Additional Stubs Research Articles

A wideband balanced filtering coupled‐line coupler with improved directivity based on coupled microstrip–slotline

AbstractIn this article, a wideband balanced filtering coupled‐line coupler (BFCLC) with improved directivity is designed. By using coupled microstrip–slotline, the proposed BFCLC realizes tight coupling while maintaining good isolation. A lattice equivalent circuit is introduced for the coupled microstrip–slotline. Good differential‐mode transmission and high common‐mode suppression are achieved through the application of microstrip/slotline transition structures. Additional stubs are taken to compensate for the odd‐ and even‐mode phase velocities of the coupled microstrip–slotline. Transmission zeros can also be adjusted to improve selectivity. Based on the proposed BFCLC, a coupler with a smaller size using solely the slotline is designed. Two proposed couplers are manufactured to validate the theoretical design, and a good agreement between the simulation and measurement is presented.

A compact wideband monopole antenna with DGS for WiMAX/WLAN/5G applications

In this research, a complex wideband antenna with different applications in wireless communication devices is proposed. The proposed wideband antenna resonates at different four frequencies, which include the wireless devices band, an Ultra-Wideband (UWB), and an X-band. This rectangle-shaped antenna with additional stub antennas has FR4 material used as a substrate with dimensions of (26 × 40 × 1.6 mm3). The resulting resonant frequencies cover Wireless Local-Area Network (WLAN) at 2 GHz and 5.3 GHz, Multiple Input Multiple Output (MIMO) at 6.7 GHz, and X-band at 8.7 GHz. The implementation of Defected Ground Structure (DGS) facilitates the reduction in size and increase in antenna performance, and by using the additional stubs, it provides a multi-sharpened band. It has an omnidirectional radiation pattern. Simulation results show that the proposed antenna provides a wide range of frequencies (4-9 GHz).

A compact microstrip patch antenna with DGS for WiFi/WiMAX/WLAN

In recent years, the study of microstrip patch antennas has witnessed significant advancements, offering numerous advantages and promising prospects compared with conventional antennas. These antennas are characterized by their lightweight compact size, low cost, low profile, small dimensions, and excellent conformability. Additionally, microstrip patch antennas exhibit various desirable features, such as dual and circular polarization, dual-frequency operation, broad bandwidth, flexible feedline configurations, and beam-scanning omnidirectional patterns. In this paper, a microstrip patch antenna design tailored for the 2.4 GHz frequency band is proposed, showcasing its potential for applications in wireless communication devices. The antenna is engineered to operate across multiple bands, including the wireless device band, Ultra Wide Band (UWB), and X band. It has a truncated rectangle shape with additional stubs, whereas the substrate material employed is FR4. The resulting design achieves resonance at four different frequencies, effectively covering the Microwave Access (WiMAX) band at 2.5 GHz and 4 GHz. Notably, the implementation of Digital Global Systems (DGS) plays a crucial role in reducing the antenna size while simultaneously enhancing its performance. The proposed microstrip patch antenna demonstrates great potential for meeting the increasing demand of modern wireless communication devices. Its multiband operation, compact size, and improved performance, achieved through the integration of DGS, make it a promising candidate for various wireless communication applications.

A Wideband Dual-Polarized Ring-Loaded Cross Bowtie Antenna for Wireless Capsule Endoscopes: Design and Link Analysis

This work presents a novel on- body wideband dual-polarized antenna to stabilize and enhance the link performance of wireless capsule endoscopy systems. By introducing a cross-bowtie structure with a planar compact feed method, the antenna achieves a dual-polarized performance with high port-to-port isolation. A loaded ring with additional stubs is also implemented to further enhance the bandwidth and provide a flat in-band performance from 381 to 990 MHz. The proposed antenna is measured with both homogeneous phantom and ex vivo test to validate the impedance matching performance. To validate the effectiveness of the proposed on- body antenna on the communication link, a capsule helical antenna with omnidirectional radiation pattern is designed and measured. Finally, comprehensive link studies are conducted considering the varied capsule orientations and locations, with a peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{21}\vert $ </tex-math></inline-formula> value of–25.5 dB at the 60 mm implant depth and an acceptable link loss due to the capsule position error. The proposed on- body antenna can be regarded as a good candidate for a practical capsule endoscopy system due to its stable and enhanced transmission performance when compared with its counterparts.

Millimeter-Wave High-Efficiency Double-Layer Transmitarray Antenna Using Miniaturized Dual-Polarized Elements

A high-efficiency wideband double-layer transmitarray antenna (TA) using miniaturized array elements is proposed in the study for millimeter-wave (mm-Wave) applications. The transmitarray consists of 484 dual-polarized elements. Each element is composed of only two layers of identical modified Jerusalem crosses printed on a dielectric substrate. Additional stubs are used for size reduction, leading to a compact size with a periodicity of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.44 \lambda _{0}$ </tex-math></inline-formula> . It contributes to a high aperture efficiency for the proposed TA. TA is designed, fabricated, and measured. It achieves a peak gain of 28.67 dBi at 31 GHz and a high aperture efficiency of 44%–61.3% within the 1 dB gain bandwidth, which is 10.3% (29.5–32.7 GHz) in the measurement. The proposed dual-polarized double-layer TA demonstrates simplified design complexity, reduced thickness and mass, and lower cost compared with the conventional TAs. It also exhibits high radiation gain and high aperture efficiency.

Tunable balanced bandpass filter with wide frequency‐tuning range and high selectivity

AbstractA tunable balanced bandpass filter (BPF) with a wide frequency‐tuning range (FTR) and high selectivity is presented. The designed BPF is implemented by utilizing varactor‐tuned square ring resonators (SRRs) with parallel‐coupled feedlines. A wide FTR with an almost constant absolute bandwidth (CABW) can be realized by varactors Cv2 connected between SRRs. Four transmission zeros (TZs) can be obtained by the mixed electric and magnetic coupling, source‐load (S‐L) frequency‐variant coupling, and four shunt quarter‐wavelength open and short stubs. Meanwhile, two TZs on both sides of the passband keep the relative position unchanged to achieve high selectivity. The other two are generated to improve the out‐band rejection. In addition, by employing additional stubs and capacitances on the symmetry plane, the common‐mode (CM) suppression can be enhanced. For verification, a tunable balanced BPF with 0.62‐1.27 GHz and four TZs was designed, manufactured, and tested. And experimental results agree well with the simulated ones.

A single layer broadband microstrip ring antenna for wide-angle scan phased array

ABSTRACT In this paper, a broadband microstrip ring antenna with single layer and compact size is proposed. The bandwidth of conventional microstrip ring antenna is increased from 1%~3% to 15% by loading an additional stub. A simple formula is presented as the design guideline of the proposed antenna. Based on the proposed antenna element, a linear array working at 19 ~ 21 GHz is designed and fabricated, the array can steer to 60° with gain reduction less than 3.5 dB, good agreement is observed between the experimental and simulated results.

Design and Realization of a Frequency Reconfigurable Antenna with Wide, Dual, and Single-Band Operations for Compact Sized Wireless Applications

This paper presents a compact and simple reconfigurable antenna with wide-band, dual-band, and single-band operating modes. Initially, a co-planar waveguide-fed triangular monopole antenna is obtained with a wide operational frequency band ranging from 4.0 GHz to 7.8 GHz. Then, two additional stubs are connected to the triangular monopole through two p-i-n diodes. By electrically switching these p-i-n diodes ON and OFF, different operating frequency bands can be attained. When turning ON only one diode, the antenna offers dual-band operations of 3.3–4.2 GHz and 5.8–7.2 GHz. Meanwhile, the antenna with single-band operation from 3.3 GHz to 4.2 GHz can be realized when both of the p-i-n diodes are switched to ON states. The proposed compact size antenna with dimensions of 0.27λ0 × 0.16λ0 × 0.017λ0 at the lower operating frequency (3.3 GHz) can be used for several wireless applications such as worldwide interoperability for microwave access (WiMAX), wireless access in the vehicular environment (WAVE), and wireless local area network (WLAN). A comparative analysis with state-of-the-art works exhibits that the presented design possesses advantages of compact size and multiple operating modes.

Design of Series-Fed, Single-Layer, and Wideband Millimeter-Wave Microstrip Arrays

A series-fed millimeter-wave (mm-wave) microstrip linear array with single-layer structure and wide operating bandwidth is proposed and investigated. The antenna array simply consists of a microstrip line and a series of short stubs that are periodically introduced on one edge of the microstrip line, at an interval of about one guide wavelength. Owing to the perturbation of the additional stubs, the original symmetrical E-field distributions on the two opposite edges of the microstrip line become asymmetrical, and the intensities of the equivalent magnetic currents are unequal and unable to cancel each other out as in a pure microstrip line. As a result, the stub-loaded microstrip line can radiate effectively, producing broadside radiation patterns. The introduction of stubs can also generate an extra resonant mode, which combines with the resonant mode of the microstrip line, yielding a wide bandwidth of over 20%. In addition, the microstrip array is simply fed by a coaxial probe, without involving any complex feeding network. Therefore, the array configuration is very simple and compact. For demonstration, a $1 \times 4\,\,1$ -D microstrip linear array operating at 27 GHz is fabricated and tested. The measured results show that the array has an impedance bandwidth of 21.40%, an average realized gain of 12.18 dBi, and a first sidelobe level (FSLL) of about −13 dB. Moreover, the FSLL can be decreased to −28.4 dB by tapering the width of the microstrip line. Finally, the design is extended to realize a $4 \times 4\,\,2$ -D microstrip planar array. This planar array can achieve an impedance bandwidth of 19.15% and an enhanced gain of 18.30 dBi.

An Angular-Displacement Microwave Sensor Using an Unequal-Length-Bi-Path Transversal Filtering Section

A class of angular-displacement microwave sensor based on a microwave signal-interference transversal filtering section (TFS) with unequal-electrical-length paths is reported for the first time. It consists of a bi-path TFS composed of two in-parallel transmission-line segments with distinct lengths, which is modified by adding a rotational open-circuit-ended stub as the rotor to a curved section as the stator of one of its line segments. In this manner, the spectral positions of the transmission zeros, which are produced in its filtering transfer function through destructive signal-energy interactions, are modified with the rotation of this additional stub. This allows single/multi-band angular displacement microwave-sensing capabilities in terms of transmission-zero inter-spacing variation for passbands/stopbands and stopband-peak-level modification to be attained by means of the mechanical rotation of the rotor. The theoretical operational principles of this type of bi-path-TFS-based angular-displacement microwave sensor and design curves for specific values of its electrical parameters are provided. Moreover, for experimental validation purposes, a proof-of-concept prototype of the devised TFS-based microwave sensor approach operating at 961 MHz with 180° dynamic range is prototyped in microstrip technology and measured. A comparative analysis of the developed angular-displacement microwave sensor with the state-of-the-art is also presented.

Design and Fabrication of a Novel Compact Low-loss Microstrip Diplexer for WCDMA and WiMAX Applications

In this paper, a novel miniaturized microstrip diplexer using two bandpass filters (BPFs) is designed and fabricated. The filters consist of stub loaded coupled lines. Additional stubs and T-shape feeding structures are added to miniaturize the size of the presented diplexer. With the adopted special structure, low insertion losses and compact size are obtained. The introduced diplexer operates at 2.12 GHz for WCDMA application and 3.94 GHz for WiMAX application. The obtained insertion losses are 0.25 dB at 2.12 GHz and 0.26 dB at 3.94 GHz. A design technique for analyzing the proposed resonator is introduced to tune the resonance frequencies and obtain a compact size. The size of the proposed diplexer is 23.4 × 16.9 mm 2 (0.038 λ g 2 ). The measurement result of the fabricated diplexer validates the design technique and simulation results.

Electrically Small, Planar, Complementary Antenna With Reconfigurable Frequency

An electrically small, planar, complementary antenna with endfire radiation patterns is investigated in this paper. It mainly consists of an electric dipole and a segmented loop that functions as an equivalent magnetic dipole. There is also an additional stub used to adjust the maximum radiation direction and a slotted circular patch for impedance matching. Two modes of the electric dipole and magnetic-dipole loop are excited and combined, realizing an impedance bandwidth of 6.1%, a gain of 4.85 dBi, a front-to-back ratio (FTBR) of 18.5 dB, and an efficiency of over 90%. Furthermore, it is found that the resonance frequency of the loop relies on the length of its small segments. Therefore, two p-i-n diodes are introduced to the loop to manipulate its resonance frequency. Also, two extra p-i-n diodes are added to adjust the resonance frequency of the electric dipole. Consequently, two reconfigurable bands (1.5 and 2.4 GHz) with consistent endfire radiation patterns are achieved for the first time in a complementary antenna.

Diagonally Fed Square Microstrip Antenna for Wideband Dualpolarized Response

A novel method of increasing the length of surface current distributions to enhance the bandwidth of a microstrip antenna is proposed in this paper. Introduction of sinusoidal perturbations and additional stubs along the edges of a square microstrip antenna with diagonal feed reduces the frequency of the higher order TM11 mode towards the frequency of fundamental mode of the patch by increasing the path lengths of surface current yielding a band width of nearly 46.5%. Proposed antenna exhibits broadside radiation pattern at the band edge frequencies of the impedance locus. Dual polarized response is realized in the proposed configuration by embedding two asymmetric slots that causes degeneration of fundamental mode.

Wideband out-of-phase power dividers with improved isolation performance

AbstractA compact wideband out-of-phase power divider (PD) with improved isolation performance is proposed. This divider is formed by connecting an additional stub for isolation to output ports of a traditional Marchand balun with a defected ground structure (DGS) been used. To verify the design, a prototype divider is fabricated and tested. The measured results validate the 53.86% band-width centered at 3.43 GHz with more than 15 dB return loss at all ports, more than 17 dB isolation, respectively.

Compact Omnidirectional Circularly Polarized Antenna Loaded With Complementary V-Shaped Slits

A novel omnidirectional circularly polarized (CP) antenna loaded with complementary V-shaped slits is presented. It is etched on a single-layer substrate with a patch and ground plane on two sides. By arranging the complementary V-shaped slits in the patch and ground plane, horizontally polarized electric field is generated, such that the |E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">φ</sub> | = |E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</sub> | and δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</sub> -δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">φ</sub> = 90° can be realized. Meanwhile, the performance of CP wave is further improved by etching the orthogonal arc slots at the middle of the patch and ground plane. Avoiding additional stub used to generate the horizontally polarized wave, the presented antenna achieves a compact dimension of 0.52λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.52λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.026λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in free space). The realized antenna operates at 5.8 GHz with a bandwidth of 3.5% (5.65-5.85 GHz). Also, it has a peak gain of 1.26 dBic at 5.75 GHz. A good agreement is obtained between the simulated and measured results.

Design and fabrication of a wideband reflectarray antenna in Ku and K bands

The purpose of this paper is design of a wide band single layer reflectarray antenna using a new broadband cell. The proposed cell consists of two parts. The first part is a circular patch and the second one is a ring with some additional stubs, which are attached to the patch and ring in a symmetrical form. The circular patch and ring elements are designed at frequencies of 20 GHz and 15 GHz respectively. In order to increase the reflectarray antenna bandwidth, at first the dimensions of the patch, ring and stubs are optimized to attain uniform phase response in the frequency range from 11 GHz to 20 GHz. Then an air layer is considered under the dielectric substrate. The reflectarray antenna is designed based on this optimized wideband unit cell. A wideband horn antenna is also designed as a feed antenna for the proposed reflectarray structure. The reflectarray antenna with horn are simulated. The 1 dB gain-bandwidth of 4.66 GHz is obtained (27.4% fractional bandwidth) in the frequency band of 14.72 GHz to19.38 GHz. Finally, the reflectarray antenna is fabricated and tested. It can be seen that there is a good agreement between simulation and measurement results.

Compact wideband dual circularly polarized L‐shaped slot antenna

AbstractA wideband dual circularly polarized (CP) L‐shaped slot antenna with compact size is proposed. The antenna consists of an L‐shaped slot, two asymmetric microstrip feedlines and perturbed stub at the lower left corner of the slot. The initial L‐slot is used to obtain the first CP mode in lower band while the upper CP mode is realized by the orthogonal feedlines. Then, additional stub is also introduced to widen the axial ratio (AR) bandwidth. The proposed antenna with an area of 24 × 24 mm2 was fabricated and measured to demonstrate the final design. The L‐shaped slot antenna has a −10‐dB bandwidth of 97.9% (3.6‐10.5 GHz) and a 3‐dB AR bandwidth of 94.9%. In addition, the isolation is better than 12 dB within the CP band.

Miniaturized antipodal tapered slot antenna with lower frequency band extension characteristic

AbstractAn antipodal tapered slot antenna (ATSA) is miniaturized by extending the lower operating frequency range using spidron‐shaped slots and additional impedance‐matching stubs at the tapered radiator. Simulation and measurement results show that the electrical size of the antenna, or the lowest matching frequency, is reduced by 56.4% when compared to a conventional ATSA with the same physical dimensions. The realized gain is also improved in the newly matched low‐end operating frequency.

A novel microstrip bandpass filter with an elliptic-function response using improved dual-stub resonator

In this article, a new microstrip bandpass filter (BPF) with multiple transmission zeros is designed, simulated and measured. The presented filter is based on a composite dual-stub resonator. The modified resonator with dual-bandgap resonant characteristic is composed of the parallel open- and short-circuited stubs, and cascaded by an additional stub line. The location of transmission zeros can be adjusted independently by varying the physical lengths of shunt resonant stub or cascaded stub line, so as to improve the filter selectivity. The proposed filter consists of two identical main transmission lines and three equal-length combined resonators with different length ratios between the cascaded section and open-/short-circuited stubs. Finally, a planar BPF with minimum insertion loss 0.65 dB, centred at 2.08 GHz with a 3-dB fraction bandwidth of 26.8% and six transmission zeros is implemented and verified by experiment.

Suppression of Harmonics in Microstrip Filters Using a Combination of Techniques

Existing and newly adapted techniques for suppressing harmonic responses in microstrip filters were combined. Stagger tuning using additional stubs to shift the resonances has been adapted to quarter-wave resonators and extended to the seventh-order spurious response. Suitable resonator overlap provided transmission zeroes to cancel spurious peaks. Coupling capacitor pads acting as shorting stubs have been developed. Spurious responses were suppressed to better than $-{\hbox{33 dB}}$ , up to 6.3 GHz, in a measured filter with 1-GHz center frequency and 42% bandwidth. Suitably placed resistors have depressed the spurious level further to $-{\hbox{50 dB}}$ up to 5.6 GHz, with only 0.07-dB extra passband loss.