Iet Microwaves Antennas & Propagation最新文献

This paper presents a compact metasurface antenna with reconfigurable radiation patterns designed for 5G mm-wave applications. The antenna consists of a metasurface with 3 × 3 unit cells of modified patches, two coupling slots on the ground plane, and a reconfigurable feeding network. The method of characteristic mode analysis is initially employed to identify the modes of the metasurface layer which are responsible for steering the radiation pattern of the antenna at angles of 0° and ±30°. By analysing the surface currents of these modes, the locations of the coupling slots are determined, making it easier to excite and combine the desired modes and steer the main beam of the antenna in specific directions. The pattern reconfigurability is achieved by switching PIN diodes in the microstrip feed network to excite the appropriate coupling slots. The proposed metasurface antenna, with dimensions of 0.9λ₀ × 0.9λ₀ × 0.08λ₀ (where λ₀ is the free space wavelength at the centre frequency of 27 GHz), was fabricated and tested. The experimental results showed a wide bandwidth of 22.71% achieved by combining the resonance frequencies of the slots and metasurface layer. Furthermore, the antenna exhibits three distinct main beams at +30°, 0°, and −30° with a peak gain of 8.95 dB.

Wideband operation is a crucial topic in patch structure research. Various wideband methods have been developed for patch antennas. However, some of the key benefits of patch antennas, such as semi-space radiation and easy fabrication, are degraded. In this study, we refer to the planar inverted-F antenna (PIFA) and propose a co-plane terminal loading strategy, resulting in an antenna model termed the co-plane terminal loaded antenna (CTLA). It transforms the dipole-to-background metallic via in PIFA to a dipole-to-feed gap in CTLA. Because the gap is a coupling connection, the impedance-match and resonant-frequency performance improve, resulting in a wider bandwidth. Based on the proposed approach, three CTLAs, including an original CTLA, an improved CTLA, and a multi-path CTLA, were constructed and simulated, with relative bandwidths of 63.5%, 55%, and 62%, respectively. The radiation pattern is typically patch-like, radiating in semi-space, and hybrid polarisation over the working band. Finally, the improved and multi-path CTLAs are fabricated and measured to validate this method and ensure that the results are consistent with the simulation results accurately. This study proposes a terminal-loading method for patch structures, which results in wideband radiation. It can be used in wideband phased arrays, communication systems etc.

A circular polarised (CP) microstrip antenna loaded with sunflower-shaped metasurface (SSM) to enhance the bandwidth using characteristic mode analysis is proposed in this communication. The SSM, divided into inner and outer parts by a ring, consists of equally spaced sectors of equal angles. In this design, the coupled corner-truncated microstrip antenna with a slot in the centre is employed to obtain CP radiation by exciting two orthogonal modes, which have a 90° phase difference. Meanwhile, it demonstrates that the SSM structure significantly expands the operational bandwidth and exhibits a stable radiation pattern at high frequencies. Simulation and measurement results confirm that this SSM antenna achieves a wide operating bandwidth of 64.3% (4.5–8.76 GHz) and a 3-dB axial ratio bandwidth of 30.6% (4.7–6.4 GHz), while maintaining a compact profile of 0.68 × 0.68 × 0 0.08 λ₀³.

A low-profile circularly polarised (CP) metasurface antenna is proposed, utilising characteristic mode analysis (CMA). The antenna design features a two-layer laminated substrate, a 4×4 Butterfly-shaped metasurface, a rectangular slot, an irregular transmission line, and a ground plane. The metasurface is analysed using mode significance (MS), characteristic angle (CA), and characteristic current to determine the resonance bandwidth and CA resonance points, which exhibit a near 90° difference. At the intersection of the two MS modes, their CAs differ by nearly 90°, and their far-field radiation directions align, indicating the potential for achieving circular polarisation at the desired frequency. The integration of the metasurface with the slot antenna is simulated to validate the CMA findings. Additionally, the CP bandwidth is enhanced by modifying the transmission line branches. Measurement of the fabricated antenna reveals an impedance bandwidth (IBW) of 27.4%, a 3-dB axial ratio bandwidth (ARBW) of 10.1%, and a peak gain of 6.9 dBic at 4.4 GHz. Compared to the design without branches, IBW and ARBW have increased by 10% and 7.3%, respectively.

A design scheme of high-gain and full-angle frequency beam scanning leaky wave antenna (LWA) and array is proposed based on spoof surface plasmon polaritons (SSPPs) slow-wave transmission line (TL) for radar field applications. A row of complementary split ring resonators is periodically etched near the SSPPs TL, which can transform the fundamental mode of SSPPs TL to the fast-wave region and radiate electromagnetic waves, realising the full-angle frequency beam scanning performance. A 1-to-2 microwave power divider is designed to feed the LWA array and realised good impedance matching covers 5.8–9.4 GHz bandwidth. Simulation and experimental results indicate that the designed LWA array can realise full-angle beam scanning range of 180° (−90° to 90°) with a scanning rate of 3.83°/% performance. The peak gain values of the designed LWA element and array are 11.4dBi and 14.6 dBi, respectively, and the radiation efficiency of LWA array is maintained more than 80% within the operation frequency band.

To achieve multi-function integration and independent performance regulation of microwave and millimetre-wave (mm-Wave) shared-aperture antennas, a design method based on embedded structure fusion is proposed. In the Sub-6G band, a high-order mode annular-ring patch antenna is designed. To transform the non-broadside characteristics, the current distribution of TM₃₁ and TM₁₂ modes is reconstructed by slotting in the centre of the patch. Additionally, the electric field distribution is modified by loading shorting pins to achieve beam broadening. In the 5G mm-Wave band, a four-element high-gain substrate integrated waveguide (SIW) slotted cavity backed antenna array with low-sidelobe characteristics is obtained using the element interleaving technique. The SIW slotted cavity backed antenna array is integrated into the central area of the annular-ring patch to achieve aperture-sharing fusion. Experimental results demonstrate that the antenna operates in the Sub-6G dual-band of 2.1–2.2 GHz and 5.2–5.4 GHz, respectively. Furthermore, the widest half-power beamwidth measured in these two bands is 126° and 140°. In the mm-Wave band, the operating bandwidth is 26.5–29.5 GHz, with a gain of up to 18.8 dBi. Notably, the performance of different bands does not impact the other, and the measured isolation exceeds 40 dB. Furthermore, the antenna profile is only 0.008 λ₀. Therefore, an ultra-low-profile microwave and mm-Wave shared-aperture antenna with multi-function integration and independent performance control is realised, which has great potential for application in 5G intelligent connected vehicle communications.

This paper presents a novel wideband microstrip patch antenna (MPA) characterised by a straightforward structure and operational efficacy across four resonances. The antenna consists of a truncated square patch, a coplanar capacitive feed and a slot on the patch. The square radiating patch is strategically truncated at its four corners to perturb the electric field distribution characteristic of the TM_0,2 mode, thereby facilitating the generation of a unidirectional far-field pattern. Extensive analysis has elucidated the mechanism through which corner truncation diminishes the electric field peak associated with the TM_0,2 mode at the centre, resulting in the transformation of the dual-beam pattern into a distinct single beam pattern. In addition, unlike conventional approaches that require additional components such as shorting pins, this approach reallocates three radiative modes—specifically TM_1,0, TM_0,2, and TM_1,2—resulting in a simplified structure. Finally, a coplanar capacitive feed and a slot are employed to boost the input impedance frequency bandwidth and generate the fourth resonance, respectively. Therefore, four adjacent resonances are simultaneously excited by this method and a wide frequency bandwidth of approximately 80% with stable unidirectional radiation pattern and same polarisation are fulfilled. A prototype of the antenna is fabricated and measured to validate the design procedure.

This work presents the effect of temperature change on the capacitance of silicon PIN diodes and the resulting change in performance of RF limiters at very high frequency (VHF). Device temperatures were varied between −25 ºC and 100 ºC, with small-signal parameters (including device capacitance) extracted at regular temperature increments and bias voltages from −20 Vdc to +3 Vdc using a multi-bias parameter extraction method. It was found that the junction capacitance of the four PIN diodes under investigation increases with temperature, as expected from carrier lifetime behaviour, while results also confirmed prior observations of an inverse relationship between forward-biased series resistance and temperature. Devices were subsequently tested in two different limiter topologies through high-power transient measurements. It was found that the combination of increased capacitance and decreased resistance with increasing temperature increases the transient spike leakage and decreases the flat leakage of a limiter. It was also concluded that, for VHF, an anti-parallel topology provides the best performance over a wide range of temperatures.

Ultra-wideband (UWB) systems utilise a broad frequency spectrum to achieve high data transmission rates and enhanced precision, creating a demand for specialised UWB antennas. Circularly Polarised (CP) antennas are considered essential for maintaining robust performance under varied environmental conditions. Among them, the crossed dipole is effective for UWB CP applications, but its relatively large size could limit its use in various systems. A miniaturised crossed dipole design employing the Koch fractal structure is proposed and the measurement results are presented. The prototype antenna achieved an effective bandwidth covering 88% of the frequency range from 1.4 to 3.6 GHz. Additionally, a 4 × 4 array using this design was tested in the same frequency band, demonstrating beam-steering capabilities up to 30°. The proposed antenna has demonstrated effective deployment in diverse communication systems and phased array applications within ultra-wideband (UWB) CP environments.