Conventional Open-loop Resonator Research Articles

Design and Fabrication of a Novel Compact Bandpass Filter to Improve Spurious-Free Band

AbstractIn this paper, a new microstrip slow wave open loop resonator is proposed. This resonator overcomes the substantial limitation of the conventional slow wave open loop resonators, which limits the spurious-free band of those resonators. The new proposed resonator improves the spurious-free band up to 8 times of the fundamental frequency, which is 3.16 times of the conventional slow wave open loop resonators. For the proposed resonator the coupling factor and the external quality factor curves, which are the design curves of a narrowband filter, are extracted using a full wave simulator, i. e. HFSS. These curves are utilized for the design of two three-pole Chebyshev bandpass filters. One of these filters is fabricated. Simulation and measurement results are reported which are in good agreement. Designed filters provide 75 % and 83 % of footprint reduction in comparison with the conventional open loop resonator filters. Different parameters which can improve the spurious-free band are explained in the paper.

Simple and Compact Balanced Bandpass Filters Based on Magnetically Coupled Resonators

A simple strategy is proposed to design differential-mode bandpass filters with good common-mode (CM) rejection using simple resonators. Specifically, the CM rejection is enhanced by using conventional open-loop resonators as well as folded stepped-impedance resonators without the addition of printed or lumped elements along the symmetry plane of the filter or the use of defected ground solutions. The novelty of the present proposal is that a good CM rejection is achieved by the use of magnetic coupling instead of the more commonly employed electrical coupling. Magnetic coupling inherently yields poorer CM transmission as requested by good differential filters. The resonators, due to their geometrical simplicity, can easily be cascaded to implement high-order filters. The use of simple geometries also simplifies the design methodology and makes final tuning based on electromagnetic simulation simpler or unnecessary.

Miniaturized Mixed Electric and Magnetic Coupling Bandpass Filter Based on Interdigital Resonator

By integrating the interdigital structure into a conventional open-loop resonator, a compact mixed electric and magnetic coupling bandpass filter is designed and fabricated for the first time. Due to the high intensity inner coupling capacitor, which is generated by interdigital lines, not only did the size of the filter sharply decrease, but the electric field was strengthened. Therefore, by properly adjusting the ratio of electric and magnetic coupling, the transmission zeros very close to the passband is obtained readily. Based on mixed electric and magnetic coupling, a fourth-order bandpass filter with multiple transmission zeros is realized without requiring either a cross-coupled path or source-load coupling. For design purposes, the equivalent-circuit model is also derived and verified. Advantages of this filter include its miniaturized size of only 0.06λ0 × 0.045λ0, its sharp cutoff slope, as well as the tiny discrepancies between simulation and measurement.

Resonance characteristics of capacitively loaded CPW open‐loop resonators

AbstractCapacitively loaded coplanar waveguide (CPW) open‐loop resonators (OLRs) are proposed for maximum miniaturization in uniplanar microwave applications. It is shown that these resonators can be used to achieve a slow‐wave effect without occupying extra surface area. Also, the resonators have a size reduction of about 50% at the same resonance frequency, as compared with the conventional open‐loop resonator, as well as a higher performance of about 25–30%. The reduction in size of these types of resonators, and their performance (mainly the Q factor), can be controlled by the fingers within the OLR. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 298–300, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11042