An impulse-radiating antenna (IRA) can effectively focus its radiation in the near field by using... more An impulse-radiating antenna (IRA) can effectively focus its radiation in the near field by using an ellipsoidal reflector. In this paper, three IRAs with ellipsoidal reflectors (elliptic IRAs) are numerically analyzed and compared with an IRA with a typical parabolic reflector (parabolic IRA). The ellipsoidal reflector is parameterized by the distance between the center of the reflector and its closest focus (F), the distance between the two optical foci (Φ), and the diameter of the reflector (D). The IRAs have the same F/D, i.e., 0.5, but different Φ/D's, i.e., 0.5, 1.0, and 1.5. The electric fields in the near-field region and the reflected voltage in the feeding transmission line are analyzed. The elliptic IRAs have a larger impulse and a smaller beam in the near-field region than does the parabolic IRA. The maximum impulse amplitude and the minimum beam width do not occur at the optical focus for the input pulse considered in this paper. The amplitudes of the tail waveform and the reflected voltage in the transmission line are increased.
Two reflector-type impulse-radiating antennas with focal length to diameter ratios of 0.25 and 0.... more Two reflector-type impulse-radiating antennas with focal length to diameter ratios of 0.25 and 0.5 are numerically analyzed. The numerical model is developed using the method of moments code in the EIGER code suite. The performance of the numerical model is validated by comparing the radiated field measured on boresight and the reflected voltage measured in the transmission line with the results from the numerical model. Using the numerical model, the contribution of each part of the antenna to the radiated field and the reflected voltage is identified. The reflected voltage waveform in the transmission line and the electric field waveforms both in the nearand far-zones are presented. The impulse and prepulse amplitudes, spot sizes, and power budgets are also presented.
A method to analyze the variation of the jamming power received by an unmanned aerial vehicle (UA... more A method to analyze the variation of the jamming power received by an unmanned aerial vehicle (UAV) receiver according to the change in the attitude of the small UAV is presented. The main interest of the study is in the variation of the polarization loss factor (PLF) in the UAV jamming link due to attitude change, which may be caused by the wind or intended movement. The attitude change is modeled by a combination of three successive rotations using roll, pitch, and yaw, which are defined as UAV rotations. The proposed method is applied to a jamming link, where a small UAV with an omnidirectional antenna is jammed by a jammer antenna on the ground. The method is applied to a plane ground and over a simulated terrain. The variation of the PLF according to the change of UAV attitude may be higher than the generally expected PLF at locations where the height difference between the UAV and the jammer is large, and near the locations where the jammer is located close to the vertical pla...
The Journal of Korean Institute of Electromagnetic Engineering and Science, 2015
Negative impedance converter(NIC)-based non-Foster impedance matching is proposed for an electric... more Negative impedance converter(NIC)-based non-Foster impedance matching is proposed for an electrically small antenna. The antenna considered in this work is a resistively loaded vee dipole(RVD) antenna, which has considerable reflection at the feed point because of its large negative input reactance. The non-Foster matching circuit built near the feed point consists of two-stage NIC circuit and a capacitor connected between the stages. The NIC is realized by using operational amplifiers(op-amps) and resistors. The circuit is designed by considering of the input impedance according to the finite open-loop gain of the practical NICs. The stability test of the impedance-matched RVD antenna is performed. The non-Foster matching circuit is implemented with the RVD antenna. The measured impedance demonstrates that the proposed non-Foster matching circuit effectively reduces the input reactance of the RVD antenna.
2011 IEEE International Symposium on Antennas and Propagation (APSURSI), 2011
In this paper, a radiation pattern-reconfigurable antenna is designed to operate over DCS 1800 an... more In this paper, a radiation pattern-reconfigurable antenna is designed to operate over DCS 1800 and PCS 1900 frequency bands. The electrical shape of the proposed antenna is symmetric about the vertical center axis. Depending on the switching state, the antenna alternates its beam direction between the two patterns with no input impedance variation. The antenna size is optimized in order to use PIN diodes and FET switches as the antenna switching elements. The equivalent linear circuit models of both elements are then illustrated, corresponding to on and off states. The simulated results show that the antenna can apparently change its directivity by controlling the switching state.
In this paper, two radiation pattern-reconfigurable antennas are designed to operate near the fre... more In this paper, two radiation pattern-reconfigurable antennas are designed to operate near the frequency of 1.8 GHz. The geometry of the proposed antennas is symmetric with respect to the vertical center line. The electrical shapes of the antennas are composed of a monopole-loaded loop and an open wire. The open wire functions as either a director or reflector for the two antennas. Depending on the switching state, the antennas can select between two beam directions with no input impedance difference. The sizes of each antenna are then optimized to achieve beam switching capability using PIN diodes and FETs. The reflection coefficients and gain patterns for two bias conditions using both switches are measured and compared with the simulated results. The measured results show that the proposed antennas can clearly alternate their beam directions using the switching components.
A simple procedure to calibrate numerical data in a manner which allows for accurate comparison t... more A simple procedure to calibrate numerical data in a manner which allows for accurate comparison to experimental data is presented. A simple dipole is used to demonstrate the procedure. The numerical calibration procedure is essentially the same as the experimental calibration procedure which makes it possible to make good comparisons. The antenna, along with three calibration standards, are numerically modelled and experimentally measured. Standard S-parameter calibration procedures are used for both. The calibrated numerical data and the measured data are compared in terms of reflected voltage in the feed line. Agreement is shown to be improved significantly with the calibration technique.
Two offset IRAs are numerically modeled and analyzed. The reflector of the offset IRA is an offse... more Two offset IRAs are numerically modeled and analyzed. The reflector of the offset IRA is an offset portion of a paraboloid that is carved out by the intersection of the paraboloid and a cone whose apex is at the focal point of the paraboloid. A pair of conical curved plates is placed on the surface of the cone as TEM feed arms. The TEM feed arm of the first IRA is conical throughout its length and terminated at the reflector through two electrically small resistors. The TEM feed arm of the second IRA is partly conical and tapered to one electrically small resistor. The second IRA performs better in terms of the reflected voltage in the transmission line. The second IRA is further analyzed and compared with a center-fed IRA. The radiated waveforms both in the far-and near-zones, radiation patterns, impulse and prepulse amplitude distributions as functions of observation angle, spot sizes, and power budgets for the offset IRA and the center-fed IRA are presented and compared. The results show that the tail waveform of the offset IRA is significantly lower in amplitude and simpler in shape than that of the center-fed IRA. Both IRAs have a shadow behind the reflector; the shadow location of the offset IRA may be useful in bistatic radar applications.
2009 IEEE International Geoscience and Remote Sensing Symposium, 2009
Landmine detection is a hazardous operation. To reduce the human casualties during landmine detec... more Landmine detection is a hazardous operation. To reduce the human casualties during landmine detection, unmanned ground vehicles (UGV) can be used. There are many landmine detection modalities that can be used with a UGV. However, the ground-penetrating radar (GPR) and the metal detector (MD; electromagnetic induction sensor) are fast and may be the most reliable means of landmine detection. In addition, GPR and MD sensors can easily be packaged in one sensor head. It is also easy to configure the sensor heads in an array. To combine GPR and MD sensor data, a series of experiments has been performed. The GPR and MD combined sensor is scanned over a 2 m × 2 m × 1 m soil box at a constant height. The soil box contains stony sand and a landmine, which is buried at 200 mm depth when measured from the surface of the ground to the top of the landmine. The control parameters for the experiments are sensor height and soil moisture. The sensor height is varied from 40 mm to 100 mm with 20 mm increment from the soil. The soil moisture conditions considered in the experiments are dry and wet. The stony sand used in the experiments contains rocks with approximately 100 mm diameter scattered in a random manner and a brick placed 200 mm apart horizontally from the landmine. The GPR and MD responses are recorded for all control parameter combinations and later analyzed. The GPR images are generated using time-domain back projection (TDBP) algorithm. The GPR images and MD responses are compared for the soil conditions and sensor heights. A combination algorithm, which enhances GPR images using MD responses, is also presented.
This work describes the delay-sum back projection (DSBP) algorithm that can be used in penetratio... more This work describes the delay-sum back projection (DSBP) algorithm that can be used in penetration imaging radar, such as the ground-penetrating radar. In DSBP algorithm, the round-trip time of the electromagnetic signal is required to properly image the target area. The round-trip time in the multi-layered media is obtained using an interpolation method. The signal path length is first calculated for a few positions in the target area. Then, the signal path lengths for other positions are interpolated. The algorithm is flexible, accurate, and fast.
Korea is one of the heavily mined countries in the world. The demand for mine detection and clear... more Korea is one of the heavily mined countries in the world. The demand for mine detection and clearance techniques has always been high in South Korea. In support of this, a new project on ground penetrating radar (GPR) for landmine detection has been launched in South Korea. The GPR under development is an ultra wideband sensor system that requires high-resolution
2014 IEEE Conference on Antenna Measurements & Applications (CAMA), 2014
A negative impedance converter (NIC) is applied to resistively loaded vee dipole (RVD) antenna ma... more A negative impedance converter (NIC) is applied to resistively loaded vee dipole (RVD) antenna matching. The RVD antenna based on the Wu-King loading profile has large reflection at the feed point because the antenna impedance has high resistance and large negative reactance at low frequencies. To effectively reduce the reflection at low frequencies, the NIC based on operational amplifiers (op-amps) is employed for impedance matching. The matching network is designed such that the RVD antenna is matched to a 75 ohm feeding transmission line. The stability of the network is investigated based on the transient responses obtained from a circuit simulator. The reflection performance of the impedance-matched RVD antenna is measured and shown that the NIC-based matching network improves the impedance matching of the RVD antenna at low frequencies.
2012 IEEE International Geoscience and Remote Sensing Symposium, 2012
This paper introduces a multiple landmine extraction algorithm from the data which are obtained f... more This paper introduces a multiple landmine extraction algorithm from the data which are obtained from the ground penetrating radar (GPR). Conventional algorithms focus on extracting a single landmine. The landmine, however, is not buried under the ground alone in the real cases; it is buried with stones or other landmines. Therefore, detection of multiple landmines is an important problem. The proposed algorithm is composed of two steps. The first step finds the number of buried landmines using the energy projection method. The second step extracts individual buried objects from the data that have multiple landmines using the symmetric filtering method. The experiments show that the proposed algorithm demonstrates the potential of detecting multiple landmines.
In this paper a method is presented to identify landmines in various burial conditions through fe... more In this paper a method is presented to identify landmines in various burial conditions through features obtained from two analytic methods, PCA and DFT. A GPR data set is processed to obtain landmine data. For this process, signal regulation, average filtering and the ground effect reduction are performed. After the landmine data is obtained, PCA and DFT are applied for extracting features of each landmine. A database is then constructed based on landmine features for different levels of moisture and types of ground, and burial depths of the landmines. Using the database, identification is performed by comparing features against the database. For the identification, a counting method is used. If the features of an input GPR data match those of a landmine stored in the database, the counting value for that landmine is increased. The landmine with the largest counting value is given as the identified landmine. Four landmines are considered buried at different depths in various ground ...
In this paper, we present a method for detecting antitank or anti-personnel landmines buried in t... more In this paper, we present a method for detecting antitank or anti-personnel landmines buried in the ground. A set of data generated by a ground penetrating radar is processed to remove the surface reflection and clutter, yielding signals for possible landmines. In order to detect landmines in the signals, features are computed and compared against a database, which contains those of various landmines. Three features are proposed to use; principal components from principal component analysis, Fourier coefficients and singular values from singular value decomposition method, each of which is chosen to represent each landmine uniquely. Detection is performed using Mahalanobis distance-based method. Examples show that the proposed method can effectively detect landmines in various burial condition.
International Journal of Antennas and Propagation, 2012
This paper presents a method to identify landmines in various burial conditions. A ground penetra... more This paper presents a method to identify landmines in various burial conditions. A ground penetration radar is used to generate data set, which is then processed to reduce the ground effect and noise to obtain landmine signals. Principal components and Fourier coefficients of the landmine signals are computed, which are used as features of each landmine for detection and identification. A database is constructed based on the features of various types of landmines and the ground conditions, including the different levels of moisture and types of ground and the burial depths of the landmines. Detection and identification is performed by searching for features in the database. For a robust decision, the counting method and the Mahalanobis distance-based likelihood ratio test method are employed. Four landmines, different in size and material, are considered as examples that demonstrate the efficiency of the proposed method for detecting and identifying landmines.
IEEE Transactions on Antennas and Propagation, 2013
ABSTRACT The resistively loaded vee dipole (RVD) antenna has many advantages as an ultra-wideband... more ABSTRACT The resistively loaded vee dipole (RVD) antenna has many advantages as an ultra-wideband (UWB) radar antenna, especially ground-penetrating radar. However, it has the drawback of having considerable reflections at the feed point due to an impedance mismatch between the antenna and the feeding transmission line. In this communication, a matching network is proposed to reduce the reflection and the design procedure is presented. The network is composed of two L-sections in cascade: an inductive L-section for high frequency matching and a high-pass type L-section for low frequency matching. It is demonstrated that the high-pass type L-section hardly destroys the high frequency matching. The RVD with the proposed matching network is implemented and the performance is measured. The results show that the RVD is matched over the desired band of 500 MHz-3 GHz, and more energy is radiated in the main pulse.
Detection and Remediation Technologies for Mines and Minelike Targets IX, 2004
The resistive vee dipole (RVD) loaded with the Wu-King profile has many advantages for use in gro... more The resistive vee dipole (RVD) loaded with the Wu-King profile has many advantages for use in groundpenetrating radar (GPR) applications. It can be designed to transmit a temporally-short pulse to a small spot on the ground. The shape of the transmitted pulse is simply related to the input signal, e.g., a derivative. The RVD also has a low radar cross section. In addition, it can be easily manufactured using a circuit board and discretely loading it with chip resistors. One drawback of the RVD is that the input impedance of the RVD increases significantly with decreasing frequency and, therefore, has a high voltage standing wave ratio (VSWR) at low frequencies, which limits the low-frequency response of the antenna. To improve the low-frequency response, a discretely-loaded resistive linear antenna (RLA) has been developed, whose basic principle of operation is the same as that of the RVD. The RLA has curved arms loaded with a modified Wu-King profile instead of straight arms loaded with the Wu-King profile. With an appropriate selection of the curve and the loading profile, the low-frequency response is significantly better for the RLA than for the RVD. The RLA has been developed using a method of moments code. The performance of the RLA is validated both numerically and experimentally.
Detection and Remediation Technologies for Mines and Minelike Targets XI, 2006
Multi-static ground-penetrating radar (GPR) uses an array of antennas to conduct a number of bist... more Multi-static ground-penetrating radar (GPR) uses an array of antennas to conduct a number of bistatic operations simultaneously. The multi-static GPR is used to obtain more information on the target of interest using angular diversity. An entirely computer controlled, multi-static GPR consisting of a linear array of six resistively-loaded vee dipoles (RVDs), a network analyzer, and a microwave switch matrix was developed to investigate the potential of multi-static inversion algorithms. The performance of a multi-static inversion algorithm is evaluated for targets buried in clean sand, targets buried under the ground covered by rocks, and targets held above the ground (in the air) using styrofoam supports. A synthetic-aperture, multi-static, time-domain GPR imaging algorithm is extended from conventional mono-static back-projection techniques and used to process the data. Good results are obtained for the clean surface and air targets; however, for targets buried under rocks, only the deeply buried targets could be accurately detected and located.
An impulse-radiating antenna (IRA) can effectively focus its radiation in the near field by using... more An impulse-radiating antenna (IRA) can effectively focus its radiation in the near field by using an ellipsoidal reflector. In this paper, three IRAs with ellipsoidal reflectors (elliptic IRAs) are numerically analyzed and compared with an IRA with a typical parabolic reflector (parabolic IRA). The ellipsoidal reflector is parameterized by the distance between the center of the reflector and its closest focus (F), the distance between the two optical foci (Φ), and the diameter of the reflector (D). The IRAs have the same F/D, i.e., 0.5, but different Φ/D's, i.e., 0.5, 1.0, and 1.5. The electric fields in the near-field region and the reflected voltage in the feeding transmission line are analyzed. The elliptic IRAs have a larger impulse and a smaller beam in the near-field region than does the parabolic IRA. The maximum impulse amplitude and the minimum beam width do not occur at the optical focus for the input pulse considered in this paper. The amplitudes of the tail waveform and the reflected voltage in the transmission line are increased.
Two reflector-type impulse-radiating antennas with focal length to diameter ratios of 0.25 and 0.... more Two reflector-type impulse-radiating antennas with focal length to diameter ratios of 0.25 and 0.5 are numerically analyzed. The numerical model is developed using the method of moments code in the EIGER code suite. The performance of the numerical model is validated by comparing the radiated field measured on boresight and the reflected voltage measured in the transmission line with the results from the numerical model. Using the numerical model, the contribution of each part of the antenna to the radiated field and the reflected voltage is identified. The reflected voltage waveform in the transmission line and the electric field waveforms both in the nearand far-zones are presented. The impulse and prepulse amplitudes, spot sizes, and power budgets are also presented.
A method to analyze the variation of the jamming power received by an unmanned aerial vehicle (UA... more A method to analyze the variation of the jamming power received by an unmanned aerial vehicle (UAV) receiver according to the change in the attitude of the small UAV is presented. The main interest of the study is in the variation of the polarization loss factor (PLF) in the UAV jamming link due to attitude change, which may be caused by the wind or intended movement. The attitude change is modeled by a combination of three successive rotations using roll, pitch, and yaw, which are defined as UAV rotations. The proposed method is applied to a jamming link, where a small UAV with an omnidirectional antenna is jammed by a jammer antenna on the ground. The method is applied to a plane ground and over a simulated terrain. The variation of the PLF according to the change of UAV attitude may be higher than the generally expected PLF at locations where the height difference between the UAV and the jammer is large, and near the locations where the jammer is located close to the vertical pla...
The Journal of Korean Institute of Electromagnetic Engineering and Science, 2015
Negative impedance converter(NIC)-based non-Foster impedance matching is proposed for an electric... more Negative impedance converter(NIC)-based non-Foster impedance matching is proposed for an electrically small antenna. The antenna considered in this work is a resistively loaded vee dipole(RVD) antenna, which has considerable reflection at the feed point because of its large negative input reactance. The non-Foster matching circuit built near the feed point consists of two-stage NIC circuit and a capacitor connected between the stages. The NIC is realized by using operational amplifiers(op-amps) and resistors. The circuit is designed by considering of the input impedance according to the finite open-loop gain of the practical NICs. The stability test of the impedance-matched RVD antenna is performed. The non-Foster matching circuit is implemented with the RVD antenna. The measured impedance demonstrates that the proposed non-Foster matching circuit effectively reduces the input reactance of the RVD antenna.
2011 IEEE International Symposium on Antennas and Propagation (APSURSI), 2011
In this paper, a radiation pattern-reconfigurable antenna is designed to operate over DCS 1800 an... more In this paper, a radiation pattern-reconfigurable antenna is designed to operate over DCS 1800 and PCS 1900 frequency bands. The electrical shape of the proposed antenna is symmetric about the vertical center axis. Depending on the switching state, the antenna alternates its beam direction between the two patterns with no input impedance variation. The antenna size is optimized in order to use PIN diodes and FET switches as the antenna switching elements. The equivalent linear circuit models of both elements are then illustrated, corresponding to on and off states. The simulated results show that the antenna can apparently change its directivity by controlling the switching state.
In this paper, two radiation pattern-reconfigurable antennas are designed to operate near the fre... more In this paper, two radiation pattern-reconfigurable antennas are designed to operate near the frequency of 1.8 GHz. The geometry of the proposed antennas is symmetric with respect to the vertical center line. The electrical shapes of the antennas are composed of a monopole-loaded loop and an open wire. The open wire functions as either a director or reflector for the two antennas. Depending on the switching state, the antennas can select between two beam directions with no input impedance difference. The sizes of each antenna are then optimized to achieve beam switching capability using PIN diodes and FETs. The reflection coefficients and gain patterns for two bias conditions using both switches are measured and compared with the simulated results. The measured results show that the proposed antennas can clearly alternate their beam directions using the switching components.
A simple procedure to calibrate numerical data in a manner which allows for accurate comparison t... more A simple procedure to calibrate numerical data in a manner which allows for accurate comparison to experimental data is presented. A simple dipole is used to demonstrate the procedure. The numerical calibration procedure is essentially the same as the experimental calibration procedure which makes it possible to make good comparisons. The antenna, along with three calibration standards, are numerically modelled and experimentally measured. Standard S-parameter calibration procedures are used for both. The calibrated numerical data and the measured data are compared in terms of reflected voltage in the feed line. Agreement is shown to be improved significantly with the calibration technique.
Two offset IRAs are numerically modeled and analyzed. The reflector of the offset IRA is an offse... more Two offset IRAs are numerically modeled and analyzed. The reflector of the offset IRA is an offset portion of a paraboloid that is carved out by the intersection of the paraboloid and a cone whose apex is at the focal point of the paraboloid. A pair of conical curved plates is placed on the surface of the cone as TEM feed arms. The TEM feed arm of the first IRA is conical throughout its length and terminated at the reflector through two electrically small resistors. The TEM feed arm of the second IRA is partly conical and tapered to one electrically small resistor. The second IRA performs better in terms of the reflected voltage in the transmission line. The second IRA is further analyzed and compared with a center-fed IRA. The radiated waveforms both in the far-and near-zones, radiation patterns, impulse and prepulse amplitude distributions as functions of observation angle, spot sizes, and power budgets for the offset IRA and the center-fed IRA are presented and compared. The results show that the tail waveform of the offset IRA is significantly lower in amplitude and simpler in shape than that of the center-fed IRA. Both IRAs have a shadow behind the reflector; the shadow location of the offset IRA may be useful in bistatic radar applications.
2009 IEEE International Geoscience and Remote Sensing Symposium, 2009
Landmine detection is a hazardous operation. To reduce the human casualties during landmine detec... more Landmine detection is a hazardous operation. To reduce the human casualties during landmine detection, unmanned ground vehicles (UGV) can be used. There are many landmine detection modalities that can be used with a UGV. However, the ground-penetrating radar (GPR) and the metal detector (MD; electromagnetic induction sensor) are fast and may be the most reliable means of landmine detection. In addition, GPR and MD sensors can easily be packaged in one sensor head. It is also easy to configure the sensor heads in an array. To combine GPR and MD sensor data, a series of experiments has been performed. The GPR and MD combined sensor is scanned over a 2 m × 2 m × 1 m soil box at a constant height. The soil box contains stony sand and a landmine, which is buried at 200 mm depth when measured from the surface of the ground to the top of the landmine. The control parameters for the experiments are sensor height and soil moisture. The sensor height is varied from 40 mm to 100 mm with 20 mm increment from the soil. The soil moisture conditions considered in the experiments are dry and wet. The stony sand used in the experiments contains rocks with approximately 100 mm diameter scattered in a random manner and a brick placed 200 mm apart horizontally from the landmine. The GPR and MD responses are recorded for all control parameter combinations and later analyzed. The GPR images are generated using time-domain back projection (TDBP) algorithm. The GPR images and MD responses are compared for the soil conditions and sensor heights. A combination algorithm, which enhances GPR images using MD responses, is also presented.
This work describes the delay-sum back projection (DSBP) algorithm that can be used in penetratio... more This work describes the delay-sum back projection (DSBP) algorithm that can be used in penetration imaging radar, such as the ground-penetrating radar. In DSBP algorithm, the round-trip time of the electromagnetic signal is required to properly image the target area. The round-trip time in the multi-layered media is obtained using an interpolation method. The signal path length is first calculated for a few positions in the target area. Then, the signal path lengths for other positions are interpolated. The algorithm is flexible, accurate, and fast.
Korea is one of the heavily mined countries in the world. The demand for mine detection and clear... more Korea is one of the heavily mined countries in the world. The demand for mine detection and clearance techniques has always been high in South Korea. In support of this, a new project on ground penetrating radar (GPR) for landmine detection has been launched in South Korea. The GPR under development is an ultra wideband sensor system that requires high-resolution
2014 IEEE Conference on Antenna Measurements & Applications (CAMA), 2014
A negative impedance converter (NIC) is applied to resistively loaded vee dipole (RVD) antenna ma... more A negative impedance converter (NIC) is applied to resistively loaded vee dipole (RVD) antenna matching. The RVD antenna based on the Wu-King loading profile has large reflection at the feed point because the antenna impedance has high resistance and large negative reactance at low frequencies. To effectively reduce the reflection at low frequencies, the NIC based on operational amplifiers (op-amps) is employed for impedance matching. The matching network is designed such that the RVD antenna is matched to a 75 ohm feeding transmission line. The stability of the network is investigated based on the transient responses obtained from a circuit simulator. The reflection performance of the impedance-matched RVD antenna is measured and shown that the NIC-based matching network improves the impedance matching of the RVD antenna at low frequencies.
2012 IEEE International Geoscience and Remote Sensing Symposium, 2012
This paper introduces a multiple landmine extraction algorithm from the data which are obtained f... more This paper introduces a multiple landmine extraction algorithm from the data which are obtained from the ground penetrating radar (GPR). Conventional algorithms focus on extracting a single landmine. The landmine, however, is not buried under the ground alone in the real cases; it is buried with stones or other landmines. Therefore, detection of multiple landmines is an important problem. The proposed algorithm is composed of two steps. The first step finds the number of buried landmines using the energy projection method. The second step extracts individual buried objects from the data that have multiple landmines using the symmetric filtering method. The experiments show that the proposed algorithm demonstrates the potential of detecting multiple landmines.
In this paper a method is presented to identify landmines in various burial conditions through fe... more In this paper a method is presented to identify landmines in various burial conditions through features obtained from two analytic methods, PCA and DFT. A GPR data set is processed to obtain landmine data. For this process, signal regulation, average filtering and the ground effect reduction are performed. After the landmine data is obtained, PCA and DFT are applied for extracting features of each landmine. A database is then constructed based on landmine features for different levels of moisture and types of ground, and burial depths of the landmines. Using the database, identification is performed by comparing features against the database. For the identification, a counting method is used. If the features of an input GPR data match those of a landmine stored in the database, the counting value for that landmine is increased. The landmine with the largest counting value is given as the identified landmine. Four landmines are considered buried at different depths in various ground ...
In this paper, we present a method for detecting antitank or anti-personnel landmines buried in t... more In this paper, we present a method for detecting antitank or anti-personnel landmines buried in the ground. A set of data generated by a ground penetrating radar is processed to remove the surface reflection and clutter, yielding signals for possible landmines. In order to detect landmines in the signals, features are computed and compared against a database, which contains those of various landmines. Three features are proposed to use; principal components from principal component analysis, Fourier coefficients and singular values from singular value decomposition method, each of which is chosen to represent each landmine uniquely. Detection is performed using Mahalanobis distance-based method. Examples show that the proposed method can effectively detect landmines in various burial condition.
International Journal of Antennas and Propagation, 2012
This paper presents a method to identify landmines in various burial conditions. A ground penetra... more This paper presents a method to identify landmines in various burial conditions. A ground penetration radar is used to generate data set, which is then processed to reduce the ground effect and noise to obtain landmine signals. Principal components and Fourier coefficients of the landmine signals are computed, which are used as features of each landmine for detection and identification. A database is constructed based on the features of various types of landmines and the ground conditions, including the different levels of moisture and types of ground and the burial depths of the landmines. Detection and identification is performed by searching for features in the database. For a robust decision, the counting method and the Mahalanobis distance-based likelihood ratio test method are employed. Four landmines, different in size and material, are considered as examples that demonstrate the efficiency of the proposed method for detecting and identifying landmines.
IEEE Transactions on Antennas and Propagation, 2013
ABSTRACT The resistively loaded vee dipole (RVD) antenna has many advantages as an ultra-wideband... more ABSTRACT The resistively loaded vee dipole (RVD) antenna has many advantages as an ultra-wideband (UWB) radar antenna, especially ground-penetrating radar. However, it has the drawback of having considerable reflections at the feed point due to an impedance mismatch between the antenna and the feeding transmission line. In this communication, a matching network is proposed to reduce the reflection and the design procedure is presented. The network is composed of two L-sections in cascade: an inductive L-section for high frequency matching and a high-pass type L-section for low frequency matching. It is demonstrated that the high-pass type L-section hardly destroys the high frequency matching. The RVD with the proposed matching network is implemented and the performance is measured. The results show that the RVD is matched over the desired band of 500 MHz-3 GHz, and more energy is radiated in the main pulse.
Detection and Remediation Technologies for Mines and Minelike Targets IX, 2004
The resistive vee dipole (RVD) loaded with the Wu-King profile has many advantages for use in gro... more The resistive vee dipole (RVD) loaded with the Wu-King profile has many advantages for use in groundpenetrating radar (GPR) applications. It can be designed to transmit a temporally-short pulse to a small spot on the ground. The shape of the transmitted pulse is simply related to the input signal, e.g., a derivative. The RVD also has a low radar cross section. In addition, it can be easily manufactured using a circuit board and discretely loading it with chip resistors. One drawback of the RVD is that the input impedance of the RVD increases significantly with decreasing frequency and, therefore, has a high voltage standing wave ratio (VSWR) at low frequencies, which limits the low-frequency response of the antenna. To improve the low-frequency response, a discretely-loaded resistive linear antenna (RLA) has been developed, whose basic principle of operation is the same as that of the RVD. The RLA has curved arms loaded with a modified Wu-King profile instead of straight arms loaded with the Wu-King profile. With an appropriate selection of the curve and the loading profile, the low-frequency response is significantly better for the RLA than for the RVD. The RLA has been developed using a method of moments code. The performance of the RLA is validated both numerically and experimentally.
Detection and Remediation Technologies for Mines and Minelike Targets XI, 2006
Multi-static ground-penetrating radar (GPR) uses an array of antennas to conduct a number of bist... more Multi-static ground-penetrating radar (GPR) uses an array of antennas to conduct a number of bistatic operations simultaneously. The multi-static GPR is used to obtain more information on the target of interest using angular diversity. An entirely computer controlled, multi-static GPR consisting of a linear array of six resistively-loaded vee dipoles (RVDs), a network analyzer, and a microwave switch matrix was developed to investigate the potential of multi-static inversion algorithms. The performance of a multi-static inversion algorithm is evaluated for targets buried in clean sand, targets buried under the ground covered by rocks, and targets held above the ground (in the air) using styrofoam supports. A synthetic-aperture, multi-static, time-domain GPR imaging algorithm is extended from conventional mono-static back-projection techniques and used to process the data. Good results are obtained for the clean surface and air targets; however, for targets buried under rocks, only the deeply buried targets could be accurately detected and located.
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Papers by Kangwook Kim