Integrated Miniature Multiband Antenna Designed for WWD and SAR Assessment for Human ExposureRead the full article
International Journal of Antennas and Propagation publishes research on the design, analysis, and applications of antennas, along with studies related to the propagation of electromagnetic waves through space, air, and other media.
Chief Editor, Professor Koziel, engages in research focused on surrogate-based modeling and optimization including space mapping technology for engineering design at Reykjavik University.
Latest ArticlesMore articles
Radar Working State Recognition Based on Improved HPSO-BP
In this paper, a recognition model based on the improved hybrid particle swarm optimisation (HPSO) optimised backpropagation network (BP) is proposed to improve the efficiency of radar working state recognition. First, the model improves the HPSO algorithm through the nonlinear decreasing inertia weight by adding the deceleration factor and asynchronous learning factor. Then, the BP neural network’s initial weights and thresholds are optimised to overcome the shortcomings of slow convergence rate and falling into local optima. In the simulation experiment, improved HPSO-BP recognition models were established based on the datasets for three radar types, and these models were subsequently compared to other recognition models. The results reveal that the improved HPSO-BP recognition model has better prediction accuracy and convergence rate. The recognition accuracy of different radar types exceeded 97%, which demonstrates the feasibility and generalisation of the model applied to radar working state recognition.
A Hybrid Algorithm Based on a Modified Sine Cosine Algorithm and Least Square and Its Application to Microwave Imaging
With the rapid development of materials science and medical imaging technology, traditional optimization algorithms cannot solve the problem of inverse scattering of complex scatterers well. Therefore, more and more imaging algorithms for solving complex scatterers were proposed. In this paper, a novel hybrid algorithm is put forward for the microwave imaging problem. First, the proposed algorithm improves the search path of the traditional sine cosine algorithm, which obtains better global search capability. Second, the least square is introduced to form judging and contrasting mechanisms, which forms the parallel algorithm simultaneously, in order to make the proposed algorithm more suitable for the diverse microwave imaging problem. To prove the efficiency of the proposed algorithm, several examples, including ten benchmark functions, two engineering design problems, and three different microwave imaging problem tests are adopted. As expected, the results show that the proposed algorithm achieves not only superior optimal value but also the reconstruction of the complicated permittivity of the scatterer compared with several traditional optimization algorithms.
A Novel Adjacent Sensors-Based Mechanism to Increase Performance of Wireless Sensor Networks
Wireless Sensor Networks are widely used nowadays to support the decision-makers in different applications by monitoring and collecting the environmental parameters in specific areas. Sensors are deployed in such areas either randomly or formally. In a high-density Wireless Sensor Network, several sensors are randomly deployed in a small area. This will make the adjacent sensors collect same data and send them to the sink, which will increase the power consumption in those sensors. Adjacent sensors are considered critical because of their effect on the network performance. In this paper, the effect of the adjacent sensors is minimized because of the above-mentioned criticality and performance influence of these sensors. The proposed mechanism is evaluated by using MATLAB simulator and is then compared with the low-energy adaptive clustering hierarchy (LEACH) protocol. Results prove that the proposed mechanism outperforms the LEACH protocol by 21% in terms of the network lifetime and by 18% in terms of the number of the transmitted packets to the cluster heads and reduces the number of the transmitted packets to the base station by approximately 3% by avoiding the duplicated packets.
A Novel Design of CPW Feed Planar Omnidirectional Circularly Polarized Antenna
A novel planar omnidirectional circularly polarized (CP) antenna is presented. The omnidirectional circular polarization characteristics of the planar antenna are the result of the combined effect of a planar quasi-magnetic dipole (PQMD) and a printed electric dipole (PED) in this paper. The CP radiation pattern of the proposed antenna can be achieved by distributing appropriate current amplitude and phase to both elements, respectively. A power divider is used to adjust the amplitude and phase relationship between two basic components. In order to achieve a planar structure, coplanar waveguide (CPW) feed is adopted to feed the quasi-magnetic dipole for the first time. The overall electrical size of antenna is 1.61λ × 0.38λ. Finally, the correctness of our theoretical analysis is verified by processing and measuring this antenna. Through the analysis of the measurement results, we have obtained the following conclusions: the operating bandwidth of the proposed antenna obtained by measurement is from 5.67 to 5.86 GHz, in which the reflection coefficient is less than −10 dB and the axial ratio is less than 3 dB. Within the available bandwidth, the proposed antenna achieves omnidirectional radiation characteristics with a gain between 0.89 and 2.48 dBic.
Design of Planar Microstrip Ultrawideband Circularly Polarized Antenna Loaded by Annular-Ring Slot
A miniaturized planar microstrip circularly polarized ultrawideband (UWB) antenna loaded by annular-ring slot is proposed and implemented in the paper. With the annular-ring slot loaded in the radiating patch of the antenna, the side of the radiating patch is connected by the asymmetric inverted L-shaped microstrip. At the same time, a quarter of a circle is cut off from the radiating patch. The above designed structure shows improvements on the operating frequency band and realization of the circular polarization radiation. A tapered microstrip is placed between the feed line and the radiating patch to achieve the slow-changing impedance transformation. The results of simulation and measurement demonstrate that the 3 dB axial ratio (AR) fractional bandwidth of the antenna structure achieves 21.25%. The peak gain within the 3 dB axial ratio bandwidth fluctuates between 3.74 and 4.59 dBi. The antenna shows good impedance matching in the ultrawideband range. With the compact structure of the UWB antenna, it has potential application in various wireless communication devices.
Millimetre-Wave Metamaterial-Based Sensor for Characterisation of Cooking Oils
The characterisation of the cooking oils presents a significant challenge due to minor changes in their dielectric behaviour. In this paper, a new metamaterial-based sensor incorporating a split-ring resonator (SRR) with a microstrip transmission line is presented to characterise cooking oils. The design demonstrates metamaterial characteristics of negative permittivity and permeability simultaneously at the resonance frequency. Furthermore, its operation in the range of millimetre-wave frequencies can further enhance its sensitivity, especially for liquid materials. The sensor’s novelty is the operation at millimetre-wave frequencies that offers a high shift in the transmission coefficient while operating at 30 GHz. The sensor’s performance analysis is undertaken by using six MUTs with dielectric constants ranging from 0.126 to 4.47. The presented structure designed on 12 × 8 mm2 Rogers substrate offers a sensitivity of 1.12 GHz per unit change in dielectric constant. The phase's shift demonstrates a lower percentage error than the amplitude and linearly moves towards higher frequencies with the increase in dielectric constant and tangent loss of MUT. The designed sensor can be prominently useful for detecting liquids' chemical characteristics in chemistry and medicine fields.