Search Results (86)

This communication presents an accurate and computationally efficient approach for wideband radar cross-section (RCS) estimation and scattering point reconstruction using infinitesimal dipole modeling (IDM) with compressive sensing. The proposed method eliminates the need for field sampling at numerous frequency points across the wideband range through Green’s function adjustment. Additionally, compressive sensing is employed for induced current calculation to reduce both frequency and angular sampling requirements. Numerical validation demonstrates that the method achieves a 50% reduction in field sample data and an 82.3% reduction in IDM processing time while maintaining comparable accuracy through Green’s function adjustment. Furthermore, compared to approaches without compressive sensing, the method shows a 55.1% and a 75.5% reduction in error in averaged RCS for VV-pol and HH-pol, respectively. The proposed method facilitates efficient wideband RCS estimation of various targets while significantly reducing measurement complexity and computational cost. Full article

An orientation controllable radar cross section (RCS) enhancement surface is presented in this paper, which can be used to improve the road pile detectability of on-board microwave radar for autonomous driving system. In addition, the RCS enhancement orientation can be controlled in a specified direction without interfering with other microwave systems. We first designed a modified one-dimensional VanAtta array with adjustable phase for retrodirective backtracking the incoming electromagnetic waves, which can achieve wide-angle RCS enhancement. Then, we arranged the one-dimensional VanAtta array in another dimension forming a two-dimensional array, enabling adjustable orientation RCS enhancement due to the controllable phase of the reflected electromagnetic waves. We designed, manufactured, and tested a 4 × 8 array to validate the theory and assess the design’s feasibility. Finally, six orientation controllable VanAtta arrays were mounted on the outside surface of a cylinder road barrier, and measurements demonstrated that RCS enhancement of over 10 dB have been achieved compared to the same pile with perfect electric conductor surface. Full article

A co-design of radar cross section (RCS) reducing surface and array antenna on a single-layer printed board is presented in this paper. To achieve this goal, two kinds of artificial magnetic conductors (AMCs) are designed and optimized. The first kind of AMC shares the same geometry with the array element and thus is simultaneously used as the array element. The other kind of AMC generates opposed-phased reflections for a normal incident wave, and when they are in a checkerboard configuration, the RCS is reduced via phase cancellation of opposed-phased reflections. In the range of 10 GHz to 16 GHz, the designed bi-functional surface achieves an 8 dB decline in monostatic RCS, while the array antenna obtains a gain of 15 dBi, a side-lobe less than −10 dB, and a cross-polarization less than −20 dB at 13.5 GHz. To validate the calculation results, a prototype is fabricated and measured. To feed the array antenna, a T-type power divider network is etched under the ground and the array is fed via coupling slots on the ground. The measured results agree with the simulation results. Full article

In this paper, a broad-angle low-scattering microstrip antenna for dual-polarization is designed based on characteristic mode analysis (CMA). The modal analysis of the reference antenna under dual-polarization incident plane waves is first carried out to guide radar cross section (RCS) reduction (RCSR) design in broad-angle range. Then, through the modifications on the radiation patch and ground, the modal currents of the important scattering modes in broad-angle range are cut off. Hence, a broad-angle low-RCS aperture-coupled microstrip antenna for dual-polarization is obtained. However, the radiation performance decreases due to the ground modification. A frequency selective surface (FSS) structure is designed and fills in the ground modification areas. With the FSS structure, the proposed antenna shows a good radiation and scattering performance. A low-RCS antenna prototype is fabricated and tested. The antenna works from 2.79 GHz to 2.87 GHz (2.82%), and the gain is 6 dBi at 2.84 GHz. For the co-polarization, it can realize RCSR from 0° to 90°, and the average and peak RCSRs are 9.0 dB and 17 dB, respectively. For the cross-polarization, it can realize RCSR from 0° to 18° and 22° to 90°, and the average and peak RCSRs are 5.0 dB and 20 dB, respectively. In the meantime, its transmission and radiation performance keeps well. The measured and simulated results are in good agreement, which validates the design. Full article

A novel frequency-selective polarization converter (FSPC) is proposed based on the new method of combining a polarization conversion metasurface (PCM) with a bandpass frequency-selective surface (FSS), which provides an efficient transmission band and broadband radar cross-section (RCS) reduction. The upper and lower layers are combined to form the proposed FSPC. In the upper layer design, the bowtie-shaped structure is used to achieve polarization conversion on both sides of the transmission band. Regarding the lower layer design, the second-order bandpass FSS is employed, which acts as an equivalent ground for the polarization conversion layer outside the passband and provides a highly efficient transmission window within the passband. Ultimately, the magnitude of the co-polarized reflection of the FSPC that is below −10 dB ranges from 5.1 GHz to 16.1 GHz, with a relative bandwidth of 104%, and the co-polarized transmission window with an insertion loss of less than 1 dB is presented ranging from 8.7 GHz to 12.6 GHz, with a relative bandwidth of 36%. Furthermore, by arranging the upper bowtie-shaped PCM in a checkerboard pattern, the monostatic RCS can be effectively reduced in a broad frequency range. Samples of the proposed design are fabricated for the measurement verification of performance. The results show that the measurement results match well with the simulation results. Compared with other designs, the proposed FSPC exhibits efficient co-polarized transmission, with insertion loss as low as 0.34 dB and the passband flatness being good. Full article

In this study, we present a novel ultra-wideband passive polarization conversion metasurface (PCM) that integrates double V-shaped patterns with circular split-ring resonators. Operating without any external power supply or active components, this design effectively manipulates the polarization state of incident electromagnetic waves. Numerical and experimental results demonstrate that the proposed PCM can convert incident linear polarization into orthogonal states across a wide frequency range of 7.1–22.3 GHz, encompassing the C-, X-, Ku-, and K-bands. A fabricated prototype confirms that the polarization conversion ratio (PCR) exceeds 90% throughout the specified band. Furthermore, we explore an additional application of this passive metasurface for electromagnetic stealth, wherein it achieves over 10 dB of monostatic radar cross-section (RCS) reduction from 7.6 to 21.5 GHz. This broad effectiveness is attributed to strong electromagnetic resonances between the top and bottom layers, as well as the Fabry–Pérot cavity effect, as evidenced by detailed analyses of the underlying physical mechanisms and induced surface currents. These findings confirm the effectiveness of the proposed design and highlight its potential for future technological applications, including 6G communications, radar imaging, anti-interference measures, and electromagnetic stealth. Full article

An electromagnetic (EM) absorber-embedded Ka-band double-layer tapered slot antenna (DLTSA) is proposed in this work. The EM absorber is placed on both sides of the tapered radiating slots as a means of achieving the reduced monostatic radar cross section (RCS) at the X-band. A conventional tapered slot antenna (TSA) with EM absorbers at the same position suffers from the distorted current distribution from the feedline to the radiating slots and causes a degraded radiation performance with a tilted beam. In contrast, the DLTSA with EM absorbers maintains the impedance and radiation characteristics of the antenna without the EM absorbers, while achieving the reduced monostatic RCS for the cross-polarized incident wave. The functionality of the reduced RCS is verified with the 4-by-4 DLTSA array design. The 4-by-4 array prototype with FGM-125 EM absorbers is matched at the Ka-band with a 14.7 dBi boresight gain at 35 GHz. The monostatic RCS is measured in an indoor environment, showing 6.5 dB monostatic RCS reduction at the X-band on average, verifying the computed expectations. This work validates the possible use of EM absorbers at the front side of a missile seeker composed of end-fire radiating elements. Full article

Small targets with low radar cross-section (RCS) and high velocities are very hard to track by radar as long as the frequent variations in speed and location demand shorten the integration temporal window. In this paper, we propose a technique for tracking evasive targets using a continuous wave (CW) radar array of multiple transmitters operating in the millimeter wavelength (MMW). The scheme is demonstrated to detect supersonic moving objects, such as rifle projectiles, with extremely short integration times while utilizing an adaptive processing algorithm of the received signal. Operation at extremely high frequencies qualifies spatial discrimination, leading to resolution improvement over radars operating in commonly used lower frequencies. CW transmissions result in efficient average power utilization and consumption of narrow bandwidths. It is shown that although CW radars are not naturally designed to estimate distances, the array arrangement can track the instantaneous location and velocity of even supersonic targets. Since a CW radar measures the target velocity via the Doppler frequency shift, it is resistant to the detection of undesired immovable objects in multi-scattering scenarios; thus, the tracking ability is not impaired in a stationary, cluttered environment. Using the presented radar scheme is shown to enable the processing of extremely weak signals that are reflected from objects with a low RCS. In the presented approach, the significant improvement in resolution is beneficial for the reduction in the required detection time. In addition, in relation to reducing the target recording time for processing, the presented scheme stimulates the detection and tracking of objects that make frequent changes in their velocity and position. Full article

The measurement and analysis of the interaction between Bessel vortex electromagnetic (EM) and several standard targets are presented in this paper. With the aid of the angular spectrum expansion (ASE) method and physics optics (PO) theorem, scattering results on the plates (metal and dielectric) and a sphere could be derived. Furthermore, plane near-field scanning and near-far field conversion methods were implemented to compare the theoretical radar cross section (RCS). In the experiment, the quasi Bessel vortex wave was generated by a holographic metasurface antenna, and the whole measurement was performed in an anechoic chamber. The results of both the theory and measurement show that the scattered fields of the plate and sphere still had characteristics of the vortex EM wave, and the scientificity and accuracy of the measured RCS were verified. Our work involved a vortex scattering experiment in the microwave frequency band, which provides strong support for the application of vortex waves in radar detection and target recognition. Full article

Stealth reconfigurable transmitarray antennas (RTAs) are essential components in wireless communication and radar detection systems. Therefore, in this study, we propose a 1-bit RTA with out-of-band radar cross-section (RCS) reduction. The antenna consists of an absorptive frequency selective transmission (AFST) layer and RTA layer separated by air. Specifically, the AFST layer achieves out-of-band RCS reduction and in-band transmission utilizing the first three resonant modes of a bent metallic strip with a centrally loaded resistor. Meanwhile, the RTA layer adopts a receiver–transmitter structure with an active receiving dipole and a passive orthogonal transmitting dipole. 1-bit phase shift is achieved by alternating two pin diodes integrated on the active dipole to reverse its current direction. To evaluate the proposed design, a 16 × 16-element prototype was designed, fabricated, and measured. For scattering, the bandwidth of 10 dB RCS reduction was about 52.5% and 43.8%, respectively. For radiation, the measured gain was 20.1 dBi at 7.5 GHz, corresponding to an aperture efficiency of 12.7%. The gain loss of beam scans to ±60° was about 5 dB in both two principal planes. Full article

A new type of fully polarimetric retrodirective array (RDA) using a PON-type structure is proposed in this paper. The fully polarimetric property is the result of the proposed phase conjugation circuits, which perform phase conjugation processing on the x, y, and z polarization electric field components of the incident wave when combined with a tri-polarized antenna array. It enables the retrodirective array to receive and retransmit an arbitrary polarized incident wave. The measured results of the monostatic radar cross-section (RCS) show that the −5 dB beam width of the array was greater than 95° at 9.6 GHz for different polarized incident waves. Furthermore, the proposed RDA has better retrodirectivity performance on arbitrary polarized incident waves when using a wide-beam antenna, and if we further incorporate modulation and demodulation into the circuits, it has the potential to be applied to the wireless communications field. Full article

This paper proposes a 2-D fully polarized Van Atta array, which consists of four tri-polarized antenna elements. The tri-polarized antenna element comprises a monopole antenna and a low-profile microstrip antenna that widens the beam by folding four electric walls. This configuration enables the Van Atta arrays to receive and transmit arbitrarily polarized incident waves over a wider range. The measurement results indicate that the proposed Van Atta array exhibits a −5 dB radar cross-section (RCS) greater than 95° when TE-polarized waves are incident and greater than 134° when TM-polarized waves are incident, significantly surpassing the 2-D dual-polarized array. Full article

The analysis and processing of active radar image information is an important method for determining the payload orientation of non-cooperative targets. However, a challenge for spacecraft carrying parabolic antenna payloads is that active radar imaging is susceptible to defocus, making it difficult to achieve a reliable estimate of the orientation of such payloads. As such, this paper proposes a method for estimating the orientation of spacecraft parabolic antenna payloads based on radar-measured radar cross section (RCS) sequence data. By utilizing the step effect produced when the ground-based radar observes the parabolic antenna payload, the mathematical model for estimating the orientation of the parabolic antenna payload is established through the analysis of the geometric relationship between the radar observation vector and the antenna payload orientation in the orbital coordinate system. This method employs an optimized model and particle swarm optimization to achieve the pointing estimation of the parabolic antenna payload. The simulation results demonstrate that the proposed algorithm can accurately estimate the pointing direction of the antenna payload, with the maximum error being better than three degrees, and it has good robustness. The results of real data processing further verify the effectiveness of the algorithm. Full article

In wireless communication and radar systems, long-distance signal transmission poses significant challenges that affect overall system performance. In this paper, we propose an innovative bistatic radar cross section (RCS) testing system designed to address these challenges, with a particular focus on its long-distance signal transmission capabilities. This system is capable of accurately measuring the RCS of a target and improving multipath channel modeling accuracy by using precise RCS values. The integrated upper computer software extracts amplitude and phase information from received echo signals, processes these data, and provides detailed outputs including the target’s RCS, one-dimensional image, and two-dimensional image. The experimental results obtained prove that this system can not only achieve effective long-distance signal transmission but also substantially enhance the accuracy of RCS measurements, offering reliable support for multipath channel modeling. However, the conclusions drawn are preliminary and require further experimental validation to fully substantiate this system’s performance. Future work will focus on improving system accuracy, minimizing the impact of environmental noise, and optimizing data-processing methods to enhance the efficiency of wireless communication and radar applications. Full article

Accurate measurement of a Radar Cross-Section (RCS) is a critical technical challenge in assessing the stealth performance and scattering characteristics of radar targets. Traditional RCS measurement methods are limited by high costs, sensitivity to environmental conditions, and difficulties in distinguishing local scattering features of targets. To address these challenges, this paper proposes a novel RCS measurement method based on enhanced imaging and scattering center extraction. This method integrates sub-aperture imaging with image fusion techniques to improve imaging quality and enhance the detail of target scattering characteristics. Additionally, an improved sequence CLEAN algorithm is employed to effectively suppress sidelobe effects and ensure the accuracy of scattering center extraction. Experimental results demonstrate that this method achieves higher precision in RCS measurement of complex targets and is particularly effective in environments with strong interference, where it successfully separates the scattering contributions of the target from those of the interference sources. This method offers a new technological approach for precise RCS measurement of radar stealth targets in the future. Full article