Uwb radar technology pdf

Compared with the UWB antennas for similar applications in [23], higher values of gain are provided Remote in11,this Sens. Simulated E-plane and H-plane radiation patterns of the designed Vivaldi antenna. Simulated Figure E-plane 8. Simulated E-planeand and H-plane radiation H-plane radiation patterns patterns of designed of the the designed Vivaldi Vivaldi antenna. GHz, b 1. Total Vivaldi antenna. Figure Total gain as a function of frequency of the designed Vivaldi antenna.

Radar Prototyping Result 2. Radar Prototyping Result According to the above antenna design method, 16 identical Vivaldi antennas were fabricated. According to the above antenna design method, 16 identical Vivaldi antennas were fabricated. According Then, the array wasto the above antenna assembled by the design method, proposed design16 identical method. AllVivaldi antennaantennas elementswere werefabricated.

For the switch atconnected the array was assembled by the proposed design method. For the switch at the center to frequency of 1. For the switch at the 48 dB. Finally, a MIMO radar system for through-wall detection was manufactured. Corresponding to the radar design block diagram in Figure 1, Figure 11 displays the photography of Corresponding to the radar design block diagram in Figure 1, Figure 11 displays the photography of Corresponding the designed MIMO to theradar radarsystem.

Figure Figure Photograph of Photograph of designed MIMO radar prototype. To avoid further calibration procedures, all the paths between each antenna and the VNA were of the same EM length. Therefore, only one path required calibration.

The designed parameters of the TWR system are given in Table 1. However, when considering the existence of a concrete wall with Assume the one-way travel time in the imaging area from the transmitter Tx1 is Tt1 and the receiver Rx1 is Tr1. For a pair of transmitting and receiving antennas, Tx1 and Rx1, the whole travel time behind time delay. According to the designed sparse MIMO array, we can positions.

Secondly, the refraction and scattering of EM waves inside and outside the wall mean that obtain the whole travel time from all transmitters and receivers at the pair of Tx1-Rx2, Rx3, … Rx8 to Tx8 the original propagation path is not a straight line.

The above two points are briefly illustrated in Figure In the TDBP algorithm, the travel time for the wave field to propagate from the transmitter to the target and scatter back to the receiver must be known. Assume that there are M paths passing through the wall from one antenna. The point p in the imaging area is a pixel on the m-th path. The average propagation velocity of an EM wave inside the wall is vw. The thickness of the wall is d2. The distance from the equivalent phase center of MIMO antenna array to the surface of the wall is d3.

The distance from the point p to the wall is d1. Flow chart of the improved TDBP algorithm. The one-way travel time of any antenna can be computed similarly. Figure Flow Experiment Results In this section, three experiments are conducted to illustrate the performance and effectiveness of the designed MIMO radar system for 2D imaging.

All parameters used in the experiments are the same as given in Table 1. The frequency range B of the radar system is 0. The number of frequencies is , which causes the unambiguous range to be The imaging method is mainly based on the BP algorithm.

To make the target imaging clearer, background subtraction and direct coupling subtraction are also conducted for the real experimental data before applying the imaging algorithm. The direct coupling wave signal is obtained by collecting data while facing the MIMO array towards the open sky in an open area. Therefore, the received signal only contains the direct coupling component between the antenna elements.

In general, the direct coupling data of one measurement result can be directly subtracted and applied to most 2D imaging of experimental scenes. The method of obtaining the background component is to measure the data without the real targets human or corner reflector in the experimental scene. Then, we can simply subtract the saved signal containing the background when we do the real measurement. This background removal method can eliminate the reflections of the wall, other stationary clutter, and the direct coupling between the antenna elements.

It is relatively complicated and may be limited by the actual imaging situation. Because the background data are different for each specific imaging scene, the background data of each new experimental scene needs to be measured. Preliminary Experimental Tests In order to test the actual target imaging ability of the designed MIMO radar system, the experiments were preliminarily carried out in the air.

In the first experiment, two small dihedral corner reflectors DCR were used as the targets in an open space. The experimental setup is shown in Figure 14 and the imaging results are shown in Figure It can be observed that the two targets can be focused in 2D imaging. Compared to the results obtained by background removal Figure 15c,d , it is obvious that the method of removing the presampled direct coupling Figure 15a,b is simple and can roughly distinguish the positions of the DCR targets.

However, due to the influence of clutter signals, such as ground reflection, there are more noise points and artifacts in the direct coupling removed images. It is worth noting that after utilizing the CC-TDBP algorithm, the imaging results can further suppress the artifacts and clearly distinguish the exact locations of the DCR targets, no matter the methods of removing direct coupling or background, which are shown in Figure 15 and Figure 15d, respectively.

In conclusion, Remote Sens. Experiment Experiment Experiment setupfor setup setup for for dihedral dihedralcorner dihedral cornerreflector corner imaging. We can see that the In the second experiment, to validate the human imaging performance of the designed radar two human targets marked by the red circle are clearly focused.

In this preliminary experiment, even system, two humans acted as targets in the near range, as shown in Figure We can see that the two human targets marked by the red circle are clearly focused.

In this preliminary experiment, even if the direct if direct waveisisremoved removed Figure17a , 17a , thedesigned designed MIMO radar radar system can can clearly detect detect the if the the direct wave wave is removed Figure Figure 17a , the the designed MIMO MIMO radar system system can clearly clearly detect the the human human targets in the air. Experiment setup for human imaging.

Experiment setup Experiment setup for for human human imaging. Imaging results Through-Wall Experiment Results 4. Through-Wall Experiment Results In the third experiment, to assess the through-wall performance of the designed MIMO radar In the third experiment, to assess the through-wall performance of the designed MIMO radar system In and the proposed the third experiment,improved BP algorithms, to assess the scene the through-wall consisted of performance oftwo the humans designedhidden MIMObehind radar system and the proposed improved BP algorithms, the scene consisted of two humans hidden behind a solid wall with thickness of The walls are made of brick and concrete.

After preliminary measurement a solid wall with a former thicknessreflection of The experimental setup is shown in Figure electromagnetic waves is 0. The MIMO dielectric constant of the wall is about 4. The experimental setup is shown in Figure The MIMO array wasconstant dielectric placed parallel along of the wall the azimuth is about 4. Thedirection on thesetup experimental side of the wall. The MIMO array was placed parallel along the azimuth direction on the side of the wall.

The equivalent phase center array wasline of the array placed wasalong parallel measured about 15 direction the azimuth cm away from on the the surface side of theofwall. The The originalphase equivalent point center line of the array was measured about 15 cm away from the surface of the wall.

The original of the coordinate center line of the system array wasof the imagingabout measured region15was cmthe midpoint away from the of the equivalent surface phaseThe of the wall. Background subtraction was applied to filter the reflections from data regardless of the wall effect.

Background subtraction was applied to filter the reflections from the wall and the direct coupling among the antennas. It can be observed that the two targets in 2D the wall and the direct coupling among the antennas.

It can be observed that the two targets in 2D imaging Figure 19a can be easily reconstructed and distinguished. The locations of the targets are imaging Figure 19a can be easily reconstructed and distinguished. The locations of the targets are marked by the red circle in Figure 19a, which verifies the imaging and detection performance of the marked by the red circle in Figure 19a, which verifies the imaging and detection performance of the designed MIMO radar system after the EM wave is attenuated due to the wall.

The experimental result was improved and the corrected 2D imaging result is shown in Figure 19b. It can be observed that the positions of the targets in the image basically coincides with the intersection positions of the white lines. The reconstructed locations of the two human Remote targets Sens. Wall 15 cm Remote Sens. The intersection of white lines in Figure 19a is the real positions of the targets. Then, the improved BP imaging algorithm mentioned in Section 3 was applied, which considers the existence of the wall.

Figure It can beExperimental observed that the setup for positions for the of the targets in the image basically the through-wall through-wall scene. Experimental setup scene. The reconstructed locations of the two humanFirsttargets of all, were much closer we directly utilizedtothe theCC-TDBP actual positions, algorithm which demonstrates proposed in Section the2.

Background subtraction was applied to filter the reflections fromwall. The locations of the targets are Wall marked by Human 1 circle in Figure 19a, which verifies the imaging and detection performance of the the red Human 1 designed MIMO radar system after the EM wave is attenuated due to the wall. However, it is worth Human15 2 cm noting that the wall effects, such as refraction dispersion and change of theHuman EM wave 2 speed, will impact the aforementioned data processing, generating an extra time delay and shifting of the targets.

The intersection of white Human lines2 in Figure 19a is the real positions of the targets. It is obvious that the targets appear Human more 1 distant compared to the intersection points. Then, the improved BP imaging algorithm mentioned in Section 3 was applied, The reconstructed locations of the two human targets were much closer to the a actual positions, which demonstrates the effectiveness b of the improved BP algorithm for more Figure accurate Experimental location of human setup for targets the behind through-wall the wall.

Human 1 Human 1 Human 2 Human 2 a b Figure Discussion In this paper, a linear sparse MIMO radar system which can be used for through-wall detection was designed and analyzed. The array design methods can reduce the number of antennas while maintaining the azimuth resolution. The traditional Vivaldi antenna was improved by antenna miniaturization technology, so that the characteristics of high gain, ultra-wideband, and low frequency were realized.

This miniaturization approach may also be utilized to improve the bandwidth characteristics of other similar printed antennas. Concerning the imaging, the TDBP imaging algorithm based on cross correlation was presented in detail. In addition, we considered the effect of the wall on the refraction of EM waves and the changes of velocity in the through-wall detection experiment Section 4. Finally, the significance and characteristics of this research are discussed in the following four points.

The direct significance of the MIMO radar system studied in this paper is to improve traditional synthetic aperture methods. The designed radar system with optimized UWB Vivaldi antennas has the characteristics of fast data acquisition speed, required azimuth resolution, low cost, and can be applied to through-wall detection.

The Vivaldi antenna has been designed, simulated, manufactured, and successfully used in through-wall imaging, which is one of the contributions to the through-wall radar technology. The period data 64 channels data acquisition time of the MIMO radar system is approximately 35 s. However, this relatively long sampling time is due to the specific VNA that operated as the transceiver. It is an old model Agilent Na which is not designed for fast acquisition.

In fact, the MIMO radar does not have mechanical moving parts, so it can acquire data much faster than synthetic aperture radar SAR based on the movement of the transceiver along a rail [17]. In addition, compared with the current research [9,37] which is limited to simulation and validation, we developed the actual radar system to carry out experimental verification, which is more conducive to illustrate the effectiveness of the proposed system design and imaging algorithm.

Generally, the dielectric constant of the wall is larger than that of the air. The transmitted EM waves have to pass the wall twice to reach the radar receivers, which further reduces the energy of the received target signal. In terms of amplitude attenuation, the first reflection from the front wall is the strongest and the higher-order reflection can be neglected. The signal information of the targets hidden behind walls, such as back walls and human targets, are mainly conveyed by the first transmission.

It is worth noting that the reflection of the human body is relatively low compared with wall reflection and the direct coupling between the antennas. Moreover, the attenuation of the wall makes the collected human target signal weaker, which certainly increases the difficulty of through-wall imaging [38].

Therefore, in the third experiment, background removal is used to improve the imaging performance. Based on the VNA platform, the system is more flexible. For example, we can properly change the operating frequency range and frequency points of the system according to the specific application scenario.

Thus, the range resolution and maximum ambiguity range can be improved. In particular, when the wall is thicker, the low-frequency UWB range can be chosen to improve the penetration of EM waves. As the detection distance increases, the energy received by the radar system will inevitably be attenuated. As shown in Figures 15 and 19, when multiple targets are distributed at different distances in the imaging scene, the relatively weak energy of distant targets may be concealed in clutter.

Therefore, we still need to study an effective way to solve this problem, such as adding amplifiers or shielding devices to the radar system to improve energy in the next step. In future research, the application of MIMO through-wall radar to extract vital signs such as breathing, heartbeat, arm swing or human micro-Doppler [39,40] will be explored. Moreover, it is worth mentioning that the existence of multiple walls, the detection of moving targets, real-time positioning imaging, and even three-dimensional imaging will also be challenging research tasks in our future work.

Low-frequency UWB miniaturized Vivaldi antennas were designed and realized to ensure good system performance of wall penetration. The aperture length of the designed MIMO array is about 1. It is worth noting that the wall effects, such as refraction dispersion and change of the EM wave speed, are not ignored for the data processing.

The through-wall imaging model is proposed and human targets were reconstructed more accurately in through-wall experiments. The results of the experiments demonstrate that, both in range and azimuth direction, the proposed imaging methods can effectively suppress artifacts and focus the different targets, and the designed MIMO radar system can detect and localize human targets behind a wall.

Author Contributions: Writing—original draft preparation, Z. Conflicts of Interest: The authors declare no conflict of interest. References 1. Amin, M. Baranoski, E. Through-wall imaging: Historical perspective and future directions. Lan, F. Life-sign detection of through-wall-radar based on fourth-order cumulant.

Radar, signal, and image processing techniques for through the wall imaging. Nikolic, M. Estimating moving targets behind reinforced walls using radar. IEEE Trans. Antennas Propag. Design and prototype of radar sensor with Vivaldi linear array for through-wall radar imaging: An experimental study. Ralston, T. Real-time through-wall imaging using an ultrawideband multiple-input multiple-output MIMO phased array radar system.

Guo, S. IEEE J. Earth Observ. Wang, M. Time-division MIMO through-the-wall radar imaging behind multiple walls. Dehmollaian, M. Through-the-wall imaging using differential SAR. Laviada, J. Broadband synthetic aperture scanning system for three-dimensional through-the-wall inspection. IEEE Geosci. Yang, J. Random-frequency SAR imaging based on compressed sensing. Jin, T. Image-domain estimation of wall parameters for autofocusing of through-the-wall SAR imagery.

Bliss, D. Fishler, E. MIMO radar: An idea whose time has come. Narayanan, R. Electronics , 6, Pieraccini, M. Zhuge, X. Sparse multiple-input multiple-output arrays for high-resolution near-field ultra-wideband imaging.

IET Microw. Feng, W. Schwartz, J. Ultrasparse, ultrawideband arrays. Control , 45, — Maaref, N. Fioranelli, F. Methods Citations. Figures and Topics from this paper. Ultra-wideband Radar Antenna Device Component. Citation Type. Has PDF. Publication Type. More Filters. In recent years, ultra-wideband UWB radars are gaining popularity in the radar field mainly inindustrial and commercial areas.

The UWB radar has the potential of dramatically improving thecontrol … Expand. See-through-wall imaging using ultra wideband short-pulse radar system. View 1 excerpt, cites background. View 2 excerpts, cites background. Experiments for ultra-wideband imaging radar with one-dimentional Synthetic Aperture. The experiments to acquire the basic data of the ultra-wideband radar have been performed.

In the experiments, targets are located at the back of the extruded polystyrene foam Styrofoam wall, and … Expand. Ultra-wideband technology for defence applications. This paper deals with the use of ultra-wideband technology restricted to impulse radio UWB for military purpose related to radar, telecommunication or localisation. After defining what a UWB signal … Expand. Impulse wave estimation based on analytic wavelet in UWB-radar.