Iet Microwaves Antennas & Propagation最新文献

In the design of horn array antennas, usually there is a challenge with the grating lobe problem and consequently quite low aperture efficiency. A new configuration for horn array antennas is presented which introduces high aperture efficiency with suppressed grating lobes in both E-& H-plane radiation patterns. The proposed array unit cell is a dual-mode horn loaded by two corrugations in E-plane. A sample 4 ⨯ 4 array of the proposed unit cell is designed to operate at Ku band. The simulation and measurement results show 13.3% operating bandwidth over which the grating lobes are totally suppressed and the aperture efficiency is above 70%. The antenna measured gain is also 27 dBi with 2 dB variation over the bandwidth. The results show that the aperture efficiency of 98% is achievable making use of the proposed topology.

A wideband end-fire stepped slot antenna with gain enhancement and filtering capability is proposed. On one hand, a parasitic dipole serving as a director is introduced in the stepped slot to improve the radiation gain of the slot antenna without increasing its physical size. It is found that a gain enhancement of about 2 dB can be achieved after adopting such approach. On the other hand, an absorptive branch possessing a nearly complementary frequency response with regard to the one of the slot antenna is in-parallel loaded at the microstrip feedline. It allows the partial dissipation of the out-of-band/non-radiated RF-signal power of the antenna to attain both an RF-quasi-absorptive behaviour and filtering capability. It is found that after loading the dissipative branch, the out-of-band radiation efficiency of the slot antenna is reduced to less than 20%. The measured results of a fabricated proof-of-concept antenna prototype show a reasonable agreement with the simulated ones and verify the RF performance merits of the proposed stepped slot antenna, such as wide RF operating band covering the 3.39−4.73-GHz range, end-fire radiation with a front-to-back ratio (FBR) above 10 dB, flat radiation gain, and co-integrated filtering functionality with RF-quasi-absorptive capability.

A technique to enhance the bandwidth of a circularly polarised antenna using the filter-antenna design approach is presented. The design relies on adding a resonator coupled to the radiation element—an L-shaped slot antenna in the case of global navigation satellite systems. This change in the feeding structure broadens both the impedance and the axial ratio (AR) bandwidths and allows more design flexibility. Compared with a reference L-shaped slot antenna with a conventional feed, the proposed antenna design achieves a doubling of the impedance matching bandwidth from 19% to 41% over the frequency range from 1.2 to 1.81 GHz and a wider AR bandwidth from 35% to 44.5% in the range from 1.17 to 1.84 GHz. The AR bandwidth covers the entire impedance bandwidth. The effect of a metal reflector on antenna performance is also investigated and discussed.

A miniaturised high-isolation K-/Ka-band diplexer with exceeding adjacent channels using 3D antarafacial channel integration and vertical-quasi-coaxial-based matching network is proposed. For smaller size, lower loss and lower channel interference, the high-order low-pass filter for the K-band channel and the four-line-interdigital-coupled wideband bandpass filter for the Ka-band channel are respectively designed on two low-loss glass-based substrates, and these two substrates are integrated on the two antarafacial surface of the mounting board. The vertical-quasi-coaxial (VQC) embedded in the mounting board is not only used as three-dimensional (3D) interconnection of the two antarafacial channels but also designed as the constituent part of the matching/isolation network, and this can effectively decrease the impedance traction caused by the Ka-band filter for the K-band channel of the diplexer. In addition, four transmission zeros of the K-band filter are designed at the whole passband of the Ka-band channel to improve the isolation to the K-band channel for guaranteeing the performance of the diplexer at the Ka-band channel. Furthermore, working principle, design method and test solution of this proposed K-/Ka-band diplexer are well illustrated, and the high-isolation (>40 dB) in very adjacent wideband channels at K-band (18–23.5 GHz) and Ka-band (25.8–31.6 GHz) is achieved within a tiny size of 9 × 4 × 0.87 mm.

Continuous beam steering approach with minimal power consumption is highly desirable in modern antenna designs. A simple mechanical method for achieving beam steering in the Fabry–Perot resonator antenna (FPRA) is presented. It involves rotating the upper phase gradient metasurface (PGM) mechanically to change the aperture phase distribution, so the beam is continuously steered in the azimuthal plane while maintaining a large elevation angle. The proposed PGM unit cell comprises a hexagonal ring and patch printed on both sides of the substrate, along with a honeycomb lattice. A prototype antenna operating at 5.65 GHz is fabricated and measured to validate the feasibility. Measurement results show that the FPRA achieves a gain of 14.9 dBi, and can continuously steer its beam in the azimuthal plane with an elevation angle of around θ = 50°. Measured radiation patterns in eight azimuthal directions (φ = 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°) are consistent with the simulated results. Compared with other electrical tuning methods, our design has a compact size and requires lower power for the PGM rotation.

The design of a wideband diplexer integrated with a 16-slot Continuous Transverse Stub (CTS) antenna array is presented. The diplexer-antenna array module covers the whole WR34 band. The Tx and Rx bands cover 21.7–26 and 27.5–33 GHz ranges, respectively. The diplexer is designed to have a 100 dB attenuation in the stopband and 40 dB isolation between the channels. The antenna array has a high gain, between 26.9 and 31 dBi, at the lowest and highest frequencies. For the preliminary exploration of monolithic metal 3-D printing of complex geometry integrated RF front ends, two prototypes were manufactured in AlSi10 Mg. One-piece fabrication eliminates complicated assembly, enhances reliability, and reduces weight, which is more desirable for space applications. Due to several factors, namely, an unpolished inner surface and imperfect printing quality, the diplexer had a poor measured performance. The measured results of the antenna array had a relatively better agreement with simulations. Although, the realised gain was affected by the much lower effective conductivity of the unpolished 3-D printed material. Hence, the measured realised gain was between 27.8 and 30.9 dBi in the 29–33 GHz range.

A semi-analytic solution for scattering from a semi-elliptical cavity with arbitrary orientation placed in a perfect electric conductor plane is suggested. By imposing the boundary conditions at an elliptical border, three independent equations containing the Mathieu functions series are extracted. Finally, the solution of the problem is reduced to the solution of a simple system of linear equations by using Mathieu function addition theorem and the orthogonal properties of the angular Mathieu functions. Some examples are presented to demonstrate the reliability and the accuracy of the proposed solution.

The authors extend the resonant modal theory (RMT) developed previously for a metal object to an arbitrary source region consisting of metals, dielectrics, or a combination of both. The influences of dielectrics on the fields are replaced by equivalent volume sources through the use of the compensation theorem in electromagnetic theory. The resonant frequencies can be determined by finding the roots of the determinant of the matrix resulted from the discretisation of the real homogeneous volume–surface integral equation derived from the requirement that the difference of stored field energies in the source region vanishes. As applications of the extended RMT, three examples have been investigated. The first example is a dielectric resonator antenna and is designed by exciting the first resonant mode of the composite structure in which the dielectric cylinder is combined with a conformal metallic strip. The second example is a dual-band dielectric-coated metallic wire antenna. The third example studies the resonant modes of a rectangular patch antenna.

The authors present the design, fabrication and testing of a W-band monopulse antenna. This antenna consists of three main building blocks: an array with 48 × 48 slots, a tapered corporate-feed network and a comparator. The comparator has four input ports to generate sum and difference patterns in orthogonal cardinal planes for monopulse operation. A novel octuple excitation is adopted for the corporate network to achieve a side lobe level lower than −20 dB for the sum patterns and simultaneously reduce drastically the manufacturing complexity. Diffusion bonding technology is used for fabrication. Twenty-four etched copper sheets with a thickness of 0.2 mm are stacked to realise the prototype. The total size of the antenna is $��40.76�\times �40.76�\times �1.51�{\lambda }_0^3�$, with λ₀ being the wavelength at the centre frequency (94 GHz). The antenna presents an isolation better than 12 dB among the input ports in the 84–100 GHz band. The realised measured gain is 40.7 dBi at 94 GHz. The measured 3-dB gain bandwidth is 17.4%. The difference patterns at 94.0 GHz present null depths of −24.0, −18.0, −17.5, and −17.4 dB, in the E-, H-, 45°-, and 135°-planes, respectively.

The authors presents a low-profile wideband circularly polarised (CP) millimetre-wave (mmWave) elliptical integrated lens antenna (ILA) fabricated by dielectric 3D printing technology. The proposed lens is integrated with a dielectric polariser and an air cavity for phase compensation, which can transfer incident waves from linearly polarised (LP) to planar CP waves over a wide bandwidth. Compared to the classic bifocal ILA, the proposed lens has a low profile. The phase compensation is performed by introducing a specifically shaped air cavity, which greatly reduces the length and weight of the lens. The polariser causes the two electric field components Ex and Ey to degenerate with an orthogonal phase difference, which results in the wideband characteristics of the antenna. The polariser, air cavity and lens can be conveniently and precisely fabricated by low-cost 3D printing technology. Measurements show that the proposed ILA has a wide axial ratio (AR) bandwidth of 21.9–32.6 GHz, while the gain reaches 22.54 dBic with a 38% size reduction and a 60.7% weight reduction. Benefiting from the low profile, high gain, wide bandwidth and low cost, the proposed ILA has great potential to be the candidate antenna for 5G applications and satellite communications.