model accounting for the key contributions to the Doppler signature for the human motion in a forest environment. Analytical techniques are combined with full wave numerical methods such as Method of Moments (MoM) enhanced with Fast Multipole Method (FMM) to achieve a realistic representation of the signature from the scene. Mutual interactions between the forest and the human as well as the attenuation due to the vegetation are accounted for. Due to the large problem size, parallel programming techniques that utilize a Graphics Processing Unit (GPU) based cluster are used.

Experimental assessment of slant-path rain attenuation variability in the Ka-band

Summary This study is based on the results of a slant-path Ka-band propagation experiment carried out in Madrid, Spain, regarding rain attenuation, which is the main propagation impairment in this frequency band. The experimental and statistical results correspond to seven complete years of measurements, a period large enough to accomplish a comprehensive analysis in order to characterize the variability of rain rate and attenuation. It is shown that year-to-year variability is significant in temperate climates as Madrids. The aforementioned significance is also apparent with regards to seasonal, monthly, worst-month and hourly variability concerning rain attenuation, which are also discussed and related when possible to the variability of the rain phenomena, either represented by the total amounts of rainfall in the different periods or by rain rate statistics. Copyright

Detection of moving human micro-Doppler signature in forest environments with swaying tree components by wind

The objective of this paper is to investigate human motion in forest medium with swaying tree components due to time-varying wind effects and to observe the characteristics of the received Doppler signature from the scene. We provide the results of an accurate model accounting for the key contributions to the Doppler signature in this scenario. A realistic walking motion is generated using an analytical model extracted from empirical data. The swaying canopy motion is modeled by employing a spring response mechanism to the wind force. The backscattered field calculations from the scene comprise of contributions from the forest (including trunks, branches, and the ground) and human, and the interactions between them. An analytical forest scattering model, which accounts for the ground effects, is used to calculate the contribution from the forest. The attenuation effects due to the vegetation are accounted for. In order to characterize the effects of human motion accurately, a full wave technique, namely, method of moments (MOM) enhanced with fast multipole method (FMM), is employed for the human scattering calculations. A parallel version of MOM-FMM is implemented on a graphics processing unit based cluster to handle the large problem size. The human walking signatures created by the model are analyzed for different winds.

Fade and Interfade Duration Characteristics in a Slant-Path Ka -Band Link

Satellite-to-earth links are subject to several propagation effects in the troposphere, being rain attenuation the impairment that can cause the deepest fades. In this paper, the duration of both fades and the intervals between consecutive fades (interfade intervals) are characterized on the basis of the results of a long-term slant-path Ka-band propagation experiment carried out in Madrid, Spain. The experimental and statistical results included in this paper correspond to seven complete years of measurements, a period large enough to characterize not only the average-year statistics of fade dynamics but also their variability, which is assessed on the basis of annual statistics of durations. The obtained average-year statistics of fade durations are in many cases close to the predictions made by the International Telecommunication Union-Radiocommunications and Communications Research Center Canada models, although the predictions could be improved with a better selection of the parameters of the distributions used in the models. Interfade duration statistics are also presented and related to recent modeling efforts. The interannual variability of statistics, such as the relative number of fades, is quantified and found to be low, except for the higher attenuation thresholds or the highest durations considered in this paper.

Propagation measurements on terrestrial links in Madrid

Propagation in the millimeter-wave band has been analyzed using experimental measurements on three terrestrial links working at 38, 75 and 85 GHz carried out in Madrid, Spain. Rain attenuation is the most relevant impairment in such band. Statistics obtained from experimental attenuation time series have been compared with several model predictions. The experimental drop size distributions provided by a disdrometer and a 24 GHz Doppler radar have been used to estimate rain attenuation.

Micro-Doppler signature of human walking in forest environment

Summary form only given. Detecting, tracking and monitoring human motions in dense environments, such as forests, play an important role in security and surveillance operations. Several different radio-frequency devices such as Doppler radars have been developed for this purpose. In particular, micro-Doppler radar systems are able to detect phase variations between the transmitted and received signals which correlate with the motion of body parts as the human moves. Many authors have investigated micro-Doppler effects to classify and identify different human motions. Originally, backscattered signals from human have been computed using a simple approach with point scatters to calculate the radar cross section (RCS) for body parts modeled as simple shapes, such as cylinders, ellipsoids or spheres. An iterative physical optical (PO) approach has also been employed at higher frequencies. These approaches, however, do not incorporate mutual coupling effects between the different human parts and the environment. In this paper, we propose to use an analytical forest model integrated with a fullwave human scattering model to calculate the micro-Doppler signatures from the scene as the human moves. The analytical forest model is a first-order solution, which accounts for the ground effects. The human scattering model uses Method of Moments (MoM) enhanced by the Fast Multipole Method (FMM), which includes the mutual coupling effects between body parts. The forest is created by using finite cylinders distributed randomly in space to replicate the trunks and branches. In this solution, the contribution of mutual coupling between the cylinders to the micro-Doppler signature is assumed negligible. Due to the complexity of the human scattering model which can be result in 200,000 unknowns, we implement the MoM-FMM algorithm on a High Performance Graphics Processing Unit (GPU) cluster. The human walking signatures created by the model are analyzed for different test cases such as different speed and paths for the human as well as different forest properties.