Open-circuited Stubs Research Articles

Tunable bandpass filter with low‐loss and enhanced selectivity based on controllable coupled negative resistance

A tunable bandpass filter (BPF) with low-loss and enhanced selectivity based on controllable coupled negative resistance is presented. Owing to the use of the coupled negative resistance, the insertion loss and the selectivity are improved significantly from 800 to 1000 MHz. Furthermore, a novel method of introducing an open-circuited stub and a short-circuited stub to control the negative resistance effect is proposed, which makes the adjustment of the negative resistance much more flexible. The measured active BPF shows a bandwidth of 56 MHz, an insertion loss of − 0.44 dB, a noise figure of 2.6 dB, 1 dB compression point of 0 dBm and third-order intercept point of 8.8 dBm at 900 MHz.

The Design of Wideband Microstrip Bandpass Filter Using Dual Stepped Impedance Stub-Loaded Resonator

In this paper, a uniform impedance resonator (UIR) with a pair of identical stepped impedance open-circuited stubs loaded at two symmetrical positions with respect to its center is presented and analyzed for the design of a wideband micristrip bandpass filter (BPF). With compared to the conventional single open-ended stub loaded in the middle of the UIR or paired uniform stubs located at the two symmetrical position, the proposed resonator has the advantage of providing more freedom to adjust the bandwidth. Meanwhile, the two transmission zeros at both lower and higher sides of the passband ensure the filter has a good roll-off rate at the passband edge.

Balanced wideband BPF design using multi-mode slot-line resonator for MB-OFDM applications

This paper presents a new balanced wideband band-pass filter (BPF) that is designed using a multi-mode slot-line resonator (MMSLR) with microstrip feed-lines. To obtain good differential operation and meanwhile reject unwanted common-mode (CM) noises, the balanced BPF is arranged in a symmetric fashion. For differential-mode (DM) operation, by locating the first three resonant modes of the MMSLR in the desired passband and feeding the MMSLR with tightly coupled microstrip feed-lines, we obtained a wideband response that meets the requirement of the OFDM group-B bandwidth specification (4.752–6.336 GHz). For CM operation, an open-circuited stub is effectively added to the feeding lines at the output port so that the transmitted CM signals can be attenuated. The measurement agrees well with the simulation. For the designed balanced wideband BPF, the measured minimum DM insertion loss is 0.63 dB in the DM passband, in which the CM suppression is larger than 17.6 dB.

Dual-Band Planar Crossover With Two-Section Branch-Line Structure

A dual-band planar crossover with simple structure is proposed. This crossover is derived from the conventional single-band two-section branch-line crossover by doubly extending the length of its vertical transmission lines, which realizes the dual-band operation. Closed-form equations for design parameters are derived, which simplifies design procedure of the proposed crossover and shows that the available bandwidth of the passband increases with the increasing frequency ratio. By adding one short-circuited stub and one open-circuited stub to the originally proposed dual-band crossover, two types of modified dual-band crossovers and their closed-form design equations are proposed for smaller and larger frequency ratios applications. For verification, four different dual-band crossovers are designed and simulated, of which two microstrip crossovers operating at 1/1.8 and 1/2.3 GHz are fabricated and measured. The measured results are in good agreement with the simulated ones.

Synthesis and Design of Wideband Dual-Band Bandpass Filters With Controllable In-Band Ripple Factor and Dual-Band Isolation

In this paper, an exact synthesis and design procedure has been proposed for a class of wideband dual-band bandpass filters (BPFs) with both controllable in-band ripple factor and isolation between the dual passband. Two multi-mode resonators (MMRs) with short-circuited stubs are parallel connected to form the basic structure of the proposed dual-band BPFs. Up to two pairs of transmission zeros (TZs) could be created with reference to the dual wide passbands. By choosing the impedances of the two paralleled MMRs, one pair of TZs could be moved from imaginary to real frequencies, whereas the second pair of TZs could be adjusted by folding one of the MMRs to form coupled lines. For these two prototypes, short-circuited stubs are utilized to excite the two paralleled MMRs, but not adequate to obtain a determined coupling degree. To provide an additional freedom for controlling the in-band ripple factor, a combination of short- and open-circuited stubs is used. A generic synthesis procedure is developed for the filter design. First, a generalized Chebyshev transfer functions with one TZ at the origin and symmetrical with respect to the origin has been discussed and frequency transferred to form a dual-band filtering function. Next, by equating of the dual-band circuit response and the filtering function, the circuit parameters could be obtained. Three filter prototypes have been designed and measured with good matching between these two sets of results.

Compact UWB bandpass filter with reconfigurable notched band

A compact bandpass filter is presented for ultra-wideband (UWB) applications with a reconfigurable notched band to reject unwanted signals from the WiMAX systems. A single pin diode is used for the purpose of switching the notch. An optical switch, comprised of a silicon dice activated using near infrared light is also investigated as an alternative to the pin diode. While the switch is in the ON state this reconfigurable filter behaves as a bandpass filter with a notch at 3.5 GHz and a full band response is obtained in the OFF state. The filter offers excellent performance for the lower-band frequency of a UWB system, ranging from 3.1 to 5.0 GHz and exhibits very low passband insertion loss. Also, transmission zeros are generated at the passband edges to enhance the signal selectivity. A filter sample has been designed and fabricated to provide experimental verification on the proposed filter. A good agreement has been achieved between simulated and measured results with both the pin diode as well as the optical switch. The proposed reconfigurable filter with notched band was able to achieve 40% size reduction as compared to an embedded open-circuited stub.

A compact UWB CPW bandpass filter with short‐ended H‐shaped resonator and controllable notched band

AbstractAn ultra‐wideband (UWB) bandpass filter (BPF) using the hybrid microstrip and coplanar waveguide (CPW) structure is proposed in this article.The BPF composes of CPW feed lines and H‐shaped microstrip resonator. By a CPW/microstrip back‐to‐back coupling structure, the UWB BPF was realized with the passband covering the entire UWB band (3.1–10.6 GHz). A narrow notched band achieved by etching slots on the lower impedance part of the H‐shaped resonator to form an open circuit stub. At last, three U‐slot DGSs are used to achieve a good upper‐stopband rejection. The measured results are in good agreement with the simulated results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1577–1581, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27663

A novel miniaturized UWB antenna with four band‐notches

AbstractIn this article, an effective design method is presented to design a miniaturized UWB antenna with four band‐notches. By carefully integrating C‐shaped slots, L‐shaped open circuit stub, and T‐shaped parasitic strip onto the primitive miniaturized antenna, four band‐notches (VSWR > 2) could be achieved at 3.38–3.65 GHz, 4.95–6.05 GHz, 7.42–7.78 GHz, and 8.1–8.9 GHz to reject WiMAX, WLAN, X‐band satellite communication, and ITU 8 GHz band signals. Simulated and measured results show that this antenna could operate from 3.15–11.1 GHz (VSWR < 2), and maintain omnidirectional directivity patterns at H‐plane. Moreover, the proposed antenna has a very compact size of 18.6 × 22 × 1.5 mm3. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1202–1206, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27546

Miniaturised Horst‐type Wilkinson power divider with simple layout

A Wilkinson power divider with an open-circuited stub and extra-transmission lines between two output ports is presented. Compared with the modified Wilkinson power divider presented by Horst, the proposed power divider has the advantages of less occupation area on a printed circuit board and simple layout, where the isolation resistor, one open-circuited stub and extra-transmission lines are constants. The experimental circuit shows good agreement with theoretical simulation.

A novel compact configuration for dual-mode microstrip resonators and dual-band bandpass filter applications

In this article, a novel compact dual-mode resonator formed by a square loop having folded arms and mitered bends is proposed.Degenerate modes can be excited by shifting the gaps between the folds. Thus, the center frequency can be arranged at a fixed value because the total electrical length of the proposed configuration is not changed. A novel compact dual-mode dual-band bandpass filter is also designed by locating the one resonator within the other. Additionally, to suppress the harmonic of the first passband, open-circuited stubs are connected to the end of the feedlines. Two dual-mode dual-band bandpass filters with the elliptical and linear phase filtering characteristics for both passbands have been designed, fabricated, and tested. Calculated, simulated, and measured results are in a good agreement. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:775–779, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27444

Vivaldi antenna impedance bandwidth dependence on stripline to bilateral slotline transition

The Vivaldi Antenna is known to have a theoretically unlimited instantaneous frequency bandwidth.Vivaldi design geometry which uses an open circuit stub stripline to bilateral slotline transition is the limiting factor of this design. It is shown that a shorted stub transition increases the bandwidth toward the theoretical limit. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:937–941, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27413

Dual‐band bandstop filter using stub‐loaded resonators with sharp rejection characteristic

Dual-band bandstop filters using open-circuited stub-loaded resonators are presented. The first and second resonant frequencies of the open-circuited stub-loaded resonator can be flexibly controlled by tuning the length and position of the open-circuited stub. To illustrate the concept, a dual-band bandstop filter has been designed, fabricated and measured. The prototype of the dual-band bandstop filter achieved attenuation of 42 and 44 dB at 2.4 and 5.2 GHz.

AN OPTIMAL DESIGN OF CPW-FED UWB APERTURE ANTENNAS WITH WIMAX/WLAN NOTCHED BAND CHARACTERISTICS

In this paper, a printed slot antenna fed by a co-planar waveguide for ultra wide bandwidth (UWB) with dual notch bands has been presented and discussed. The band notches are realized by etching one C-slot resonator inside a plaque shape exciting stub as well as symmetrically adding a pair of open-circuit stubs at the edge of the slot resulting in dual stop band flltering properties for WiMAX, WLAN application. Surface current distributions are used to analyze the efiects of the slot and open circuit stub. The proposed antenna is fabricated and experimental results show that it has an impedance bandwidth of 2.6{14.34GHz for VSWR • 2, except dual frequency stop-bands of 3.3{3.7, 5.04{6.0GHz. From the simulation results, it is observed that the radiation patterns are omnidirectional in the H- plane and dipole like nature in the E-plane. The gain varies from 3.7dB to 5.7dB over the whole UWB region excluding at notch bands.

A COPLANAR WAVEGUIDE FED ULTRA WIDEBAND HEXAGONAL SLOT ANTENNA WITH DUAL BAND REJECTION

In this paper a printed regular hexagonal slot antenna with a hexagonal stub fed by a coplanar waveguide line has been considered for ultra wide bandwidth. This antenna is then modifled to obtain dual band rejection. The Wireless Local Area Network (WLAN) and Wireless Microwave Access (WiMAX) band rejections are realized by incorporating a C-shape slot within the exciting stub as well as a couple of Z-shape open circuit stubs symmetrically inserted at the edge of the slot. The length and width of the C-shape slot and Z-shape stub ofier su-cient freedom for selecting and shifting the notch bands. Magnitude of S11, impedance, gain and radiation characteristics of them are studied and discussed here. From the measured results, it has been observed that the impedance bandwidth, deflned by magnitude of S11 6 i10dB, reaches a value of 8.18GHz (2:96 » 11:14GHz) except dual frequency stop bands of 3.28{3.7GHz and 5.1{5.90GHz. From the experimental results, it is observed that the radiation patterns are omnidirectional in the H-plane and dipole in nature in the E-plane. The antenna gain varies from 4.8dB to 5.3dB over the whole operating band excluding the notch bands. Surface current distributions are used to analyze the efiects of the C-slot and Z-shape stub. Measured group delay has very small variation within the operating band except notch bands and hence the proposed antenna may be suitable for UWB applications.

A Printed Single-Layer UWB Monopole Antenna With Extended Ground Plane Stubs

In this letter, a compact coplanar-waveguide-fed single-layer printed antenna with an ultrawideband (UWB) rectangular monopole radiator etched with a half-elliptical slot is presented. Collaborating with the UWB radiator, two symmetrical open-circuit stubs are extended from the ground plane to jointly achieve an ultrawideband impedance match with a compact size. The proposed antenna is fabricated and tested in an anechoic chamber, showing an ultrawide operating frequency range from 3.7 to 10.1 GHz with a quasi-omnidirectional gain from 2.0 to 7.3 dBi. With the advantages of a reduced size, an improved voltage standing wave ratio (VSWR), and a monolayer configuration without any back ground plane, the proposed antenna can be used in a wide range of UWB applications.

COMPACT INTERDIGITAL CAPACITOR COUPLED DUAL-BEHAVIOR RESONATOR (ICDBR) FILTER WITH SUPPRESSION OF SPURIOUS RESPONSES

A compact interdigital capacitor coupled dual-behavior resonator (DBR) fllter with high spurious responses suppression is proposed in this paper. The technique is based on two equivalent topologies of J-inverter and dual-line equivalent circuit of open- circuited stubs. The flrst compact equivalent topology capacitive inverter is a high pass structure, and consequently, the spurious responses can be suppressed efiectively at low frequencies. The second equivalent topology …-network is employed in realizing a compact size and adding new transmission zeros dedicated to the spurious responses suppression at high frequencies. Further compactness is achieved with a dual-line equivalent circuit of open-circuited stubs. The relevant equations are given in the paper. Finally, a 3rd-order compact DBR fllter is designed and measured. This structure has a high degree of miniaturization (83%) in comparison to the classical one. Measurement results show good agreement with the simulated ones.

DUAL-MODE DUAL-BAND BANDPASS FILTER BASED ON SQUARE LOOP RESONATOR

In this paper, a dual-mode dual-band microstrip bandpass fllter utilizing asymmetric square loop resonators is proposed. A pair of bent open-circuited stubs is installed to the loop as perturbation stubs. By stretching the perturbation stubs more than half-wavelength of the loop, the degenerated modes in a loop are split for dual-band operation. Two asymmetric resonators are cascaded to form two bands. Even- and odd-mode analysis method is used to deduce the resonant frequencies of two bands. Based on the transmission line theory, resonant frequencies of the two resonances are derived. According to the resonant conditions, a kind of dual-mode dual-band bandpass fllter can be easily designed. Finally, a dual-band fllter with two bands centering at 1.9GHz and 2.6GHz is designed in a comprehensive way. Measured results of experimental circuit show good agreement with simulated responses.

Design of compact low‐pass filter with large reject band using open circuit stubs and two‐cascaded DGS quasitriangular resonators

AbstractThis article investigates a quasitriangular of defected ground structure (DGS) for low‐pass filters (LPFs) application. An equivalent RLC circuit model is presented and its corresponding parameters are as well extracted using the parametric relationships. The LPFs using the proposed DGS pattern combined with open stubs are designed and fabricated. The proposed LPF presents the advantages of small size, low insertion loss and ultrawide stopband with 20 dB attenuation from 4 GHz to >20 GHz. The simulated results obtained by equivalent circuit model and full‐wave electromagnet show good agreement with the measured ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:122–127, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27260

Performance Improvement of 40-Gb/s Electroabsorption Modulator Integrated Laser Module With Two Open-Circuit Stubs

In this letter, we propose and demonstrate a compact, low-cost, and easy to manufacture microstrip line with two open-circuit stubs to alleviate impedance mismatching of a packaged 40-Gb/s electroabsorption modulator integrated laser (EML) module. For comparison, two 1550-nm EML modules are fabricated, the only difference being that one of them is made with open-circuit stubs, while the other is not. It is revealed that the open-circuit stubs technique expands the 3-dB modulation bandwidth from 25.2 to 33.6 GHz, and the suppression of the input return loss below -10 dB in the range of the higher frequency of the sub-assembly with chip is also successfully demonstrated. Further evidence showing the advantage of the EML module with open-circuit stubs over the one without open-circuit stubs include the effective reduction in the RMS jitter of the eye diagram from 1.4 to 1.2 ps, as well as the improvement of the sensitivity, which changes from -8.3 to -9.5 dBm measured with the same receiver.

A High Slow-Wave Factor Microstrip Structure With Simple Design Formulas and Its Application to Microwave Circuit Design

This paper proposes a new microstrip slow-wave structure. The unit cell comprises a Schiffman section of meander line and a shunt open-circuited stub. No via-holes and ground-plane patterns are required. Simple design formulas can be used to obtain line parameters, such as the characteristic impedance and phase velocity. According to the analysis, the characteristic impedance and slow-wave factor of the proposed slow-wave line can be independently controlled by merely two layout parameters. The proposed uniplanar structure only requires a single-layer substrate and is simply constructed using the conventional printed circuit board manufacturing process. A branch-line and a rat-race coupler were designed and fabricated using the proposed structure to demonstrate its feasibility. Their sizes are only 8.49% and 4.87% of the conventional ones, respectively. This novel slow-wave structure should find wide applications in compact microwave circuits.