Iet Microwaves Antennas & Propagation最新文献

The traditional co-polarised metasurface achieves 360° phase coverage only at the resonant frequency but not full phase coverage across a wide bandwidth. This paper proposes a multilayer structure metasurface, which composes of five layers of metal patch and four layers of medium, forming the Fabry–Perry resonator, using the principle of the cancellation of two polarisation conversion, which can achieve a wideband efficient co-polarisation transmission. Based on the metasurface transmission phase principle, 360° phase coverage has been achieved by changing the geometric parameters of the intermediate metal patches. Through phase compensation arrangement, a metalens is designed using the proposed metasurface unit cell. At the same time, horn antenna is used as a feed to feed the metalens, which can significantly improve the gain of the antenna within a wideband. Simulated and measured results show that the proposed metalens antenna operates at 22–26 GHz, and the maximum measured gain of the metalens antenna reaches 24.16 dBi at 25 GHz, which is 10.85 dB higher than the horn antenna without metasurface compensation, showing good focusing performance. The proposed multilayer metasurface breaks the narrow band limit of the traditional stacked metasurface in principle, opening a way in the broadband metasurface design.

This paper presents a novel millimetre-wave (mmWave) 2D wide-angle scanning (WAS) phased array antenna (PAA) based on decoupling surface (DS). The proposed element is a coaxial feeding stacked patch antenna structure that consists of an L-shape coaxial probe, substrate integrated waveguide cavity, slot layer, radiating patch, DS and defective ground structure. The simulated impedance bandwidth for the element is 14.85% (26.18–30.34 GHz). The simulated result of the 2 × 2 array shows that the designed antenna based on DS achieves an isolation of ≥19 dB within the bandwidth. To validate the scanning capabilities of the proposed antenna, an 8 × 8 PAA prototype is fabricated and measured. The measured scanning range of the prototype achieves a 2D WAS range of ±56° at 27 GHz. The proposed antenna shows great potential in application scenarios, such as automotive radar and satellite communication due to its compact design and ability to achieve WAS in two dimensions.

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.

Implementation of reconfigurable metasurfaces demands a complex structure. The design methodology for metasurface elements based on PIN diodes requires targeted optimisation tailored to the varying application environments and cannot be directly transplanted from one methodological approach to another. In addition, inclusion of varactors often imposes undesirable high-power consumption with complex analog drive circuitry. Furthermore, the design method for the reconfigurable metasurface element has not been simplified and unified, hindering the rapid deployment of metasurface applications. The authors propose a general design model based on low-power embedded circuitry for a multi-function metasurface element and give the corresponding numerical analysis. The authors present a reconfigurable method based on the general design model and prove that the method achieves independent regulation of amplitude and phase for the reflected electromagnetic wave. Through analysis of the sensitive area at the bottom of the embedded circuit, a gradient descent algorithm is proposed to find the optimised phase points according to device sensitivity of the application scenario and suitable strategy. Finally, the authors demonstrate that the designed metasurface element possesses phase control capability and decent phase consistency obtained via far-field scanning experiments. The proposed element design method will provide a theoretical reference for the integrated design of metasurface.

A 1:3-way power divider/combiner has been proposed for much improved bandwidth and isolation between output ports. The matching network for the super wide bandwidth frequency range is designed using a combination of the Klopfenstein taper and the triangular taper. The proposed design yields bandwidth from 1.5 to 20 GHz (18.5 GHz) for return loss better than 15 dB and isolation better than 20 dB. The insertion loss for the entire frequency band is 0.8 dB which is only 0.34 dB for the ultra-wide bandwidth (3.1–10.6 GHz). The maximum phase imbalance of 3.32° and amplitude imbalance of 0.199 dB between all the output ports have been achieved over the entire bandwidth. The simulated results have been validated experimentally.

To get simultaneously sparse and constant modulus excitation to reduce the complexity of the array and the mutual effect of neighbouring elements, a novel algorithm via alternating optimisation-alternating direction of the multipliers method is developed. This method uses the total transmitting power as the objective function to optimise the sparsity and the amplitude of excitation simultaneously. Numerical results are provided to verify its effectiveness.