Design Of Wide-band Filters Research Articles

The feed line resonator (FLR) method and it’s application to superconducting wideband filter design with extreme sharp skirt

This paper proposes the novel concept and method of the feed line resonator (FLR). By introducing the external quality factor adjusting line, the feed lines can be transformed to resonators, and can be used not only for providing external coupling, as well as generate extra transmission poles in the passband. The conditions for generating transmission poles by using the FLR are systematically investigated. The key advancement of the FLR method is that extra transmission poles are introduced, without increase the number of conventional resonators, the filter bandwidth can be extended and the selectivity also improved. The triple-mode FLR was proposed which can realize six extra transmission poles in the pass band and n transmission zeros out-of-band. A five-section multi-mode resonator proposed for wideband filter. Single-, two-, three- and four-stage wideband superconducting filters were designed to demonstrate the FLR method. These filters exhibit extreme sharp skirts, the attenuation slop at lower and higher band can reach 273.9 dB GHz−1 and 523.7 dB GHz−1, respectively. The passband is from 2.26 GHz to 5.54 GHz with the fractional bandwidth of 95%. The measure results agree well with the simulated ones.

Compact high‐selectivity high‐temperature superconducting wideband bandpass filter using triple‐mode stub‐loaded loop resonator

A triangle triple-mode stub-loaded loop resonator (SLLR) is proposed in this letter and used for wideband filter design. Also, this SLLR can produce multiple transmission zeros for high-selectivity bandpass filter (BPF) design without adding extra circuit unit. To verify the unique characteristics of the proposed SLLR, a compact wideband BPF is designed and fabricated using high-temperature superconducting YBCO thin films on a MgO substrate. Furthermore, a novel meander structure is introduced to realize compact size and strong input/output coupling design. The measured results show that the 3-dB fractional bandwidth is of 50.6% (2.55-4.28 GHz), and the selectivity factor of the passband is 0.87 with a maximum insertion loss of 0.07 dB, indicating good agreement with the theoretical expectation.

MULTI-MODE SUBSTRATE INTEGRATED WAVEGUIDE WIDEBAND FILTER DESIGN WITH WIDE STOPBAND REJECTION USING COMPLEMENTARY SPLIT RING RESONATORS AND DEFECTED GROUND STRUCTURES

MULTI-MODE SUBSTRATE INTEGRATED WAVEGUIDE WIDEBAND FILTER DESIGN WITH WIDE STOPBAND REJECTION USING COMPLEMENTARY SPLIT RING RESONATORS AND DEFECTED GROUND STRUCTURES

Synthesis Design of Wideband High-Selectivity HTS Filter by Cascading Dual-Mode Resonators

A synthesis method for wideband filter design using dual-mode resonators is presented, which is helpful for the design of miniature high-order dual-mode filters. Using the frequency transformation for dual-mode resonators, the infinite frequency in lowpass prototype can be mapped to band-edge to create a quasi-transmission-zero, resulting in a new technique to improve filter selectivity. Dual-mode resonators are found to be either suitable for wideband filters or dual-band filters, depending on the relative positions of transmission zeros in the filter response. A demonstration filter composed of 11 dual-mode resonators is designed and fabricated for the first time, which surpasses a conventional 17-pole filter in both size and selectivity.

Improved modeling of parallel‐coupled three‐line for wideband filters

ABSTRACTAn improved equivalent circuit of a parallel‐coupled three‐line section is derived for the design of wideband filter. Compared with the conventional model, the cross‐coupling between nonadjacent lines is taken into consideration and shows a better accuracy. A wideband filter composed of three‐line sections is then synthesized using the new equivalent circuit. The simulation and measurement results agree well with the theoretical ones, which validates the new model as well as the synthesis method. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2392–2395, 2014

Split Ring Resonators With Tapered Strip Width for Wider Bandwidth and Enhanced Resonance

This article presents a modified edge-coupled split ring resonator (SRR). The proposed SRR is composed of two concentric metallic rings with a nonuniform strip width, which is tapered based on the current and voltage profile in the SRR structure. In contrast to other SRR miniaturization methods, which are based on increasing the equivalent capacitance of the SRR, the proposed SRR benefits from both increased capacitance and inductance to preserve the strength and bandwidth of the resonance. It is also shown that compared to a uniform SRR, a tapered SRR with the same electrical size provides a stronger resonance with 84% wider bandwidth, as desired in wideband filter design. The theory and simulation results are validated through measurement.

Wideband cross‐coupled filter using defected stepped impedance resonator

AbstractA novel wideband cross‐coupled band‐pass filter based on defected stepped impedance resonator (DSIR) is presented in this article. Although the DSIR has opposite impedance characteristic and field distribution to the microstrip SIR, its resonant property is similar to the latter. The internal coupling coefficients of DSIRs are found to be large enough for the wideband filter design. A four‐pole, cross‐coupled band‐pass filter with f0 = 1.6 GHz and FBW = 12% is designed and fabricated using the folded DSIR. Experimental result has good agreement with the simulation. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 558–561, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24972

Compact Wideband Bandpass Filter Using Hybrid Hairpin and Half Wave Parallel Coupled Resonator in Multilayer Microstrip Configuration for X-band Application

This paper presents a new design of wideband filter for X-band application using hybrid hairpin resonator and half wave coupled line resonator in multilayer microstrip configuration. Different resonator shapes were put on two substrates with different dielectric constants. In this work R/T Duroid 6010 and R/T Duroid 5880 with dielectric constant 10.2 and 2.2 respectively were used as the substrates, producing a very small filter size, only at 10 × 10 cm2. This configuration is not only producing compact size filter, but also high bandwidth since the overlapping gap between two resonators produces a tight coupling which is needed for wideband filter. The filter can cover whole X-band frequencies by producing 44% bandwidth at 10.2 GHz center frequency with excellent responses, where the measured passband return loss for this filter is better than –12.5 dB and the insertion loss is better than 2.3 dB.

A Dual Wideband Filter Design Using Frequency Mapping and Stepped-Impedance Resonators

A dual-wideband filter design implemented by stepped-impedance resonators, which involves the frequency mapping approach, is presented in this paper. The dual-band filter can be divided into two parts: the wideband virtual passband filter and the narrowband virtual stopband filter. Both filters are designed by conventional synthesis methods, under the assumption that the common connecting lines serve as J- and K-inverters simultaneously. The basic building resonators formed by paralleling open- and shorting-stubs are implemented by unbalanced stepped-impedance resonators, exhibiting the desired resonating frequencies and susceptance slope parameters at these two bands. Two filters are tested to validate this design.

Ultra wideband filter design based on composite right‐/left‐handed transmission line

AbstractA novel design method of ultra wideband filter based on the composite right‐/left‐handed transmission line theory is presented in this article. Defected ground structure and microstrip interdigital capacitor are introduced to satisfy the necessity of ultra wideband (UWB) filter. A four‐cell composite right/left‐handed UWB filter is fabricated and measured. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2379–2381, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22733

Aperture-Backed Microstrip-Line Stepped-Impedance Resonators and Transformers for Performance-Enhanced Bandpass Filters

A novel class of microstrip bandpass filter is configured using the impedance transformers and an improved stepped impedance resonator (SIR). This SIR is composed of a central narrow strip section with an aperture on ground and two wide strip sections at the two sides. This low-high-low SIR resonator has a promising capability in achieving an extremely large ratio of first two resonant frequencies for design of a bandpass filter with ultra-broad stopband. The two quarter-wavelength transformers with low and high impedances, referred as to impedance- and admittance-inverters, are modeled and utilized as alternative types of inductive and capacitive coupling elements with highly tightened degrees for wideband filter design. After extensive investigation is made on the two transformers and the proposed SIR, the two novel bandpass filters are constructed, designed and implemented. Two sets of predicted and measured frequency responses over a wide frequency range both quantitatively exhibit their several attractive features, such as ultra-broad stopband with deep rejection and broadened dominant passband with low insertion loss.

Wideband bandpass filter design with three-line microstrip structures

A systematic procedure is described for designing wideband bandpass filters based on parallel coupled three-line microstrip structures. It starts with modal analysis of a three-line coupled microstrip circuit. A database of modal eigenvoltage coefficients and modal characteristic impedances for a specified value of substrate ɛr is established. The relation between the circuit parameters of a three-line coupling section and an admittance inverter circuit is derived, so that the filters can be synthesised by a standard procedure. As compared with traditional parallel coupled lines, the proposed three-line design has the following two important features for the design of wideband filters: the tight line spacings of end stages can be greatly relaxed; and the stopband rejections are improved. Four filters with fractional bandwidths from 40% to 70% are fabricated on substrates with low and high dielectric constants. Prediction and measurement results are in good agreement.