Series Stubs Research Articles

Design of Coplanar Stripline Bandpass Filter With Reconfigurable Filter Switch

ABSTRACTThis article has designed a bandpass filter using a coplanar stripline stub (CPS) resonator consisting of open and short‐ended strip lines connected to the PIN diode switches. The use of spurline stub resonators inside CPS results in bandpass and bandstop filters, depending on the PIN diode switch configurations. The work presents a novel circuit architecture aimed at reducing the parasitic resonance of the spurline resonators and acquiring the necessary series stub characteristics. The proposed filter resonates at 6.9–9, 1.7–4.7, and 8.4 GHz when the PIN diodes are forward and reverse‐biased, respectively. It also resonates at 1–2.1, 4.8–5.3, and 6.9–9 GHz when one diode is reverse‐biased, and the other is connected in forward bias. An insertion loss below −0.55 dB and a return loss less than 10 dB have been obtained during simulation and measurement. The designed filter can find different applications for the 1.8 GHz GSM band, 2.4/5.8 GHz (WLAN), 3.6 GHz (WiMAX), long‐term evolution (LTE), and WIFI. The filter can be used in various multi‐frequency systems owing to its compact size. The measured and simulated findings of the proposed CPS spurline stub resonator wideband bandpass filters are substantially consistent.

Coplanar waveguide‐serially‐connected coplanar strip dual stub structure for wideband bandpass filters

In this paper, a kind of coplanar waveguide (CPW)-fed series stub structure is proposed and its application in wideband bandpass filters (BPFs) is developed based on the coplanar strip (CPS) dual stubs. Compared with its conventional CPS dual-series-stub counterparts, the proposed one excited by even-mode CPW lines possesses enhanced immunity against unexpected resonance of the CPS-based series stubs. By virtue of this attractive performance, desired resonance can be well realized with predicted in-band characteristics. Subsequently, the application in its constituted wideband BPFs is investigated with synthesis design method. In final, one third-order and one fifth-order BPFs are designed, fabricated, and measured to verify the proposed structure. Measured results are found in reasonably good agreement with the synthesized and the simulated ones.

Proposal of Coplanar Stripline Series Stub Structure for Wideband Bandpass Filters

In this article, a simple kind of coplanar stripline (CPS) open-circuited series stub structure and its application in wideband bandpass filters (BPFs) are proposed and developed. Compared with its conventional dual-shunted CPS series stub counterparts, the proposed one is capable of achieving desired characteristics as the specified transmission-line (TL) prototypes behave. Based on such equivalent prototypes, three types of CPS open-circuited series stubs are then investigated to reveal the immunity against unexpected resonance caused by the underlying surface-wave-like mode. For demonstration, two examples, a second-order and a third-order wideband BPFs, are synthetically designed for equal-ripple Chebyshev response with prescribed fractional bandwidth (FBW) and return loss (RL). Finally, these two proposed filters with a respective FBW of 49%/70%, an RL of 16.426 dB, and a central frequency of 2 GHz are synthesized, simulated, fabricated, and measured. Measured and simulated results are reasonably in good agreement with each other, thus firmly validating the flexibility of the presented CPS series stub structure in the application of wideband BPFs.

Miniaturized dual-band CPW Wilkinson power divider using T-network adopting series stubs with a high frequency ratio

In this paper, a compact dual-band coplanar waveguide (CPW) Wilkinson power divider (WPD) is presented. Two arbitrary frequency bands are obtained by replacing the quarter-wavelength transmission lines in the conventional design by two compact ones separated by a series stub. The proposed methodology facilitates a maximum frequency ratio around 7 without incorporating reactive components, making it attractive for high frequency applications. To validate the design procedure, a dual-band CPW-based WPD that operates at 0.5 and 2.5 GHz is simulated and measured. Results show input/output ports matching better than –20 dB along with 30 dB isolation between the output ports. Furthermore, transmission parameters of –3.56 dB and –5.6 dB are obtained at the first and the second design frequencies, respectively. Simulated results agree very well with the measured ones.

Arbitrary coupling arbitrary phase couplers with improved bandwidth

In this study, an arbitrary coupling and arbitrary phase coupler with improve bandwidth is proposed. The proposed couplers use a series stub of electrical length θ at all ports which acts as matching element and thereby improves the effective bandwidth of the coupler. A lossless transmission line model is used to obtain design equations and design graphs. Return loss, isolation, amplitude and phase imbalances all four conditions are considered for bandwidth calculation. Two 3 dB couplers with phase difference of 30° and 45° and the third coupler with 4.77 dB coupling and phase difference of 60° are fabricated and measured to validate the proposed topology. Bandwidth improvement is obtained in all the cases. In some cases, the effective bandwidth is more than 100%.

Compact size of a Wilkinson power divider using impedance coordinate tracking based on T‐shaped line

AbstractThis article presents the compact size of the Wilkinson power divider using T‐shaped line through the impedance coordinate tracking progress at Smith‐chart. After the series line impedance, electrical length, and stub impedance were calculated, the T‐shaped line was designed through the impedance coordinate tracking in the Smith‐chart. This reduced the entire size of the proposed power divider by an average of 4.81 times (79.2%) more than conventional structure. The experimental results of the S21, S31, and S11 are 3.06 dB, 3.08 dB, and 25.04 dB at center frequency of 2.318 GHz, respectively. The experimented S‐parameter difference between S21 and S31 is 3.0 dB. This proposed Wilkinson power divider can be applied to mobile communications and wireless medical communication systems.

Analysis and Design of Helical Antenna for Capture of Meteorological Images of NOAA Satellites

This article presents the design, the characterization and the construction of a helical antenna in axial mode to receive weather images of Colombia transmitted from NOAA (National Oceanic and Atmospheric Administration) satellites. The antenna has been located in Bogota (latitude: 4°36'34''N, longitude: 74°04'54''W; 25822 m above sea level), it has received Automatic Picture Transmission (APT) signals of good quality with circular polarization on the right (RHCP); those ones have been fed to a sharp SDR (generic software RTL-SDR) and decoded through the WXtoImg software in the receiver. In order to improve the performance of the antenna, the helix has been built with a coaxial cable of 0.0047λ diameter (RG-213 / U), the length of the feed cable has been minimized to 55 cm, (less than λ/2), and an impedance coupling network using a series stub has been designed. The physical design has represented an important aspect, since some wrong dimensions have caused distortions in the received signal. The experimental results show radiation diagrams with a gain of eight dBi and bandwidth of 30 kHz with respect to 3dB at the central frequency of 137 MHz, which are comparable with the simulations and theoretical analysis. With the above, the design of the circuit is validated; it guarantees its performance and confirms the practical utility of the antenna.

Coplanar Stripline Series-Stub With Even Mode Suppression

Coplanar stripline (CPS) series stubs, both the short-circuit and open-circuit terminated stubs, are presented. It is shown that the parasitic even mode (a surface-wave-like mode) on the series stub generates an undesired resonance. An equivalent lattice circuit that describes the desired and undesired modes of the stub is developed. A method to suppress the even mode is presented so the desired series stub characteristics may be obtained.

Improvement of stop‐band performance of a CPW bandpass filter using DGS

ABSTRACTA CPW‐based bandpass filter (BPF) is designed in S‐band by open ended series stubs. Two open ended stubs with opposite orientation are placed closely into a CPW line to offer greater field confinement. They provide band accept response with one attenuation zero. An enhanced selectivity is achieved by using four such stubs in symmetric manner. Defected ground structures (DGS's) are used to reject higher harmonics and to obtain a wide stop‐band. To validate the design, a prototype was fabricated. In good agreement with the theoretical results, the measured results of the S‐band bandpass filter achieve insertion loss of <0.2 dB, fractional bandwidth (FBW) of 67% with rising and falling edge selectivity of 35.9 dB/GHz and 45.7 dB/GHz respectively, and around 8‐GHz stop‐band. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:593–597, 2016

Vertical microstrip-to-microstrip transition through the highpass-filter topology for ultra-wideband (UWB) applications

A vertical microstrip-to-microstrip transition with ultra-wideband (UWB) filtering response is proposed and constituted based on the highpass or UWB bandpass filtering structure with the composite series or shunt stubs. By centrally feeding a slotline resonator on the common ground, two microstrip feed lines in the top and bottom layers are interconnected to make up a three-pole signal transmission network. Based on the ideal transmission-line model, this proposed transition is at first synthesised with the Chebyshev equal-ripple frequency responses. Next, the transition is formed on a two-layered dielectric substrate and its frequency response is simulated via the commercial electromagnetic simulator to confirm the predicted three-pole transmission behaviour from the synthesis approach. Finally, a prototype vertical transition centred at 6.0 GHz is fabricated and measured, showing the good agreement among predicted, simulated and measured results over a wide frequency band.

Slotline Switch Based on a Lattice Circuit

Slotline switches are required for many slotline applications, such as tunable slot antennas and slotline antenna feed networks. The current practice is to place a pin diode or MEMS device across the slot to create a short circuit when the switch is in the OFF state. In this letter, a slotline short circuit series stub is incorporated into a lattice circuit to achieve a switch with a theoretical 0 dB insertion loss, infinite isolation and infinite return loss over a narrow bandwidth. Measured results demonstrate a near zero insertion loss, approximately 40 dB of isolation and greater than 15 dB return loss at 4.25 GHz, with an approximate 40% bandwidth defined by return loss and isolation greater than 10 dB.

Design of coplanar waveguide band‐pass filter for S‐band application

Coplanar waveguide (CPW) has a huge demand for designing band-pass filter (BPF). In this study, the filter designed by open-ended CPW series stub which acts as a resonant circuit thus giving a band-pass response. As the number of open stub discontinuity is increased, the frequency response and roll-off rate of the proposed BPF has improved gradually. Electromagnetic simulated and measured results show a very good agreement with each other. The proposed filter is designed to obtain a frequency range of 1.97–4 GHz (S-band) having rising edge and falling edge selectivities of 35.9 and 45.7 dB/GHz, respectively.

Implementation of harmonics-free narrow-band microstrip bandpass filter using complementary split ring resonator

This article discusses harmonics-rejected microstrip narrow-band bandpass filter (NBBPF) using complementary split ring resonator (CSRR) structure. The proposed harmonics-rejected NBBPF is first derived from the established lumped element LC bandpass filter (BPF) and then converted into a distributed microstrip BPF by using series and open transmission line stubs. This microstrip BPF resonates with centre frequency fo and its 2nd- and 3rd-order harmonics (2fo and 3fo) because of their inherent nature. These unwanted 2nd- and 3rd-order harmonics will degrade the overall performance of wireless systems. Therefore harmonics rejection is the best solution to boost the behaviour of wireless systems. The harmonics-rejection behaviour of this microstrip BPF is improved by embedding CSRR in its ground plane. In order to verify the superior performance of the desired design, distributed BPF is designed, simulated, realised and tested. To authenticate the harmonics-rejection ability of the proposed BPF, BPFs with and without CSRRs are fabricated and the experimental results are compared. This comparison shows that the projected design has acceptable bandpass frequency responses to the fo and wide stop-band performance in 2fo and 3fo because 2nd- and 3rd-order harmonics are suppressed by the CSRRs. The measured results are in line with the simulated results. The performance valuation plainly indicates that the proposed design both has superior harmonics-rejection ability and is also very easy to manufacture. Hence, the planned NBBPFs have the potential to be an ultimate device in future harmonics-free narrow-band communication system with minimum design complexity.

Coplanar Waveguide Filter using Stub Resonators for Ultra Wide Band Applications

The paper presents a compact coplanar waveguide filter employing stub resonators for ultra wide band applications. A cascade connection of series and shunt stubs quarter wavelength long is used for achieving bandpass characteristics. The performance requirement of the filter decides the number of cascaded sections. The filter has reduced insertion loss in its passband and good attenuation in lower and upper stopbands. The flat group delay in the passband ensures its use in communication applications. Measured frequency response of the fabricated prototype shows good agreement with simulated response.

A flexible CPW series resonator using phase compensation method on polyimide film at 5.8‐GHz

ABSTRACTIn this article, a flexible coplanar waveguide (CPW) series resonator combined with short‐ and open‐end CPW series stubs on polyimide film is presented. To obtain equivalent circuit of each stub, a new phase compensation method is applied. The accuracy of equivalent circuit with this method is confirmed by comparison between electromagnetic simulation and circuit simulation results. Based on equivalent inductance and capacitance for short‐end series stub and open‐end series stub, respectively, a CPW series resonator is designed without optimization at 5.8 GHz. The measured frequency responses of the series stubs and resonator are in good agreement with the predicted simulation results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:193–196, 2015

Millimeter‐wave coplanar waveguide series stubs on BCB and low resistivity silicon

ABSTRACT30–225 GHz coplanar waveguide (CPW) series stubs are studied in a benzocylobutene and 10‐Ω‐cm silicon stack. Truncated side grounds improve the rejection of a 230 GHz CPW band pass filter (BPF). Silicon shielding using a grounded CPW line provides 1.79 dB insertion loss for a 215 GHz BPF. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:375–380, 2014

Novel Ultra‐Wideband Filter Using Coplanar‐Waveguide‐To‐Microstrip Transition and Stubs

ABSTRACTThis letter presents a novel ultra‐wideband (UWB) filter using coplanar‐waveguide (CPW)‐to‐microstrip transition and stubs. The proposed filter is implemented by the CPW series stubs and microstrip shunt stubs. The transition includes a via that not only connects the series and shunt stubs but also can improve the out‐of‐band rejection. The proposed filter has been analyzed, verified, and fabricated. Both simulation and measurement results demonstrate the higher rejection cutoff frequencies above 18 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2269–2271, 2013

A novel approach to transform an open circuit series stub to a short circuit shunt stub for the implementation of high-pass butterworth filter

A new approach for transforming an open circuit series stub to short circuit shunt stub is presented.A mathematical identity is also derived. Additional transmission lines of particular lengths are also used while performing this transformation. The simulations and the experimental results verified that the derived mathematical identity can be used for the implementation of high-pass maximum flat Butterworth filter. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:497–501, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27354

Bandwidth Limits of Multilayer Array of Patches Excited With Single and Dual Probes and With a Shorting Post

Maximum achievable bandwidth of a multilayer patch array is investigated. It is found that while the bandwidth increases significantly from one layer to two layers, but does not increase any further with additional layers. Furthermore, the bandwidth of a dual probe-fed patch with a series stub increases significantly from that of a single probe-fed patch array. A simple circuit model is presented to explain such bandwidth characteristics. A comparison of the electrical performances of single, dual probe-fed patches and a patch with a shorting post are presented. The circular polarization performance of a four probe-fed patch array is also shown.

Design of planar bandpass filters from tapered slot resonators

AbstractA compact planar bandpass filter is designed using a tapered slot resonator, which is formed using two tapered slot antennas connected in a face‐to‐face configuration. The tapering profile and dimensions of the resonator control the characteristics of the filter. The success of the method is demonstrated via full wave electromagnetic simulations and measurements. Passbands of 30–50% centred at about 6 GHz with an insertion loss of less than 1 dB and a peak‐to‐peak group delay of less than 0.5 ns are achieved in two filters having different tapering profiles and fabricated on RT6010 substrate with an overall dimension of 25 mm × 30 mm. The use of an open‐ended series stub within the coplanar waveguide feeder of the filters extends their high stopband beyond 15 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1190–1194, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25118