Square-loop Resonator Research Articles

Frequency-Selective Rasorber Based on High-Q Minkowski Fractal-Shaped Resonator for Realizing a Low Radar Cross-Section Radiating System

In this article, a novel design of compact frequency-selective rasorber exhibiting absorption–transmission–absorption characteristics and having high passband selectivity has been proposed. A square-loop resonator with mounted lossy elements serves as the elemental broadband absorber from 4 to 12 GHz. The transmission frequency at 8.4 GHz is realized by printing a Minkowski fractal-shaped resonator with a high-Q factor on the resistive layer, which provides a transmission pole at the frequency corresponding to the passband of a double-cross-slot-shaped bandpass layer. The functioning of the proposed frequency-selective rasorbers (FSR) is explained by a corresponding equivalent circuit model. The proposed FSR exhibits higher selectivity at the passband, thus making it a suitable candidate for shielding the narrowband radiating system. Measurements performed on the fabricated prototype of a 17 × 17 unit cell array provides experimental validation. Further, a low radar cross-section antenna is realized by integrating a patch antenna with the proposed FSR, which achieves an average out-of-band monostatic radar cross-section (RCS) reduction of 11.92 and 5.04 dB in the lower (4–7.5 GHz) and upper (9.2–10.8 GHz) absorption bands, respectively, while maintaining the other antenna parameters. Furthermore, the bistatic total RCS reduction of 77% and 60% are achieved in the lower and upper frequency bands, respectively.

X-Band Microstrip Bandpass Filter Design using Square Loop Resonator and Defected Ground Structure

Filter is an important part in telecommunication system including in radar system. To get the better performance in selecting the signal, a ftlter must have a good Q-Factor. In this paper, an investigation of a ftlter design for synthetic radar has been successfully done. This ftlter has been designed to work at x-band using square loop resonator (SLR). A Defected Ground Structure (DGS) has been implemented to this work to increase the Q-factor of the ftlter. The result of measurement getting that the center frequency at 9.51 GHz with the bandwidth 610 MHz and PCB size of this ftlter is 22 mm x 16 mm.

Design and implementation of microstrip dual‐band filtering power divider using square‐loop resonator

This Letter presents a dual-band filtering power divider (FPD) by employing square-loop resonator loaded by open stubs. The even- and odd-mode equivalent circuits of the proposed resonator are analysed and design equations are derived. For demonstration, the power divider (PD) is fabricated and measured. The simulated results of the PD not only show a good selectivity but also it does good isolation. Finally, the comparisons of the measured and simulated results of the dual-band FPD are presented, which are in good agreement. The measured results show that the dual-band FPD has better than -30/-36 dB isolation, -16.5/-18 dB return loss, and -3.9/-4.0 dB insertion loss at centre frequencies of 3.1 and 5.3 GHz, respectively.

Subwavelength Metamaterial Unit Cell for Low-Frequency Electromagnetic Absorber Applications

In this paper, we propose a subwavelength metamaterial unit cell for low-frequency electromagnetic absorber applications. To realize a periodic array for a metamaterial absorber, the footprint size and thickness of a unit cell must be miniaturized to a subwavelength. We achieved the electrical size of the unit cell as 0.027λ × 0.027λ × 0.043λ at 2.4 GHz by introducing the inductive lump elements to a symmetric square-loop resonator. The performance of the proposed absorber was demonstrated by full-wave simulations and measurements. An inductance tolerance of 2% yielded errors of 1.2% and 1.25% in the absorptivity and absorption frequency, respectively. A prototype with 13 × 27 unit cells was fabricated and its absorptivity was measured to be 99.6% at 2.4 GHz.

Design of a Compact Dual-Mode Dual-Band Bandpass Filter Using Stacked-Loop Resonators Structure

Design, fabrication and measurement of a high-selectivity dual-mode dual-band bandpass filter are presented in this paper. The resonance frequencies of the filter are 1.8[Formula: see text]GHz and 2.4[Formula: see text]GHz which are generated by a meander-loop resonator and a square-loop resonator. The two dual-mode single-band-loop resonators are stacked on each other and create a dual-band bandpass filter. Some advantages of our design are compact size, high selectivity, low loss and also no dependence of two bands, resonance frequencies on each other. The measurement results exhibit that the minimum insertion losses are 0.19[Formula: see text]dB for 1.8[Formula: see text]GHz and 0.32[Formula: see text]dB for 2.4[Formula: see text]GHz. Moreover return losses are better than 43.2[Formula: see text]dB and 40.6[Formula: see text]dB for 1.8[Formula: see text]GHz and 2.4[Formula: see text]GHz, respectively. The proposed filter has a size of [Formula: see text][Formula: see text]mm2. This microstrip filter is fabricated on RT/Duroid6010 substrate with dielectric constant 10.8 and thickness 1.27[Formula: see text]mm and its equivalent circuit is also offered. The measured results exhibit good agreement with the simulated ones.

Reconfigurable dual-mode band-pass filter with switchable bandwidth using PIN diodes

A reconfigurable band-pass filter with switchable bandwidth, for wireless applications is demonstrated using a dual-mode microstrip square-loop resonator. The proposed filter has been designed on Rogers RO4003C and achieves switchable bandwidth by changing the length of two tuning stubs with the implementation of two strategically placed p-i-n diodes as switching elements. The filter was designed with a center frequency of 2.4 GHz and the two distinct operation states have bandwidths, 113 MHz (4.8%) with an insertion loss of 1.2 dB and 35 MHz (1.5%) with an insertion loss of 1.5 dB. The physical size of the fabricated reconfigurable filter including the implementation of the DC bias lines is comparable to the size of a conventional filter.

Effects of narrow slits on frequency response of a microstrip square loop resonator and dual‐mode filter applications

AbstractIn this letter, the effect of narrow slits on resonance characteristics for a microstrip square loop resonator (SLR) with mitered bends is investigated and a new formula to calculate the resonance frequency of SLRs loaded inductively by means of slits is derived as a function of the number of slits.A novel dual‐mode SLR configuration performing a slow‐wave characteristic obtained by using narrow slits is proposed to use in design of microstrip dual‐mode bandpass filters. Also, a new perturbation technique based on the change of electrical lengths is presented for the excitation of two degenerated modes of these type resonators. Additional, two dual‐mode bandpass filters having linear phase and elliptical frequency characteristics have been designed, fabricated and tested to verify the proposed filter topology. Experimental results agree with simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:143–146, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27237

Dual-mode microstrip filters with adjustable transmission zeros

A new type of dual-mode microstrip square-loop resonator that produces asymmetrical frequency responses is proposed. The coupling between degenerate modes of the proposed dual-mode resonator is discussed depending on the perturbation size. The effect of non-orthogonal input/output feed lines located along a straight line on the frequency response is investigated using full-wave electromagnetic simulations. Two second-order bandpass filters using this type of dual-mode microstrip resonator are designed, fabricated and measured to demonstrate the dual-mode microstrip filters exhibiting transmission zero (TZ) shifting property. The one of the second-order filters produces a filter characteristic with two TZs in the upper stopband, whereas the other one has two TZs in the lower and upper stopbands. The shifting property of one of the TZs from one side of the passband to the other side is realised by only changing the perturbation size. The fourth-order filters of this type are also investigated. Both simulated and measured results are presented.

Equivalent circuits and transmission zeros of the coupled square-loop resonator

The purpose of this paper is to present various equivalent circuits of the coupled square-loop resonator which can be used for realization of narrow bandstop filters like notch filters. Furthermore, it is made clear that those circuits vary by the relation of characteristic impedances of component lines in the resonator.