Iet Microwaves Antennas & Propagation最新文献

A 1 × 4 magneto-electric dipole (ME dipole) antenna array for 77 GHz automotive radar is proposed. The ME dipole is fed by a fork-shaped microstrip line coupling through a dog-bone slot. To meet the requirements aimed at automotive radar applications, the beamwidths of the proposed antenna are well-designed. Specially, a method of adding passive elements on both sides of the array is proposed to increase the 3 dB beamwidth from ±34° to ±52° in azimuth. Additionally, in elevation, a 3 dB beamwidth of ±10° is achieved by designing the spacing between array elements. Moreover, based on low-loss printed circuit board substrates, radiation efficiency of the proposed array can reach approximately 90% at 77 GHz. Furthermore, a 4 × 4 array is established by arranging four 1 × 4 subarrays spacing 1.95 mm (half a free-space wavelength at 77 GHz) to study the interactions between subarrays for multiple input multiple output scenarios. A 1 × 4 and a 4 × 4 antenna prototypes are fabricated and measured to validate the correctness of this design. The results show that the proposed antenna is an eligible candidate for the medium- and short-range automotive radars.

A novel design of a high-frequency multiband with a circular polarisation antenna based on a four-patch antenna system consolidated with an Archimedean spiral antenna for CubeSat applications. The geometry and size are compatible with the CubeSat standard structure dimensions of 10 × 10 cm². The antenna consists of a spiral antenna in the middle of four patch antennas surrounding it; the first antenna structure consists of two sets of two orthogonal identical patch antennas with a 90° phase shift to cover the band from 1.55 to 1.94 GHz at L-band, 2, 2.1, and 2.3 GHz at S-band, the second antenna is an Archimedean spiral antenna to cover all C-bands, all X-bands, all Ku-bands, all K-bands, and from 26 to 29 GHz at Ka-band. The measured results show that the reflection coefficients (S₁₁) and (S₂₂) achieve < −10 dB and the axial ratio achieves <3 dB, with a reference impedance of 50 Ω. The simulated and the measured results give a better agreement.

Ever-increasing bandwidth requirements from various industries drive the need for the ever-increasing bandwidth of antennas used for testing. Broadband Double-Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state-of-the-art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial-to-ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber-filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented.

Radio wave propagation modelling in railway environments is of fundamental importance in designing reliable train communication systems. Parabolic equation (PE) methods have been widely applied to the modelling of wave propagation in tunnels due to their high computational efficiency and fidelity. The finite-difference parabolic equation (FDPE) and the split-step parabolic equation (SSPE) methods are two commonly used approaches to solve PE numerically. However, the relevant literature is still missing a comprehensive study of their performance, including the selection of parameters such as discretisation steps and the tradeoffs involved in terms of their accuracy and efficiency, especially as current wireless systems shift to high frequencies. In this study, a systematic analysis of the error and computational complexity of the FDPE and SSPE methods for radio wave propagation modelling in tunnels is provided. Guidelines for the choice of their parameters are provided, and their performance is demonstrated through both numerical examples and experimental measurements in actual tunnel cases.

An antenna array design method of trade-off between high gain and low profile is proposed. A high-gain circularly polarised (CP) substrate integrated waveguide (SIW)-fed magnetoelectric dipole (ME-dipole) antenna array with metallic radiating structures is presented for millimetre-wave (MMW) applications. The CP antenna element comprises a set of horizontally and vertically metal plates and a metallic cavity that is excited by an X-shaped coupling slot etched on the broader side of SIW. The metallic cavity is designed to improve the gain and axial ratio (AR) performances. Utilising this antenna element, a proof-of-concept is established through the design of a 2 × 2 subarray and a 4 × 4 array. The fabricated 4 × 4 CP antenna array has a measured impedance bandwidth of 6.1% (36.4–38.7 GHz), with |S₁₁| ≤ −10dB. The measured 3dB AR bandwidth is 5.4% (36.0–38.0 GHz). The measured maximum gain achieved is 19.1 dBic. The height of the proposed array is 0.74λ₀ which is larger than the heights of typical SIW-based microstrip arrays (0.1–0.4λ₀) and lower than the heights of metallic arrays (larger than 2λ₀).

A planar antenna with dual-linearly polarised end-fire radiation is proposed. A tapered double-sided symmetrical spoof surface plasmon polariton (SSPP) transmission line (TL) with tilted unit cells is proposed. The SSPP TL can operate in two types of first high-order modes: the first high-order even mode and the first high-order odd mode. A two-port feeding structure is designed to feed the SSPP TL. When the signal is fed from port 1, the energy travels through the substrate integrated waveguide and eventually excites the even mode on the SSPP TL, leading to vertically polarised radiation. Conversely, when the signal is input from port 2, the energy travels through the stripline-to-slotline transition and eventually excites the odd mode on the SSPP TL, generating horizontally polarised radiation. According to the measured results, a 54.6% overlapping bandwidth is obtained. The horizontal and the vertical polarisations achieve a maximum gain of 14.7 and 12.2 dBi, respectively.

A reconfigurable inductorless negative-refractive-index transmission-line (NRI-TL) metamaterial phase shifter for sub-6 GHz 5G antenna applications is proposed. The design consists of a microstrip transmission line loaded both in series and in parallel with varactor diodes to provide continuous tuning of the phase of the transmitted signal by varying the bias voltage applied to the varactors, without the need for variable inductor components. The total measured differential phase shift is 190° at 3.2 GHz, with a measured insertion loss of 1.5–2.7 dB in the frequency range of 3.2–3.6 GHz, when the biasing voltage of the varactors is varied between 0 and 7 V. The total size of the microstrip NRI-TL phase shifter is 19.4 mm × 24 mm. The proposed reconfigurable phase shifter has been incorporated into the feeding network of a two-element antenna array to demonstrate its use in beam-steering applications. The measured results for the reconfigurable array show good impedance matching between 3 and 3.35 GHz for all biasing values, allowing continuous beam steering over a scanning range of 60°.

A low-cost W-band leaky-wave antenna with two-dimensional scanning capability is presented. By using the low-loss transversal long-slot array structure with a single-layer parabolic reflector, the antenna realizes a passband from 85 to 102.8 GHz with Voltage Standing Wave Ratio <2. This antenna has a backward radiation direction, which changes with frequency in one dimension, and with the feeding wave front direction in the other dimension. The maximum sidelobe is measured to be −14.2 dB, 5 dB lower compared to the previous-published longitudinal long-slot array. A low-cost, low-loss, low-profile design is provided for W-band 2-D beam scanning, with backward scanning capability, which is easy to fabricate and could be used for high-solution sensing and point-to-point communications.

Silicon-based packaging is highly suitable for miniaturised and cost-effective integrated systems. However, traditional silicon-based antenna-in-package (AiP) has disadvantages, such as high loss, low efficiency and narrow bandwidth. A glass-silicon active package system architecture is proposed. Its active part is integrated on a silicon substrate, while the antenna array in the package system is made of glass, which has high radiation efficiency. The proposed antenna structure is an H-type aperture-coupled microstrip patch antenna. The authors use a ball grid array to form cavity and two shielding structures to improve the scanning performance of the array. Furthermore, by adding grounding points, the resonance singularity within the shielding structure is eliminated. A test array, composed of 8 × 8 elements was fabricated for the purpose of validating the design. It can achieve wide-angle scanning greater than ±60° and bandwidth of 29%. This design can be applied for ka-band communications and radar systems.

A gain enhancement technique in pyramidal horn antenna using a slot type band pass frequency selective surface (FSS) is presented. The horn antenna without FSS has achieved a measured gain of 10.5 dBi at 10 GHz, while the antenna with the single layer slotted FSS yields an enhanced measured gain of 14.2 dBi (an improvement of 3.7 dB or 134%). Conventionally, such a gain enhancement would 5 times increase in its dimensions (flaring). However, the authors achieve the same with only 2 times increase in dimensions. Another interesting value addition of the proposed idea is that an FSS sheet can be added to the existing horn antenna to increase its gain without altering the antenna itself. Such a scheme is highly beneficial in strategic applications. The proposed gain enhanced horn antenna can be recommended to be utilised in several X-band applications, such as radar systems (weather, surveillance, traffic control and military), satellite communications and point–point microwave links that require high gain and small form factor.