Pair Of Parallel Coupled Lines Research Articles

Design of Compact UWB Filter Using Parallel-coupled Line and Circular Open-circuited Stubs

This article encompasses the design of compact ultra-wideband (UWB) bandpass filter with low insertion loss and high selectivity using circular open-circuited stubs (COSs). Low insertion loss from two COSs and Multiple Mode Resonator (MMR) from three pairs of parallel-coupled lines are constituted to obtain the UWB band. The proposed filter has multiple resonant frequencies in the passband and two transmission zeros perceived at stop band/passband transition edges. It has a 3-dB fractional bandwidth of 110% and it covers the entire UWB band of 3.1–10.6 GHz. The measured passband insertion loss and group delay are 0.35 dB and 0.42 ns, respectively. Moreover, the presented filter is a single-layered structure since it is more comfortable to be integrated into a printed circuit board (PCB). The simulated and measured performance of the presented filter is in good agreement. The filter finds its application in low power handling single-layered PCBs, unlicensed short and medium distance communications.

Design of Notched-Wideband Bandpass Filters With Reconfigurable Bandwidth Based on Terminated Cross-Shaped Resonators

In this paper, a series of novel reconfigurable-bandwidth notched-wideband bandpass filters (NWB BPFs) with controllable notch bands are proposed. The proposed filters start from a passive filtering structure, which is formed by a terminated cross-shaped resonator (TCSR) with a pair of parallel-coupled lines and two open-ended stubs. Theoretical analysis finds that the filter bandwidth can be independently controlled by the TCSR, while the center frequencies and bandwidth of notch bands are mainly controlled by the rest parts. According to this, a BPF with controllable notch bands can be designed. To achieve the reconfigurable-bandwidth NWB BPFs with controllable notch band, whose bandwidth and center frequency can be maintained unchanged under different work states, two PIN diodes and a varactor are employed. By controlling the work states of PIN diodes, three bandwidth states can be achieved with fixed center frequency. By controlling the applied voltage on the varactor, other NWB BPF with independently tunable lower passband edge can be realized. For verification, three prototypes are designed and measured. The measured results agree well with the theoretical analysis and simulated ones, verifying a simple and effective design approach of reconfigurable-bandwidth NWB BPFs.

Synthesis Design of Equal-Ripple and Quasi-Elliptic Wideband BPFs With Independently Reconfigurable Lower Passband Edge

This paper presents a new synthesis design of equal-ripple and quasi-elliptic wideband band-pass filters (WB BPFs) with independently reconfigurable lower passband edge. The synthesis design starts from a 5th-order LC circuit. By using optimum multipole concept, a T-shaped resonator for the design of Chebyshev BPF without redundant elements can be directly derived, which is formed by a pair of parallel-coupled lines and short-ended stub. To sharpen the selectivity and maintain equal-ripple response, a pair of transmission zeros are introduced through replacing the short-ended stub by its multi-section counterparts. Thus, two prototypes, whose equivalent LC circuits can be directly derived, are presented for the synthesis of equal-ripple and quasi-elliptic BPFs. To realize the desired reconfigurable response, a capacitor is used. By controlling the capacitance value, the lower passband edge can be independently tunable in continue manners while the upper one is fixed. For validation, two prototypes with fixed and reconfigurable band-width are fabricated and measured. As the measured and simulated results agree well with each other, a high-efficiency design of reconfigurable-bandwidth WB BPFs is validated.

Compact Microstrip NWB/DWB BPFs With Controllable Isolation Bandwidth for Interference Rejection

In this paper, a novel and planar topology, which can be used to design notched-/dual-wideband bandpass filters (NWB/DWB BPFs) with controllable isolation bandwidth, is presented for interference rejection. Here, the isolation band is referred to notch band for NWB BPFs, while stopband between two passbands for DWB BPFs. The proposed topology is started from a novel T-shaped resonator with two poles and three zeros. Then, a pair of parallel-coupled lines and two open-ended stubs is added. With the help of the added parts, the extra four poles are introduced, and another two zeros are suppressed or excited according to whether it is required to realize a notched- or dual-band response. Due to the existence of multiple transmission poles and zeros, the excellent filtering responses, i.e., high isolation level, sharp selectivity, and good passband flatness, can be achieved. Besides, it is found that the isolation bandwidth of BPFs based on the proposed topology can be continuously varied from a narrow notch band to a wide stopband while the outer two passband edges are maintained unchanged by using suitable para-meters. To validate this, two prototypes are designed and measured, including a six-mode NWB BPF with 3-dB passband fractional bandwidth (FBW) of 94.1% and 20-dB notch FBW of 2.39%, and a three-mode DWB BPF with 3-dB passband FBWs of 36.2% and 22.6% and 20-dB stopband FBW of 14.5%.

Tunable microstrip lowpass filter with compact size and ultra‐wide stopband

A compact varactor-tuned microstrip lowpass filter (LPF) with a large cutoff frequency tuning range and an ultra-wide stopband is presented. By employing a pair of parallel coupled-lines and a low-impedance stub loaded with a varactor diode, the introduced filter can successfully realise the tunable cutoff frequency function. Besides, both radial patch resonators and stepped-impedance resonators are introduced to achieve an ultra-wide stopband in all the states in this design. A varactor-tuned microstrip LPF is designed, fabricated and measured. The measured results show that the proposed LPF provides not only a large cutoff frequency tuning range of 91.3% from 0.85 to 2.28 GHz, but also an ultra-wide stopband which extends to 20 GHz.

A MINIATURIZED TUNABLE BANDPASS FILTER WITH CONSTANT FRACTIONAL BANDWIDTH

This paper presents a miniaturized tunable bandpass filter, consisting of two coaxial dielectric resonators and a pair of parallel-coupled lines. A coaxial dielectric resonators and a microstrip line form a new step-impedance resonator (SIR), which is different from a conventional SIR. Varactor diodes are connected to SIRs to tune the center frequency. The gap between parallel-coupled lines controls the inter-stage coupling coefficient. Lumped inductors used for coupling to I/O ports can reduce design complexity. The variations of coupling coefficient and external quality factor with tuning frequency are analyzed using HFSS software. A appropriate coupling coefficient which satisfies with constant fractional bandwidth within the tuning range is available. A tunable filter has been made of dielectric ceramics with dielectric constant of 38, fabricated on dielectric substrate and measured using Networks analyzer. Center frequencies vary from 0.43 GHz to 0.78 GHz, 3 dB fractional bandwidth from 6.4% to 6.8% when bias voltages are applied from 0 V to 10 V. The measured results validate the approach and agree with the simulation.

A DESIGN APPROACH FOR DUAL-BAND WILKINSON POWER DIVIDER WITH TWO PAIRS OF COUPLED-LINE SECTIONS

This paper presents a design approach for dual-band Wilkinson power dividers. Two pairs of parallel coupled-lines are used to replace the quarter-wavelength transformers in the conventional Wilkinson power divider to obtain dual-band operation. Using even- and odd-mode analysis, the closed- form design equations are derived for design parameters and design procedures of the proposed dual-band power divider are given. For veriflcation purpose, a practical power divider, which operates at 1GHz and 2.1GHz with 3dB power dividing ratio, is designed, fabricated and tested. The simulated and measured results are in good agreement.