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In this study, a novel technique to achieve multi-band performance for both reduced and conventional size circular microstrip patch antennas loaded with metamaterial has been proposed. Incorporation of symmetric slotting concept with the concept of additional mode modification for both MNG (µ negative) and ENG (ɛ negative) metamaterial loaded circular patch antennas have been shown. The use of metamaterial creates an unconventional mode, whereas symmetrical slotting not only modifies another band but also improves the gain by around 1 dB of unconventional mode for MNG loaded antenna. Design algorithms for metamaterial loaded circular patch antennas have been developed to achieve size reduction and highly directive multiband property. Based on these design algorithms, at first a reduced size triple band circular patch antenna loaded with MNG metamaterial has been shown where around 35% size reduction is achievable. Later, a triple band conventional size circular patch antenna partially loaded with ENG metamaterial has been designed with high gain and directive performances for all three bands compared to previously reported such antennas.

A new and compact sensor based on the complementary split-ring resonator (CSRR) structure is proposed to characterize the relative permittivity of various dielectric materials, enabling the determination of soil water content (SWC). The proposed sensor consists of a circular microstrip patch antenna supporting a 3D-printed small cylindrical container made out of Acrylonitrile-Butadiene-Styrene (ABS) filament. The principle of operation is based on the shifting of two of the antenna resonant frequencies caused by changing the relative permittivity of the material under test (MUT). Simulations are performed enabling the development of an empirical model of analysis. The sensitivity of the sensor is investigated and its effectiveness is analyzed by characterizing typical dielectric materials. The proposed sensor, which can be applied to characterize different types of dielectric materials, is used to determine the percentage of water contained in different soil types. Prototypes are fabricated and measured and the obtained results are compared with results from other research works, to validate the proposed sensor effectiveness. Moreover, the sensor was used to determine the percentage of water concentration in quartz sand and red clay samples.

A self-decoupled technique is described that enables the radiating elements in the antenna array to be densely packed for multiple-input multiple-output (MIMO) wireless communications systems. High isolation between the adjacent antenna elements is obtained by fixing the radiating elements in an orthogonal configuration with respects to each other. Current from the adjacent ports cancels their impact which results in low mutual coupling. The additional benefit of this configuration is realizing a densely packed array. The ground plane of each radiating element on the array board itself are isolated to mitigate surface wave propagations to suppress mutual coupling between the antenna elements. The radiating elements are based on a modified edge-fed circular patch antenna that includes a curved slot line and open-circuited stub to widen the array’s impedance bandwidth with no impact on the antenna’s footprint size. The proposed technique was verified with the design of an antenna array of matrix size 4 × 4 centered at 3.5 GHz. The array had a measured impedance bandwidth of 4 GHz from 1.5 GHz to 5.5 GHz, which corresponds to a fractional bandwidth of 114%, peak gain of 3 dBi and radiation efficiency of 84%. Its average diversity gain and envelope correlation coefficient (ECC) over its operating band are 9.6 dB and <0.016, respectively. The minimum isolation achieved between the radiating elements is better than 15 dB. The dimensions of the array are 0.4 × 0.4 × 0.039λ_g^3. The proposed array has characteristics suitable for sub-6 GHz wireless communication systems

Due to the low-profile and multiband properties circular patch antennas (CPA’s) have become more popular. The proposed F-slotted CPA enhances performance attributes including bandwidth, gain, and miniaturization by using an F-shaped slot in the patch and a partial ground plane. An inset feed is used to design a dual band F-slotted CPA for S-band and C-band applications. F-slotted CPA is fed by using line feeding technique with an impedance of 50 Ω. The top plane of the F-slotted CPA has a modified circular patch, while the ground plane is a partial ground plane. The parametric analysis of the F-slotted CPA is obtained to verify the performance of the proposed antenna. A finite element method tool, Ansoft HFSSv13 is used to simulate the F-slotted circular patch antenna (CPA). The proposed F-slotted CPA resonates at 2.8 GHz and 4.8 GHz frequencies with obtained S11 of – 25.8 dB, – 14.6 dB respectively and offers VSWR of 1.1 and 1.4 at 2.8 GHz and 4.8 GHz respectively Fractional bandwidths of 28.5 % (2.5-3.3 GHz) and 10.41 % (4.5-5 GHz) are achieved at 2.8 GHz and 4.8 GHz frequencies respectively, with S11 of – 25.8 dB and – 14.6 dB. 3 dBi gain of 3 dBi has been observed. F-slotted CPA occupies an area of 40 40 1.6 mm3. These results make the F-slotted CPA suitable for S-band and C-band applications.

In this study, a single band 28 GHz antenna with defected ground structure (DGS) has been proposed. The integration of a DGS is explored to exploit ground plane defects for achieving wideband operation. Through systematic design and optimization, our approach achieves remarkable bandwidth enhancement, expanding from 0.75 GHz to 5.78 GHz, covering frequencies from 26.43 GHz to 32.21 GHz, resulting in an impressive impedance bandwidth of 20.5%. Notably, the proposed methodology significantly improves the reflection coefficient, reducing it from -16 dB to -57 dB. Furthermore, the antenna demonstrates a gain of 5.123 dBi and an enhanced voltage standing wave ratio (VSWR) of 1.0056348. Comparative analysis against existing works underscores the superior performance of our antenna design, affirming its potential for various applications. This work presents a novel DGS featuring a circular microstrip patch antenna (MPA) with dimensions of 8×8×0.5 m3, utilizing Rogers RT5880LZ substrate (ε=2) with a thickness of 0.5 mm.

This paper presents a low-cost circular patch antenna sensor developed for measurement of moisture content in lentils and rice. The proposed sensor was modeled and simulated in HFSS after that the prototype was fabricated by chemically etching the FR4 material of 1.6 mm thickness. Measurements were conducted using a Vector Network Analyzer. The presented antenna sensor is resonating at 2.45 GHz frequency. Calibration equations were obtained by utilizing moisture content and reflection coefficients values. The moisture content varied between 2.04 and 11.11% based on wet weight. A good agreement between the actual and calculated values of moisture content validates that this proposed antenna sensor could serve as a moisture sensor for rice and lentil grains. For rice, the sensitivity is found to be 0.0071, and the regression coefficient is equal to 0.9976. In case of lentil, the values of the regression coefficient and sensitivity are 0.9981 and 0.0088, respectively. Furthermore, a real-time moisture sensing setup has made using a laptop with LabVIEW software, ESP32 microcontroller, VNA, and an Ethernet connection. The moisture content values can be seamlessly displayed in real time on mobile devices or laptop for convenient monitoring and analysis.

This paper presents a passive wireless long-range displacement sensor that is based on the circular patch antenna, and the detecting range of the sensor can be customized. The sensor consists of a chipped circular antenna with two opened rectangular windows, a substrate, and a ground plate with a sloping channel. No bonding between the antenna and the ground plate allows for the chipped antenna to slide along the sloping channel. The channel will drive the current flow on the plate once the chip is activated, increasing the effective electrical length and, consequently, decreasing the resonant frequency of the circular antenna. The sensing mechanism equates the measuring displacement to the relative movement of the antenna with respect to the ground that achieves the measurement of long-range displacement and, thus, the proposed sensor can avoid stress damage to the antenna due to excessive deformation. Three different range sensors were simulated in the the Ansoft high frequency structure simulator (HFSS). The results show that the resonance frequency of the antenna has a linear relationship with the varying chute depth beneath the chip. Three sensors were fabricated, and the experimental results also validated that the sensitivity of the sensor can be adjusted.

This paper presents a novel defected ground structure-based slotted circular patch antenna for mm-Wave application. A circular patch antenna with a compact size of 10 mm×8 mm×0.75 mm is fabricated in the lab. The designed antenna has a 2 GHz impedance bandwidth that covers the frequency range of 42GHz to 44GHz. It achieves a directional radiation pattern for millimeter-wave applications and has a maximum realized gain of 6 dBi at the operating frequency of 42.65 GHz. Defected ground structure (DGS) is loaded on the bottom of the dielectric substrate, which improves the gain and reduces the surface wave propagation. The proposed antenna has achieved circular polarization which makes it suitable for the mm-Wave application.

Recent studies and research have centred on new solutions in different elements and stages to the increasing energy and data rate demands for the fifth generation and beyond (B5G). Based on a new-efficient digital beamforming approach for 5G wireless communication networks, this work offers a compact-size circular patch antenna operating at 60 GHz and covering a 4 GHz spectrum bandwidth. Massive Multiple Input Multiple Output (M–MIMO) and beamforming technology build and simulate an active multiple beams antenna system. Thirty-two linear and sixty-four planar antenna array configurations are modelled and constructed to work as base stations for 5G mobile communication networks. Furthermore, a new beamforming approach called Projection Noise Correlation Matrix (PNCM) is presented to compute and optimise the fed weights of the array elements. The key idea of the PNCM method is to sample a portion of the measured noise correlation matrix uniformly in order to provide the best representation of the entire measured matrix. The sampled data will then be utilised to build a projected matrix using the pseudoinverse approach in order to determine the best fit solution for a system and prevent any potential singularities caused by the matrix inversion process. The PNCM is a low-complexity method since it avoids eigenvalue decomposition and computing the entire matrix inversion procedure and does not require including signal and interference correlation matrices in the weight optimisation process. The suggested approach is compared to three standard beamforming methods based on an intensive Monte Carlo simulation to demonstrate its advantage. The experiment results reveal that the proposed method delivers the best Signal to Interference Ratio (SIR) augmentation among the compared beamformers.

This work, presents the design and realization of two new miniaturized circular antennas as well as their effects on the human body. The first step consists in simulation each bi-band antenna at 2.5 GHz and at 5.2 GHz for wireless applications using the simulators HFSS and CST Microwave studio. The second step is manifested by the type of permeability substrates, the modifications of the radiating element and the ground plane as well as the modification of the feeding technique. All these miniaturization methods were used to limit the peak of specific absorption rate (SAR) in the human body. The SAR is calculated on a 1 and 10 g tissue mass respectively. The performed tests show that the SAR rate, which affects the human body tissues and obtained by the antenna with a full ground plane, is lower than that provided by the antenna with a truncated ground plane. Furthermore, the SAR rate observed in the different frequency bands for the antenna 2 complies with the standards proposed by the international commission on non-ionizing radiation protection.