Open Stubs Research Articles

Design of Tri-Band Balanced Filter With Wideband Common-Mode Suppression and Upper Stopband Using Square Ring Loaded Resonator

In this brief, a novel multi-mode square ring loaded resonator (SRLR) is presented, and a tri-band balanced bandpass filter (BPF) with good performances is developed. The multi-mode SRLR consists of a ring resonator and six open stubs, and its resonant characteristics is obtained by the odd/even-mode method. Compared with conventional SRLR, the symmetrical SRLR has more degree of freedom in controlling the resonance modes. Thus, a wide upper DM stopband can be achieved by choosing proper electrical lengths of open stubs. Moreover, frequency dispersion technique is used to enhance common-mode (CM) suppression in the proposed balanced tri-band BPF. By loading a cross-shaped stub and open-loop stub to the center of the first and second order SRLR respectively, five CM transmission zeros (TZs) are produced. Therefore, a wideband CM suppression can be achieved with the DM response almost intact. To verify this design method, a tri-band balanced filter operating at 2.4, 3.5 and 5.2 GHz has been designed, simulated and fabricated. Measured results exhibit good agreement with the simulated ones.

Multilayer triple band bandpass filter with a floating U-shaped SIR and split ring resonator

A multiple band bandpass filter (BPF) is designed using multilayer arrangement. The bandpass filter has three passbands having centre frequencies at 2.45 GHz, 4 GHz and 5 GHz. First a single band BPF is designed which includes a pair of coupled resonator and a split ring resonator in a multilayer arrangement. This geometry of the filter structure is studied and validated by fabrication and measurement. The initial single band filter structure is further improved to provide triple band BPF. All these bands are realized by a stub loaded U-shaped step impedance resonator (SLU-SIR). However, to improve the response of the second and third band a modified split ring resonator and a pair of open stubs are used. Each passband can be controlled individually. A mathematical analysis is done to study the proposed SLU-SIR using transmission line model. The proposed filter provides compactness and low insertion loss. A prototype is measured using vector network analyser (VNA) and shows a good matching with the simulated result.

Compact ultra‐wideband bandpass filter with configurable stopband based on diamond‐shape resonator

An ultra-wideband compact bandpass filter (BPF) with configurable stopband by tuning transmission zeroes is proposed in this paper. The ultra-wideband bandpass response is based on a diamond-shape resonator consisting of a pair of broadside coupled diamond-shape microstrip lines, within which a diamond shape defected ground structure (DGS) is etched in the middle. Flexible transmission zeros realized by open and short stubs can be easily adjusted to improve band selectivity and harmonic suppression. Measurement result shows that the dedicated device has a 3 dB fractional bandwidth of 148% (0.94-6.36 GHz) with 20 dB rejection stopband from 6.87 to 9.7 GHz (77.5%) which agrees good with the simulate performance. The overall size of the proposed BPF is 0.27 λg × 0.23 λg.

Design of Dual Band and Tri-band Bandpass Filter (BPF) with Improved Inter-band Isolation Using DGS Integrated Coupled Microstrip Lines Structures

A novel approach to design dual-band as well as a triple-band BPF with improved isolation is ventured in this paper. In dual-band filter, dual mode property of coupled line filters is utilized to obtain resonant frequencies at 2.4 GHz and 7.4 GHz suitable for WLAN and WiMAX application respectively. Additionally a rectangular-ring DGS element is introduced within the coupled line filter to obtain a separate mid-band resonance at 5.2 GHz. The frequency shifting property of the pass bands due to cross-coupling between the microstrip line resonators and the DGS element is mostly eliminated by implementing stepped impedance open stub (SIOS) technique. All filter configurations are fabricated, measured and compared with the simulated models to validate the practical effectiveness. Stop band isolation > 40 dB and insertion loss (IL) < 0.8 dB is attained in all the filter configurations.

Miniaturized Chipless RFID Tags Based on Periodically Loaded Microstrip Structure

A compact chipless radio frequency identification (RFID) tag-based on slow-wave technology is introduced in this paper. The tag consists of a resonant circuit based on open stub resonators periodically loaded by shunt stubs allowing a coding capacity of 9 bits and operating in a frequency range from 2 to 4GHz. The receiving and transmitting antennas of the tag are particularly designed to minimize the tag size as much as possible. The proposed tag presents a robust bit pattern with a compact and fully printable structure using FR4 substrate for a low-cost tag.

Design of K-band modified hairpin filter with harmonic suppression using GaAs MMIC process

PurposeThe purpose of this paper is to present a K-band modified hairpin bandpass filter on a planar circuit with harmonic suppression and compact size.Design/methodology/approachThe inter-connect transmission lines of conventional hairpin filter are replayed by T-shaped open stub to achieve transmission zero for second harmonic. This filter is simulated and optimized by using electromagnetic simulation software and tested on-chip.FindingsThis proposed filter shows the return loss of better than −10dB, the insertion loss of better than 2 dB in pass-band and suppression of more than 40 dB at second harmonic.Originality/valueThe proposed filter can be designed on monolithic microwave integrated circuit, PCB or LTCC and it is useable for microwave and microwave and millimeter-wave systems.

Dual‐band circularly polarized multiple‐input multiple‐output antenna for GSM and lower LTE applications

A circularly polarized multiple-input multiple-output (MIMO) antenna is presented for global system for mobile (GSM) (710 MHz) and lower long term evolution (LTE) (900 MHz) frequency bands. The antenna consists of four ports with four impedance transformers on the bottom substrate and elliptical rings on the upper substrates. Impedance transformers include open stub and irregular microstrip lines in order to control impedance matching and resonant frequencies. Two upper substrates that contain orthogonal elliptical rings cause the circular polarization property of the proposed antenna. The results of measurement for the presented antenna show its performance with S-parameters of less than −10 dB in the frequency ranges of 699-750 MHz for GSM and 880-1115 MHz for lower LTE applications. Also, the gain and radiation efficiency are higher than 5dBi and 70%, respectively.

Quad-band bandpass filter based on sextuple-mode and dual-mode stub-loaded resonators

A quad-band bandpass filter (BPF) employing a sextuple-mode and a dual-mode stub loaded resonator are presented in this paper. The proposed sextuple-mode resonator generates the first, second and the fourth passband while the third passband is achieved by the dual-mode open stub-loaded resonator. The proposed sextuple-mode resonator modified from quintuple-mode resonator produces five resonant modes while the sixth-mode is generated by the coupling of the open ends of two stub resonators. Based on the odd- and even-mode analysis of the sextuple-mode resonator, the odd- and even-mode resonant frequencies can be flexibly controlled by tuning the corresponding resonator dimensions. Subsequently, the proposed sextuple resonator is combined with dual-mode open stub loaded resonator to achieve the quad-band BPF, centered at 1.75/2.45/3.50/5.25 GHz. The size of filter is about 0.13λg×0.22λg, where λg is guided wavelength on the substrate at 1.75 GHz. The measured results agree well with the simulated results.

Sharp Skirt Dual-Mode Bandpass Filter with Overlay Plate to Control Upper Passband Edge

This paper presents design and analytical model for Sharp Skirt Dual-Mode Bandpass Filter for RF receivers. Proposed filter is designed using open stub loaded H shaped resonator. Based on analytical model insertion loss S21 and return loss S11 for proposed filter are demonstrated. Inductive Overlaying plate is proposed to control upper passband edge of proposed filter to improve frequency selectivity with fixed center frequency. The proposed filter has sharp frequency selective range from 5.1GHz to 9.2GHz. With overlay plate, frequency selective range is tuned to 5.1GHz-8.6GHz. Without overlaying plate the proposed filter has return loss greater than 10dB and insertion loss of 0.7dB. Lower and upper passband edges are at 5.1GHz and 9.2GHz with attenuation level of 52dB and 54dB respectively. With overlaying plate, the filter has same S 11 and S 21 parameters, but upper passband edge is shifted from 9.2GHz to 8.6GHz.

Analysis and Design of RF Filters with Lumped and Distributed Elements

Radio frequency (RF) and microwave filters characterize a class of electronic filter, intended to function on signals in the frequency range between megahertz to gigahertz. A Lumped element RF filters is a passive device whose size across any dimension is much smaller than the operating wavelength so that there is minimal change in phase of waveform between the input and output connections. RF filters can also be designed using distributed elements in which all the inductors and the capacitors are replaced by the open and short circuit stubs. This paper concentrates on an analysis and design of low pass filter with the help of only lumped elements and a high pass filter with both lumped and distributed elements.

Triband Compact Printed Antenna for 2.4/3.5/5 GHz WLAN/WiMAX Applications

This research presents a triband compact printed antenna for WLAN and WiMAX applications. The antenna structure consists of a folded open stub, long and short L-shaped strips, and asymmetric trapezoid ground plane. Besides, it is of simple structure and operable in 2.4 GHz and 5 GHz (5.2/5.8 GHz) WLAN and 3.5/5.5 GHz WiMAX bands. The folded open stub and long and short L-shaped strips realize impedance matching at 2.4, 3.5, 5.2, and 5.8 GHz, and the asymmetric trapezoid ground plane fine-tunes impedance matching at 5.2, 5.5, and 5.8 GHz. In addition, the equivalent circuit model consolidated into lumped elements is also presented to explain its impedance matching characteristics. In this study, simulations were carried out, and a prototype antenna was fabricated and experimented. The simulation and experimental results are in good agreement. Specifically, the simulated and experimental radiation patterns are omnidirectional at 2.4, 3.5, and 5.2 GHz and near-omnidirectional at 5.5 and 5.8 GHz. Furthermore, the simulated and measured antenna gains are 1.269–3.074 dBi and 1.10–2.80 dBi, respectively. Essentially, the triband compact printed antenna covers 2.4 GHz and 5 GHz (5.2/5.8 GHz) WLAN and 3.5/5.5 GHz WiMAX frequency bands and thereby is a good candidate for WLAN/WiMAX applications.

A novel neural-based approach for design of microstrip filters

This paper presents an intelligent design methodology of microstrip filters in which a dynamic neural network model based on Bayesian Regularization Back-Propagation (BRBP) learning algorithm is used. In this approach, a Low-Pass Filter (LPF) composed of multiple open stubs, and stepped impedance resonators is initially designed for which an Artificial Neural Network (ANN) is trained to improve the performance of the filter. The predicted and measured results of the filter verify the effectiveness of the presented method, suggesting an excellent in and out-of-band performance. According to the measurement, the filter has a very small transition band from 2.087 to 2.399 GHz with 3 and 40 dB attenuation points, respectively, leading to a sharp roll-off rate of 118.6 dB/GHz. In addition the optimized filter has an ultra-wide stopband, extending from 2.399 to 15.01 GHz with attenuation level of 22 dB are The overall size of the fabricated filter is only 0.190λg×0.094λg, where λg is the guided wavelength at 3 dB cut-off frequency (2.087 GHz). A performance comparison with some of the recent published LPFs presented, showing the superiority of the proposed filter.

Design of Capacitive Planar Power Transmitter and Receiver for Cavity Resonance-Enabled Wireless Power Transfer

This letter proposes a planar capacitive power transmitter (Tx) and differential power receiver (Rx) for cavity resonance-enabled wireless power transfer. The power Tx consists of an inverted L-shaped open stub. The power Rx consists of two inverted L-shaped open stubs based on method of image, and a differential output can be obtained by it. Our power Tx and Rx are explained by the equivalent circuits and are designed through electromagnetic simulation. From the measurement results at multiple positions, it was revealed that the higher RF-dc efficiency was achieved at all positions than the conventional monopole probes.

Miniaturized low‐pass filter design with wide stopband using complementary split‐ring resonator

AbstractA miniaturized microstrip low‐pass filter (LPF) design comprises of meander lines, rectangular patches, open‐circuit stubs, and a complementary split‐ring resonator placed in between the input/output ports has been presented in this article. The proposed filter has insertion loss of 0.10 dB in passband with a bandwidth of 3.8 GHz. It also has a wide stopband bandwidth of 9.9 GHz with minimum attenuation of 28 dB (between 4.1 GHz and 14 GHz). Wide stopband has been achieved by introducing the open stubs and impedance transforms the patch resonators. Group delay of designed LPF quantified to be less than 0.22 ns in the passband. The simulated and measured results have been compared and found to be in good agreement. This filter finds its applications in Global System for Mobile Communications (GSM) and the industrial, scientific and medical (ISM) bands with harmonic suppression in modern communication receivers.

Realization of Multiple Transmission Zeroes for Bandpass Filters With Simple Inline Topology

The realization method of multiple transmission zeroes (TZs) for second-order bandpass filters (BPFs) is presented in this brief. A modified filter topology with mixed couplings is investigated at first. With the cancelation effect of electric and dominant magnetic couplings, two close-to-passband TZs can be easily realized for a second-order inline filter. Furthermore, the dual-function feature of loaded quarter-wavelength ( $\lambda $ /4) resonators is analyzed. Besides of filtering response, $\lambda $ /4 resonators can be used to realize two more TZs in the stopband. At last, multiple open stubs are loaded asymmetrically at feeding lines, each of which can generate one TZ independently. Due to the asymmetric loading, the extra circuit area of bandstop structures is reduced by half. For demonstration, a wideband BPF using $\lambda $ /4 resonators and four asymmetric open stubs is designed, fabricated, and measured. The stopband suppression can be improved to 10.2 GHz without sacrificing in-band properties or enlarging circuit size. Good agreement can be observed between the measured and simulated results of the proposed BPF.

High isolation diplexer using stub‐loaded resonators

This Letter reports a high isolation diplexer using stub-loaded resonators (SLRs). Each SLR can generate one transmission pole and one transmission zero (TZ). By changing the length of the open stub, the frequency of the TZ can be adjusted. The upper channel filter using the capacitive coupled SLRs can have TZs above the passband, while the lower channel filter using inductive coupled SLRs can have TZs below the passband. With those TZs, the isolation of the diplexer is greatly improved. A high isolation diplexer is designed and fabricated to validate the design concept.

Microwave Three-Dimensional Capacitive Stubs

Introduction. Microstrip filters are widely used in a variety of radio-electronic systems, including telecommunications. Low frequency filters (LPFs) are constructed on the basis of quasi-lumped inductances and capacitances. Quasi-lumped capacitances are performed as microstrip sections with a wide signal conductor or open stubs. Traditional quasi-lumped elements are two-dimensional (2D). Three-dimensional (3D) quasi-lumped elements have 1.5 to 4 times greater reactivity values. The purpose of the paper is to analyze 3D-stubs charateristics. Capacitive 3D-stub transfer characteristic. The 3D-stub is a deaf metalized hole. In the presented paper hole is a square with rounded corners. Dependencies of 1D-model parameters of 3D-stub are shown. From a comparison of 3D- and 1D-transfer characteristics of the 3D-stub it is shown that the 3D-stub in the first approximation can be simulated by a 1D-model in the form of a long line stub. Influence of parasitic inductance on stub notch frequency. For a 1D-model, the stub notch frequency is determined by a quarter-wave condition of it’s length. Stub’s T-junction brings in parasitic reactivities. The parasitic inductance and stub form a series oscillatory circuit. The resonance frequency of this circuit is equal to stub notch frequency. Since traditionally this inductance is negative, the notch frequency increases and stub and LPF transfer characteristics slope decreases. In order to reduce the inductance influence for stub and line contact it is suggested to use a small contact pad. 3D-stub notch frequency and parasitic inductance dependences. The dependences of the notch frequency and parasitic inductance on the 3D-stub heterogeneity depth and contact pad length are analyzed. According to simulation results for a variant with a contact pad inductance values can be not only negative, but also positive. If inductance is positive, notch frequency is less than according to quarter-wave condition. In this case, stub and LPF transfer characteristics slope is higher compared to quarter-wave condition. Discussion of the results. With an increase of the 3D-stub heterogeneity depth from 0.5 to 1 mm, its wave impedance is less in 1.4 ... 3.5 times compared to 2D-stub, and the capacity is greater in 1.6 ... 4.1 times. Contact pad between the stub and line allows to optimize the stub parameters from the condition of the required transfer characteristics slope. Conclusion. 3D-stub has significantly better parameters than 2D-stub. Since the LPF requires the specified capacitance values, depending on the 3D-stub inhomogeneity depth, the area of the 3D-stub is less than 1.6 ... 4.1 times. The 1D-model of the 3D-stub allows to characterize the stub by equivalent wave impedance and relative dielectric permittivity and can be used as the first approximation model for the design and simulating of microstrip LPFs based on capacitive 3D-stubs.

Investigation of integrated solid state nano‐ionic metal–insulator–metal switches for electronically reconfigurable band‐stop filter applications

A proof of concept of application of Nano-Ionic Conductive-Bridging Metal-Insulator-Metal (MIM) switches in electronically reconfigurable band stop filters, through design, and experimental results are presented in this article. Two similar designs of band stop filters with different mechanism of operation are proposed herewith. One is a microstrip, resonant open stub based band stop filter and the other is a microstrip tuned shorted stub based band stop filter. Electrical length of the stubs in both these devices are tuned by an integrated MIM switch forcing them to resonate at different frequencies and thus achieving electronically switchable band stop filtering characteristics. Working mechanism of the devices is validated with the help of developed electrical equivalent circuit models. Analysis on time stability of switch states for 1000 minutes with affirmative results is also presented herewith. These devices are fabricated without any soldered electrical components and without the use of any clean room technologies, using proven low cost method, and are promising to work at very-low power and have the potential to be directly printed on low cost flexible substrates like paper, for potential disposable applications.

Compact bandstop filters using coupled lines and open/short stubs with multiple transmission poles

A compact bandstop filter (BSF) using parallel-coupled lines and open stubs with four transmission poles (TPs) is proposed. Through theoretical equation deduction, the positions of these four TPs can be obtained. Good roll-off skirts and stopband suppression characteristics of the BSF can be realised with the help of multiple TPs. To improve transition band roll-off rates, another BSF with five TPs is designed, where a short-circuited T-stub is loaded on the middle of the above BSF circuit structure. For demonstration, two filter examples with centre frequencies at 2 and 1.8 GHz are implemented with generation of four and five TPs, respectively, for theoretically calculated certification. Good agreement between simulated and measured results validates the design method.

A high capacity tunable retransmission type frequency coded chipless radio frequency identification system

This article presents a 12-bit frequency coded chipless RFID system in the frequency range of 3 to 6 GHz. The system consists of a fully printable chipless tag and a pair of high-gain reader antennas. The tag also incorporates its own antennas to improve the read range. Information is encoded into frequency spectrum using a multi-resonant circuit. The circuit consists of multiple microstrip U and L-shaped open stub resonators patterned in a unique configuration. The proposed configuration aids in capturing more data in a reduced space as well as tunable frequency operation. Tag and reader antennas utilize techniques such as stepped impedance feeding line, defective partial ground plane, and stair-step patch structure to achieve wide-band impedance bandwidth in miniature size. The results of the wireless measurements in the non-anechoic environment show that the proposed system has a reading range of more than 20 cm. The presented system possesses great potential for low-cost short-range inventory tracking.