A new class of wideband microstrip bandpass filters is proposed under multiple resonances of an asymmetric ring resonator. Two capacitive coupling elements are placed at two perpendicular positions of a squared ring, whereas a pair of open-circuited stubs is formed in the symmetrical plane of these two excited ports similar to a dual-mode ring filter in shape. By stretching the paired stubs close to one-eighth of a wavelength, the first two even-order resonances move down to be quasi-equally located at two sides of the first odd-order resonance, thus forming a triple-resonance ring resonator. As interdigital coupled lines are installed at two ports instead of lumped capacitors, two extra resonances can be moved into passband, thereby making up a quintuple-resonance ring resonator. To provide an insight into their operating mechanism, these ring resonators are characterized in terms of transmission line theory. Afterwards, various wideband microstrip ring resonator bandpass filters with one or two asymmetric ring resonators are optimally designed and fabricated. Simulated results are confirmed via experiment, showing good wideband filtering performance with widened/deepened upper stopband and sharpened rejection skirts outside the wide passband.

Wideband Microstrip Ring Resonator Bandpass Filters Under Multiple Resonances

A novel, compact, and highly selective ultra-wideband bandpass filter was developed on a microstrip line and presented in this letter for use in wireless communication applications. The basic filter is composed of five short-circuited stubs separated by nonredundant connecting lines that contribute to the filter selectivity as well. In addition, a cross-coupling between the feed lines (input and output) was introduced which generated new pairs of attenuation poles at each side of the passband. As a result, the filter exhibited extremely sharp rejection skirts around the target passband without the need for increasing the number of transmission line sections. The filter was successfully designed, simulated, and fabricated. The theoretical, EM-simulated, and experimental performance is presented in this work where excellent agreement between them was obtained

A Novel Ultra-Wideband (UWB) Bandpass Filter (BPF) With Pairs of Transmission Zeroes

In this letter, pseudo-interdigital stepped impedance resonators (PI-SIRs) are used to design the bandpass filter (BPF) with dual-band response. By tuning the impedance ratio (K) and physical length of SIRs, the BPF has good dual-passband performances at 2.4/5.2GHz and high isolation between the two passbands. It is shown that the dual-band BPF has a smaller area and lower insertion loss in comparison of previous works. Good agreement is shown between the full-wave electromagnetic simulation and the measurement

Compact and Low Loss Dual-Band Bandpass Filter Using Pseudo-Interdigital Stepped Impedance Resonators for WLANs

In this paper, a method for representing electromagnetic emissions from a printed circuit board (PCB) using an equivalent dipole model deduced from near-field scanning is proposed. The basic idea is to replace the PCB with a set of infinitesimal dipoles that generate the same radiated fields. Parameters of the equivalent dipoles are determined by directly fitting to the measured magnetic near fields. In closed-environment simulations, the equivalent method is extended to a dipole-dielectric conducting plane model to account for the interactions between the PCB and enclosure by including the basic physical features of the PCB. The electromagnetic emissions can then be predicted by solving the equivalent model with numerical methods, thereby, significantly reducing the simulation time and storage costs. A basic test board and a more complex practical telemetry PCB are modeled in different configurations and compared with measurements and full-field simulations, confirming the validity and efficiency of the model.

Modeling Electromagnetic Emissions From Printed Circuit Boards in Closed Environments Using Equivalent Dipoles

Atri-bandbandpassfilterusingstubloadedresonator (SLR) and defected ground structure (DGS) resonator is proposed in this letter. The DGS resonator on the lower plane constructs the first pass-band, and the SLR on the upper plane forms the second and third pass-bands, in which a DGS loop is properly used to pro- videthecouplingbetweentheSLRs.Thethreepass-bandsarecom- bined together with a common T-shaped feed line, and a reason- able tuning method is adopted to tune the three pass-bands with smooth responses. A compact tri-band filter with three pass-bands centered at 2.45, 3.5, and 5.25 GHz is designed and fabricated. The measurement results agree well with the full-wave electromagnetic designed responses. Index Terms—Defected ground structure (DGS) resonator, stub- loaded resonator (SLR), tri-band filter, T-shaped feed line.

http://ieeexplore.ieee.org/iel5/7260/5458313/05445051.pdf

Design of Tri-Band Filter Based on Stub

A novel method is proposed to synthesize dual-band bandpass filters (BPFs) from a prototype low-pass filter. By implementing successive frequency transformations and circuit conversions, a new filter topology is obtained which consists of only admittance inverters and series resonators, and is thereby easy to be realized by using conventional distributed elements. A dual-band BPF with center frequencies of 1.8GHz and 2.4GHz is designed and fabricated using microstrip lines and stubs. The simulated and measured results show a good agreement and validate the proposed theory.

Synthesis of dual-band bandpass filters using successive frequency transformations and circuit conversions

A novel compact ultra-wideband (UWB) bandpass filter (BPF) using a microstrip stepped-impedance four-modes resonator is developed in this paper. By controlling the resonant frequencies of the first four modes of the resonator, we get four transmission poles within the passband of the filter. Moreover, by enhancing the coupling between the resonator and the input/output feed lines, we obtain two additional transmission poles. As a consequence, we realize a UWB bandpass filter that has six transmission poles in its passband, although only one resonator is utilized. A design method, based on network analysis and optimization in the z-domain, is established to determine the circuit and geometrical parameters of the filter. The measured filtering characteristics of the filter show good agreement with the theoretical predictions and satisfy well the Federal Communications Commission's indoor limit.

A Novel Compact Ultra-Wideband Bandpass Filter Using a Microstrip Stepped-Impedance Four-Modes Resonator

A design of a compact ultra-wideband (UWB) bandpass filter is presented in this paper The filter is synthesized by a modified theory using Z-transform technique In order to get sharp attenuations of the filter, shunt two-section open-circuited stubs are employed to produce transmission zeros in the lower and upper stopbans A 3-degree UWB filter is designed and implemented in the form of microstrip lines, and the measured characteristics show good agreement with the theoretical and simulated results

A compact UWB bandpass filter using two-section open-circuited stubs to realize transmission zeros

In this paper, a novel dual-band bandstop filter (DBBSF) is proposed by using composite shunt resonators, and an approximate design method is developed based on the lumped-element circuit of the filter. Both the midband frequencies and the stopband widths of the dual bands of the filter can be controlled separately. A dual-band BSF with center frequencies of 1.7 and 2.3 GHz is designed and fabricated using microstrip lines. The measured frequency response agrees excellently with theoretical predictions, validating well the proposed design theory and filter structure.

Novel microstrip dual-band bandstop filter with controllable dual-stopband response

A transmission-line-theory-based novel synthesis theory is proposed to design an ultra-wideband bandpass filter to meet Federal Communications Commission (FCC)'s spectrum limit. One-wavelength parallel coupled stepped-impedance resonators (SIRs) are used to achieve a fraction passband from 3.1 GHz to 10.6 GHz (greater than 100%). An unsymmetrical SIR is employed to replace the conventional centrally-symmetrical one, so that the coupling gap is successfully enlarged to alleviate the requirement on fabrication precision. A simpler equivalent circuit for the parallel coupled-line is used in this synthesis to avoid calculation of parameter J [7]. As an example, a filter with two-stages is synthesized, simulated and fabricated. The good agreement between the measured and predicted results validates the effectiveness of newly proposed synthesis theory. Meanwhile, the designed filter exhibits good characteristics of low insertion loss, sharp skirts, flat group delay and good stopband (especially in lower one) as well.

T. Anada

Papers

Synthesis of dual-band bandpass filters using successive frequency transformations and circuit conversions

A Novel Compact Ultra-Wideband Bandpass Filter Using a Microstrip Stepped-Impedance Four-Modes Resonator

A compact UWB bandpass filter using two-section open-circuited stubs to realize transmission zeros

Novel microstrip dual-band bandstop filter with controllable dual-stopband response

Synthesis of ultra-wideband bandpass filter employing parallel coupled SIRs of one-wavelength