International Journal of RF and Microwave Computer-Aided Engineering最新文献

With the continuous development of the radar field, millimeter-wave radar target detection, as a major tool, faces important challenges in improving detection performance. Especially in some application scenarios, due to multitarget interference and other reasons, the detection performance of the traditional variability index (VI) constant false alarm rate (CFAR) (VI-CFAR) algorithm decreases significantly in the case where both side windows contain interfering targets. To solve this problem, this paper introduces an innovative algorithm, Kullback–Leibler Divergence and Otsu’s Method Enhanced VI-CFAR (KLOVI-CFAR), to better adapt to the multitarget background environment. By combining the KL scattering and Otsu method, we realize the adaptive rejection of outliers in the reference window and further automatically select the detection algorithm adapted to the processed background environment. The results of simulation experiments verify the excellent detection performance of KLOVI-CFAR in multitarget environments with interfering targets in both side windows. The algorithm not only effectively improves the detection capability and antijamming but also shows good detection performance in homogeneous environment and clutter edge cases. The research results in this paper provide a useful reference for improving the radar target detection algorithm.

Multiport network model (MNM) of microstrip patch antennas is an extension of cavity model analysis. In MNM, electromagnetic fields present under and outside patch are modeled separately and the patch is considered as a planar element with multiple ports at its edges. The MNM approach was previously used for the analysis of different patches such as rectangular and circular. However, MNM analysis for irregular-shaped hexagonal patch antenna is not studied yet. Analysis of hexagonal patch antenna is required for its several advantages over other patches such as equivalent surface current distribution with less size compared to circular patch and higher bandwidth. In this work, the irregular-shaped hexagonal patch antenna is analyzed using MNM technique. The antenna is decomposed into rectangular and right-angle triangular segments. Multiport impedance (Z) matrices are calculated for all elements based on Green’s functions of corresponding shapes. Finally, the current distribution of the complete patch is obtained by connecting these elements using Z matrices. The irregular-shaped patch antenna is fabricated, and its responses are measured to verify the results obtained from MNM analysis. MNM can estimate antenna performance with ~3.5% average error with respect to simulated responses in terms of antenna performance parameters.

This paper presents radio frequency energy harvesting (RFEH) using a rectenna system for 3.1 and 5.75 GHz frequencies. The antenna used in this work is a Vivaldi antenna with a new structure. Mounting the newly designed parasitic element on the proposed Vivaldi antenna has improved the gain and directivity of the antenna. The parasitic element is introduced as the director element. The arms of the director element are expanded exponentially. We simulated the proposed antenna design in CST Studio Suite and simulated the proposed rectifier in an advanced design system (ADS). The substrates chosen for the antenna and rectifier are of low-cost type. We have used the voltage doubler technique for the rectifier. Good impedance matching using two stubs has made it possible to connect the rectifier to the antenna. We obtained RF to DC measurement results for the proposed design, which are 56.3% for 3.1 GHz at 8.5 dBm input power and 33.4% for 5.75 GHz at 6.5 dBm input power, respectively. After combining the antenna and the rectifier, the maximum efficiency measured for the power input of 5 dBm at the frequency of 3.1 GHz is equal to 50.8%, which is suitable for energy harvesting.

Machine learning-assisted electromagnetic simulation has become an effective acceleration tool for designing microwave components by introducing high-precision models and optimization algorithms, featuring fast design and high efficiency. However, enormous amount of data generated from the blind preliminary and computationally expensive simulation is required to predict the accuracy response. An efficient geometric parameter optimization method for microstrip bandpass filter (BPF) based on a one-dimensional convolutional neural network is proposed. Nonlinear convergence factor, adaptive weight, and Gaussian difference mutation strategies are integrated using the whale optimization algorithm to avoid the local optimum and improve optimization accuracy. Computational efficiency is improved significantly with small-scale training data. The validity and efficiency of the proposed method are confirmed by fifth-order microstrip BPFs, and the performance of the predicted structure parameters is significantly improved, which shows great promise for application in optimization and performance improvement in microwave electromagnetic simulation.

A miniaturized high-performance metasurface (MTS) antenna with cross-shaped strips is designed, which can be applied to wireless communication systems. The resonant frequency of the main mode of the proposed MTS is reduced by embedding a 2 × 2 cross-shaped strip array in the gaps of the 3 × 3 circular MTS array, resulting in a lower operating frequency and miniaturization. The main mode of the MTS and the probe mode are excited simultaneously by the L-probe structure, resulting in a dual-mode resonance for a broadband performance. The entire design mechanism of the antenna is explained analytically through characteristic mode analysis (CMA) method. Additionally, the cross-polarization levels in H-plane are effectively suppressed by a metal via positioned at the MTS center. Measured results show a wide impedance bandwidth of 32.6% (reflection coefficient ≤ −10 dB) with an MTS size of 0.44λ₀ × 0.39λ₀ (where λ₀ is the free-space wavelength of 6.6 GHz). The achieved peak gain is 7.1 dBi, with a 2 dB gain bandwidth of 36% (5.25-7.55 GHz) and a low cross-polarization level below -20 dB.

Electromagnetic cloaking with monitors within waveguide plays a pivotal role in minimizing the risk of detection while intercepting sensitive information which holds immense potential in both military and communication sectors. However, the integration of electromagnetic cloaking and monitoring is challenging and even more difficult to realize in waveguide. To address these challenges, we propose a metadevice design method based on the internal multiport method (IMPM) for ensuring effective monitoring while maintaining electromagnetic cloaking in the complex environments of waveguide systems. Strategically adjusting the distribution and arrangement of auxiliary scatterers in proximity to the monitoring apparatus can flexibly regulate the behavior of electromagnetic wave propagation to enhance the cloaking performance of metadevice. The cases presented in the paper validate the designed metadevices that are capable of achieving both cloaking and monitoring for monitors within waveguide systems.

The design of a rocket-borne data transmission system is presented in this article. This data transmission system is used for Meridian Space Weather Monitoring Project II sounding rocket. The major function of this data transmission system is to transmit payload data and rocket telemetry data to ground station. The data transmission system achieves power greater than 4 W (36 dBm). The amplitude unbalance is 1.60% (0.14 dB) and the phase unbalance is 1.74°. Total power consumption of the data transmission system is less than 24 W (28 V power supply). The radiation performance of the data transmission antenna is good. Based on the actual condition of solid rocket, the relevant heat dissipation and vibration reduction measures are designed under the demand of miniaturization. The data transmission system has been tested by performance test, environmental simulation test, system integration test, and other tests; the test results show that it has good working performance, good stability, and high reliability.

A finite difference delay modeling (FDDM) method accelerated by adaptive cross approximation-singular value decomposition (ACA-SVD) is developed to solve time-domain combined field integral equations for transient electromagnetic scattering. In the proposed method, the variable s in the Laplace domain is expressed as a difference function about z in the z-transform domain to achieve the temporal discretization, thus improving the stability of the solution. And the method is purely algebraic and does not depend on the Green’s function. It takes advantage of the rank-deficient nature of the impedance submatrix blocks in the FDDM to reduce the memory requirement and the computational cost. The rank-deficient submatrix blocks can reach the maximum compression level through the ACA-SVD. Numerical results about the electromagnetic scattering from perfect electric conducting objects are given to verify the validity and efficiency of the proposed method.

In this paper, a new equivalent circuit of a rectangular dumbbell-shaped defected ground structure (DGS) with an ideal transformer is proposed. The proposed circuit incorporates a parallel resistor in the DGS gap, enabling the extraction of the coupling coefficient of DGS occurring in the narrow line gaps. Both circuit simulations and measurements demonstrate excellent agreement, confirming excellent performance compared to the measured results. Unlike the conventional equivalent circuit, which consists only of the lumped element, this one has an accuracy of only DGS units. In the proposed circuit, an ideal transformer has higher accuracy for the DGS in parallel with a resistor. We observed that increasing the resistance of the parallel resistor on the DGS unit leads to a decrease in the coupling coefficient and, conversely, decreasing the resistance prompts an increase in the coupling coefficient. The goal of this study is to develop a new equivalent circuit for a DGS unit with the ideal transformer, especially to find the coupling coefficient that occurred in the DGS gap. Here, we analyzed that the structure of the DGS unit had a gap, and the coupling coefficient must be built into any value. To demonstrate the effectiveness of the proposed circuit, DGS was used to design and conduct fabrication and measurement. The advantages of the proposed circuit analysis of the DGS behavior can be used to develop the attenuation pole as a one-pole low-pass filter, paving the way for future applications and developments in microwave and RF circuit design.

In this paper, we present a millimeter-wave beamforming antenna array for the fifth generation (5G) of mobile networks and beyond. One of our priority objectives was to minimize the antenna array’s total physical size, by paying attention to avoid radiation performance degradation, such as bandwidth and efficiency. Another priority objective was to avoid mutual coupling (MC) between radiation elements and enhance the gain of the antenna to meet the requirements and challenges of the 5G. In these prospects, we have designed a 4 × 3 Chebyshev modified rectangular antenna array, engraved on the dielectric substrate of the top layer. The antenna array is powered across a 4 × 4 Butler matrix, engraved on the dielectric substrate of the bottom layer. The prototype overall size is 35.76 × 45.56 × 1.589 mm³. Hence, four switched main lobes pointed according to the angles -14°, +26°, -23° and +12°. The corresponded maximum gains at 28 GHz are 11.1, 10.5, 11, and 11.5 dB, respectively. Moreover, a reduction of the MC is ensured by using a CSRR metamaterial carved into the ground plane (GP) of the upper dielectric substrate layer. Experimental and simulation results concord well and show a multiband behavior at 26 GHz and in Ka-band. The impedance bandwidths are 1.5%, 2.7%, and 2.43% at 26, 28, and 40 GHz, respectively. A low MC, between the antenna array’s elements, is also achieved, and the levels of the transmission coefficients vary between -11 dB and -68 dB.