Shunt Stubs Research Articles

Design and fabrication of a microstrip triplexer with wide flat channels for multi-band 5G applications.

In this paper, a new microstrip triplexer is designed to work at 2.5 GHz, 4.4 GHz and 6 GHz for mid-band 5G applications. All channels are flat with three low group delays (GDs) of 0.84 ns, 0.75 ns and 0.49 ns, respectively. Compared to the previously reported works, the proposed triplexer has the minimum group delay. The designed triplexer has 18.2%, 13.7%, 23.6% fractional bandwidths (FBW%) at 2.5 GHz, 4.4 GHz and 6 GHz, respectively. The obtained insertion losses (ILs) are low at all channels. These features are obtained without a noticeable increase in the overall size. A novel and simple resonator is used to design the proposed triplexer, which includes two pairs of coupled lines combined with a shunt stub. A perfect mathematical analysis is performed to find the resonator behavior and the layout optimization. The type of shunt stub is determined mathematically. Also, the smallness or largeness of some important physical dimensions is determined using the proposed mathematical analysis. Finally, the designed triplexer is fabricated and measured, where the measurement results verify the simulations.

Design of a fractal triple-band reconfigurable filtering antenna for multiband applications

This letter constitutes a novel triple-band reconfigurable filtering antenna used for Bluetooth, WiMAX and WLAN applications. First, a compact triple-band reconfigurable filter is instigated which is composed of two pairs of Stepped Impedance Resonators (SIRs) and a pair of Uniform Impedance Resonators (UIRs). The SIRs are entrenched at the upper and lower half of feed lines operating at 2.4 and 5.4 GHz, respectively. A pair of UIRs operating at 3.5 GHz is folded and enclosed near the upper SIR. A shunt stub is tapped at the source-load feeding lines to upgrade the selectivity of the filter. The proposed filter uses four PIN diodes to initiate different reconfigurable multiband operations. A fractal antenna is implemented with a modified binary tree topology. The ground plane of the proposed antenna is reformed with a stub. The improved antenna structure enables three radiating bands with enhanced performance. Later, the designed filter is integrated into the antenna to implement the intended triple-band reconfigurable filtering antenna.

Harmonic Suppressed Wilkinson Power Divider Using Parallel Resonant Shunt Stub

This paper proposes a harmonic-suppressed Wilkinson power divider (HS WPD) utilizing parallel resonant shunt stubs (PRSSs). PRSSs are integrated into the conventional WPD by adding functionalities such as bandpass filtering, harmonic suppression, and physical port separation. The resonance conditions and design equations of the PRSS are theoretically derived and verified through circuit simulations. Using the PRSS, we designed an HS WPD operating at 1 GHz. The fabricated HS WPD demonstrated an insertion loss of 3.2 dB at the fundamental frequency, with a wide 3 dB bandwidth of 129%. The harmonic suppression levels at the 2nd and 3rd harmonic frequencies are measured to be 21.0 dB and 25.8 dB, respectively. The measured input return loss at the fundamental frequency was 27.9 dB, whereas the output return loss was 24.6 dB. Additionally, the HS WPD demonstrates isolation levels at the fundamental, 2nd, and 3rd harmonic frequencies, with levels of 29.2 dB, 17.8 dB, and 47.1 dB, respectively. It also exhibited broadband isolation (>8.7 dB) across the frequency range of 100 kHz to 3.35 GHz. The PRSS design allows for the physical separation of the ports without requiring additional circuitry. Compared to previously reported PDs, the proposed design offers multiple functions in a compact size, making it highly suitable for various microwave systems.

Compact dual‐frequency impedance transformer for frequency‐dependent complex source and load

SummaryThis study presents a compact hybrid dual‐frequency impedance transformer that is suitable for sources and loads having frequency‐dependent complex impedances. The basic transformer comprises two transmission lines and two shunt stubs, and this configuration is adequate for the design of a dual‐frequency impedance transformer for a few sources and loads. Compared with other studies, this work presents a distinct derivation concept to obtain the circuit parameters, thus enabling the achievement of a compact circuit. For some particular sources and loads that the basic structure is difficult to match because of line width limitations, lumped elements are added to overcome the limitation and further reduce the circuit size. The derived design formulas avoid errors caused by frequency‐dependent deviations in the component values due to parasitic effects, which constitute a critical problem in Radio Frequency (RF) circuits that employ lumped elements. The simulated results are in good agreement with the measured results, and the frequency responses obtained herein validate the proposed structure and design procedure.

Transmission-Mode Phase-Variation Planar Microwave Sensor Based on a Step-Impedance Shunt Stub for High Sensitivity Defect Detection, Dielectric Constant, and Proximity Measurements

Transmission-Mode Phase-Variation Planar Microwave Sensor Based on a Step-Impedance Shunt Stub for High Sensitivity Defect Detection, Dielectric Constant, and Proximity Measurements

Dual-Band Power Amplifier With Bandwidth Extension Based on Broadband Harmonic Control Part Dual Transmission Line

This paper presents a dual-band (DB) high-efficiency power amplifier (PA) with extended bandwidth. A novel output matching network (OMN) that integrates harmonic control into DB fundamental matching design is proposed. Bandwidth of the DB PA can be efficiently extended by the OMN presented since it can offer DB broadband harmonic control while maintaining the input impedance at DB fundamentals. By precise control of the characteristic impedance on the part dual transmission line (part-DTL) and the double shunt stub (DSS), these two structures are made equivalent to the series and parallel transmission line (TL) performance at DB fundamentals. Additionally, the part-DTL modulates the input impedance in broadband near DB harmonics to pure reactive, and the DSS optimizes the imaginary part of the input impedance at DB harmonics. For validation, a DB PA is designed and fabricated with a Cree CGH40010F GaN transistor. The fabricated DB PA features the saturated output power of 42.4 dBm and 41.7 dBm with the power-added efficiency of 73.5% and 68.4% at 2.6 GHz and 3.5 GHz, respectively. Specially, the bandwidth of the DB PA is extended to over 300 MHz and 200 MHz.

Quadrature Wilkinson power divider using cross-type short-circuited shunt stub for good amplitude and phase balance

This paper introduces a new design of a quadrature 3-dB power splitter using a quadrature Wilkinson power divider and a cross-type short-circuited shunt stub for printed circuit board (PCB) circuit design. For 3-dB power splitting and a relative 90° phase difference, several types of quadrature 3-dB power splitters are commonly used in RF and microwave applications, including Lange coupler, directional coupler, branch-line coupler, and quadrature Wilkinson power dividers. Among them, quadrature Wilkinson power dividers often utilize a Schiffman phase shifter and λ/4 short-circuited shunt stubs for compensation circuit.In this paper, the aforementioned schemes have been evaluated by image rejection ratio (IRR) bandwidth (BW) related to amplitude and phase imbalance property. The new design of the quadrature Wilkinson power divider adopting the proposed cross-type short-circuited shunt stub offers superior −25-dB IRR BW compared with other quadrature 3-dB power splitters in PCB fabrication. In measurement, the proposed quadrature Wilkinson power divider provided a −25-dB IRR BW of 3.50 GHz, operating at a center frequency of 9.5 GHz. The designed power splitter offered an operating frequency of 2.64 GHz, satisfying −25-dB IRR BW, 10-dB impedance BWs, and 20-dB isolation BW.

A 2-V 1.4-dB NF GaAs MMIC LNA for K-Band Applications.

A 1.4-dB Noise Figure (NF) four-stage K-band Monolithic Microwave Integrated Circuit (MMIC) Low-Noise Amplifier (LNA) in UMS 100 nm GaAs pHEMT technology is presented. The proposed circuit is designed to cover the 5G New Release n258 frequency band (24.25-27.58 GHz). Momentum EM post-layout simulations reveal the circuit achieves a minimum NF of 1.3 dB, a maximum gain of 34 dB, |S11| better than -10 dB from 23 GHz to 29 GHz, a P1dB of -18 dBm and an OIP3 of 24.5 dBm. The LNA draws a total current of 59.1 mA from a 2 V DC supply and results in a chip size of 3300 × 1800 µm2 including pads. We present a design methodology focused on the selection of the active device size and DC bias conditions to obtain the lowest NF when source degeneration is applied. The design procedure ensures a minimum NF design by selecting a device which facilitates a simple input matching network implementation and obtains a reasonable input return loss thanks to the application of source degeneration. With this approach the input matching network is implemented with a shunt stub and a transmission line, therefore minimizing the contribution to the NF achieved by the first stage. Comparisons with similar works demonstrate the developed circuit is very competitive with most of the state-of-the-art solutions.

Ultra-Wideband Power Amplifier Design Strategy for 5G Sub-6-GHz Applications.

This paper presents a strategy to design ultrawideband power amplifiers with a fractional bandwidth of approximately 200%. It exploits a simple output matching network, which consists of a series transmission line together with a shunt stub, to compensate the output parasitic network of the device. Following this, a multisection transformer is implemented to obtain the optimal load at the intrinsic drain plane. As design examples, several output matching networks were designed for two different size GaN HEMT devices. One of these examples was implemented and characterized, and a drain efficiency from 52% to 70% and an output power between 40 dBm and 42.5 dBm were obtained, over 67% of the 5G sub-6-GHz band (i.e., 0.1 to 4 GHz). The aforementioned results, to the best of the authors’ knowledge, represent the state of the art in broadband power amplifiers.

A New Design Approach for a Compact Microstrip Diplexer with Good Passband Characteristics

This paper presents an efficient theoretical design approach of a very compact microstrip diplexer for modern wireless communication system applications. The proposed basic resonator is made of coupled lines, simple transmission line and a shunt stub. The coupled lines and transmission line make a U-shape resonator while the shunt stub is loaded inside the U-shape cell to save the size significantly, where the overall size of the presented diplexer is only 0.008 λg2 . The configuration of this resonator is analyzed to increase intuitive understanding of the structure and easier optimization. The first and second resonance frequencies are f o1 = 895 MHz and f o2 = 2.2 GHz. Both channels have good properties so that the best simulated insertion loss at the first channel (0.075 dB) and the best simulated common port return losses at both channels (40.3 dB and 31.77 dB) are achieved. The presented diplexer can suppress the harmonics acceptably up to 3 GHz (3.3 fo1 ). Another feature is having 31% fractional bandwidth at the first channel.

A dual‐band impedance transformer with a single series line for frequency‐dependent loads

This paper proposes a novel dual-band impedance transformer for matching frequency-dependent complex loads. The transformer consists of four shunt stubs and a single series transmission line. The equations for the transformer are derived concisely. The design values of the four stubs are determined by the analytical formulas and the parameters of the single series line are obtained by solving a nonlinear equation. The characteristic impedances of the four stubs can be adjusted. The design freedom is greatly enhanced and the possibility of using lines with extremely high or low impedance is reduced significantly. Two numerical examples are presented for illustrating the design process, and a prototype is fabricated and measured for verification. Compared with the existing works, the design not only shows high design freedom but also has the smallest electrical length of the series line. Therefore, the transformer has a good application prospect for the dual-band active circuits.

A Compact and Wideband Dashboard Antenna for Vehicular LTE/5G Wireless Communications

A wideband, low-profile, 3D automotive antenna for Long-Term Evolution (LTE) and 5G applications is presented in this paper. Different from other cellular antennas typically placed under the shark-fin cover or inside a car’s plastic spoiler, the proposed antenna is designed to be integrated inside the vehicle’s dashboard. The 35.5 × 40 × 45 mm3 antenna is compact, lightweight and robust. At the same time, this antenna is capable of operating from 670 up to 5000 MHz, covering the entire LTE/5G band (overall fractional bandwidth of 198%). A shunt stub was introduced between the monopole and ground plane to achieve a low LTE band and provide mechanical robustness for the proposed structure. Simulated performance in terms of reflection coefficient, radiation pattern and realized gain is described, showing a good agreement with the measurement results. Specifically, the antenna has a gain higher than −1 dBi at the low-frequency band (i.e., below 1 GHz) and higher than 3 dBi at the upper-frequency band (i.e., above 1.7 GHz). As per requirements, the ground plane size and layout can be properly chosen to fit the antenna into the available volume as well as to optimize the antenna’s performance.

Design of wideband impedance transformers with different number and different mounting positions of the shunt stubs

Design of wideband impedance transformers with different number and different mounting positions of the shunt stubs

A compact dual‐band frequency‐dependent impedance transformer using two resizable shunt stubs

AbstractThis paper presents a dual‐band impedance transformer for frequency‐dependent loads with two resizable shunt stubs. The proposed transformer is composed of a single‐band matching network and a dual‐band susceptance stub network (DSSN). The single‐band matching network only consists of a one‐section matching network when the load is within the derived circle areas. The design parameters of the DSSN can be adjusted freely. The bandwidths at the two bands can be enhanced, and the possibility of using transmission lines with extremely high or low impedance is reduced significantly. All the parameters are obtained by solving the analytical design formula. Two examples are presented for illustrating the design process, and a prototype is fabricated and measured for verification. Good agreement between the simulation and the measurement is obtained. Compared with the previous works, the transformer not only has the shortest electrical length but also obtains wide bandwidths. Therefore, the transformer is very applicable for dual‐band systems, especially the dual‐band active device circuits.

Tunable bandstop filter using graphene in terahertz frequency band

In this paper, a planar graphene-based bandstop filter is designed and simulated for the resonant frequency of 1THz. The transmission line model of the bandstop filter is considered, which consists of open-circuited shunt stubs that are interconnected through unit elements. The bandstop filter design is carried out from the normalized low pass Chebyshev prototype. By using frequency transformation, Richard’s transformation, and Kuroda’s identity, the desired bandstop filter can be designed from the low pass prototype. The graphene layer is introduced between the conductor layer and the dielectric for supporting the propagation of plasmonic waves. The simulation results show that the desired frequency response can be obtained for the designed graphene-based bandstop filter. By varying the chemical potential of the graphene layer, the resonant frequency of the bandstop filter can be tuned over the range of 0.1THz with the constant absolute bandwidth.

A 50 W dual‐band high‐efficiency gallium nitride high electron mobility transistor power amplifier with three‐stage L‐type DC bias circuit at 1.8 and 2.6 GHz

AbstractA 50 W dual‐band high‐efficiency gallium nitride (GaN) high electron mobility transistor (HEMT) power amplifier with a three‐stage L‐type DC bias circuit capable of individually adjusting second‐harmonic impedances is proposed for 1.8 and 2.6 GHz frequencies. The output network of this power amplifier is composed of an output matching network comprising five‐stage transmission lines and a three‐stage L‐type DC bias circuit with three L‐type circuits and one transmission line. The one‐stage L‐type circuit comprises a series transmission line and a quarter‐wavelength open‐ended shunt stub. For the high‐efficiency performance of the power amplifier, the output matching network is matched to the optimum impedances of the fundamental frequencies, and the DC bias circuit optimizes the impedances individually at the second‐harmonic frequencies without affecting the matched fundamental frequency impedances in the output matching network. Measured results show that the proposed dual‐band GaN HEMT power amplifier achieved gains of 15.6 and 13.8 dB as well as maximum power‐added efficiencies of 70.5% and 66.3% with 47 dBm output power at 1.8 and 2.6 GHz, respectively.

Short-circuited stub-loaded spoof surface plasmon polariton transmission lines with flexibly controllable lower out-of-band rejections.

This Letter proposes an approach to develop a spoof surface plasmon polariton (SSPP) transmission line (TL) by loading short-circuited (SC) shunt stubs. Lower out-of-band rejections can be flexibly controlled without affecting the upper cutoff frequency by independently modifying the stubs. Dispersion analysis of the SSPP unit is realized by theoretical calculation and circuit simulation to predict the upper cutoff frequency of the proposed SSPP TL simultaneously. Also, parametric sweeping of the SC shunt stubs is performed based on circuit simulation to investigate their impacts on the lower and upper out-of-band rejections of the proposed SSPP TL. In addition, electric field distributions of different types of TLs are simulated and compared to study the transmission characteristics of the proposed SSPP TL. The lower cutoff frequency can be flexibly tuned in a wide range, from 1.2 to 2.1 GHz, in the simulations. The measured 3-dB fractional bandwidth is about 128.1%, covering a range from 1.19 to 5.43 GHz. The numerical and experimental results are compatible, which verifies the feasibility of the proposed approach. This approach can offer more convenience and flexibility for controlling the rejections of the SSPP by introducing up to four tuning parameters. More importantly, the proposed SSPP TL avoids using the substrate integrated waveguide (SIW) technique, which shows the potential to decrease the transverse width (0.44λg), especially at lower frequencies (e.g., 1.2 GHz), and to reduce the complexity in designing the high-efficiency transition. This work paves the way for the development of novel SSPP-based microwave devices.

High-Efficiency Triple-Band RF-to-DC Rectifier Primary Design for RF Energy-Harvesting Systems

Radio Frequency (RF) energy harvesting has been emerged as a potentially reliable method to replace the costly and difficult to maintain source of low-power wireless sensor networks. A plethora of dual-band rectifier designs has been proposed in the literature operating in various frequency bands. In this paper, a triple-band RF-to-DC rectifier that operates in the frequency bands of LoRaWAN, GSM-900, and WiFi 2.4 GHz is presented. The system is composed of an impedance-matching circuit, an RF-to-DC rectifier, that converts the ambient RF energy into DC voltage able to feed low-power devices, and an output load. The proposed system resonates at three different frequencies of 866 MHz, 948 MHz and 2423 MHz, which fall within the aforementioned frequency bands of interest. The feasible solution of the proposed system was based on a dual-band rectifier operating in the frequency bands of LoRaWAN and GSM-900. A series of shunt stubs was utilized in the initial design to form the feasible solution of the proposed system. The proposed triple-band rectifier was optimized using a powerful optimization algorithm, i.e., the genetic algorithm. The overall system exhibited improved characteristics compared to the initial design in terms of its resonance. Numerical results demonstrated that the overall system exhibited an efficiency of 81% with 3.23 V of the output voltage, for an input power of 0 dBm and a load of 13 kOhm.

Design of Microstrip Dual-Mode Wideband Bandpass Filter with Controlled Center Frequency and Bandwidth Using Bandstop Filter Topology

ABSTRACT This paper discusses a new method for designing a microstrip dual-mode, sharp skirt, wideband bandpass filter with controlled center frequency and bandwidth from bandstop filter topology. A meander closed loop resonator with directly connected orthogonal feed lines provides a Bandstop filter (BSF) with reduced size. A pair of L-shaped open stubs introduced along the diagonal axis D-D1 realizes a wide passband within the rejection band (0.93–4.13 GHz) of the bandstop filter with sharp stopbands on either side of the passband. Furthermore, the effect of L-shaped open stubs susceptance on passband edges is demonstrated. A quarter wavelength stepped impedance shunt stub (SISS) connected at is proposed to achieve additional transmission zeros in the upper and lower rejection bands to improve the sharpness of filter response. Both center frequency and bandwidth of the proposed filter are controlled by the impedance ratio (R) of the SISS element. The proposed filter is simulated using ADS, fabricated and measured using Vector Network Analyzer (VNA). A good agreement is achieved between simulated and measured results.

Dual‐band impedance transformer with single shunt stub for complex impedance loads

AbstractThis letter presents a novel impedance transformer that can transform two unequal frequency‐dependent complex loads (FDCLs) to a resistive load at two diverse bands. The proposed transformer contains four sections of transmission lines and one shunt stub. The design parameters of the transformer are obtained from the analytical formulas. The feasibility analysis of the transformer is discussed and an example based on microstrip technology is implemented and measured for verification. The good agreement between the simulated results and measured results proves the validity of the proposed configuration and design method. Compared with the reported works, the transformer not only features single shunt stub and shorter total electrical length at transmission direction, but also provides simpler analytic design equations and less likely to use the very high‐ or low‐impedance transmission lines.