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Feature Selection (FS) is critically important for optimising the performance of Intrusion Detection Systems (IDSs) used in Wireless Sensor Networks (WSNs). However, selecting an optimal number of relevant features from massive IDS data sets has been an ongoing FS research problem. Many approaches use Machine Learning (ML), such as nature-inspired population-based and Differential Evolution (DE)-based algorithms for FS. However, the main drawback of DE is that it has a premature convergence issue, which leads to false convergence. In this paper, a novel mutation strategy is proposed to alleviate premature convergence and to develop a modified DE-based FS algorithm called DE with maturity extension (DE-ME). The novel mutation is achieved by changing the mutation factor in the DE/rnd/1 based on K-Nearest Neighbour (KNN) as the most efficient implementation without adding further complexity to the design process. The proposed DE-ME algorithm improves the FS operation with significant performance improvements in terms of overcoming premature convergence and increasing accuracy for selection. The DE-ME algorithm was used to select the most effective features from 41 features in the Network Security Laboratory Knowledge Discovery in Databases (NSL-KDD) dataset. The accuracy of DE-ME is high at 99.66 %, its False Positive Rate (FPR) is low at 0.464 %, and the true positive rate (TPR) achieved is 99.80 %. In addition, the number of features selected by DE-ME is 6 out of 41 features in the dataset.

A simple arrangement of wheel-shaped copper microstrip antenna is presented for operation in the 24 GHz frequency band. In this structure, a coaxial feed probe was utilized to generate vertical polarization, and a wheel-shaped microstrip with four coupling arms was used to produce horizontal polarization. An antenna comprising of two copper sheets assembled between the air-substrate was manufactured and characterized experimentally. The measured and simulated values are in close compliance with each other. A stable in-band omnidirectional radiation patterns were achieved thereby ensuring a proper combination of the field vectors from the feed probe and the radiating arms. The antenna occupied an overall footprint of 8 mm to fruitfully realize −10 dB impedance bandwidth >3 GHz and radiation efficiency of ~100%. In the operating frequency band from 22.5 to 25.7 GHz, axial ratio