This research paper presents the design, simulation, fabrication, and characterization of a compact antenna operating in the Industrial, Scientific, and Medical (ISM) band $(4.65 \text{GHz}-6.075 \text{GHz})$ and provides a high gain wideband (1.4250 GHz) for wearable devices. This antenna is designed for wearable medical devices. The designed antenna has shown good performance including its return loss (>-35dB), Bandwidth $(1.425 \text{GHz})$, radiation pattern, gain 10 dB, and efficiency.

This study introduces a compact monopole antenna designed for near-field breast tumor detection within the 915MHz ISM band. By integrating rectangular slots along the antenna's non-radiating edges, the design achieves a 59% size reduction, resulting in a compact footprint of 0.4 lambda( g )& times; 0.27 lambda( g ). To enhance its performance, a partially reflective surface (PRS) is added beneath the antenna, significantly boosting gain from 1.86 dBi to 5.3 dBi, while maintaining high radiation efficiency between 95% and 99% across the 907-920MHz range. A key feature of this study was its S-parameter analysis using a realistic three-dimensional breast phantom composed of both adipose and fibroglandular tissues. This study shows that the antenna's reflection coefficients are sensitive to tumor size, enabling the detection of structural variations in breast tissue. Furthermore, the electromagnetic behaviour of the antenna was modelled to assess the how power is transmitted and reflected through different breast layers, with and without the PRS. Specific absorption rate (SAR) analysis confirmed that the sensor operates safely at power levels up to 215mW. The experimental results closely aligned with simulations, confirming the antenna's reliability and effectiveness in detecting early-stage breast cancer by identifying tumors of varying sizes in both adipose and fibroglandular tissue environments.

A miniaturized Antipodal Vivaldi Antenna (AVA) based on linearly flared radiating fins for wireless and medical applications is proposed. The proposed design uses an FR4 substrate with a linearly flared microstrip patch AVA in ultrawide band (UWB). Furthermore, the compactness of the design is achieved by using the innovative linearly flared radiating fins, which can be viewed as a performance enhancer. An antenna operates in the frequency range of 3.1-10.6 GHz. It is designed, fabricated, and measured over the entire UWB spectrum. The size of the proposed antenna is 50 & times; 32 & times; 1.6 mm3 (0.516 lambda 0 x 0.331 lambda 0 x 0.016 lambda 0 at 3.1 GHz). The antenna exhibits a measured peak gain of 13.71 dBi at 10.6 GHz and a spectrum average gain of 7.61 dBi. The proposed antenna achieves a % fractional bandwidth of 174%, which is higher than that of most reported AVAs while occupying a smaller electrical volume. Experimental studies show stable performance and radiation parameters, which indicate that it has potential application for wireless and medical applications.

This article presents a high-gain, non-invasive Vivaldi antenna array sensor for microwave breast tumor imaging, operating over a wide frequency range of 3.2 to 7.8 GHz with a compact footprint of 1.2λg × 0.9λg. The antenna features a simplified microstrip-fed design that achieves a peak gain of 10 dBi while maintaining strong sensitivity in differentiating between healthy and malignant breast tissues. A key innovation of this work is the development of a realistic, biomimetic breast phantom modelled in CST Microwave Studio, whose anatomical shape, closely resembling an actual human breast, has not been previously reported in the literature. Comprehensive performance evaluation includes both simulated and measured S-parameters, along with Specific Absorption Rate (SAR) analysis conducted at multiple tumor locations and sizes. The SAR results reveal significant contrasts between healthy and tumor-embedded regions, validating the sensor’s ability to detect tumors accurately. Additionally, Power Distribution Analysis (PDA) is performed across each layer of the multilayer phantom over the entire operational bandwidth, offering detailed insight into the incident, reflected, and absorbed electromagnetic power. Experimental validation corroborates the simulation outcomes, demonstrating the proposed sensor’s potential for early-stage breast cancer detection through its high gain, broadband operation, and enhanced tissue sensitivity. Finally, a detailed implementation of the Confocal Microwave Imaging (CMI) algorithm is presented, which reconstructs a high-contrast 2D image that accurately localizes the tumor within the phantom.

This paper presents a circular-shaped filtering antenna design. By incorporating a rectangular slot into a conventional circular patch antenna, the design introduces a filtering feature with an adjustable radiation null, which can be easily controlled by varying the length of the slot. The antenna operates at a frequency of 5.8 GHz, making it suitable for WLAN/WiFi applications. It achieves an impedance bandwidth of 5.70-5.93 centered at 5.8 GHz, with a radiation null at the upper edge of the band at 6.05 GHz. The antenna also exhibits flat in-band realized gain characteristics, around 7.74 dBi. Additionally, simulated results show unidirectional radiation in the boresight direction with extremely low cross-polarization. The proposed design is straightforward, yet it effectively combines filtering performance with a simple configuration.

Here, a planar design of a filtering antenna is presented. The design mainly comprises a semi-circular substrate integrated waveguide (SIW) cavity as a driven element and a rectangular parasitic patch with loaded metallic vias. The coax feed is used to excite the SIW cavity and the cavity excites the rectangular patch by a coupling mechanism. The loaded four metallic vias help realize the gain characteristic’s sharp selectivity with radiation null at both edges of the operating band. The simulated investigation shows that broadband response is achieved by using such a topology. The measured results show a broad band response of 7.90% impedance bandwidth with a flat realized gain performance of 7.34 dBi in the entire operating band. The proposed design offers attractive features such as small foot prints, high gain, small cross polarization, high selectivity, and a high front-to-back ratio.

A novel 4-port MIMO self-diplexing antenna design is presented, utilizing half-mode substrate integrated waveguide (HMSIW) technology. This antenna operates at 4.9 GHz for WLAN and 5.8 GHz for ISM communications, achieving approximately 30 dB isolation. The half-mode topology reduces the antenna size by 50% while retaining the TE110 mode characteristics. To increase bandwidth, a rectangular slot is added in each cavity, splitting the mode into odd-TE110 and even-TE110. Careful optimization of antenna parameters and the perpendicular arrangement of radiating elements ensure effective self-diplexing. A prototype is manufactured, with experimental results confirming simulations. The antenna shows peak gains of 5.2 dBi at the lower frequency and 5.9 dBi at the upper frequency, with efficiencies exceeding 94% in both bands. All MIMO-diversity parameters also met satisfactory levels.

A new design for a 4-port multiple input multiple output (MIMO) self-diplexing antenna is introduced, utilizing half-mode substrate integrated waveguide (SIW) technology. This antenna operates simultaneously at 4.9 GHz for WLAN and 5.8 GHz for ISM band communications, maintaining an isolation of approximately 30 dB. By employing the half-mode topology, the antenna size is reduced by 50% while preserving the dominant mode TE110 characteristics. To enhance bandwidth, a rectangular slot is etched at the centre of each cavity, splitting the dominant mode into odd-TE110 and even-TE110 modes. Through careful optimization of antenna parameters and the perpendicular placement of radiating elements for different frequencies, the design ensures self-diplexing property. To validate the design, a prototype of the antenna is manufactured, and experimental results are verified with simulations. The proposed antenna demonstrates a peak gain of 5.2 dBi in the lower-frequency band and 5.9 dBi in the upper-frequency band, with a high efficiency exceeding 94% in both of the frequency bands. Additionally, all MIMO-diversity parameters were found to be within satisfactory limits.

This work presents a 2x2 sequentially rotated patch antenna array designed for a body-area network (BAN) biotelemetry system operating in the unlicensed 5.8 GHz band. Circular polarization is achieved by truncating two diagonally opposite corners of the square patches, which excites two orthogonal modes within the antenna. This design enables the generation of circularly polarized radiation. A prototype of the antenna array was fabricated and experimentally validated, demonstrating strong agreement between simulated and measured results in terms of impedance bandwidth, axial ratio, gain, and radiation characteristics. With its compact and low-profile design, the proposed antenna is well-suited for wearable devices operating in the ISM band.

A compact self- diplexing multiple-input multiple-output (SD-MIMO) antenna has been designed using a quarter-mode substrate integrated waveguide (SIW) cavity for wireless communication applications. This design employs two quarter-mode (QM) SIW cavities-one circular and -one rectangular in the self-diplexing element, which allows for high isolation (>20 dB) across the operating channels without the need for additional isolation networks. This feature provides a significant advantage over traditional designs that typically require extra isolation components to maintain high isolation between closely spaced antenna elements.

This work presents a 4x4 dual sequentially rotated patch antenna array designed for a body-area network (BAN) biotelemetry system operating in the unlicensed 5.8 GHz band. The array is constructed using four 2x2 circularly polarized antenna modules, each employing truncated square patches to excite two orthogonal modes, thereby generating circularly polarized radiation. To interconnect the four 2x2 units, a dual sequentially phase rotated feed network is implemented across the 4x4 structure. A prototype of the 4x4 array was fabricated and experimentally validated, showing strong agreement between simulated and measured results. With its compact configuration, enhanced performance, and suitability for wearable integration, this design is a promising candidate for high-performance BAN biotelemetry applications.

A Self-diplexing Multiple-Input Multiple-Output (SD-MIMO) antenna design utilizing a small foot-printed quarter-mode substrate integrated waveguide (QM-SIW) cavity has been developed for wireless communication. This antenna is envisioned for high-speed data transmission in capsule endoscopy applications. The use of a pair of quarter mode (QM) counterparts of circular and rectangular SIW cavities not only leads to a compact size but also enables high isolation among input ports over the operating channels. This is a significant advantage over conventional designs, which typically require additional isolation components to achieve high isolation among the closely spaced antenna elements. The measured result shows two operating frequency bands around 4.0 and 4.78 GHz. The measured gain values corresponding to resonant dips are 4.2 and 4.1 dBi, which are comparable to other MIMO antenna designs. Furthermore, the SD-MIMO has been optimized for use within an implantable medical device (IMD). The human phantom model of the stomach shows SAR values fall below 0.362 W/Kg.

In this research, an 8-element multi-input multi-output (MIMO) antenna is presented for millimeter wave communication systems. The present design incorporates two circular rings cojoined with a monopole. Both the rings are cross-coupled for better radiation and less interference properties. The present MIMO structure is designed from the reference antenna by placing antenna elements along X and Y axis. The overall dimensions of the presented MIMO structure are 50mmx70mmx1.6mm . The bandwidth of the proposed antenna ranges from 25.4 to 29.5 GHz, which covers the mm-wave frequency spectrum of n257 and n261 bands. The present MIMO antenna is a self-isolated MIMO antenna and provides the isolation of better than -27 dB which is desirable for the MIMO communication systems. To evaluate the diversity characteristics different parameters are examined like total active reflection coefficient (TARC), channel capacity loss (CCL), envelope correlation coefficient (ECC), and Diversity gain (DG). ECC of < .003, DG > 9.9999, TARC < -19.8 dB at 28 GHz, and CCL less than 0.4 is obtained for the proposed MIMO structure in the specified frequency range. With the acceptable radiation pattern, the gain achieved by this antenna is 6.6 dBi at 28 GHz. The proposed structure is fabricated and it is found that the Simulated and measured results agree closely.

In this work, a slotted rectangular microstrip patch antenna-array-sensor is proposed for breast tumor detection operating in Industrial Scientific and Medical (ISM) frequency band at 5.8 GHz. To increase the sensitivity and better coverage region, a 1x4 antenna-array with overall size 0.96 lambda(g) x 2.5 lambda(g) has been developed instead of a single element. To excite each antenna element, a 1:4 power divider is employed in corporate feeding with microstrip technology. To acquire the conforming ability on hemispherical surface, the antenna array sensor is realized on RT Duroid 5880 of thickness 0.508 mm. A monostatic radar-based technique using microwave signals is used to detect the contrast between healthy and malignant tissues. Initially, the sensor's performance has been evaluated over a multi-layered breast equivalent phantom comprising skin and fat layers along with tumor. Specific Absorption Rate (SAR) analysis is conducted to assess the variations in the biological tissues of the breast equivalent phantom, distinguishing between healthy and malignant tissues. Also, experimental results reveal that the 1x4 array sensor provides improved sensitivity, gain, and directional energy delivery, enabling better detection of tumors at varying sizes and depths.

A compact and lightweight Quarter Mode Substrate Integrated Waveguide (QMSIW) cavity-backed slot antenna is proposed as a near-field microwave resonant sensor for breast tumor detection, operating around the ISM frequency band. The proposed design is validated using two different feeding techniques: probe feed and microstrip line feed. When placed in proximity to breast tissues exhibiting abnormalities in dielectric properties, the sensor demonstrates exceptional sensitivity in its resonance characteristics. To tune the resonant frequency of ISM band, a slot is precisely etched into the antenna patch near the magnetic walls. The QMSIW cavitybacked antenna was initially designed to operate at 2.7 GHz, and the incorporation of the slot plays a crucial role in miniaturization while maintaining the sensor's sensitivity. For performance evaluation, the sensor is first tested with a healthy breast phantom, followed by a systematic variation of the tumor's position and radius. A significant contrast between healthy and malignant tissues is observed in both simulated and measured reflection coefficients, demonstrating the sensor's effectiveness in breast tumor detection.

This article introduces a near-field microwave sensor based on a monopole antenna for breast tumor detection. The designed antenna operates at 2 GHz and is miniaturized by 37% through the etching of two pairs of rectangular slots along its edges, achieving a compact footprint of 0.28λg × 0.42λg (where λg is the guided wavelength at 2 GHz). To enhance gain, a partially reflective surface (PRS) is positioned behind the radiating monopole, increasing the antenna gain from 2.15 to 7 dBi. The monopole antenna is fabricated using Rogers RT5880 (0.787 mm thickness), while the PRS is made from Rogers TMM13i (3.8 mm thickness). The proposed antenna exhibits high radiation efficiency (95-99%) across the 1.9-2.1 GHz bandwidth. A 3D artificial female breast equivalent phantom is developed to evaluate the sensor's performance. The PRS-enabled antenna is analyzed in terms of reflected and transmitted power variations at different distances from the phantom. Simulation and experimental results confirm that integrating PRS improves the sensor's sensitivity and its ability to differentiate between healthy and malignant tissues. Furthermore, specific absorption rate (SAR) analysis indicates that an input power of 50 mW meets SAR safety standards. The proposed antenna is compact, simple, and a safer alternative to X-rays, providing a portable solution for effective breast tumor detection.

This study investigates a single-layer substrate integrated waveguide (SIW) cavity-backed slot antenna and its 1 x 4 linear array counterpart. The antenna unit comprises an SIW-based rectangular cavity, dual arc-shaped slots, and a tapered microstrip feed line. Operating in TE102 mode, the antenna exhibits dual resonant frequencies, spanning from 8.71 to 9.05 GHz, with peaks at 8.8 and 8.98 GHz. Fabricated using conventional printed circuit board (PCB) techniques, the array design is subjected to tests for reflection coefficient, gain, and radiation patterns. The measured results closely match simulations, showcasing operational frequencies from 8.65 to 9.025 GHz, with an average gain of 8.24 dBi. With dimensions of 2.15 x 2.48 x 0.023 lambda 0 mm, the array offers advantages such as a planar feeding network, compact size, affordability, and ease of fabrication. These attributes position the proposed design as an ideal candidate for X-band wireless communication transceivers.

Here, a single-layered single-fed slot antenna is realized with low cross-polarization over the full operating bandwidth. This design consists of a circular-shaped cavity resonator, employed by using substrate integrated waveguide (SIW) technique and a square-ring slot on the upper metal cladding of the cavity. The antenna is fed using a probe feed which excites the design in dual mode, that is, slot mode and inset patch mode. Due to the proximity of these dual resonances, the antenna operates over a relatively wider bandwidth than previously suggested designs with the claim of low cross-polarization. The proposed design helps to realize more than 35 dB of co-to cross-pol isolation in both E and H planes. Overall experimental results demonstrate a good radiation performance, it is confirming up to 15-20 dB improvement in cross-polarization level with enhanced enhancement bandwidth which makes it appropriate for a modern wireless application.

In this article, a compact, lightweight, quarter mode substrate integrated waveguide (QMSIW) cavity-backed antenna is proposed as a near-field microwave sensor for breast tumor detection operating in the ISM frequency band. The proposed sensor exhibits excellent responsiveness in identifying anomalies in the dielectric characteristics of breast tissues. First, a QMSIW cavity-backed antenna is designed which operates at 2.78 GHz and then a complementary split ring resonator (CSRR) slot is etched on the patch of the antenna near the magnetic walls resulting in a shift of the resonant frequency to 2.6 GHz. The slot plays a crucial role in achieving miniaturization while maintaining the same sensitivity as the antenna sensor. The proposed antenna is fabricated on RT Duroid 5880 and the overall footprint of the antenna is 0.38 x 0.3 lambda(1). An experimental validation of the sensor is performed following the preparation of realistic heterogeneous breast phantoms, both with and without a tumor. Initially, the sensor's performance is examined over the healthy breast phantom and then subsequently evaluated by systematically altering the location and radii of the tumor. The simulated and measured S-11 results exhibit a notable disparity between healthy and malignant tissues. Additionally, a specific absorption rate (SAR) analysis is conducted to examine the differences between healthy breast tissues and malignant tissues. Furthermore, a power loss analysis was performed to evaluate the magnitude of reflected and attenuated EM waves in various female breast tissues.