Multiple Attenuation Poles Research Articles

Transmission line bandpass filters with multiple attenuation poles and small number of resonators

This article considers an alternative way to generate attenuation poles (AP) in bandpass filter (BPF) with parallel type resonators and admittance inverters. It consists in using special transmission line resonators, in which one or two antiresonant frequencies ωp1, ωp2 are placed next to the main resonant frequency ω0. These frequencies ωp1, ωp2 are the poles of the input admittance Y(jω). Four new resonators are synthesized in the article. Two resonators generate one AP, and other two resonators generate two APs located near the passband of the BPFs. If we use mixed couplings between proposed adjacent resonators in BPF, then the total number of APs will become quite large. This is because each mixed coupling adds one AP. N-order BPF without cross coupling can has (3 N – 1) APs. The increased number of APs improves the BPF selectivity, including the one-sided one. With APs, the filter can provide increased attenuation in certain frequency bands and effectively suppress unwanted signals. A microstrip second order BPF with center frequency f0 = 1 GHz and bandwidth BW = 70 MHz, which has five APs, is designed. It is compared with third order BPFs with two APs.

A NEW FREQUENCY SELECTIVE WINDOW FOR CONSTRUCTING WAVEGUIDE BANDPASS FILTERS WITH MULTIPLE ATTENUATION POLES

This paper presents a novel frequency selective window for waveguide fllters. It has a resonant characteristic with two attenuation poles on both sides of a passband, that is, a dual-behavior resonance. Such frequency selective windows make it possible to construct a compact bandpass fllter having multiple attenuation poles without any additional coupling structures. As design examples, we show 3-pole Chebyshev waveguide fllters with six attenuation poles in both the microwave and the millimeter-wave regions. The validity of the present fllters is proven by the comparison of the frequency characteristics between the calculated and the measured results.

Dual‐band microstrip‐line BPFs using tap‐coupling resonators

AbstractWe focused on various dual‐band microstrip‐line bandpass filters (BPFs) based on tap‐coupled resonators. Three types of BPFs, the basic type, multiple‐pole type, and wideband type, were proposed and designed by classical filter theory based on the narrowband approximation method. These filters were analyzed by original computation programs and commercial circuit and electromagnetic simulators. The proposed BPFs were then fabricated and measured in the laboratory. The results confirm that the proposed BPFs produce dual passband response, multiple attenuation poles, and wide‐passband characteristics. Very good agreement is found between the results of simulations and experiments. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(6): 25–33, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10212

A compact multilayer diplexer in LTCC substrate using LPF with multiple attenuation poles and wideband BPF

AbstractRecently, compact wideband BPFs for a UWB system have been studied actively. In this paper we propose a compact diplexer built into an LTCC substrate for a UWB system and 2.4‐GHz wireless systems. First, a wideband BPF for a UWB system and an LPF with multiple attenuation poles for 2.4‐GHz wireless systems are described. Second, we design matching circuits of a common port to retain the basic performance of both the BPF and the LPF. Third, in accordance with the results of the study, we design a compact diplexer built into an LTCC substrate. Finally, we verify the effectiveness of the proposed method by experiments. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 24–32, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10210

Quasi-elliptic dual-band filter design using stepped-impedance resonators and coupling topologies for narrow-to-wide-band applications

Design guidelines are presented for new planar quasi-elliptic dual-band filters in applications requiring high performance, compact size, ease of fabrication and integration with remaining circuitry. Novel coupling topologies between folded stepped-impedance resonators (SIRs) are utilised to generate two narrow or two wide passbands at desired centre frequencies with multiple attenuation poles between passbands. Source–load coupling is employed to place additional attenuation poles within the lower and upper stopband regions. The main feature of these dual-band filters is their approximately symmetrical response, including high selectivity of each passband and controllable fractional bandwidths for either narrowband or wideband coupling schemes, respectively. In addition, the simplicity of the design approach and the use of folded SIR structures result in compact size. Several microstrip dual-band filters in various cascaded SIR configurations with narrow or wide passbands are designed and measured. The measured results are in very good agreement with those obtained from different electromagnetic simulation packages such as Ansoft Designer and IE3D.

감쇄극 인버터를 이용한 반파장 Partial H-Plane 여파기

본 논문에서는 차단 영역 도파로로 구현된 협소한 형태의 H-plane slot을 이용하여 다수의 감쇄극을 가지는 반파장 partial H-plane filter를 제안하였다. 협소한 형태의 H-plane slot은 대역 통과 필터의 어드미턴스 인버터 역할을 하는 동시에 특정 주파수에서 공진을 발생시킨다. 따라서 제안된 필터는 어떠한 부가적인 coupling이나 추가적인 구조의 변형 없이 저지 대역에서 감쇄극을 가지는 간단한 구조로 구현되고, 감쇄극 수는 인가되는 slot의 수만큼 발생된다. 제안된 필터는 일반적인 도파로의 1/4의 단면적을 가지는 partial H-plane waveguide로 설계되므로 소형화에 유리하다 저지 대역에서 각각 4개와 5개의 감쇄극을 갖는 3단과 4단 반파장 대역 통과 필터를 H-band에서 설계하여, 이론적 주파수 응답 특성이 실험적 응답 특성과 잘 일치함을 확인하였다. This paper presents half wavelength partial H-plane filters with multiple attenuation poles using narrow H-plane slot of evanescent waveguide. The narrow H-plane slot operates as an admittance inverter o( the bandpass filter and, simultaneously, generates an attenuation pole at particular frequency. Therefore, proposed filters with attenuation poles are simply implemented without any additional coupling and extra modification of the structure. The number of attenuation poles of the filters equals to that of the H-plane slots. Moreover, proposed filters are compact waveguide filter since ones are embodied by partial H-plane waveguide which has 1/4 cross section of conventional waveguide. The third and fourth-order half wavelength filters having 4 and 5 attenuation poles, respectively, are designed in H-band and their frequency responses are confirmed by simulation and measurement.

タップ結合型共振器を用いたマイクロストリップ線路デュアルバンドＢＰＦ

We focus on various dual-band microstrip-line bandpass filters(BPFs) based on tap-coupled resonators. In this study, three types of the BPFs such as basic type, multiple poles based type and wide-band type are proposed and designed by classical filter theory based on narrow-band approximation method. These filters are analyzed by original computation programs and commercial circuit and electromagnetic simulators. And then, the proposed BPFs are fabricated and measured in our laboratory. From the results, we have confirmed that the proposed BPFs produce dual pass-band response, multiple attenuation poles and wide-passband characteristics. We also have observed very good agreements between the simulations and experiments.

A Compact Multilayer Diplexer in LTCC Substrate Using LPF with Multiple Attenuation Poles and Wideband BPF

Recently, compact wideband BPFs for UWB system are studied actively. In this paper we propose a compact diplexer in LTCC substrate for UWB system and 2.4GHz wireless systems. Firstly, a wideband BPF for UWB system and an LPF with multiple attenuation poles for 2.4GHz wireless systems are described. Secondly, we design matching circuits of a common port to keep basic performance of both the BPF and the LPF. Thirdly, in accordance with the result of the study, we design a compact diplexer in LTCC substrate. Finally, we verify the effectiveness of proposed method by experiments.

A novel waveguide bandpass filter with multiple attenuation poles using four‐armed square‐loop FSSs

AbstractThis paper presents a waveguide filter loaded with frequency selective surfaces (FSS) that can realize multiple attenuation poles. As the FSS resonant element, a square‐loop FSS with arms is proposed. The authors have studied the design of the shape of the resonant element for the FSS by using the genetic algorithm (GA). There have been problems, namely, that the shape obtained by GA is complex and that the optimization design by GA requires a considerable amount of time. In this paper, these problems are eliminated by means of a square‐loop FSS with arms. The proposed resonant element has a resonance (full transmission) at the center frequency while it has antiresonances (full reflection) on both sides. By means of these antiresonances, attenuation poles can be created. The resonant frequencies can easily be controlled by adjusting the element shape. As an example, a three‐stage waveguide filter loaded with FSSs with a total of six attenuation poles in the X band is designed. By comparison of the numerical results and the experimental results, effectiveness of the proposed shape is verified. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(4): 26–33, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20305

Planar‐circuit bandpass filters consisting of arbitrarily shaped elements

AbstractThis paper presents an arbitrarily shaped circuit as a planar circuit filter optimized by using a genetic algorithm and develops new, never‐before‐seen planar circuit elements. A GA optimization algorithm, which can arbitrarily set the input/output line width and shielding box dimensions according to the optimization conditions for the planar circuit filter, and a method for analyzing planar circuit filters of arbitrarily shaped elements by the method of moments are discussed. As a design example, the authors perform optimizations based on the specifications for a conventional bandpass filter; the resulting filters construct a passband without filter synthesis using an equivalent circuit, and have a smaller size and multiple attenuation poles. The effectiveness of the planar circuit filters with arbitrarily shaped elements is examined by fabricating the filter structures obtained by the GA, performing an experiment, and making a comparison with analytical results. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(2): 1–8, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20292

Novel waveguide filters with multiple attenuation poles using dual-behavior resonance of frequency-selective surfaces

This paper develops novel waveguide filters consisting of frequency-selective surfaces (FSSs) in order to realize both the drastic size reduction and multiple attenuation poles in stopbands at both sides of passband. The FSS provides not only a passband but also attenuation-pole frequencies in stopbands since the FSS has both the aperture-element and the patch-element behaviors. In the present design method, the shape of each FSS is designed by a genetic algorithm so that the resonant curve of FSS can be fitted to that obtained from an equivalent-circuit approach. By using such FSSs and quarter-wavelength waveguides, a bandpass filter with six attenuation poles like an elliptic-function filter has been constructed. Furthermore, a technique of the size reduction by controlling adequately the resonant response of each FSS is presented. In this filter, the FSSs are closely located at the interval of the length much shorter than a quarter wavelength. It is shown from the design example that the half longitudinal length of the former example can be obtained, keeping both the passband response and attenuation poles in stopbands. The effectiveness of the waveguide filters with FSSs is validated by good agreement between the calculated and the measured results.

Out‐of‐band improvement by BPFs with multiple attenuation poles using a condition of variable coupling length of a parallel partially coupled‐line section

AbstractA combination of two microstrip‐line resonators, which are partially coupled, are considered in a parallel partially coupled‐line bandpass filter (BPF), where one resonator is one half‐wavelength (λ/2) long, and the other (whose one end is grounded) is only one quarter‐wavelength (λ/4) long. Therefore, the length of a coupled‐line section can be varied based on the position of the grounded end. Five conditions of the movable coupling length are simulated, which greatly influences the spurious responses of the BPF. This property is numerically investigated in this paper. The analysis shows that, based on the grounding position, this method is capable of realizing improved out‐of‐band characteristics by locating the multiple attenuation poles in the stopband and improved spurious responses up to five times of the passband frequency (5f0) of a parallel partially coupled‐line BPF. An empirical model of the BPF is fabricated, and the numerical results are verified via comparison with the experiment. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 4–9, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21064

Out-of-Band Improvement by Microstrip Line BPFs with Multiple Attenuation Poles in Stopband Using Various Conditions of Coupling Length of Partially Coupled-Line Section

In a partially coupled-line bandpass filter (BPF), a combination of two microstrip line resonators which are partially coupled, are considered, where one resonator is half-wavelength (λ/2)-long, and another whose one end is grounded, is only quarter-wavelength (λ/4)-long. Therefore, the length of a coupled-line section can be varied based on the position of the grounding end, and five conditions of the movable coupling length have been simulated which will greatly influence the spurious responses of a BPF. This property is numerically investigated in this paper. The analysis shows that, based on the grounding position, this method is capable of realizing the improved out-of-band characteristics by locating the multiple attenuation poles in the stopband and improved spurious responses up to five times of the center frequency (5 f0). A few empirical models of BPF are fabricated, and the numerical results are ensured by comparing with the experimental results.

Heuristic models of half-wavelength resonator bandpass filter with attenuation poles

Half-wavelength resonator bandpass filters (BPFs) with improved skirt characteristics are proposed in a heuristic manner. 'Tapping' for I/O and/or interstage coupling is the key concept here because the resulting half-wavelength open-ended resonators have open stubs which lead to anti-resonances near the resonant frequencies. Hence, transmission zeros appear near the resonant frequencies. i.e. the attenuation poles are created close to the passbands. Using this concept, excellent bandpass characteristics with multiple attenuation poles are obtained by using both I/O and interstage tap-coupling. The results of an experiment involving a coplanar structure are presented which confirm the concept.