Rectangular Loop Resonator Research Articles

Design of a Compact Quad-Channel Microstrip Diplexer for L and S Band Applications

In this paper, two novel dual-band bandpass filters (BPFs) and a compact quad-channel diplexer working at 1.7/3.3 GHz and 1.9/3.6 GHz are proposed. In the proposed diplexer design, triangular loop resonators and rectangular loop resonators are used together to reduce the circuit size and improve diplexer performances. Insertion loss (IL) and return loss (RL) of the proposed diplexer are better than 0.8 dB and 21 dB, respectively, at these four operating frequencies. Output ports isolation parameter is better than 30 dB. With the achieved specifications, the proposed diplexer can be used in L and S band applications.

Numerical model & design of wideband band reject filter with closed loop rectangular resonator

ABSTRACT Numerical model of a wideband band reject filter using closed rectangular loop resonator is presented using transmission lines. The prototype design of wide band reject filter centred at 3 GHz with lower cut-off frequency of 2 GHz and upper cut-off frequency of 4 GHz is fabricate from the optimal values obtained from the numeric model on a substrate (FR4) with a dielectric constant of 4.3, loss tangent of 0.02–0.03 and substrate height of 1.6 mm. For bidirectional operations, the length-to-width ratio of filter is 2:1. The impedance of the transmission line which is connected between input and output ports is taken as double the feed line impedance while the impedance of the other half wavelength is considered as four times the feed line impedance. The design has obtained bandwidth of more than 60%. It is observed that the full wave electromagnetic results are in good agreement with the experimental and numerical results.

A CPW-fed rectangular nested loop antenna for penta band wireless applications

A miniaturized coplanar waveguide (CPW) fed rectangular nested loop antenna is proposed for penta band wireless applications. Multiband and antenna compactness are obtained by using rectangular loop resonators. The proposed antenna has been optimized by increasing the number of loop iterations. The designed antenna comprises four rectangular loops, it constructs the antenna to excite 1.01 GHz, 1.67 GHz, 2.30 GHz, 2.92 GHz and 3.48 GHz frequency bands. The fabricated geometry has a dimension of 30 × 30 × 1.6 mm3, which is developed on a low-cost Flame Retardant-4 substrate having εr = 4.4 and tanδ = 0.02. The resonance behavior of the proposed antenna is verified by employing LC quasi-static design equations. The measured reflection coefficient and far-field pattern are exhibited to support the performance of the designed antenna for wireless applications.

High-selectivity adjustable dual-band bandpass filter using a quantic-mode resonator

A novel adjustable dual-band bandpass filter using a quantic-mode resonator consisting of stepped impedance resonators (SIRs) and coplanar waveguide resonators (CPWRs) is proposed in this paper. The SIRs provide the lower passband with two transmission poles (TPs), while the upper passband is introduced by CPWRs and two TPs are obtained. Furthermore, an equivalent rectangular loop resonator (RLR) derived from the CPWRs is also introduced, providing another TP for the upper passband. One of the marked features of the filter is that the two passbands can be adjusted independently because of the independent resonant paths of different resonators. Besides, this filter has four transmission zeros (TZs), promising good stopband rejection and high band-to-band isolation. The measured results are consistent with the simulated results.

Characteristic Mode Analysis and Design of Wide Band MIMO Antenna Consisting of Metamaterial Unit Cell

This paper presents a full wave simulation and characteristic mode-based design of a multiple-input-multiple-output (MIMO) antenna at 5.8 GHz for wireless local area network applications. The driven analysis comprises two antennas that are placed orthogonal to each other. A metamaterial unit structure in the form of a rectangular loop resonator is placed around the antenna element to reduce the electromagnetic interference and to increase the isolation between the two monopoles. A characteristic mode technique is employed to find out the dominant mode of the proposed antenna without a feeding port. It was revealed that mode 1 was the dominant mode among the three modes used. The MIMO antenna is constructed and measured using a vector network analyzer. A good isolation of less than 25 dB was attained with a wide impedance bandwidth of 65.5%.

A Frequency Selective Rasorber With Three Transmission Bands and Three Absorption Bands

A frequency selective rasorber (FSR) with three transmission bands and three absorption bands is proposed in this paper. The FSR is constructed via cascading a lossy resistive surface and a multiple bandstop frequency selective surface (FSS) separated by air spacer. The transmission characteristics are obtained by the impedance poles of the interdigital capacitor-meander inductor resonators in the resistive surface and also the rectangular loop resonators in the FSS. The absorption bands are achieved using the ohmic loss of the resistors in the resistive surface along with the reflections of the FSS. The physical principle of operation of the multiband FSR is explained based on an equivalent circuit model. A prototype is fabricated and measured. The experimental results exhibit three transmission bands at 6.1 GHz, 8 GHz and 10 GHz with insertion loss below 0.9 dB, 0.8 dB and 0.8 dB, respectively. The effective absorption bands are in range of 7.05 GHz - 7.55 GHz, 8.87 - 9.35 GHz and 12.59 GHz - 14.22 GHz, respectively. The simulation results show the angular stability of the FSR response. In addition, the effect of FSR dimensions on the transmission/absorption bands is studied.

MR-WPT With Reconfigurable Resonator and Ground for Laptop Application

A magnetic resonance wireless power transfer (MR-WPT) system with a reconfigurable planar receiver (Rx) to optimize transfer efficiency (TE) for laptop application has been investigated. The proposed MR-WPT system consists of a general four-coil system: a source coil and a transmitter Tx) coil in a Tx part and an Rx coil and a load coil in an Rx part. To enable performance comparison, the Rx coil uses either a rectangular loop resonator or a slit ground resonator (SGR) and both resonators are connected with a p-i-n diode to reconfigure and optimize the MR-WPT system’s TE along the transfer distance between the Tx and Rx parts. Mobile devices, including laptops, need a ground plane for practical use; therefore, the Rx coil is replaced by only an SGR, which operates as both a resonator and a ground. This letter, experimentally and theoretically proves that a reconfigurable MR-WPT system with an SGR has sufficient efficiency without the ferrite sheet typically used in practical MR-WPT applications.

Dual‐band bandpass filter using loop resonator with independently‐tunable passband

A dual-band microstrip bandpass filter using the rectangular loop resonator (RLR) is proposed. A microstrip open stub is implemented to perturb modes of the RLR, and the two modes form the low-frequency passband. The stepped impendence microstrip lines are adopted to excite the RLR and the lines also work as the resonant stubs, i.e. one is 3/4-wavelength resonance stub and another is full-wavelength resonance stub. As a result, the second passband is introduced. Furthermore, each passband can be tuned independently through the corresponding resonant paths (parameters), which are discussed in detail. Without the connection stub between stepped impendence microstrip lines and RLR, this dual-band bandpass filter will degenerate to a dual-mode single-band bandpass filter and the corresponding results are also obtained and demonstrated. The measured results agree with the simulated results well.

Polarisation‐dependent absorber based on resistor‐loaded rectangular loop resonators

This Letter presents a design of a polarisation-dependent resistor-loaded resonant absorber at microwave frequencies. The unit cell includes a metallic loop and a metallic ground plane, separated by a 3.2 mm FR-4 substrate. A resistor is used to connect the top and bottom layers to create an optimal load for dissipation of the power accepted by the structure in a desired polarisation. Experiments performed on a prototype consisting of 10 × 10 unit cells demonstrate that the absorber can achieve near unity absorption in co-polarised direction and almost full reflection in cross-polarised direction at its working frequency of 2.52 GHz. The measured bandwidth of the absorber reaches 0.17 GHz (6.7%), which is wider than comparable designs using electric-field-coupled-LC resonators. The optimal resistor selection and the effect of radio-frequency behaviour of the loading resistor on the absorbing properties is investigated.

Normalization-Free Chipless RFIDs by Using Dual-Polarized Interrogation

A reliable encoding/detection scheme for chipless radio frequency identification (RFID) tags, free from any normalization procedure, is presented. The key strategy of the present approach consists in storing the information in the difference between vertically and horizontally polarized reflection coefficients of a completely passive tag. The measured reflection coefficients are preemptively filtered in the time domain to remove most of harmful effects due to the antenna coupling and environment multipath, and finally they are subtracted to obtain the differential response. A couple of chipless tag configurations suitable for providing the desired spectral response are presented. The resonators consist of an artificial impedance surface comprising either concentric rectangular loop resonators or square loop resonators loaded with stubs. The presented approach is experimentally verified in a non-anechoic environment, and its robustness is proved. This calibration-free approach could pave the way to practical applicability of chipless RFID tags in realistic scenarios with unknown response.

Metamaterial-Based Design of Planar Compact MIMO Monopoles

A systematic design of planar MIMO monopole antennas with significantly reduced mutual coupling is presented, based on the concept of metamaterials. The design is performed by means of individual rectangular loop resonators, placed in the space between the antenna elements. The underlying principle is that resonators act like small metamaterial samples, thus providing an effective means of controlling electromagnetic wave propagation. The proposed design achieves considerably high levels of isolation between antenna elements, without essentially affecting the simplicity and planarity of the MIMO antenna.

HF-BAND WIRELESS POWER TRANSFER SYSTEM: CONCEPT, ISSUES, AND DESIGN

High-frequency (HF) band wireless power transfer systems ofier the promise of cutting the last cord, allowing users to seamlessly recharge mobile devices as easily as wireless communication. Yet there are still many technical issues that need to be overcome. Among them, one of the most di-cult problems is maintaining impedance match over a short range, where the distance between a transmitter and receiver could vary. In this paper, the efiect of impedance mismatch of a HF- band wireless power transfer system is carefully investigated and two compensation methods are suggested to overcome this within a short range, where frequent impedance mismatch can occur. Each method has pros and cons. In order to verify the feasibility of the proposed methods, HF-band wireless power transfer systems, with a pair of rectangular loop resonators, were designed. The e-ciency and input impedance variation were simulated and measured. From these results, proposed methods show enhanced e-ciency performance than a typical wireless power transfer system without any compensation circuits.

구형 공진기와 계단 임피던스 개방 스터브를 사용한 고효율 광대역 대역 통과 필터 특성

본 논문에서는 구형 공진기와 SIOS(Step-Impedance-Open-Stub)를 사용하여 삽입 손실이 적고, 차단 특성이 아주 좁고, 광대역 특성을 갖는 대역 통과 필터를 연구하였다. SIOS는 일반 <TEX>$0.25\;{\lambda}$</TEX> 개방 스터브보다 약 30 %의 길이를 줄일 수 있고, 또한, SIOS의 길이에 따라 임피던스 값을 조정함으로써 필터의 특성 개선에 적용할 수 있다. 본 논문의 객관성을 입증하기 위해서 이중 모드 구형 공진기를 사용한 최적화된 광대역 대역 통과 필터를 구현하였다. 전송 선로 모델을 사용하여 계산한 주파수 특성 결과는 실험값과 아주 잘 일치하였다. 본 논문에서 구현된 필터의 주파수 특성은 필터의 3 dB 대역폭은 51.75 %(3.206 GHz)이고, 삽입 손실은 0.44 dB, 30 dB 차단 특성은 저 주파수 대역에서 221 MHz(<TEX>$4.326{\sim}4.587\;GHz$</TEX>), 고주파수 대역에서 181 MHz(<TEX>$7.739{\sim}7.954\;GHz$</TEX>)이다. 최대 차단 특성은 저주파 대역에서 -61.8 dB, 고주파 대역에서 -76.3 dB이다. This paper presents a compact, low insertion loss, sharp rejection and wide band microstrip band pass filter that is composed rectangular loop resonator and Step-Impedance-Open-Stub(SIOS). The SIOS can be reduce length about 30 % more than general 0.25 <TEX>$\lambda$</TEX> open stub. And the stub can the advantage of tuning impedance magnitude. In order to demonstrate agrement of this paper prove, the optimized wide band pass filters are realized and experimented. A transmission line model used to calculate the frequency response of the new filters shows good agreement with measurements. The filter has 3 dB fractional bandwidth of 51.75 %(3.206 GHz), an insertion loss of better than 0.44 dB from 4.587 GHz to 7.793 GHz, and two rejection of greater than 30 dB within 221 MHz(<TEX>$4.326{\sim}4.587\;GHz$</TEX>) at low frequency band, 181 MHz(<TEX>$7.739{\sim}7.954\;GHz$</TEX>) at high frequency band. Maximum rejection characteristics of the filter are -61.8 dB at low frequency and -76.3 dB at high frequency.

Relative RF coil performance in carotid imaging

Computer simulations and measurements on human volunteers were used to test the extent to which the quality of carotid imaging might be improved by coil arrays that are not limited by a constraint on the number of RF coil receiver ports. Analytic near-field equations for the magnetic and electric fields of a rectangular loop resonator were used to estimate the relative signal-to-noise ratio (rSNR) along the length of a simulated carotid artery as a function of loop size, loop position and vessel depth. The sizes, positions and number of elements in a linear coil array that resulted in the maximum composite SNR along the length of a simulated carotid artery were then estimated. The linear array results were used to predict the total number of elements needed for optimal imaging of the carotid arteries. Also, three normal volunteers were imaged with a variety of RF coils, and the rSNR measurements along the lengths of the carotid artery were evaluated for each coil combination. The analytic simulation and the human volunteer measurements both show that improved SNR (e.g., >300% at the bifurcation) can be obtained with coils tailored to each specific region of the carotid artery in comparison to that obtained with four-element arrays designed and used to image the entire carotid artery. The resulting number of coil ports, 16 to 24, required for full coverage of the carotid arteries is consistent with the number of channels just becoming available on recently developed clinical scanners.

Immunity testing cell using a rectangular loop resonator comprised of a conducting channel plate and a capacitive gap

AbstractTEM cells that are popular in immunity measurements require high operating power. In this paper, an immunity testing cell using a rectangular loop resonator is proposed. The testing cell is expected to generate high electric field strength at comparatively low power. The resonator comprises a conducting channel plate and a capacitive gap set onto the ground plane. The testing cell has a size of 1/10 wavelength at the testing frequency and therefore is suitable for immunity testing at low frequency. In this study, the electric and magnetic field distribution inside two different types of proposed resonators are analyzed by the FDTD method. Comparison of analytical and experimental results shows a close match. The electric field strength inside the two resonator types is increased by 31.2 and 14.3 dB, respectively, relative to that of the TEM cell of similar size. In the latter type of resonator the electric field deviation inside a square area of 100 mm length is suppressed to 2 dB. Moreover, the resonator covered with a shield case for practical use shows an increase of 11.2 dB in the electric field strength over the level of the similar size TEM cell. The amplitude deviation remains the same as that of the bare resonator. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(7): 22–30, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10011