Feed Line Structure Research Articles

A compact microstrip quint-band bandpass filter using shorted stub-loaded SIRs based on the interdigital feedline structure

ABSTRACT A compact microstrip quint-band bandpass filter (BPF) composed of two pairs of shorted stub-loaded step-impedance resonators (SSLSIRs) with interdigital feedline structure is designed in this paper. The two pairs of resonators are bent and placed back-to-back on the upper and lower sides of the feedline in order to miniaturise the filter. Due to the symmetric structure of the resonators, the even-odd mode analysis method can be used to derive the resonant frequency equations. Based on the simulation, the filter is fabricated on the substrate of Rogers 4350 and measured. The measured S-parameter results are in good agreement with the simulation results. The operating frequencies of five passbands are measured at 2.2/2.8/4.3/5.4/6.7 GHz and the 3-dB fractional bandwidth (FBW) is 12.7/3.8/6.6/3.2/6.9%, respectively. The measured in-band minimal return losses and the insert losses within five passbands are 11/12/13/12/13 dB and 1.7/2.5/2.7/1.5/1.6 dB. Furthermore, the proposed BPF has good frequency selectivity with steep skirt property via the interdigital feedline structure, which yields seven transmission zeros (TZs). The four measured band-to-band isolations among the five passbands are higher than 20 dB. The filter’s total dimension occupies only 0.18 λg × 0.15 λg, where λg represents the free space wavelength corresponding to the centre frequency of the lowest passband.

Design and Simulation of Elliptical Shaped Microstrip Patch Antenna Using HFSS

Abstract: The elliptical patch antenna presents a comprehensive study on the design, fabrication, and performance analysis of an operating at 2.4 GHz, employing FR4 substrate material. The elliptical shape is chosen for its unique radiation characteristics and compact form factor, making it suitable for integration into modern wireless communication systems. The design process involves careful consideration of key parameters, including patch dimensions, feedline structure, and ground plane geometry. Advanced simulation tools, such as electromagnetic simulators, are employed to optimize the antenna's performance, achieving desirable characteristics such as low return loss and enhanced bandwidth. Utilizing FR4 as the substrate material offers several advantages, including costeffectiveness, ease of procurement, and compatibility with standard PCB manufacturing processes. The dielectric properties of FR4 are thoroughly analyzed and incorporated into the antenna design process to ensure accurate simulation results. The proposed elliptical patch antenna has promising applications in various wireless communication systems, including Wi-Fi, Bluetooth, and IoT devices, operating in the 2.4 GHz frequency band. Its compact size and robust performance make it a compelling choice for space-constrained and high-performance wireless communication applications. This contributes valuable insights into the design and optimization of patch antennas, particularly those using FR4 substrates, and serves as a foundation for the development of efficient and cost-effective wireless communication solutions in the 2.4 GHz spectrum.

Dual-band magneto-electric dipole antenna with high-gain for base-station applications

The paper presents the results of a novel high-gain dual-band magneto-electric dipole (MED) antenna. The antenna comprises two pairs of horizontal metal plates of different heights that are excited by a Γ-shaped feedline structure. The antenna is entirely made of metal plates. Compared to traditional MED antennas, the proposed design exhibits dual-band operation with a higher radiation gain whose frequency ratio can be modified by simply adjusting the heights of the two magneto-electric dipole segments. This feature is necessary for cellular base-station applications. The operation and characteristics of the antenna are validated by the measurements. The measured results confirm the proposed antenna achieving fractional bandwidths of 13.31% (801.9–916.2 MHz) and 19.76% (1710.7–2085.7 MHz) for S11 ≤ −10 dB. It has stable unidirectional radiation patterns and optimum radiation gains of 9.2 dBi and 7.8 dBi at the first and second operating bands, respectively.

Wideband Band-Pass Filter Design Using Coupled Line Cross-Shaped Resonator

In this paper, a wideband bandpass filter with a coupled line cross-shaped resonator (CLCSR) is proposed. The proposed bandpass filter is composed of two open-end parallel coupled lines, one short-end parallel coupled line, one branch microstrip line, and the parallel coupled line feed structure. With the use of the even and odd mode approach, the transmission zeros and transmission poles of the proposed bandpass filter are analyzed. The coupling coefficient of the parallel coupled line feed structure is big, so the distance between the parallel coupled line is too small to be processed. A three microstirp lines coupled structure is used to realize strong coupling and cross coupling. This structure also can reduce the return loss in passband and increase the out-of-band rejection. The transmission zeros can be adjusted easily by varying the lengths of the open-end parallel coupled line or the short-end parallel coupled line. The proposed bandpass filter is fabricated and measured. The simulated results agree well with the measured ones, which shows that the design method is valid.

A Miniaturized Design of Dual-band Antenna for Bidirectional Brain Machine Interface Applications

A novel miniaturized printed monopole antenna for ultra-wideband (UWB) bidirectional brain machine interface (Bi-BMI) applications, based on defected feed line and parasitic structures, is designed and tested. The proposed antenna structure consists of a rectangular radiating patch and two inverted L-shaped slots located in the transition distance between patch and feed line, with a meander line parasitic structure in which a resonance frequency with narrow bandwidth nearly to 2.4 GHz and a running fractional bandwidth of more than 100% are provided (3.19–10.63 GHz). Inserting a meander line parasitic structure caused the antenna to resonate in 2.4 lower frequency bands in order to transfer controlling command in BMI application. In addition, by inserting a pair of inverted slots on the feed line and radiating patch’s corners, an excitation has been taken further in the resonance; therefore, a much wider impedance bandwidth is possible to be processed. To illustrate the usefulness of the proposed antenna for BMI applications, the Specific Absorption Rate (SAR) distribution, one of the most important characteristics in the implanted sensors, in the mode of an implanted antenna inside the full head voxel model, under Dura matter, and external antenna with the distance of 20 cm from the implanted antenna, is presented. The proposed antenna has great radiation characteristics, such as very low SAR, high fidelity and almost omnidirectional radiation patterns over the whole band.

THz CMOS On-Chip Antenna Array Using Defected Ground Structure

In this paper, we design a THz CMOS on-chip patch antenna with defected ground structure (DGS) and utilize it to implement a broadband and high gain on-chip antenna array. It is verified from the simulation that the DGS not only can increase the gain and bandwidth of the antenna element, but also can increase the isolation between the antenna elements in the on-chip array. Therefore, it allows the design of the compact 1 × 2 and 2 × 2 on-chip antenna array with high gain and broad bandwidth. The element spacing and feedline structures of the antenna array are designed and optimized by the simulations. The designed antenna element, and 1 × 2 and 2 × 2 antenna arrays are fabricated in a commercial 65 nm CMOS process. In the on-wafer measurement, they exhibit an antenna gain of 3.1 dBi, 7.2 dBi, and 8.2 dBi with a bandwidth of 14.0%, 21.3%, and 28.0% for the reflection coefficient less than −10 dB, respectively, at 300 GHz. This result corresponds to very good performance compared to the reported THz CMOS on-chip antenna array. Therefore, the designed CMOS on-chip antenna element and array using DGS in this work can be effectively applied to build low-cost and high performance THz systems, because they can be fully implemented in a conventional CMOS process without requiring any additional processes or manufacturing techniques.

A dual‐band superconducting filter with a large bandwidth ratio

In this study, we propose a stepped-impedance-stub loaded interdigital capacitor resonator for design of a dual-band band-pass filter with a large bandwidth ratio. The presented resonator has strong and weak couplings in the upper passbands (UPs) and lower passbands (LPs), respectively, so as to form a large upper/lower bandwidth ratio. Adopting a dual-branch phase-matched feedline structure can meet the external quality factors required for the UP/LP. Therefore, these two passbands, defined by their respective center frequencies and bandwidths, can be manipulated independently. A four-pole dual-band example filter with a lower bandwidth of 20 MHz at 1576 MHz and an upper bandwidth of 200 MHz at 2450 MHz is successfully designed on an YBCO/MgO superconducting wafer. The filter exhibits excellent frequency responses. The upper/LPs show insertion losses below 0.07/0.22 dB and return losses above 15.3/15.3 dB. The stopband rejection is better than 57 dB until the first spurious passband up to 6150 MHz (3.9fL).

High diversity gain super‐wideband single band‐notch MIMO antenna for multiple wireless applications

A two-element super-wideband (SWB) MIMO antenna is proposed in this study. A step impedance microstrip feed line structure is introduced to achieve an SWB impedance bandwidth of 185%. This antenna is designed to be circularly polarised at 1.575 GHz (L 1 -band) and 26.0 GHz (K-band) by using closed ring resonator on the radiating patch. The EBG structures are used to improve FBR in lower (1.5-5 GHz) and higher bands (25-35 GHz). The proposed antenna is designed with compact size 55.6 × 50.5 × 1.6 mm 3 on FR-4 substrate including exotic diversity performance. This MIMO antenna is suitable for defence and handheld devices covering GPS/DCS/PCS/UMTS/Wi-BRO/ISM/IRNSS/LTE (M/HB)/BLUETOOTH/IoT/WiMAX/X/Ku/K/Ka-band and it is also suitable for 5G (sub-6 GHz/mm) applications with channel capacity of 11.34 bps/Hz. Simulated results of MIMO antenna like radiated power-based ECC and diversity parameters are also verified experimentally, which are in the acceptable range. Finally, this antenna is tested in a realistic environment for SAR application.

Circularly polarized stacked patch antenna array with enhanced bandwidth for S‐band applications

In this article, a circularly polarized coupled slot 1 × 4 stacked patch antenna array with enhanced bandwidth is proposed for S-band applications. Initially, a patch antenna radiating at 2.79 GHz is designed and maximum energy from feedline to patch element is coupled using two rectangular slots. Whereas, a parallel feedline structure is designed to provide polarization flexibility by creating 0, 90, and 180o phase differences. Then, a truncated patch element is vertically stacked in the design to achieve broader bandwidth of 600 MHz over frequency range from 2.4 to 3.0 GHz. Finally, a coupled slot 1 × 4 array stacked antenna array having feedline line structure to provide 90o phase difference for circular polarization is designed and fabricated for measurements. It is observed that the final design achieved target specification having impedance matching (|S11| (dB) < −10 dB over 2.4 to 3.0 GHz, broad band circular polarization, and 11.5 dBic total gain. Overall, a good agreement between simulated and measurement results is observed.

Compact Tunable Balanced Bandpass Filter With Constant Bandwidth Based on Magnetically Coupled Resonators

In this letter, a compact high-selectivity and common-mode (CM) suppression tunable balanced microstrip bandpass filter (BPF) with constant bandwidth is designed by adopting the magnetically coupled resonators with step-impedance parallel coupling feedline (SIPCF) structure. The desired coupling coefficient $K_{12}$ and external quality factor $Q_{e}$ can be obtained by the mixed coupling between the two resonators and SIPCF structure, respectively. Two differential-mode (DM) transmission zeros (TZs) near the lower and upper passband edges are created by the mixed coupling and source–load coupling, respectively. Furthermore, intrinsic high CM suppression in the DM tunable operating passband can be maintained because of the magnetically coupled resonator structure. Finally, a compact tunable balanced BPF prototype with constant fractional bandwidth of 6.5% is implemented and fabricated. The measured results agree well with the simulated ones.

CPW fed grid dielectric resonator antennas with enhanced gain and bandwidth

Metal embedded grid artificial dielectric resonator antennas (GDRAs) fed by different coplanar waveguide (CPW) feeding techniques at mm-wave frequencies are investigated in detail. GDRAs involve embedding tall nickel metal inclusions in polymethyl-methacrylate (PMMA) using deep X-ray lithography and electroforming, which dramatically increases the effective permittivity of the polymer up to 5-6 times and results in miniaturized antenna structures operating at millimeter-wave frequencies. The options for different coplanar waveguide (CPW) feeding at 22.6-26.6 GHz and 26.6-29.3 GHz are studied by applying a thin 300 μm PMMA layer between the feed layer and metal inclusions of the GDRA to avoid short-circuiting the underneath feed line structures. In addition, this results in a GDRA structure that improves the impedance bandwidth up to 16.26%, while providing a maximum realized gain of 7.2 dBi across the frequency band with excellent broadband patterns and −18 dB cross-polarization levels.

Compact Selective Bandpass Filter With Wide Stopband for TETRA Band Applications

A selective miniaturized bandpass filter with wide stopband for TETRA band applications is presented in this paper. Basic resonator used in the filter construction is an open stub-loaded-short-circuited stepped-impedance resonator, which has the inherent property of having harmonics far from the fundamental mode. The high selectivity of the filter is obtained by virtue of the transmission zeros around the passband. The transmission zeros are generated because of the mixed electric and magnetic coupling between the resonators and the feedline structures. The selective filter has a miniaturized size of $0.078\lambda _{g}\times 0.082\lambda _{g}$ with a wide stopband extended up to 4.91 times the operating frequency.

Multi‐band proximity coupled microstrip antenna for wireless applications

AbstractA novel and simple design of a multi‐band proximity coupled microstrip antenna for operating in the WiFi (2.4–2.48 GHz), WiMAX (3.44–3.53 and 5.25–5.85 GHz), and WLAN (5.15–5.35 GHz and 5.470–5.725 GHz or 5.725–5.825 GHz) bands is proposed. Apart from that, an additional band covering (3.8–4.2 GHz) is achieved, which may be used for fixed satellite communication. The proposed multiband antenna consists of a V‐slotted patch in conjunction with parasitic element, and L‐shaped microstrip line feed structure. Slot in the patch is introduced to reduce the overall size of the antenna and L‐shape feed is used for proper energy coupling to the parasitic element. The simulated gains are 3.47/1.62/0.72/6.22 dBi at 2.44/3.5/3.8/5.5 GHz, respectively, and the antenna shows broadside radiation characteristics. The simulated results are in good accord with the measured results.

60 GHz antenna array for millimeter‐wave wireless sensor devices using silver nanoparticles ink mounted on a flexible polymer substrate

AbstractThis paper demonstrates a mm‐wave high‐gain antenna design that is printed on a flexible polymer substrate using silver nanoparticles ranging from 50 to 200 nm in inkjet printing technology. Specifically, it shows that inkjet technology can leverage to fully fabricated antennas with this technology, where it provides both the characterization and preparation of an antenna. The initial fabrication problem addressed via ink formulation for printing a homogeneous layer with an excellent electrical conductivity. A planar series fed antenna array was analyzed by using the Transmission Line Model with tapering feed line structure. The excitation coefficients in both E and H planes follow a uniform aperture distribution. The realized antenna has 24 dBi gain, the side‐lobe level of elevation direction at the center frequency is lower than −15dB. In combination with the planar antenna structure, polymer substrate, and inkjet printing enables the production of structures with high gain that are widely applicable for mm‐wave wireless sensors and portable communication devices.

A high-temperature superconducting filter with controllable transmission zero**Project supported by the National Natural Science Foundation of China (Grant No. 61371009) and the Chinese Ministry of Science and Technology (Grant No. 2014AA032703).

This paper presents a novel microstrip feedline structure to introduce an extra and controllable transmission zero (TZ) with high rejection for a narrowband filter. This structure loads a reconfigurable capacitor at the end of the input feedline without changing the main structure of the filter. The capacitor is recognized by a 2-bit inter-digital capacitor array. The asymmetrical microstrip feedline structure is suitable for multiple-pole filter designs. A low-loss six-pole high-temperature superconducting bandpass filter with a reconfigurable TZ is designed and fabricated. The center frequency of the filter is 5.22 GHz with TZ at the lower stopband. The TZ can be tuned among four different states. The out-of-band rejection at the TZ frequency is higher than 90 dB, and the insertion loss is lower than 0.92 dB. The measured results are consistent with the simulations.

Compact tri-band bandpass filter using asymmetric stub-loaded stepped-impedance resonator with multiple transmission zeros

In this paper, a tri-band bandpass filter (BPF) using asymmetric stub-loaded stepped-impedance resonator (SL-SIR) is presented. The asymmetric characteristic of SL-SIR broadens degrees of freedom for three controllable modes design. Also, the coupling coefficients (Mij) and the external quality factors (Qei) at each passband of the filter can be independently adjusted by the proposed mixed-type feedline structure. Besides, multi-transmission zeros are produced to improve the isolation and selectivity of the passbands. Finally, a tri-band BPF is operated at 1.9 GHz (time division long term evolution – TD-LTE band), 3.2 GHz (worldwide interoperability for microwave access – WiMAX band), and 5.8 GHz (wireless local area networks – WLAN band) and their insertion loss are 1.03, 0.94, and 1.27 dB, respectively. The measured results of the fabricated tri-band BPF exhibit good agreement with simulated results.

Four-Arm Spiral Antenna Fed by Tapered Transmission Line

This letter presents a four-arm Archimedean spiral antenna with a novel integrated tapered transmission line feed structure. The center-fed spiral antenna consists of a radiation region with an Archimedean spiral configuration and a transmission region that comprises four spiral-shaped transmission lines with exponentially decreasing widths. The tapered transmission line, acting as an impedance transformer, provides a broadband matching network between the 50-Ω input impedance and the higher impedance of the radiation region. Using this design, a mode-1 spiral antenna attains a return loss of greater than 15 dB and a 3-dB broadside axial ratio throughout the 0.8–3-GHz band. The fabricated antenna demonstrates good agreement between the simulated and measured results.

Compact dual-band antennas with large frequency ratio and bandwidth enhancement for wireless applications

In this paper, compact single-feed dual-band antennas for different wireless applications are proposed. First, a dual-band antenna with a comparatively large frequency ratio of 2.58 is designed. Then, a novel dual-band antenna is introduced in order to enhance the upper frequency band. The technique consists of modifying the feed line structure, which leads to a 9.23% of impedance bandwidth at the central frequency of 6.5 GHz instead of 2.06%. The designed antennas are fabricated and tested in the laboratory and in a small anechoic chamber in order to measure their reflection coefficient, gains, and efficiencies. Good agreement between simulated and measured results is obtained. The designed antennas are particular because they have low profile, very simple single-feed technique, can be designed for large frequency ratios, and also the bandwidth can be clearly enhanced. Therefore, they can be used for different wireless applications.

High-Temperature Superconducting Bandpass Filter Using Asymmetric Stepped-Impedance Resonators With Wide-Stopband Performance

This paper presents a wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF). The filter is implemented by the asymmetric stepped-impedance resonators (SIRs) with only one step discontinuity, which leads to low loss and compact size. With varied characteristic impedance ratios and length ratios, the diversity of asymmetric SIR has been studied, and the spurious resonant-mode responses are discussed. Adopting different asymmetric SIR units operated at the same fundamental frequency $f_{0}$ (2.4 GHz), its wide upper stopband can be realized by dispersing the higher order spurious resonant modes of these resonators. Furthermore, a modified input/output (I/O) feedline structure has been utilized to enhance the stopband performance. Finally, a fourth-order HTS BPF for wireless application is designed and fabricated on a MgO wafer with double-sided YBCO films. The filter measurement shows excellent performance with 0.05-dB minimum insertion loss and better than −20-dB rejection level in the stopband up to 10.46 GHz (about 4.4 $f_{0}$ ). In addition, the size of the HTS filter is 12.45 mm $\times$ 23 mm (i.e., 0.256 $\lambda_g$ by 0.472 $\lambda_g$ , where $\lambda_g$ is the guided wavelength at the center frequency).

Metal Mountable Ladder Feed Line UHF-RFID Tag Antenna

&lt;p&gt;A microstrip dipole UHF-RFID tag antenna that can be mounted on metal object is presented in this paper. The antenna, which has a very simple structure without any shorting pin and shorting plate, is composed of ladder feed line, rectangular loop, capacitive tip-loading and T-match structure. The insertion of ground plane in the tag antenna design reduces the negative impact of metal object to the performance of the tag antenna. The tag is designed to operate in the Malaysia frequency range with the center frequency of 921 MHz. The performance of the tag is evaluated through simulation and measurement in terms of impedance matching, antenna reflection coefficient and tag reading range. The measured reading range obtained when the tag is in free air and on metal object is 2.3 m and 2.2 m respectively.&lt;/p&gt;