Iet Microwaves Antennas & Propagation最新文献

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.

The design of three-dimensional (3D)-printed heterogeneous ceramics exhibiting isotropic and anisotropic dielectric permittivities at microwave frequencies is studied for dielectric resonator antenna (DRA) applications. The heterogeneous ceramics are engineered by using periodic structures made up of subwavelength unit cells filled with zirconia ceramic and air. Ceramic stereolithography (CSLA) allows the 3D printing of a one-piece ceramic block mixing isotropic and anisotropic dielectric regions. In order to demonstrate the possibility of exploiting such 3D-printed ceramics, a singly fed dual-band circularly polarised DRA is presented. To achieve circular polarisation at both bands, the relative permittivity of the dielectric resonator is locally controlled by introducing anisotropic dielectric regions. The 3D-printed DRA is finally measured, and its results agree well with the simulations.

A dual-band liquid cylindrical dielectric resonator antenna with pattern diversity at two different frequency bands is proposed using the lower order and higher order modes of the HEM and TM modes namely HEM_11δ, HEM_12δ+1, HEM_31δ+1, HEM_13δ, TM_01δ, and TM_02δ. The proposed antenna is designed to cover the GPS L2 band and the lower Wi-Fi band at 1.227 and 2.4 GHz frequencies, respectively. The HEM modes which constitute the primary radiating modes achieved around 20.84% and 19.35% impedance bandwidth at lower and higher bands, respectively. In the later stage, beam-steering is performed, whereby the realised broadside HEM modes at both lower and higher bands were passively steered with simple physical re-orientation of the antenna structure. For this, the liquid's natural fluidic property of adhering to gravity is taken as an advantage which makes the proposed antenna adaptively steer its radiation pattern always towards the sky, irrespective of the tilt angle of the antenna. This concept of passively steering two modes at two different frequency bands without the use of any mechanical, electrical, or other associated components is presented for the first time.

In order to employ periodic corrugated microstrip lines for reducing or suppressing electromagnetic interference in high-speed or high-frequency circuits, a precise method is necessary to calculate and measure the characteristic impedance of periodic microstrip lines. The equation for characteristic impedance (depending on frequency) of lossless periodic microstrip lines was obtained based on the transfer matrix method. A time domain pulse was used to measure the instantaneous impedance of conventional microstrip lines, and when the instantaneous impedance does not change with distance, it can be identified as the characteristic impedance of microstrip lines. However, when the time-domain pulses are employed to measure the instantaneous impedance of periodic microstrip lines, rapid oscillations occur with distance. Therefore, a standard for spacing between adjacent grooves in the microstrip line can be suggested by analysing the interaction between the time-domain pulses and the microstrip line grooves. Once such a standard is satisfied, many grooves etched along the microstrip line would no longer be distinguished by the time-domain pulses. Such a principle and method can be used to determine the instantaneous impedance for the microstrip lines that have periodic grooves. On the other hand, when several periodic structures with different lattice constants coexist on a microstrip line, they can also be distinguished via the instantaneous impedance. A time domain reflectometer was used for measuring the instantaneous impedance of periodic microstrip lines, and the measured results are in agreement with the theoretical analysis.

A two-layered wideband single-fed circularly polarised (CP) antenna is presented by the authors. A single-fed corner-truncated square patch with four identical rectangular matching branches acts as a bottom-driven patch to generate CP radiation. To broaden the 3-dB axial ratio (AR) bandwidth, a similar patch with a larger size is loaded atop the driven patch as a parasitic patch. The measured results show that the proposed CP antenna has a 17.9% impedance bandwidth from 2.13 to 2.55 GHz and an 11% 3-dB AR bandwidth from 2.15 to 2.4 GHz, respectively. The measured total gain is 7.1 dBic. The results indicate that the proposed antenna is a good candidate for Wireless Local Area Network band applications.

A new multi-band frequency response controlling method using groove loading technique on the narrow wall of an open-ended waveguide is proposed by the authors. The feature of this scheme is a larger stopband spacing that is independent of the position of the loading structure. A tri-band antenna is designed as an example to verify the effectiveness of the idea. Two notches are introduced, and the bandwidths, as well as stopband spacings, can be adjusted by independent parameters. The tri-band prototype can be fabricated using 3D printing technology or machining technology. Reasonable agreement between the measured and simulated results of impedance and radiation characteristics have been achieved.