Offset Feed Research Articles

Wideband Radiation From an Offset-Fed Split Ring Resonator With Multi-Order Resonances

In this letter, we exhibit the design of an ultrawideband antenna, covering WLAN, WIMAX, and the forthcoming 5G communications band, i.e., from 2.3 to 6.1 GHz, by using the natural oscillating modes of a split ring resonator (SRR). The antenna is composed of a radiating SRR and a coplanar waveguide feeding structure. The excitation of multiple resonances on a single SRR is achieved through an offset feeding technique. In order to improve the impedance bandwidth of the proposed antenna, the width of the SRR's branch is tuned, and several slits are carefully designed on the ground region. Detailed analysis reveals that the proposed antenna can not only radiate in an ultrawideband but also resonate at its lowest mode of a high quality. This peculiar property indicates that the antenna would be a good candidate for incorporating sensing and communication applications.

A Simple Design of Compact Dual-Wideband Square Slot Antenna With Dual-Sense Circularly Polarized Radiation for WLAN/Wi-Fi Communications

A novel compact dual-wideband, dual-sense, circularly polarized (CP), square slot antenna with the simple structure is presented in this communication. The right-hand circular polarization in the +z-direction for the lower frequency is mainly realized by an inverted L-shaped strip, and the left-hand circular polarization in the +z-direction for the upper frequency is mainly achieved by an offset feed structure. A parasitic matching stub is helpful to improve the input impedance matching. The overall dimension of the prototype is only $50 \times 50 \times 1~\text{mm}^{3}$ . An optimized antenna is fabricated and measured. The measured 10 dB return loss bandwidth is 111% (1.82–6.36 GHz). Its measured 3 dB axial-ratio bandwidths in the broadside direction are 55% (1.91–3.36 GHz) at lower band and 29.3% (4.78–6.41 GHz) at upper band, which can fully cover all the wireless local area network and wireless fidelity bands. What is more, this antenna has stable antenna gain and good radiation patterns within these two CP bands.

Offset fed slot antenna for broadband operation

In this paper, a microstrip fed rectangular slot antenna with wideband characteristics is proposed. Both the impedance and radiation characteristics of the proposed antenna are presented. It is shown that a properly offset feed can give a dual resonance nature, which can be optimized to enable wideband behavior. From HFSS simulation, an impedance bandwidth (-10 dB) of 49.92 % (2.51 GHz to 4.18 GHz) about the center frequency of the band is obtained. Prototype measurement demonstrates a bandwidth of 45.30 % (2.51 GHz to 3.98 GHz). Simulated radiation patterns show bidirectional behavior, which is stable in the band with a peak gain of 5.7 dBi and a gain variation of 2 dBi.

An offset CPW-fed triple-band circularly polarized printed antenna for multiband wireless applications

An offset coplanar waveguide (CPW)-fed triple-band circularly polarized tilted asymmetrical E-shaped printed antenna for multiband wireless applications is presented in this paper. The antenna mainly consists of a tilted asymmetrical E-shaped patch and excite by a 50 Ω offset CPW feed line using a transformer for impedance matching to generate wide quad operating bands. By properly embedding rectangular slots in the tilted asymmetrical E-shaped patch and triangular stubs loaded modified CPW ground plane, the antenna reveals triple-band circular polarization (CP) features. Numerical analysis and experimental validation of the antenna structure have been carried out and results are presented. The mechanism of triple-band CP operation, analysis of surface current distributions, design procedure, and parametric study of the design is discussed in details. It is well suited for the application of UMTS-2100, 3.5/5.5 GHz WiMAX, 5.2/5.8 GHz WLAN, ITS, downlink of X-band satellite communication, and ITU 8 GHz bands.

Gap bridging of 6061 aluminum alloy joints welded by variable-polarity cold metal transfer

6061 aluminum alloy joints at different gap widths were welded successfully with the same parameters (except wire offset). Bead formation, microhardness, shear strength, fracture characteristic, and forming mechanism were investigated. The results indicated that the shear strength of the joints decreased with increasing gap width. The gap width had little impact on the hardness of joints, and the fracture mode of the samples at different gap widths was ductile fracture. The wire offset and wire feeding speed had significant effects on the bead formation. The results of high-speed video and current waveform analysis showed that the variable-polarity cold metal transfer (CMT) Advance (C + A) process had better gap-bridging ability due to a lower heat input and higher deposition rate compared with the conventional CMT mode.

Low-Profile Two-Arm Inverted-L Antenna Design for Vehicular HF Communications

Design of an electrically small, low-profile vehicular on-the-move (OTM) wideband high frequency antenna with 24 kHz instantaneous-tuned bandwidth is discussed for near vertical incidence skywave (NVIS) communications. Improvement in performance is obtained by applying multiarming and offset feed antenna modifications. These allow for attaining the desired gain >−20 dBi at 3 MHz with a lower profile compared to traditional OTM 3 kHz bandwidth antennas. Specifically, the addition of the second arm improves the bandwidth, whereas NVIS gain is enhanced by offset feeding. The electrical dimensions of the proposed two-arm design over the platform are $\lambda /13 ~(\text {L}) \times \lambda /30 ~(\text {W}) \times \lambda /400$ (H) at the lowest frequency of operation. Antenna performance and achieved benefits under the condition of mechanical breakdown are also discussed. The scaled prototype of the proposed antenna mounted on a selected vehicular platform is built using additive manufacturing. Measurement results agree well with simulations thereby verifying the design procedure and all the discussed findings.

Optimization of an Offset Receiver Optics for Radio Telescopes

The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam’s edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure.

WITHDRAWN: Design and development of compact microstrip patch dual band antenna for wireless applications

Abstract In this paper, a novel dual band microstrip patch antenna based on composite patch antenna and radiating part. By selecting a suitable offset feed position, it is feasible to provide 50 Ω characteristic impedance and thus making better impedance matching. The proposed antenna has been improved broader bandwidth by using RT Duroid substrate. The radiating part is plays a important role in creating a lower operating band (2.45 GHz) in addition to achieve miniaturization. The proposed antenna has to be fabricated with RT/Duroid substrate and dimensions of 19 × 22 × 0.8 mm. The measured −10 dB bandwidth of 200 MHz at 3.45 GHz and 990 MHz at 5.45 GHz, which is quite useful for Industrial, Scientific and Medical (ISM) and WLAN applications.

Design and Development of Compact Microstrip Patch Antenna for Wireless Applications

In this paper, a novel dual band microstrip patch antenna based on composite patch antenna and radiating part. By selecting a suitable offset feed position, it is feasible to provide 50Ω characteristic impedance and thus making better impedance matching. The proposed antenna has been improved broader bandwidth by using RT Duroid substrate. The radiating part is plays a important role in creating a lower operating band (2.45 GHz) in addition to achieve miniaturization. The proposed antenna has to be fabricated with RT / Duroid substrate and dimensions of 19 × 22 × 0.8 mm. The measured -10 dB bandwidth of 200 MHz at 2.45 GHz and 990 MHz at 5.45 GHz, which is quite useful for Industrial, Scientific and Medical (ISM) and WLAN applications.

Investigation of microstrip‐fed low‐profile broadband circularly polarized rectangular dielectric resonator antennas

AbstractA microstrip‐fed low‐profile broadband circularly polarized rectangular dielectric resonator antenna (RDRA) suitable for WLAN applications based on IEEE 802.11.a standards was designed and tested. In addition, a new iterative method for the estimation of resonance frequency with the consideration of the effect of the substrate was investigated in this article. The RDRA exhibits broadband and circular polarization (CP) by utilizing the asymmetrical offset feeding mechanism to excite two orthogonal degenerate modes ( and ). The RDRA provides the impedance bandwidths (|S11| < −10 dB) of 10.2% and the axial ratio (AR) bandwidth (AR < 3 dB) of 1.8%. Good agreements between the simulated and measured results have been obtained.

A compact dual frequency double U-slot rectangular microstrip patch antenna for WiFi/WiMAX

This letter presents design of a compact (0.32λg × 0.15λg) dual frequency rectangular microstrip patch antenna for wireless applications. Dual frequency operation is achieved by inserting a pair of symmetric face-to-face U-slots, which results in excitation of and modes, on a narrow radiating patch upon appropriate offset coaxial feeding. In addition to compactness, the embedded slots provide two degrees of freedom for tuning the resonant frequencies independently. A physics based approach is adopted in deriving empirical expressions for lower and upper resonant frequencies by analysing the surface current distribution on the patch. Parametric studies of the slots' dimensions show that it can cover the frequency ranges from 1.72 to 4.1 GHz without giving rise to any grating lobes. This antenna geometry can be used for various standards like GSM (1800–1900 MHz), DCS (1710–1880 MHz), PCS (1880–1990 MHz), UMTS (1920–2170 MHz), LTE2300 (2300–2400 MHz), WiFi (2400–2480 MHz), WiMAX (3467–3521 MHz), etc. by appropriately choosing slot parameters. Many typical designs of the proposed antenna geometry are possible with different slot dimensions according to the requirement of these bands. One such design which supports WiFi and WiMAX has been fabricated on FR4 substrate. The measured results for this antenna are also included here.

Three-Element MIMO Antenna System With Pattern and Polarization Diversity for WLAN Applications

In this paper, a three-element compact multiple-input-multiple-output (MIMO) antenna system having both pattern and polarization (linear/circular) diversity is proposed. The proposed MIMO system consists of a chamfered-edge square patch antenna with an offset feed that provides circular polarization in broadside direction. Furthermore, two printed dipole antennas are placed adjacent to it for providing linearly polarized endfire radiation. The three-element MIMO antenna system exhibits good isolation (>15 dB) without the use of any separate decoupling structure. The match between the simulated and measured results on fabricated antenna prototype suggests that the proposed antenna can be a good candidate for pattern-and polarization-diversity MIMO applications in the 5.8-GHz WLAN frequency range.

A <inline-formula><tex-math notation="LaTeX">$4 \times 4$</tex-math></inline-formula> Dual Polarized mm-Wave ACMPA Array for a Universal mm-Wave Chipless RFID Tag Reader

A 4 × 4 dual polarized (DP) aperture-coupled microstrip patch antenna (ACMPA) array for a universal millimeter (mm)-wave chipless RFID tag reader is presented. The mm-wave DP ACMPA array is capable of reading all types of frequency domain-based chipless RFID tags (linearly polarized, orientation insensitive, cross-polarized (CP), and DP) within its operating frequency bandwidth. The developed antenna is operating over the 22-26.5-GHz frequency band with 16-dBi realized gain and over 35-dB isolation. A systematic approach is followed up for designing the mm-wave antenna array where, first, a single antenna element is designed. Then, a 1-32-way corporate feed network for the dual offset feeding of cross slots is designed using multistage power dividers. After that, the 4 × 4 mm-wave DP ACMPA array is designed, optimized, fabricated, assembled, and tested. Simulation and measurement results for different development stages of the array are described in detail. Finally, the assembled antenna is used for measuring 10 orientation insensitive (OI) thermal printed mm-wave chipless RFID tags on a paper substrate to validate its functional accuracy. The developed mm-wave DP ACMPA array with high port-to-port isolation can be used in a universal commercial mm-wave chipless RFID tag reader due to its low cost, high gain, and low-profile structure.

Fast Analysis for Aperture Efficiency and Radiation Patterns of Reflectarray Antennas

In the design procedure of the reflectarray antennas, the fast analysis of the aperture efficiency and radiation patterns is necessary before manufacture to forecast the antennas performance proximately. The fast calculation of the aperture efficiency and radiation patterns of reflectarray antennas is presented in this paper. A more general approach is introduced to calculate the spillover efficiency of a reflectarray. Meanwhile, the taper efficiency of the reflect-array is calculated with a unified set of equations. Two different fast approaches of the radiation patterns analysis-array theory and aperture field are described, and the discrete Fourier transform is applied to speed up the computational speed. On the basis of these derivations, numerical results of a Ku band reflectarray with offset feed are presented to show the performance of these approaches, and to provide the guidelines for designing and analyzing reflect-array antennas.

복합재 하니콤 코어의 형상가공 특성에 관한 실험적 연구

A composite honeycomb core is widely used for lightweight aircraft materials. However, the composite honeycomb core coupled with metal-cutting machining processes does not make a very good match. This paper describes an experimental study of the shape-machining characteristics of a composite honeycomb core, in which a five-axis gantry machine is used. The experimental conditions of the offset allowance, tooling condition and feed rate were applied. The shape machining characteristics of a flat surface, a vertical surface, and a concave surface are evaluated by comparing the machining shape and burr characteristics.

Bandwidth Enhancement Techniques for Printed Rectangular Monopole Antenna

ABSTRACTPrinted rectangular monopole antennas (PRMAs) have been investigated for increasing bandwidth. PRMAs with single, dual and triple microstrip line feed have been studied to show the effect of feed network to enhance the impedance bandwidth. Systematic study has been carried out to show the effects of patch width variation along with its offset feed, which leads to wideband antenna characteristics. The increase in bandwidth in the case of off-centred feed PRMAs is from 1.7 GHz (1.4–3.1GHz) to 3.9 GHz (1.3–5.2 GHz); this is more than 2.2 times as compared to single-centre-feed PRMA. Experiments have been carried out to verify the simulation results, which are in good agreement.

Design and analysis of bidirectional deployable parabolic cylindrical antenna

A bidirectional deployable parabolic cylindrical reflector for an L-band synthetic aperture radar is presented in this study, in which a self-deployed antenna with low weight was designed. The antenna consists of four curved surfaces formed from thin sheets of composite materials connected by hinges along the edges, and the reflective surface is provided by the front surface. The edge profiles of connecting lines were obtained through geometric analysis. A scaled model, including design and manufacture, was demonstrated to validate the process from the folded state to the fully deployed state. The non-contact synchronous vision measuring method was used to test the basic frequency of the scaled model, and the test results gave the verification of the analyses. Compared with the existing unidirectional deployable antenna, this new type of bidirectional deployable antenna can be applied to larger-size antennas and has better performance because the glass-woven tape connections were substituted with more reliable hinges. Static, modal, harmonic response, and transient response analyses of the full-sized reflector structure were modeled with the commercial finite element (FE) package ABAQUS. The modeling techniques were developed to predict the structural dynamic behavior of the reflector and the results showed that the first natural frequency was 0.865 Hz, and the reflector structure had good stiffness in three directions. This proposed structure has very high stiffness-to-mass ratio because of its hollow solid construction. A preliminary simulation of radiation properties of the parabolic cylindrical antenna, fed by an off-set linear feed horn array, was conducted to obtain the radiation pattern of the feed and the reflector.

Reduction of the In-Band RCS of Microstrip Patch Antenna by Using Offset Feeding Technique

This paper presents a method for implementing a low in-band scattering design for microstrip patch antennas based on the analysis of structural mode scattering and radiation characteristics. The antenna structure is first designed to have the lowest structural mode scattering in a desired frequency band. The operating frequency band of the antenna is then changed to coincide with that of the lowest structural mode scattering by adjusting the feed position on the antenna (offset feeding) to achieve an antenna with low in-band radar cross section (RCS). In order to reduce the level of cross polarization of the antenna caused by offset feeding, symmetry feeding structures for both single patch antennas and two-patch arrays are proposed. Examples that show the efficiency of the method are given, and the results illustrate that the in-band RCS of the proposed antennas can be reduced by as much as 17 dBsm for plane waves impinging from the normal direction compared to patch antennas fed by conventional methods.

MILLIMETER-WAVE OFFSET FRESNEL ZONE PLATE LENSES CHARACTERIZATION

Fresnel Zone Plate Lenses (FZPLs) are transparent-opaque lenses that filter the desirable phase. The centred Fresnel lenses have a strong back radiation towards the feed. In order to solve this drawback, offset feeding or offset pointing lenses are used. In this work, both offset FZPLs are studied using an optical physics method and experimentally characterized in the millimeter band. Two prototypes have been manufactured and measured, presenting a narrow beamwidth. The characteristics of pointing of this beam are studied depending on the feed gain. This work shows the pointing characteristics of the lenses, simply moving the lens in a plane.

A High-Efficiency Ku-Band Reflectarray Antenna Using Single-Layer Multiresonance Elements

A broadband single-layer reflectarray antenna composed of multiresonance square-rings elements is presented. The element is optimized to provide a linear phase curve and wide-enough phase variation. To avoid feed blockage, an offset feed configuration is used, and wave incident angle is considered to determine the appropriate element parameters that provide desirable phase shift on the antenna surface. The aperture efficiency of the antenna is maximized by optimizing feed position and characteristics. A 480-element antenna is fabricated and measured. The measured results show 1-dB gain bandwidth of 17% and radiation efficiency of 66% at 13.5 GHz center frequency.