Compact Tri-band Bandpass Filter Research Articles

A compact tri-band bandpass filter using asymmetrical stub-loaded resonator

ABSTRACT This paper proposes a novel compact tri-band bandpass filter based on two coupled asymmetrical stub-loaded resonators (ASLR). The proposed filter can achieve three resonant frequencies by tuning uniform impedance line, short-circuit stub, and open-circuit stub, respectively. In addition, the asymmetrical stub can be loaded at any position of the main branch, which will facilitate the circuit design for no impedance of special ratio is needed, and the design bound can be alleviated. Meanwhile, thanks to its simple structure, the whole filter occupies an area of 0.021 λg 2 based on RO4350B substrate, much smaller than other similar tri-band filters. Measurement results show that the filter achieves fractional bandwidths (FBW) of 7.5%, 6.4% and 4.2%, respectively for three bands. The proposed filter is small and can achieve a high-frequency selectivity at 2.45 GHz, 3.5 GHz and 5.25 GHz, corresponding to Bluetooth, World Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN), respectively. The proposed filter will find a wide application in wireless communications thanks to its attractive advantages.

Design of tri-band bandpass filter using uniform impedance resonators loaded with different impedance stubs

ABSTRACT This paper presents a design of a compact tri-band bandpass filter simply using a pair of the uniform impedance resonator loaded with an open-circuited stub. By introducing the variable impedance of the open-circuited stub, the proposed design has additional design parameter of the impedance ratio to adjust the resonant modes of the used resonator, so as to more easily achieve the different frequency bands. The resonant frequencies of the oddmode and evenmode of the used resonator are analyzed first in this study. A tri-band filter example is designed at the center frequencies of 1.9, 3.58, and 5.75 GHz, which can be used in 4 G system, 5 G communication system, and wireless local area network, respectively. The designed filter is simulated, fabricated, and then measured. The measurement shows that the insertion loss |S21|, return loss |S11|, and 3 dB fractional bandwidth for the three passbands are less than 0.25/0.37/0.9 dB, larger than 30/15/15 dB, and 17.5/12.2/8.9%, respectively. Moreover, by using the interdigital coupling of the used resonator, four transmission zeros are generated near the passband edges at 1.47, 2.56, 4.05, and 6.48 GHz, realizing high selectivity and high isolation. The measurement is consistent with the simulation, confirming the design concept.

Design of Novel Compact Tri-Band Bandpass Filter Using Embedded Resonators

ABSTRACTA novel compact tri-band bandpass filter is presented in this article. The proposed circuit utilizes a second-order embedded resonator. By controlling different parts of the embedded resonator, the operating frequencies can be controlled individually. Furthermore, by introducing source-load coupling, transmission zeros are generated near the passband, resulting in high selectivity. To verify the proposed idea, a tri-band bandpass filter with operating frequencies of 2.4/3.5/5.15 GHz is implemented, which are used to cover the WiFi and WiMax system. The design procedures are discussed in detail, and the simulated and measured results are presented.

Design of compact tri-band bandpass filter using stub-loaded quarter-wavelength SIRs

Design of compact tri-band bandpass filter using stub-loaded quarter-wavelength SIRs

A Compact Tri-Band Bandpass Filter with High Out-of-Band Rejection

This paper presents a planar tri-band bandpass filter with high out-of-band rejection over a wide band. The filter is based on two pairs of λ/4 resonators embedded inside an open loop ring resonator without any size increase, where each pair of resonators are electromagnetically coupled to each other and the feedlines. This results in the excitations of passbands, where the first passband is generated by the open loop resonators. The second and the third passbands are excited by λ/4 resonators. The proposed technique provides sufficient degrees of freedom to control the center frequency and bandwidth of the three passbands independently. In addition, the six transmission zeros created around the passbands results in a tri-band filter with high selectivity, sharp 3 dB cut-off frequency, high isolation, low passband insertion-loss and high out-of-band harmonic rejection across an ultra-broadband frequency range up to 17 GHz. The proposed technique has the ability to switch from triple to dual band by removing one pair of the inner resonators. Design methodology and simulation results of the filter are provided.

Compact tri-band bandpass filter using asymmetric stub-loaded stepped-impedance resonator with multiple transmission zeros

In this paper, a tri-band bandpass filter (BPF) using asymmetric stub-loaded stepped-impedance resonator (SL-SIR) is presented. The asymmetric characteristic of SL-SIR broadens degrees of freedom for three controllable modes design. Also, the coupling coefficients (Mij) and the external quality factors (Qei) at each passband of the filter can be independently adjusted by the proposed mixed-type feedline structure. Besides, multi-transmission zeros are produced to improve the isolation and selectivity of the passbands. Finally, a tri-band BPF is operated at 1.9 GHz (time division long term evolution – TD-LTE band), 3.2 GHz (worldwide interoperability for microwave access – WiMAX band), and 5.8 GHz (wireless local area networks – WLAN band) and their insertion loss are 1.03, 0.94, and 1.27 dB, respectively. The measured results of the fabricated tri-band BPF exhibit good agreement with simulated results.

Compact tri-band bandpass filter with two closely frequency spaced passbands

A compact tri-band bandpass filter based on a novel six-mode resonator is proposed. The filter has three passbands centered at 2.45, 5.2, and 5.8 GHz for WLAN applications. Among them, two closely frequency-spaced passbands with a small center frequency ratio (1/1.11) are realized. The 3 dB bandwidth of the two passbands are 5.8 and 5.2%, which means they have equal absolute bandwidth. Source-load-coupling structure is adopted to enhance the high-isolation performance. And the filter has six transmission zeros, resulting in high-frequency selectivity. The passband frequencies and bandwidths of the filter can be controlled. The measured results are in good agreement with electromagnetic simulation. Its circuit only occupies 0.14 λg × 0.09 λg (11.2 mm × 7.1 mm), where λg is the guided wavelength at the lowest passband center frequency.

New approach to design a compact triband bandpass filter using a multilayer structure

In this paper, a triband bandpass filter is presented using a dual-layer structure. Three H-shaped resonators are utilized in the proposed structure. The first and third resonators are placed at the top and bottom layers, respectively. The second resonator is divided into two parts: one half is on the top and the other half is at the bottom. The effective permittivity at the first and second layers is different, resulting in different resonant frequencies. The fabricated triband bandpass filter operates at 5.44/6.98/8.36 GHz, with fractional bandwidths of 6.6% 6% 2.9% and measured minimal insertion losses of 1.9/1.7/2 dB.

Compact and independently‐design tri‐band bandpass filter with bandwidth and return loss control

A compact tri-band bandpass filter with high controllability is proposed using two multipath λ /4 resonator-loaded resonators (MRLRs). Separated electric and magnetic coupling (SEMC) is applied into the filter, which introduces multiple transmission zeros (TZs) and enables each bandwidth to be separately controllable. In addition, both the return loss control and centre frequency (CF) control are implemented by changing the physical dimension of MRLRs. Owing to the usage of SEMC, three TZs can be, respectively, allocated either below or above the associated passbands. Moreover, the third passband can be far away from the first passband, e.g. 1.57/5.8 GHz ( f 1 /3.7 f 1 ), when each passband is independently designed. A filter example operating at 1.57/3.5/5.8 GHz (GPS/WiMAX/WLAN) with a size of 0.08 λ g × 0.14 λ g is designed and fabricated. Good agreement between simulation and measurement is achieved to validate its performance.

Compact Tri-Band BPF with Controllable Passbands Based on Stubs Loaded Stepped-Impedance Resonators

Abstract In this paper, a novel second-order tri-band bandpass filter (BPF) is presented by using the first three modes of stubs loaded stepped-impedance resonators (SIRs). The resonant behavior of proposed stubs loaded SIR is analyzed by even-/odd-mode method and parameters sweep, which shows its controllable first three resonant modes. As an example, a second-order tri-band BPF operating at 3.5/5.2/5.8 GHz for WiMax and WLAN applications is designed, fabricated and measured. The fabricated filter has a compact size of 0.21λg × 0.28 λg. Good agreement is shown between the simulated and measured results.

Perturbed Sierpinski carpet resonator and its usage in compact dual and triple band bandpass filters

In this paper, perturbed Sierpinski carpet fractal shaped resonator is characterized and applied in the design of multiband band pass filters (BPFs). The route to achieving compact multimode resonators starting from the Sierpinski carpet fractal shaped resonator is detailed. The proposed resonators are used to demonstrate two topologies of dual band bandpass filters with passband center frequencies at 3.5 GHz as well as 5.5 GHz, respectively. Both the designs exhibit nearly identical passband bandwidth. In the second design, it is observed that the second passband gets slightly shifted towards 5.85 GHz. However, with edge loading this shift is nullified. A scaled down version of the same resonator is designed and three such resonators are interdigitally coupled in conjunction with complementary split ring resonators to exhibit a novel technique of achieving compact triband bandpass filter. All designs have acceptable passband insertion loss in the respective bands. Accessories are used to improve passband selectivity in all designs and also a wide stop band till 10 GHz is obtained. Fabrication prototypes for all the variants are realized with simulated and measured results in good agreement. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:418–425, 2016.

Compact Tri-Band Bandpass Filter Using Novel Eight-Mode Resonator for 5G WiFi Application

This letter presents a novel compact tri-band bandpass filter (BPF) with wide third passband to satisfy the requirement of 5G WiFi. The proposed filter utilizes a novel multi-stub-loaded resonator with eight resonance modes. By utilizing these modes, a tri-band BPF with controllable operating frequencies is designed. Among the three bands, the highest one is formed by four modes to cover the 5G WiFi band. Each of the other two passbands centered at 2.4 and 3.5 GHz is realized by two modes. To validate the proposed idea, an experimental filter is implemented. Good agreement between the predicated and measured results demonstrates the proposed idea.

Compact triband bandpass filter with controllable bandwidths and high‐selectivity

ABSTRACTA novel compact microstrip triband bandpass filter (BPF) with controllable bandwidths is proposed in this article. Two sets of short‐stub loaded dual‐mode resonators, which are designed for the second and third passband (1.8 GHz/3.5 GHz for GSM/WiMAX), respectively, and asymmetric λ/4 resonator pairs for the first passband (5.8 GHz for WLAN). The three passband frequencies and bandwidths could be independently controlled. To achieve high‐selectivity, a nonuniform coupled‐line with two U‐folded shapes on one line is then proposed to introduce an additional weak I/O cross coupling, thereby bringing one pair of transmission zeros at each side of all the triple passbands. Simulated and measured results are in good agreement indicating that the proposed BPF has respective fractional bandwidths of 6.0, 3.9, and 2.7% and a stopband region with 31 dB attenuation up to 9.7 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2906–2908, 2015

Compact Tri-Band Bandpass Filter with Multiple Transmission Zeros

In this article, a compact tri-band bandpass filter with high selectivity using novel tri-mode resonators is proposed. The novel tri-mode resonator consists of a modified λ/4 stepped-impedance resonator with a closed rectangular loop and two loaded open stubs. A pair of transmission zeros are generated at the lower and upper stopband of each passband for high selectivity and excellent band-to-band isolation. A 1.90/3.50/5.75-GHz tri-band experimental bandpass filter has been designed and fabricated to demonstrate the proposed method. The measured results show six finite transmission zeros near the passbands located at 1.65 GHz with 30.14-dB rejection (TZ1), 2.64 GHz with 51.35-dB rejection (TZ2), 3.06 GHz with 49.36-dB rejection (TZ3), 3.95 GHz with 43.76-dB rejection (TZ4), 5.40 GHz with 30.67-dB rejection (TZ5), and 6.16 GHz with 35.15-dB rejection (TZ6), respectively. The circuit only occupies 0.04 λg × 0.07λg.

Compact tri‐band bandpass filter with stub‐loaded stepped‐impedance resonator

A compact microstrip tri-band bandpass filter (BPF) based on two open stub-loaded multimode λ/4 stepped-impedance resonators (SIRs) with two separate coupling paths is investigated. A source–load coupling configuration is arranged to produce several extra transmission zeros for realising high-isolation performance. The centre frequencies of three passbands can be controlled by tuning the dimensions of two high impedance lines of the proposed open stub-loaded SIRs. The bandwidth of the three passbands could be conventionally controlled by adjusting the coupling strength of two coupling paths. The prototype of the BPF achieved insertion losses of 0.46, 1.05 and 1.4 dB at 0.82, 1.67 and 2.17 GHz, respectively. The measured results are in good agreement with electromagnetic simulation. The circuit only occupies 0.126λ g × 0.108λ g, where λ g is the guided wavelength at a lower passband centre frequency.

A novel compact triband bandpass filter using SIR embedded quarter-wavelength resonators

A novel second-order triband bandpass filter using stepped-impedance resonator embedded quarter-wavelength resonators (SIREQRs) is presented in this letter. By embedding a meandered stepped-impedance resonator (SIR) into the low-impedance section of the conventional quarter-wavelength SIR, the proposed resonator is obtained. By coupling two SIREQRs with a common short-ended via-hole and feeding them through a pair of open-loop resonators, the proposed second-order triband filter is achieved. The first passband is generated by the quarter-wavelength SIRs, the second one is created by the embedded resonators, and the side-coupled open-loop resonators are utilized to construct the third one. Seven transmission zeros are generated due to the 0° feed structure and the canceling effects between electric coupling and magnetic coupling, which improve the skirt selectivity and band-to-band isolation level greatly. Furthermore, the overall circuit size is very compact with only 7.2 × 12.6 mm2 or 0.08 × 0.144 λg2 due to the embedded configuration. A triband filter prototype has been designed and fabricated, and the measured results agree well with the simulated ones. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1345–1349, 2015

A NOVEL COMPACT TRI-BAND BANDPASS FILTER BASED ON DUAL-MODE CRLH-TL RESONATOR AND TRANSVERSAL STEPPED-IMPEDANCE RESONATOR

A novel compact tri-band band-pass filter (BPF) with transversal signal interaction concepts, based on composite right/left-handed transmission lines (CRLH-TLs) resonator and parallel stepped impedance resonator (SIR), is presented. The main path is based on a dual-mode CRLH-TL resonator, which exhibits the first two passbands. The secondary path is a SIR, which contributes to the third passband and generates another transmission zero between the first and second passbands simultaneously. The proposed filter has been simulated, fabricated and measured. Both the simulated and measured results show that the filter has a high selectivity with a compact size as small as 0.18λg × 0.12λg.

Tri‐band superconducting bandpass filter with controllable passband specifications

A compact tri-band bandpass filter is designed by combining a dual-band sub-filter and a single-band one. The dual-band sub-filter comprises four stub-loaded resonators. The single-band sub-filter is inserted into the gaps of the dual-band sub-filter for size miniaturisation. Both the centre frequencies and the bandwidths of the three passbands can be independently controlled. The measurements of the fabricated superconducting filter exhibit high performance and match well with the simulations.

Tri-band filter with multiple transmission zeros and controllable bandwidths

This paper presents a compact microstrip tri-band bandpass filter (BPF) using two multimode stepped-impedance resonators (SIRs) with a 0° feed structure. The fundamental odd-mode and even-mode resonant frequencies and the third resonant frequency are utilized to determine the center frequencies of the tri-band filter. The mode-splitting technique is used by combining two SIRs with electrical coupling. Therefore, two modes generate one passband and the bandwidths can be controlled by the electrical coupling strength. The 0° feed network is applied to create one pair of transmission zeros at each side of all the triple passbands, resulting in high selectivity. Finally, a tri-band BPF with the central frequencies of 1.8, 2.4, and 5.8 GHz, and respective fractional bandwidths of 8.9, 12.5, and 5.3% are designed and fabricated. The simulated and measured results show a good agreement.

Compact Tri-Band Bandpass Filter Using Open Stub Loaded Tri-Section $\lambda /4$ Stepped Impedance Resonator

A modified tri-mode λ/4 stepped impedance resonator (SIR) is proposed, in which a shunt open stub is loaded in the conventional λ/4 tri-section SIR. The resonant frequencies and frequency ratios can be properly controlled by adjusting the loaded open stub. A compact second-order tri-band bandpass filter (BPF) based on two coupled proposed open stub loaded λ/4 tri-section SIR is presented. A pair of transmission zeros (TZs) are generated at the lower and upper stopband of each passband for high selectivity and excellent band-to-band isolation. A tri-band BPF with the central frequencies of 1.92, 3.50, 5.75 GHz, and respective fractional bandwidths of 5.4%, 4.0%, and 2.4% is designed and fabricated. Measured results show good agreement with simulations. Moreover, the circuit only occupies 0.09 λg ×0.10 λg.