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

A Fabry-Pérot (FP) antenna with wideband dual-polarization and radar cross section- (RCS-) reconfigurability adopting water-based frequency selective surface (FSS) is presented. The feed antenna is designed to switch between horizontal polarization (HP) and vertical polarization (VP) by controlling the on/off states of two PIN diodes. By optimizing the height of the FP resonant cavity, the proposed FP antenna achieves wideband and high-gain properties. In addition, the incident wave can be absorbed when the polymethyl methacrylate (PMMA) container is filled with water, which reduces the monostatic RCS. This design can be selected to be in stealth mode or radiation mode by injecting water into or extracting water from the water container. The measured results indicate that in stealth mode, the 10-dB RCS reduction band is from 4.5 GHz to 6.4 GHz, and the peak RCS reduction is 31.5 dB at 5.2 GHz. In the radiation mode, the realized gains of the FP antenna in both HP and VP at 5.2 GHz reach 16.6 dBi. Simulated and measured results verify the realizability and operational concept of the designed FP antenna.

In this article, a novel method of fault detection in nonuniformly excited linear antenna array has been reported. This method uses an evolutionary algorithm-based technique to generate approximate radiation pattern in tune with reference faulty pattern for a nonuniformly excited linear antenna array. Based on the approximation, a binary sequence-based method of exact fault detection has been developed. In order to illustrate the effectiveness of the method, 12- and 20-element Dolph Tschebyscheff linear antenna array with amplitude fault has been considered. Superiority of the proposed method has been demonstrated through comparative study.

For future wireless high-speed wireless applications, the antenna design plays an indispensable role. Electrical compactness has been challenging over the years among the research fraternity. Hence, this paper proposes an electrically compact and miniaturized asymmetric coplanar strip- (ACS-) fed MIMO to bridge this research gap. In MIMO antennas, two electrically small antennas are used and are placed on the edges of the smartphone. A ladder-shaped radiator with a C-shaped slit inserted on the ground plane makes up the antenna’s monopole radiator. A compact antenna is proposed in this paper with dimensions of 0.076 λ × 0.409 λ × 0.005 λ. This achieves dual band characteristics, which cater to 3.5/5.5 GHz (WiMAX), 5.8 GHz (WLAN), 6.3 GHz (C-band), and sub-6 GHz 5G bands. For the available aperture, reasonable gain is attained by the proposed architecture. Furthermore, fractional bandwidth of 69% and 43% in 2.6 GHz and 5.5 GHz bands, respectively, acting in accordance with the bandwidth stated by Wheeler and Chu’s limit, has been attained in this ACS-fed antenna. In both the operating frequency bands, more than 20 dB isolation between the antenna elements has been achieved. High integrity is attained by the radiation pattern, and actual deployment is granted. Moreover, the simulated results presented are in good accordance with the measured results.

In this article, a broadband semicircular antenna array geometry was examined, along with its design and configuration in the submillimeter wave range (9.35-42.89 GHz). The work has been divided into two prime phases; in the first phase of work, an innovative angular-phased 1 : 4 broadband power divider has been presented in which its isolation, insertion, and return losses are investigated. In the next phase, the proposed power divider was used to configure a 4-element antenna array, and its theoretical analysis was carried out. The angular path difference in the array was used to introduce phase difference in between the antenna elements to minimize the mutual coupling and to optimize the narrow beamwidth. Using geometry and fundamental array theory, the array factor of a novel broadband array configuration has been derived and analytically investigated.

A vector network analyzer (VNA) is an expensive and essential device for measuring the scattering coefficients of RF devices in the research and development of microwave systems. However, these VNAs are limited in that they can be only used by one user. To address this limitation, this paper presents a switching system that allows multiple users to measure each device under test using a single VNA at the same time. In particular, a four-user switching system is developed in this study. It is important to calibrate the differences between each channel that inevitably arise during implementation. For calibration, we propose and implement a technique for de-embedding the uneven characteristics between these channels. Its performance is validated by measuring insertion loss, reflection loss, and isolation for the developed switching system.

In this paper, a simple broadband multipolarized traveling-wave series-fed antenna array is proposed. The radiation unit cells are multiple squares. The square unit cell will change between circular polarized (CP) and linear polarized (LP) through a reasonable feeding mode. By adjusting the equivalent length of the unit cell, the Q value of the antenna can be reduced, resulting in the increase of the bandwidth of the array. The array consists of seven-unit cells and dual-port feeding. The unit cells which are connected by a microstrip line are arranged in a circular array. A reasonable layout of unit cells can achieve good port isolation of the array. The polarization performance of the array antenna is the same as that of the unit cell. The antenna is fabricated and measured. The measured results are consistent with the simulated results.

This letter introduces an effective self-interference cancellation (SIC) for improving isolation between transmit (Tx) ports and receive (Rx) ports of an in-band full-duplex antenna with feeding networks (FNs). A significant isolation improvement is realized by replacing the traditional FNs of the antenna with SICFNs. The coupling between Tx and Rx ports is canceled in the FNs due to the specific power ratios and phase difference. Though a Python optimization procedure, the optimal values of the key parameters of the SIC FNs can be determined. To validate the proposed SIC technique, the prototype consisting of two four-element antenna arrays and four SICFNs designed with the technique is fabricated. The results of measurements performed in an anechoic chamber show an isolation improvement of 15 dB at 3.6 GHz, while only 0.3 dB gain loss for the antenna array as a sacrifice is observed.

We investigate a practical technique for deembedding the channel filter S-parameters of manifold-coupled multiplexers (MUXs), without detaching filters from the manifold. The method is applicable for MUXs with an arbitrary number of channels and can be used for the device regardless of its bandwidth, guard band, or loss of filters. We reconfigure the N-port MUX to two simpler networks cascaded to each other. We assume that the manifold response is unknown and use the idea of applied perturbation on the channel filter, and then by comparing the response of the overall cascaded network, before and after the perturbation, we approximate the channel port response. The technique is useful in fast detecting the unexpectedly detuned channels or likely faults in the device without unnecessary plugging/unplugging; it is also useful in roughly tuning of the channel filers at the early stage of MUX tuning. The technique can be easily traced by the telecommunication community.

In this research article, a novel double-split elliptical split ring resonator (DS-ESRR) is proposed to achieve frequency-notching behavior of ultrawideband filtenna, where the semimajor and minor axes of the ellipse are taken as a bivariate random variable and expressed in Ramanujan’s correction coefficient so that more degree of freedom is available for choosing degenerated impedance and thus for variable frequency-notching applications. To verify this hypothetical method, finite sets of variables for DS-ESRR are presented in this proposed work, and a mathematical expression is formulated to estimate the resonant frequency of the DS-ESRR, such that for practical applications, frequency-notching parameters can be easily estimated accurately rather than previously used SRR like circular or square-shaped geometry. DS-ESRR is deployed at the back of a CPW-fed ultrawideband antenna for notching filter application, and the computed data is compared with the eigen mode simulation results which reveal good agreement with each other.

In this paper, an antenna array fed in series by a novel substrate-integrated waveguide (SIW) power divider is proposed for the millimeter-wave band vital sign monitoring application. The proposed antenna is printed on a single-layer substrate, with the advantages of low profile, low cost, and ease of fabrication. By branching microstrip lines alternatively at both edges of the SIW, an in-phase power divider is first constructed. Then, by appropriately adjusting the depth of microstrip branches into the SIW, the amplitude of the output power can be tuned to obtain the desired amplitude distribution. Patches are connected to the microstrip branches, respectively, and thus, a radiation pattern with a low sidelobe level is realized. More importantly, series patches can be cascaded to enhance the array gain without the additional feeding network. This leads to a compact configuration. Based on the proposed idea, a prototype is designed, implemented, and tested. The results indicate that the proposed array achieves a maximum gain of 17.8 dBi with a low sidelobe level of -25.5 dB. The attractive performance shows that the array is suitable for the millimeter-wave vital sign monitoring application.