Iet Microwaves Antennas & Propagation最新文献

The paper introduces an effective method for synthesising large wideband rotationally symmetric sparse circular arrays. Initially, the approach involves incorporating several concentric auxiliary rings within the circular aperture comprised of rotationally symmetrical folds. The array elements are then distributed solely over these rings, thereby avoiding ineffective optimisation within each fold. Furthermore, an initial spacing is established and extended along the concentric rings to quickly establish the initial distribution of the uniform array. Subsequently, the optimisation process involves refining the element positions and numbers by imposing various constraints on factors such as the spacing increment between adjacent rings, the polar angle between adjacent elements on each ring, and the initial polar angle among adjacent elements, which significantly enhances optimisation efficiency. By utilising the peak sidelobe level in wide-angle scanning as the fitness function, the synthesis problem is transformed into an optimisation conundrum, which is addressed using the covariance matrix adaptation evolutionary strategy (CMA-ES). Finally, a series of numerical examples is presented to demonstrate the effectiveness and benefits of the proposed synthesis method.

An approach to improve cross-polarisation (XP) radiation in probe-fed microstrip antennas is presented in this letter. The notable XP associated with self-diplexing antennas caused by radiator multiplexing is discussed for the first time. In order to enhance the interport isolation and polarisation purity, the proposed antenna exploits the combined advantages of the defected ground structure (DGS) and shorting pin arrays. Experimental results show that the resonant frequencies of the self-diplexing antenna are 9.56 and 11.28 GHz, accompanied by a port-to-port isolation of more than 29.4 dB. The suppression of XP around 50° range on either side of the boresight in both principal planes is greater than 12.3 and 11.1 dB for ports 1 and 2, respectively.

This paper introduces a novel compact planar end-fire antenna system featuring circularly polarised (CP) radiation and zero ground clearance. The system is constructed using a half-wavelength TE_0.5,0 mode open waveguide, which inherently generates vertically polarised electric components. By incorporating a slow-wave (SW) structure in the form of metallised blind via holes within the waveguide, a significant SW effect is achieved, resulting in a 40% reduction in the waveguide longitudinal size compared to the conventional counterpart design. Furthermore, by etching an open-ended slot in the top metallic surface of the waveguide, the edges of its aperture are enabled to generate an electric dipole mode. In this way, the horizontally polarised electric components can be achieved without increasing the antenna's footprint. With the proper combination, the design can effectively achieve the required 90°-phase difference in the end-fire direction for these two components. Finally, a 2.5 GHz antenna was designed and optimised. Aiming to mimic the practical environment of mobile terminal devices, a large metallic ground was adopted under the antenna in the simulation and experiment. The measured results indicated that an overlapped impedance |S₁₁| < −10 and axial ratio (AR < 3) bandwidth of 2.7% from 2.495 to 2.562 GHz is achieved. The proposed antenna shows great potential in wireless communication applications for mobile terminal devices.

In this paper, a novel topology for the multiway filtering power divider with a large power dividing ratio (PDR) is proposed. A three-line coupled structure and a λ/2 open-ended stub are introduced between the input port and the power dividing junction to reduce the requirement for high impedance in the low-power path and obtain filtering performance. The PDR is significantly enhanced, and the out-of-band rejection is improved. Meanwhile, a wideband port-to-port isolation is achieved through the isolation network. To verify the validity of the proposed methodology, two three-way wideband filtering power dividers with the power ratios of 5:3:2 and 8:1:1 are designed. The simulated and measured results demonstrate that the 5:3:2 (8:1:1) power divider has the bandwidth of 51.57% (48.5%) with the return loss less than −15 dB and the isolation bandwidth 80% (102%) with reference to −20 dB.

As elastic electrical connectors, fuzz buttons provide a vertical and solderless electrical interconnection in microwave modules to enhance the integration. However, prolonged use in harsh environments poses a risk of potential failure in electronic components, potentially compromising communication system reliability. This work studies the impact of fuzz button degradation in harsh environments on analog modulation (AM) and pseudo random binary sequence (PRBS) signal transmission using theoretical analysis and experimental testing. Accelerated tests are designed to obtain the fuzz button samples with different degradation levels. The surface morphology observation and elemental analysis are conducted to analyse the degradation mechanism. In addition, a transmission channel with fuzz button interconnections is designed and the corresponding equivalent circuit model is developed. Based on the proposed circuit model, the effects of fuzz button degradation on the integrity of both AM signal and PRBS signal are investigated by analysing the metrics such as waveform, eye diagram and bit error rate (BER) of the output signal. In addition, the effects of the carrier frequency of AM signals, and the transmission rate of the PRBS signals on signal transmission are also investigated. The simulation results of the circuit model show good agreements with experimental tests. The research results provide a better understanding regarding the potentially corrosive effects of harsh environments on fuzz button connectors and the negative effects on the signal integrity. Moreover, the research results provide comprehensive data support for identifying key features that are used for the development of machine learning models for fault diagnosis and localisation in radio frequency (RF) circuits with fuzz button interconnections.

A Huygens source dielectric resonator antenna (DRA) with unidirectional radiation pattern is presented. It consists of a coaxial probe exciting a rectangular, homogeneous and uniaxial anisotropic dielectric resonator (DR). To obtain a Huygens source radiation pattern, a pair of quasi-TM and TE modes are combined by controlling the permittivity tensor of the DR. A prototype operating at 2.5 GHz has been designed. The DR is made up of periodic anisotropic unit cells on a subwavelength scale and fabricated using a three-dimensional (3-D) printer. The simulated and measured results are in reasonable agreement. A relative impedance bandwidth of $��12.5�\%�$ and a front-to-back ratio larger than 15 dB at operating frequency are finally measured.

The contribution of this work is to propose an ultra-miniaturised substrate-integrated coaxial cavity (SICC) and its applications in bandpass filter (BPF) design. The proposed SICC comprises two dielectric substrates with three metal layers. The top and bottom metal layers form the cavity's broadside walls. The middle is a circular patch that shorts to the bottom wall through a blind-via ring. The circular patch also connects to a bottom-wall embedded split CPW ring through three blind vias. In conjunction with the top/bottom walls and the split CPW ring, this circular patch provides the cavity with a significant loading capacitance, resulting in a substantial resonance-frequency downshift. As a result, the SICC's resonance frequency is almost only one-tenth that of its conventional SIW cavity counterpart. Compared with the literature, this design achieves a record-high miniaturisation factor (MF). Two sample BPFs are built to verify the circuit design and demonstrate the filter applications.

An elliptical polarisation conversion metasurface (PCM) is proposed for Ka-band applications, integrated with a high-gain substrate-integrated waveguide (SIW) antenna to achieve significant radar cross section (RCS) reduction. The PCM elements, arranged in a chessboard configuration, feature a simple yet efficient design with an elliptical pattern symmetric along the diagonal, enabling effective conversion of linearly polarised waves. The antenna employs a broadband dipole excited through SIW slot coupling. Simulation results demonstrate that the PCM unit achieves a polarisation conversion bandwidth of 80.38% (25.3–59.3 GHz) with a polarisation conversion ratio (PCR) exceeding 90%. When integrated with the dipole antenna, the design exhibits a −10 dB impedance bandwidth of 15.08% (33.7–39.2 GHz) and a maximum realised gain of 9.12 dBi, representing a 1.7 dB gain enhancement at 36 GHz. Moreover, the 16 × 16 PCM array configuration achieves an RCS reduction bandwidth of 77.98% (25.85–58.92 GHz), with RCS reduction values exceeding 9 dB across this bandwidth and an average reduction of 12 dB. The proposed antenna has been fabricated and tested, with measured results showing excellent agreement with simulations in terms of $��S_{11}�$ and gain performance.

In this work, a simple analytical model based on the array factor to effect 1-bit electronic reconfigurability in one-dimensional 1-D leaky-wave antennas (LWAs) is proposed. The model, based on the array factor, outlines the discrete control of the phase constant along the longitudinal direction of the LWA $��\left({\beta }_z\right)�$ subsequently describing the beam scanning logic in the H-plane. The effectiveness of the proposed approach is evaluated by comparison against full-wave calculations. An extremely low-profile electronically reconfigurable 21-element LWA operating at X-band is then fabricated and measured to validate the proposed concept. The individual antenna element making up the array is designed at X-band and is capable of switching between radiating and non-radiating states by use of a PIN diode used to control the resonant frequency of the element. The limitations of both the proposed approach and the antenna are also evaluated.

This study proposes a novel three-dimensional integral-equation-based electromagnetic solver with surface susceptibilities of metasurfaces that satisfy the generalised sheet transition conditions (GSTCs). The metasurface is replaced by an equivalent zero-thickness sheet with surface susceptibilities, which can be extracted using the retrieval method deduced from the GSTCs. We consider the problems of composite structures with metasurfaces for greater generality and applicability. The integral equations of the problems are formulated and discretised using Rao–Wilton–Glisson (RWG) basis functions through Galerkin's testing procedure. We also propose a technique for enforcing the boundary condition at the interface, which should be carefully considered within the problem formulation of composite structures. The proposed method is validated by using a circuit-analog-based absorber to extract the surface susceptibilities. Composite structures, including flat and curved metasurfaces, are employed to verify the IE-GSTC solver, and numerical simulation results are compared with those obtained from a commercial finite-element method-based simulation (FEM-HFSS).