Iet Microwaves Antennas & Propagation最新文献

Backscatter communication (BackCom), the underlying technology for modern-day Radio Frequency Identification, has been studied as a promising solution for future ultra-low power Internet-of-Things (IoT) applications. Its development has pushed the performance boundaries significantly, in terms of communication distance, data transmission rate, and power consumption. An up-to-date review of one branch of BackCom systems, namely Ambient BackCom, which utilises the already available ambient signals, instead of a dedicated radio frequency carrier in most of the BackCom works, to establish BackCom links is conducted. This further reduces the cost and complexity of the system and opens an opportunity for mass deployment.

A novel 2-D beam steering technology using a Fabry–Pérot antenna with a liquid-based reconfigurable metasurface is presented. The antenna employs a reconfigurable partially reflecting surface to regulate phase distribution and adopts a microstrip antenna as feed to realise 2-D beam steering. The antenna beam can be tilted in four different directions by injecting liquid metal into the specific area of the microfluidic channels embedded in the metasurface. Moreover, the antenna has a simple and compact structure with a low profile. A prototype is manufactured, and good agreement between simulated and experimental results verifies the correctness of the design. The measured results of the manufactured antenna prototype demonstrate that the main beam tilts to maximum values of ±15° and ±28° in the yoz and xoz planes, respectively, between 9.5 and 9.7 GHz.

The authors propose miniaturised single-layer bandpass filters (BPFs) by utilising a kind of new triple- and quad-mode patch resonators. The triple-mode resonator consists of a shortened square patch and a loaded metallic via at the centre. Characteristics of the new resonator are studied based on the mode analysis, and the first three resonant modes can be controlled well by changing the length of four via arms and the width of the open slot. Thus, a three-pole BPF can be designed with the new triple-mode patch resonator. To realise higher-order filter, two triple-mode patch resonators are cascaded to design a six-pole BPF. Moreover, an inter-digital slot-line is further etched on the triple-mode patch resonator to achieve a new resonant mode, and a quad-mode patch resonator is achieved without increasing its size. A miniaturised four-pole BPF is implemented using the quad-mode patch resonator. For the demonstration, three-pole triple-mode, six-pole triple-mode and four-pole quad-mode patch filters are designed, fabricated and measured. The measured results are in good agreement with the simulated ones.

A new design of single-layered balanced filtering crossover with high selectivity based on square patch resonator is proposed. Originated from the degenerate modes, that is, TM₁₂ and TM₂₁ on square patch resonators, the feasibility of intrinsic common-mode (CM) suppression and channel isolation is conceived. For demonstration, a first-order balanced crossover prototype is designed. Afterwards, to enhance selectivity, a square patch resonator is subtly divided into two identical parts and then introduced into the prototype. Hence, a balanced filtering crossover with a fifth-order Chebyshev response is formed. Furthermore, stubs are deployed between adjacent patch resonators to introduce mixed couplings. Thus, two controllable transmission zeros are obtained, and better out-of-band suppression is achieved. Ultimately, the proposed crossover is fabricated and measured. High performance in terms of differential-mode filtering response, in-band CM suppression and channel isolation demonstrates the feasibility of the proposed method.

A kind of all-dielectric circularly polarised (CP) loop antenna made of high-permittivity material is proposed. The leaky-wave radiation from a high-permittivity dielectric waveguide is utilised here to support the operation of the proposed antenna. A non-closed dielectric loop covering a three-quarter circle is adopted to generate CP radiation and it is connected with the dielectric ground via one of bending ends to form an all-in-one structure of the antenna. The other end is also bent and vertical to the ground, but hanging in the air for probe feed. As two kinds of typical high-permittivity dielectric materials, zirconia ceramic and pure water are used to implement the proposed design respectively. On one hand, an all-ceramic CP loop antenna made of zirconia is proposed. And benefiting from the low loss and high melting point of zirconia, the proposed ceramic antenna has superiority in radiation efficiency and could adapt to a harsh environment. On the other hand, by using pure water and transparent container, a fully-transparent CP water loop antenna can be obtained. Finally, a 3-D printing technology is adopted in the manufacturing of ceramic structure and resin container. Measured results of both antennas demonstrate the validity of the proposed design.

The improved hybrid discretisation of volume integral equation (VIE) combined with the characteristic basis function method is proposed to analyse the scattering from complex dielectric objects in this study. To mitigate the excessive number of discrete elements which arise from the conformal discretisation on the complex dielectric objects, the hybrid discretisation is developed. For the conventional hybrid discretisation, the conformal Schaubert–Wilton–Glisson (SWG) basis functions are used to discretise the homogeneous regions, meanwhile, the non-conformal half-SWG basis functions are employed to discretise the boundary regions which separate different materials or multiscale structures. The hybrid discretisation takes advantage of the merits of both conformal and non-conformal basis functions and improves the computational efficiency for solving the VIE. In our study, a kind of edge basis function defined within boundary tetrahedral elements substitutes for the SWG basis functions to model the boundary regions, leading to the further reduction on the number of basis functions. Moreover, the characteristic basis functions extracted from the low-level basis functions are employed to construct the reduced matrix of which the size is considerably smaller than that of the system matrix derived from the VIE. Several numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

This paper proposes a new type of hybrid eighth-mode substrate integrated waveguide (EMSIW) and microstrip line (MSL) bandpass filter (BPF) with mixed electric and magnetic coupling. Firstly, two second-order EMSIW BPFs with mixed coupling and wide stopband performance are investigated. Then, in order to realise high-order BPF with decent performance, half-wavelength (λ/2) open-circuited MSL resonators are employed in the hybrid BPFs design. In the end, two third-order BPFs and a fourth-order BPF are developed by combining the EMSIW and MSL resonators together. Extra transmission zeros can be introduced due to the cross couplings in the trisection and quadruplet topologies. For demonstration, the proposed prototypes are designed, fabricated and measured. Reasonable agreements can be achieved between the measurement and simulation. The proposed third-order BPFs compete against the state of the art, exhibiting the competitive characteristics of the operating bandwidth, physical footprint and upper-stopband rejection with less order. The proposed fourth-order BPF features a compact size of 0.34 × 0.34λ₀, a low insertion loss of 1 dB, a broad 3-dB fractional bandwidth of 22.9% and an excellent lower-stopband suppression.

This letter proposes a class of sine corrugated cavity resonators (SCCR). The SCCR can present slow-wave features and provide dual-mode (TE₁₀₄ and TE₁₀₅) wideband responses with reasonable sine period and depth. Based on it, a compact high-gain bandwidth-enhanced SCCR slot antenna array is designed. The high gain is obtained with seven radiation slots and the wideband is achieved due to three modes being utilised. The three modes include the modes of TE₁₀₄ and TE₁₀₅ of the SCCR and one feed slot mode. Compared with published works, the desired TE₁₀₄ and TE₁₀₅ can be obtained straightforwardly based on SCCR. The standard WR62 waveguide is utilised to feed the antenna. For validation, direct metal 3D printing technology is used to fabricate it with aluminium and copper powders as a comparison. Both measured results were discussed and showed a good agreement with the simulated ones.

The detection and stealth abilities of array antennas depend mainly on the antennas' radiating and scattering performance, respectively. However, the operating environmental loads and assembly lead to serious structural errors, including deformation and random errors, which affect both the radiating and scattering performance. As the demand to guarantee high performance in detection as well as in stealth, a new sub-array level structural compensation method is presented to simultaneously guarantee the radiating and scattering performance of array antennas in service. First, a statistical model of scattering performance with structural deformation and random position error is established to quickly evaluate the impact of a random structural error on scattering performance. Then, the effects of structural errors in different directions on radiating and scattering performance are analysed to determine the structural adjustment direction. Moreover, the multi-objective problem considering the comprehensive compensation of radiating and scattering performance is converted into a single-object problem by constructing a fitness function to realise the sub-array level structural compensation. Finally, a typical case is used to verify the effectiveness of the compensation method. The results show that the presented method can guarantee both the radiating and scattering performance effectively, providing advantageous guidance for structural design and performance compensation for array antennas.

Since the total number of the antenna elements can be up to hundreds in a massive multiple-input multiple-output (MIMO) system, subarray-structured base station (BS) array configurations are widely adopted to achieve a good cell coverage and to reduce the required number of radio frequency chains at the same time. It is crucial for any BS product to ensure that the antenna elements perform correctly as expected. Therefore, the necessity of array diagnosis is evident, especially for large BS arrays. Furthermore, it is essential that the diagnosis can be achieved in a compact and cost-effective setup with high measurement efficiency (i.e. only a few measurement samples are required). The principle of the diagnosis method presented in this article is to obtain the S-parameters between the subarrays and the probe via solving linear equations. In the simulation, a BS array composed of 16 subarrays with each containing 3 elements is used to validate the diagnosis method at 3.5 GHz. An array composed of 4 subarrays with each containing 3 elements was used in the measurements to verify the diagnosis method with two different phase tuning matrices at 3 GHz. Successful diagnosis results have been achieved in both the simulations and the measurements.