Stable End-fire Radiation Patterns Research Articles

Novel filtering and diplexing linear tapered slot antenna with high-selectivity

In this article, a novel filtering and diplexing antenna using a linear tapered slot antenna (LTSA) are demonstrated. To begin, a highly-selective, second order bandpass filter is designed using generalized Chebyshev filter synthesis technique. Filtering and diplexing antennas are realized by co-designing the filter along with a wideband LTSA. The proposed filtering antenna exhibits 3.21% fractional bandwidth (FBW) over (4.29–4.43) GHz, high band-edge selectivity performance with 6 dBi flat in-band realized gain and stable end-fire radiation patterns with a low cross-polarization level of less than -30 dB. Further, a diplexing antenna with good bandpass filtering characteristics is also implemented. The design shows FBW of 3.32% (3.55–3.67) GHz and 3% (4.91–5.06) GHz and flat-radiation gain of 5.2 dBi and 5 dBi with sharp roll-off in Tx (lower) and Rx (upper) passbands, respectively. It also demonstrates good out-of-band suppression level of more than 20 dB, end-fire radiation patterns with cross-polarization lower than -27 dB and back-lobes lower than -14 dB for both the passbands. In order to validate their functionality, both the designs are fabricated and the experimental results correlate well with the simulated results.

Dual-band reconfigurable EBG loaded circular patch MIMO antenna using defected ground structure (DGS) and PIN diode integrated branch-lines (BLs)

In this work, a reconfigurable dual-band multiple-input–multiple-output (MIMO) antenna (RDMA) for the fifth generation (5G) 3.5 GHz and industrial, scientific and medical (ISM) 5.2 GHz has been reported. The reported antenna uses the partial ground plane defected ground structure (PGP-DGS) technique and the integration of the pin diode integrated branch lines (BLs) to obtain dual-band operation. Also, the intermediate structure, without DGS operates in wideband to narrowband reconfigurable mode. The operating frequency of the antenna can be tuned to other frequencies by changing the DGS and BLs design attributes. A novel mushroom inspired dual-band electronics bandgap structure is developed and characterized using a dispersion diagram. The proposed EBG is then placed between RDMA to obtain isolation better than −25 dB between closely packed (at λ5G/17.14) antenna elements. The proposed antenna has an acceptable realized gain above 2.5 dBi and a stable end-fire radiation pattern with the main lobe at −45∘.

Design of a Dual-Linearly Polarized Endfire Antenna

In this article, a dual-linearly polarized endfire antenna is proposed with high gain and stable radiation patterns. A double-sided slot array antenna (DSSAA) and a corrugated rectangular metal strip (CRMS) are employed to realize vertical and horizontal polarization (HP), respectively. Omnidirectional radiation pattern is obtained by etching transverse slots on both sides of the top and bottom metallic plates of a cavity. Based on the double-sided slot antenna, a DSSAA is proposed and fed by an air-substrate parallel strip line (PSL) for stable endfire radiation patterns. Then, the top plate of the DSSAA is reused as a CRMS for HP and compact size. To verify this concept, an all-metal prototype was fabricated and measured. Both the simulation and experimental results show that the DSSAA and the CRMS could offer the highest endfire gains of 12.5 and 12.9 dB, respectively, within a footprint of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.47\lambda _{0} \times 0.72\lambda _{0} \times 0.13\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the center frequency). Moreover, an overlapping bandwidth of 7.6% is realized with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert &lt; -10$ </tex-math></inline-formula> dB, gain variation less than 3 dB. This work may provide useful references for designing dual-polarized endfire antennas with stable radiation patterns, high gain, and compact size.

Compact UWB Vivaldi Tapered Slot Antenna

In this paper compact Ultra Wideband (UWB) Vivaldi Tapered Slot Antenna (VTSA) is designed simply by changing its Microstrip to Slot line (M/S) transition. To explain the effect of transition’s shapes on the size and the performance of the UWB VTSA, four models (A–D) with detailed parametric studies are analyzed, designed, and fabricated. As compared to Model A, in Model D the size (42.9 mm × 29.28 mm = 1256.112 mm2) is reduced by 19.25%, and the bandwidth (10.34 GHz) is enhanced by 24.56%, in addition, it provides 6.51 dBi maximum realized gain, and stable end-fire radiation pattern. The validity of the proposed antennas is proven by hardware measurement results.

Wideband Circularly Polarized 3-D Printed Dielectric Rod Antenna

This article presents a 3-D-printed dielectric rod antenna with wideband circular polarization. The proposed dielectric device comprises two main components: a launching part and a radiating part. The launching part consists of three cylindrical sections with stepped permittivity for wideband impedance matching to the rectangular waveguide feed. The radiating part is a tapered dielectric rod with two helical grooves that generate circular polarization. The experimental results verify that the proposed antenna exhibits a wide impedance bandwidth of 60.3% from 4.05 to 7.55 GHz, a wide 3 dB axial ratio bandwidth of 57.0% from 4.20 to 7.55 GHz, a high realized gain varying within 8.3 and 11.5 dBiC over the whole band, and the desired stable endfire radiation patterns. The 3-D printing technology provides a viable approach to realization of the proposed complicated geometry in a single piece with high accuracy and great flexibility.

Rectangular Dielectric Rod Antenna Fed by Air-Substrate Parallel Strip Line

In this paper, a rectangular dielectric rod antenna fed by an air-substrate parallel strip line is proposed. The dielectric rod has a compact and regular structure, which is easy to fabricate. The matching of the antenna is mainly determined by the parallel strip line, which simplifies the design process. Fed by an air-substrate parallel strip line, the antenna obtains a relatively uniform magnitude distribution on the surface and a moderate phase constant. With the length of 6 wavelengths at the center frequency of 6 GHz, the antenna generates a high measured gain of 16.7 dBi. The measured 1 dB gain bandwidth is about 18.3%. Over the entire operating band from 5.4 to 6.6 GHz, a stable endfire radiation pattern and a good matching are achieved by the antenna.

High-Gain Leaky-Wave Endfire Antenna Based on Hansen–Woodyard Condition

In this letter, a novel high-gain leaky-wave endfire antenna is proposed. By utilizing an air substrate parallel strip line, which is periodically disturbed by the radiating elements, such as the feedline, the phase constant of the antenna approaches the phase requirement of the Hansen–Woodyard (H–W) condition. By optimizing the size of the radiating element, which is dipole element, an approximately constant aperture distribution is obtained by the antenna. Thereby, with the characters similar to the H–W endfire antenna around the center frequency and moderate phase constant over the operating bandwidth, the antenna achieves a high gain, narrow beamwidth, and stable endfire radiation pattern. With the radiating aperture length of two wavelengths, the antenna generates the measured gain of 12.5 dBi at the center frequency of 5 GHz, operating bandwidth of 20.8%, and measured 1 dB gain bandwidth of 16.2%. Fabricated by metal, the antenna may be an attractive substitute for the long-distance communication applications, especially for the systems where cost and power capacity are important.

A Broadband and High-Gain Endfire Antenna Array Fed by Air-Substrate Parallel Strip Line

A broadband and high-gain endfire antenna array fed by an air-substrate parallel strip line is proposed in this communication. It has a simple and planar structure consisting of multiple dipole radiating elements and one parallel strip line. By utilizing the center-fed dipole working between the first and third resonances as the radiating element, the antenna array could obtain stable radiating capability over a broad bandwidth. Fed by an air-substrate parallel strip line working on the TEM mode, the antenna array achieves a moderate phase constant, which is helpful for realizing stable endfire radiation. The radiating element separation is optimized to eliminate the high-order spatial harmonics, ensuring single beam radiation. Fabricated by thin copper plates, the merits of the antenna array include lightweight, low cost, and easy fabrication. According to the measured results, the antenna array has a good match and a stable endfire radiation pattern over the operating band from 4 to 10.5 GHz with the measured gain varying from 10.1 to 13.5 dBi.

A Low-Profile Wideband CP End-Fire Magnetoelectric Antenna Using Dual-Mode Resonances

A low-profile wideband circularly polarized (CP) magnetoelectric (ME) antenna with high-gain and an end-fire radiation beam is proposed in this paper. It consists of a magnetic dipole (M-dipole) and two pairs of printed crossed strips to produce vertically and horizontally polarized E-field components, respectively. With the appropriate combination, the proposed ME antenna exhibits an inherent 90°-phase difference at endfire for these two field components. CP end-fire radiation, therefore, can be achieved. Two techniques using the L-probe coupled feeding structure to excite the M-dipole operating at both the basic ( $0.5\lambda $ -) and higher ( $1.5\lambda $ -) modes for the dual-mode resonances and using two pairs of printed strips with different dimensions for the dual-frequency resonances are introduced to realize the wideband operation. The measurement results show that the wide impedance bandwidth (IMBW) of 2.40–4.24 GHz (1.84 GHz, 55.4%) and 3 dB axial-ratio bandwidth (ARBW) of 2.36–3.86 GHz (1.5 GHz, 48.2%) are achieved. In addition, the stable end-fire radiation patterns with a peak gain of 7.57 dBi are observed over the operating band. The bandwidth for 3 dB gain variation is 2.34–3.97 GHz. Hence, the proposed antenna with its main beam in parallel with the substrate shows the potential for some point-to-point communications such as the radio-frequency identification (RFID) system.

Wideband Fish-Bone Antenna Utilizing Odd-Mode Spoof Surface Plasmon Polaritons for Endfire Radiation

A wideband fish-bone-shaped endfire antenna utilizing odd-mode spoof surface plasmon polaritons (SSPPs) is proposed in this communication. Consisting of a microstrip-to-slotline converter and a differential-mode exciter, the feeding structure of this antenna can excite odd-mode signal on the SSPP structure. The fish-bone-shaped SSPP radiator can realize endfire radiation, which is equivalent to a row of small current sources. A tapering end is introduced to the SSPP radiator, realizing broader upper bandwidth. A prototype of this antenna is fabricated. Measured results exhibit that a wide impedance bandwidth of 70.3% (2.4–5.0 GHz) for $\vert \text{S}_{11}\vert dB is obtained. Stable endfire radiation patterns and low cross polarization below −20 dB are also realized in the desired frequency band. The gain varies from 4.4 to 8.6 dBi within the whole operating band while a radiating efficiency of 90% can be observed. This antenna has a compact size of $1.36\lambda _{c} \times 0.86\lambda _{c} \times 0.012\lambda _{c}$ ( $\lambda _{c}$ is the free-space wavelength at 3.7 GHz).

Development a new wideband substrate integrated waveguide H-plane horn antenna loaded with periodically diamond patches

This paper presents a new wideband Substrate Integrated Waveguide (SIW) H-plane horn antenna. A few rows of diamond patches are printed on the top and bottom side of the dielectric slab at front of the radiating aperture of a conventional horn to improve impedance matching. The proposed antenna is numerically investigated using a software package and a prototype of the antenna is made to validate the obtained simulated results. The measured results show that the introduced antenna provides 22.7% impedance bandwidth, which covers from 20.8 GHz to 26.15 GHz with stable end-fire radiation patterns, while Side Lobe Level (SLL) is lower than −10 dB over the operating bandwidth.

Half‐mode dielectric waveguide antenna fed by a micro‐strip line with air media for endfire radiation

A half-mode dielectric waveguide antenna fed by a micro-strip line with air media is presented. The proposed antenna consists of two dielectric cuboids and an air-substrate micro-strip line. Due to similar modal field configurations, the dielectric cuboids are excited effectively by the micro-strip line, and they work as two half-mode waveguide antennas working on the TM 0 mode. With the length of 6.5 wavelength at the centre frequency of 5 GHz, a measured endfire gain of 12.2 dBi is achieved. The measured 1 and 3-dB gain bandwidths could reach 17 and 46%, respectively. Good matching is obtained over the entire operating band from 3.5 to 6.5 GHz. Compared with the antennas mounted on a large conducting plane, the proposed antenna has the advantages of a high endfire gain, a wide endfire gain bandwidth, and a stable endfire radiation pattern.

All-Metal Endfire Antenna With High Gain and Stable Radiation Pattern for the Platform-Embedded Application

This paper presents a novel high-gain endfire slot antenna array fed by air-substrate microstrip line. It has a simple and compact structure consisting of a copper strip and two copper sheets. Designed based on the slot antenna array, the antenna could be embedded into a large metallic platform. The surface wave above the antenna radiates the energy to free space. Fed by the air-substrate microstrip line, the antenna works on the TEM mode. Therefore, the antenna obtains a suitable phase constant to realize stable endfire radiation pattern and could be designed by a long structure to realize high endfire gain. Because all of the antennas are designed by metal, it has the characteristics of high strength, easy fabrication, and low cost. With the radiating aperture of 3.5 wavelength, the antenna achieves a measured endfire gain of 11.81 dBi. The measured 1 and 3 dB gain bandwidths reach 4.5% and 8.4%, respectively. Good matching and stable endfire radiation pattern are obtained over the entire operating band from 3.75 to 4.15 GHz.

Microstrip-Fed Surface-Wave Antenna for Endfire Radiation

This communication presents a microstrip-fed surface-wave antenna for endfire radiation. The antenna has the advantages of high endfire gain, wide endfire gain bandwidth, and stable endfire radiation pattern. It consists of a microstrip line with air media and a dielectric cuboid. The half-mode dielectric waveguide, which is made up by the dielectric cuboid and the air substrate introduced by the microstrip line, is the radiating structure of the antenna. Fed by a microstrip line, the half-mode dielectric waveguide couples the energy continuously with a moderate phase constant, which is helpful for the antenna to realize a high endfire gain and a stable endfire radiation pattern. With a low dielectric constant, the half-mode dielectric waveguide has a stable radiation performance within a wide bandwidth. With a length of 5.76 wavelength, the antenna achieves a maximum endfire gain of 13.3 dBi at 4.75 GHz. The 1 and 3 dB gain bandwidths of the antenna is 18.1% and 37.8%, respectively. Good matching is obtained from 3 to 6.5 GHz.

Broadband SIW Horn Antenna Loaded With Offset Double-Sided Parallel-Strip Lines

A novel substrate integrated waveguide horn antenna loaded with offset double-sided parallel-strip lines (DSPSL) is proposed in this letter. The severe mismatch between horn aperture and free space leads to narrow impedance bandwidth when the substrate thickness is much smaller than the wavelength (typically less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\lambda _0}$</tex-math></inline-formula> /6). Two groups of periodic offset DSPSL structure are placed in front of the horn aperture, which acts as an impedance transformer to realize smooth transition. Good impedance matching can be easily realized by modifying the constitutive parameters of the offset DSPSL structure. Measured results show that the impedance bandwidth can be improved up to 20.5% from 14 to 17.2 GHz with a low profile less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda _0}$</tex-math></inline-formula> /13. Stable end-fire radiation patterns are obtained across the bandwidth.

A Compact SIW-Fed Dielectric Antenna with Equivalently Tapered E-plane Profile

AbstractIn this paper, a compact substrate integrated waveguide (SIW) fed dielectric antenna with equivalently tapered E-plane profile is proposed and investigated. Firstly, transition from SIW to broadwall-detached SIW (DSIW) is analyzed, which provides basis for designing a compact SIW-fed dielectric antenna. Secondly, in order to realize an effective radiation structure while keeping geometrical size unchanged, a gradually tapered profile in E-plane is realized through perforating air-vias with different diameters into the DSIW. Effect of transition stage(s) is compared to validate the function of equivalently tapered profile. Results indicate the proposed antenna operates with 27.7 % fractional bandwidth ranging from 20.2 GHz to 26.7 GHz. Moreover, stable end-fire radiation patterns can be observed in the whole operating band. Above all, this antenna shows similarity with E-plane waveguide horn antenna but maintains advantage of planar configuration.

A Low-Profile Wideband Surface-Mountable Substrate-Integrated Waveguide Horn Antenna

A low-profile surface-mountable substrate-integrated waveguide (SIW) horn antenna with wideband performance is proposed in this letter. In order to reduce the serious impedance mismatch at the SIW horn aperture resulting from the thin substrate (0.12 λ0), a semi-open SIW horn is designed by gradually detaching upper broadwall while maintaining another one. Furthermore, in order to realize wide bandwidth for the SIW horn antenna, air-vias are drilled into the semi-open horn to realize smooth transition from semi-open horn to free space. Finally, a fabricated prototype is measured, and results indicate that a 35.7% impedance bandwidth ranging from 19.1 to 27.4 GHz and a 31.8% 3 dB gain bandwidth ranging from 19.3 to 26.6 GHz are obtained, respectively. Stable end fire radiation patterns are observed across the operating band.

Design of Compact Air-Vias-Perforated SIW Horn Antenna With Partially Detached Broad Walls

A novel substrate-integrated waveguide (SIW) horn antenna with partially detached broad walls is designed and analyzed. The conventional SIW horn antenna suffers from narrow-operating bandwidth, which mainly results from the mismatch at the horn aperture between the substrate and the free space. However, the detachment of the broad walls makes the left substrate not only act as wave-guiding structure but also impedance transformer, which brings much size reduction in comparison with conventional SIW horn antenna. Moreover, the substrate with graded dielectric constants distributed in the propagating direction is realized through perforating air-vias with different diameters to further improve the radiation performance. Results indicate that the proposed antenna operates from 17.7 to 26.7 GHz with a nearly constant peak-radiating gain between 8 and 9 dBi at end-fire direction. Stable end-fire radiation patterns can be realized in the whole operating band. Above all, the proposed technology makes it compact to design SIW horn antenna of high performance without extra extension after the aperture of the radiating horn.

A Compact Wideband SIW-Fed Dielectric Antenna With End-Fire Radiation Pattern

In this communication, a triangular-shaped dielectric antenna fed by substrate-integrated waveguide (SIW) is proposed and researched. The effect of the extended substrate’s length on performance of the proposed antenna is first researched. In order to reduce sidelobe level (SLL) at high frequency as well as increase the adjustability of the proposed antenna while maintaining its planar structure, air vias are periodically perforated into the loaded substrate to modify the permittivity. The variation trend of modifying permittivity with changing performance of the proposed antenna is studied, followed by analyzing function of the transition stage(s) of the extended substrate. Through optimizing the dielectric length and modifying the diameters of air vias to change the permittivity, the proposed antenna with wide operating bandwidth and low SLL can be realized. Measured results indicate that the proposed antenna works from 17.6 to 26.7 GHz, which almost covers the whole $K$ band. Besides, stable end-fire radiation patterns in the whole operating band are obtained. Moreover, at least 8.3-dBi peak gains with low SLL are achieved as well.

Planar Wideband Loop-Dipole Composite Antenna

A novel planar wideband balanced composite antenna is presented. The proposed antenna consists of a symmetrical dipole and an antipodal loop radiator. The return loss, radiation pattern, and gain of the antenna are numerically and experimentally studied. An impedance bandwidth of 129% (20 log |S11| <; -10dB) from 3.26 to 15 GHz has been obtained. Stable end-fire radiation patterns with good polarization purity and flat gain performances are obtained across the operating frequency range. In addition, the time domain responses of the proposed antenna are investigated. The proposed antenna can be used in compact wireless devices for point-to-point applications.