Triple-passband Filter Research Articles

Triple-Passband Cavity Filters With High Selectivity Under Operation of Triple Modes

A triple-passband filter is proposed by exploiting the first three resonant modes in a single rectangular cavity: TE101, TE011, and TM110 modes. Triple-passband frequency response is realized by generating one transmission zero (TZ) between any of two adjacent modes so that each mode contributes one passband. Beside TZs between modes, the three resonant modes are excited by properly placing two coupling apertures at input/output ports of the cavity. When cascading two single cavities, three pairs of slots are used to independently control the coupling between two respective modes of different cavities. As a result, not only two TZs between different passbands but also a pair of additional TZs below the first passband and above the third passband could be realized, respectively, thereby attaining a high selectivity of a triple-passband filter. Finally, a dual-cavity filter with triple-passband and four out-of-band TZs is fabricated and tested. The measured results have verified the validity of the proposed design well.

Open Loop Resonator-Based Triple Passband Filter for 1.5 GHz, 2.45 GHz and 3.65 GHz Applications

In this paper, a dual mode mixed open loop resonator (OLR)-based metamaterial antenna is introduced for the design of a triple-passband filter for GPS, WLAN and WiMAX applications. The antenna is embedded into a 50-Ω microstrip framework. The Rogers RT-5880, which has a succinct structure, is used as the substrate in the proposed passband filter design, where the attainment of the antenna is explored both integrally and experimentally. A partial ground system is applied in the ground layer and stepwise analysis is performed on the proposed resonator, which can pursue the fundamental even-mode resonant frequency. Based on the proposed resonator, a bandpass filter is designed and fabricated to justify the perception, focusing on 1.5 GHz, 2.45 GHz, and 3.65 GHz. In addition, the filter is evaluated using the Nicolson–Ross–Weir approach at the filtering frequency. The effective electromagnetic parameters retrieved from the simulation of the S-parameters imply that the OLR metamaterial antenna exhibits negative refraction bands. With a favorable design and double-negative characteristics, this structure is suitable for a triple passband filter, particularly at 1.5 GHz, 2.45 GHz and 3.65 GHz, which cover GPS, WLAN, and WiMAX, respectively.

Labyrinth double split open loop resonator based bandpass filter design for S, C and X-band application

Nested circular shaped Labyrinth double split open loop resonators (OLRs) are introduced in this article to design a triple bandpass filter for 3.01 GHz, 7.39 GHz and 12.88 GHz applications. A Rogers RT-5880 is used as a substrate to design the proposed passband filter which has a succinct structure where the attainment of the resonator is explored both integrally and experimentally. The same structure is designed on both sides of the substrate and an analysis is made on the current distribution. Based on the proposed resonator, a bandpass filter is designed and fabricated to justify the perception focusing on 3.01 GHz, 7.39 GHz and 12.88 GHz. It has also been observed by the Nicolson–Ross–Weir approach at the filtering frequencies. The effective electromagnetic parameters retrieved from the simulation of the S-parameters imply that the OLR metamaterial filter shows negative refraction bands. Having an auspicious design and double negative characteristics, this structure is suitable for triple passband filters, particularly for S, C and X-band applications.

Novel programmable microwave photonic filter with arbitrary filtering shape and linear phase.

We propose and demonstrate a novel optical frequency comb (OFC) based microwave photonic filter which is able to realize arbitrary filtering shape with linear phase response. The shape of filter response is software programmable using finite impulse response (FIR) filter design method. By shaping the OFC spectrum using a programmable waveshaper, we can realize designed amplitude of FIR taps. Positive and negative sign of FIR taps are achieved by balanced photo-detection. The double sideband (DSB) modulation and symmetric distribution of filter taps are used to maintain the linear phase condition. In the experiment, we realize a fully programmable filter in the range from DC to 13.88 GHz. Four basic types of filters (lowpass, highpass, bandpass and bandstop) with different bandwidths, cut-off frequencies and central frequencies are generated. Also a triple-passband filter is realized in our experiment. To the best of our knowledge, it is the first demonstration of a programmable multiple passband MPF with linear phase response. The experiment shows good agreement with the theoretical result.

Reconfigurable Multi-Band Microwave Filters

An original and simple approach to the design of fully reconfigurable multi-band microwave bandpass filters (BPFs) with an arbitrary number of passbands is reported in this paper. It exploits the use of an innovative quasi-BPF configuration made up of different sets of controllable mono-frequency resonators to separately shape each tunable passband. Thus, high-selectivity multi-band bandpass filtering transfer functions exhibiting independent control in terms of center frequency, bandwidth, and transmission zeros can be synthesized. Furthermore, as an unprecedented frequency-agility feature of the proposed reconfigurable multi-band BPF structure when compared to the state-of-the-art, its passbands can be merged together to form broader, and for certain realizations, higher order transmission bands. This allows even more degrees of reconfiguration to be achieved in the devised circuit, which can also operate as ultra-wideband BPF with flexible in-band notches or self-equalized flat-group-delay quasi-elliptic-type BPF. The theoretical foundations of the described reconfigurable multi-band BPF scheme, along with guidelines for its design and a triple-passband filter synthesis example based on the coupled-node formalism, are expounded. In addition, as an experimental proof-of-concept, two microstrip prototypes with high- Q tuning implemented through mechanically variable capacitors are manufactured and tested. They are a wideband dual-band BPF and a quadruple-band BPF with narrow-bandwidth passbands.

New Compact Triple-Passband Bandpass Filter Using Multipath-Embedded Stepped Impedance Resonators

This letter presents a new resonator configuration to design a triple-passband filter with high passband selectivity and compact circuit size. The filter includes two multipath-embedded stepped impedance resonators (SIRs), connected with magnetically coupling by via hole technique at the symmetric plane of the filter. The multipath-embedded SIR is designed at 1.575, 2.45, and 3.5 GHz. The resonant frequencies can be easily controlled by tuning impedance ratio K i and length ratio αi (where i = 1, 2, and 3) of the multipath-embedded SIR. This study provides an effective method to easily design the triple-passband filter with compact circuit size, high passband selectivity and low insertion loss.

Design of multi-layered bandpass filter with independently controllable triple-passband response

In this paper, a new multi-layered triple-passband bandpass filter using embedded and stub-loaded stepped impedance resonators (SIRs) is proposed. The filter is designed to have triple-passband at 1.8, 2.4, and 3.5 GHz. The 1st and 2nd passbands (1.8/2.4 GHz) are simultaneously generated by controlling the impedance and length ratios of the embedded SIRs (on top layer). The 3rd passband (3.5 GHz) is generated by using the stub-loaded SIR (on bottom layer). Using the embedded SIR, the even modes can be tuned within very wide frequency range and without affecting the odd modes. Therefore, the design of multi-band filters with very close passbands can be easily achieved and having a high isolation between the passbands. The filter can provide the multi-path propagation to enhance the frequency response and achieving the compact circuit size. The measured results are in good agreement with the full-wave electromagnetic simulation results.

A CAD model of triple bandpass filter implemented with mushroom structure

This article demonstrates the design of planar triple-band filter using mushroom resonator for significant size reduction of the order 80%. Here, mushroom type resonator is used to realize a triple passband filter using the coupling matrix approach. The electric and magnetic couplings between the mushroom resonators are achieved by proper positioning of corner via which have been analyzed and presented. Finally, the frequency transformation has been applied to design a highly selective 12-pole triple-passband cascaded-quartets filter. This symmetric triple-band filter is operative at center frequencies 3.41/3.56/3.72 GHz with 100 MHz bandwidth of each band. It is observed that the measured results are in good agreement with the simulated results. A significant size reduction has been achieved while realizing triple-passband filter, which is as small as 50 mm × 25 mm × 1.27 mm. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:421–428, 2014.

A novel compact triple-passband filter design based on stepped impedance stub-loaded resonators

This article presents a new compact triple-passband filter using stepped impedance stub-loaded resonators, which is based on even–odd mode analysis.The first and the third passbands are provided in even mode, whereas the second passband is produced in odd mode. Moreover, the bandpass filter (BPF) performance is good at 2.8, 3.9, and 6.7 GHz by tuning the physical length of high impedance part of the stub. Measurement results agree well with the full-wave EM simulations. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2106–2108, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27017

On the Design of a Multiple Pass-band Filter by Frequency Transformation

It is shown that the use of reactance functions for frequency transformation of a normalized low-pass filter (NLPF) to a multiple passband filter (MPBF) is straightforward and simpler than the methods using repeated low-pass to band-pass transformation or a combination of such transformations. The method gives the band edges of the MPBF corresponding to the positive and negative cutoff frequencies of the NLPF unambiguously. The transformation function is found explicitly in terms of the band edges of the MPBF and the NLPF elements are converted to those of the MPBF with ease. Furthermore, the center frequencies of the passbands are also found with ease. Dual and triple passband filters are considered for illustrating the use of the method.

Analytical design of novel triple-passband microwave filters using frequency transformations method

In this article, a triple-band filter is presented.This design is based on the suitably defined frequency transformations and uses well-established prototype synthesis techniques, and the coupling coefficients and the external quality factors can be calculated analytically. In the realization, the triple-band resonator is utilized to replace each capacitance in the low-pass prototype circuit as the building block of the triple-band filter. To validate the synthesis method, a practical triple-passband filter is designed and fabricated with passbands at 3.3–3.4 GHz, 3.5–3.6 GHz, and 3.7–3.8 GHz, respectively, which has a maximum return loss of 20 dB in each passband. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2199–2201, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26244

A Simple Method to Design a Compact Triple-passband Filter Using Novel Coupling Scheme and Multi-Layered Substrate

In this paper, a simple method to design a compact triplepassband filter is presented. The proposed filter structure is mainly composed of two half-wavelength input/output (I/O) terminated microstrip lines and three open-loop uniform impedance resonators (UIRs), which are designed for three different passbands. By properly selecting the coupling position between I/O open-ended microstrip lines and each desired resonator, three passbands can be integrated, and the insertion loss can be improved. In order to achieve compact size, the three UIRs are placed on different layers of the substrate. A filter example operated at 1.575 GHz, 1.8 GHz, and 2.4 GHz for GPS, GSM, and WLAN applications is designed using the proposed concept and then fabricated. Experiment results show a good agreement with the simulated performances.

Synthesis of Cross-Coupled Triple-Passband Filters Based on Frequency Transformation

A synthesis method is presented for triple-passband filters. The proposed method is based on a frequency transformation from the normalized frequency domain to the actual frequency domain. A novel triple-passband filter topology with cross coupling is obtained, which consists of admittance inverters and parallel resonators. The coupling coefficients and the external quality factors can be calculated analytically. To validate the theory, a triple-passband filter is designed and fabricated using microstrip structure. The theoretical response meets the specifications very well, and the measured result shows a good agreement with the simulated one.

Design of a Triple-Passband Microstrip Bandpass Filter with Compact Size

This paper presents the triplepassband microstrip bandpass filter (BPF) with compact size. Two sets of the coupled asymmetric stepped impedance resonators (SIRs) and uniform impedance resonators (UIRs) are arranged for generating the triple-passband properties. It is convenient to control the triple-passband properties by tuning the impedance ratio (K) and length ratio (γ) of the asymmetric SIRs. The UIRs are also employed to enhance the coupling between the coupled resonators at 3rd passband. The filter is designed at 2.4/5.2/8.2 GHz and achieves nearly 50% circuit size reduction compared with the previous works. This study provides a simple method to design a triple-passband filter with compact circuit size. Experimental verification is provided, and good agreement has been found between simulation and measurement.

Design of Triple-Passband Microwave Filters Using Frequency Transformations

This paper introduces a synthesis method for triple-passband microwave filters. A frequency transformation is developed for finding the locations of poles and zeros of the triple-passband filter. The poles and zeros obtained as such are optimized to achieve a transfer function with a reduced number of transmission zeros in order to reduce the number of cross-couplings. Six- and 12-pole triple-passband filters are synthesized for validation of this proposed method. A 12-pole triple-passband filter is fabricated with a microstripline structure and shown to provide good agreement between synthesis and measurement results. Finally, the frequency transformation for asymmetric triple-passband filters is briefly discussed.

Design of triple-passband bandpass filter with interdigital resonators

A triple-passband bandpass filter is proposed. With the interdigital resonators embedded into the open-loop resonators, the bandpass filter with multiple passbands can be obtained. Moreover, by adopting the method of interdigital resonators, the passband with broader bandwidth on the higher frequency band can be obtained. The measured results of the fabricated filter match well with the electromagnetic simulation, therefore the feasibility of the proposed filter is approved.

Dual-Band and Triple-Band Substrate Integrated Waveguide Filters With Chebyshev and Quasi-Elliptic Responses

In this paper, synthesis and design techniques of dual- and triple-passband filters with Chebyshev and quasi-elliptic symmetric frequency responses are proposed and demonstrated for the first time on the basis of substrate integrated waveguide technology. The inverter coupled resonator section is first investigated, and then a dual-passband Chebyshev filter, a triple-passband Chebyshev filter, and a dual-passband quasi-elliptic filter, which consist of the inverter coupled resonator sections, are synthesized from the generalized low-pass prototypes having Chebyshev or quasi-elliptic responses, respectively. Subsequently, theses filters with a symmetric response are designed and implemented using the substrate integrated waveguide scheme over the -band frequency range. The inverter coupled resonator sections composed of side-by-side horizontally oriented substrate integrated waveguide cavities are coupled, in turn, by post-wall irises. 50-Omega microstrip lines are used to directly excite the filters. Measured results are presented and compared to those simulated by Ansoft's High Frequency Structure Simulator (HFSS) software package. A good agreement between the simulated and measured results is observed, which has also validated the proposed concept of design and synthesis with the substrate integration technology.

Design of Dual- and Triple-Passband Filters Using Alternately Cascaded Multiband Resonators

A novel method for designing multiband bandpass filters has been proposed in this paper. Coupling structures with both Chebyshev and quasi-elliptic frequency responses are presented to achieve dual- and triple-band characteristics without a significant increase in circuit size. The design concept is to add some extra coupled resonator sections in a single-circuit filter to increase the degrees of freedom in extracting coupling coefficients of a multiband filter and, therefore, the filter is capable of realizing the specifications of coupling coefficients at all passbands. To verify the presented concept, four experimental examples of filters with a dual-band Chebyshev, triple-band Chebyshev, dual-band quasi-elliptic, and triple-band quasi-elliptic response have been designed and fabricated with microstrip technology. The measured results are in good agreement with the full-wave simulation results