Volume 79, Issue 11-12

This paper proposes a practical method for detecting the dominant motion characteristics of human walk and run based on micro-Doppler radar measurements. The method consists of two stages: In the first stage, the main body, i.e. torso, characteristics are identified by the help of Kalman Filtering based detection algorithm. Then, the detected torso signature is extracted from the two-dimensional (2D) range-Doppler image such that the residual image contains signatures from other body parts. In the second stage of the method, a human-Doppler threshold based envelope detection routine is employed to identify the micro-Doppler signatures from dominant swinging limps; i.e. arms and/or legs. To demonstrate the effectiveness and the validity of the proposed techniques, two measured examples from real world experiments are presented. These examples show that the signatures of main body and swinging arms are successfully detected and classified with good fidelity such that the velocity of the torso and the period/speed values of the arms are precisely estimated for much better classification of the human motion thanks to the proposed Kalman Filtering based detection, and human-Doppler threshold based envelope detection routines.

In this article, a circular compact implantable microstrip antenna is presented for bio telemetry. The proposed slotted circular patch antenna with a split ring in ground plane is constructed on dual sided Roger 6,010 with superstrate on the radiating patch leading to a volume of 33.35 mm 3 . The antenna resonates at 2.46 GHz ISM band with | S 11 | = −31.22 dB and has a gain of −37.9 dBi. According to IEEE and FCC regulations, human safety is ensured by evaluating the radiation absorption rate in the body and is considerably below the SAR threshold of 1.6 W/kg or 2 W/kg for 1 g or 10 g of body tissues. The maximum input power level for SAR limitation is 8.5 mW for 1 g and 11.5 mW for 10 gms of tissues. Homogeneous and heterogeneous body models are used for practical analysis. Antenna performance is analyzed on various body tissues, such as the liver, heart, muscle, and head phantom and validated using pork liver, heart, minced meat and with saline water. A link budget analysis is also performed for transmission coverage of the antenna using HFSS simulation and experimentally validated with LabVIEW and NI-USRP module. The findings indicate that the antenna is appropriate for implantable application for real time environment covering up to 15 m.

This paper proposes an embroidered SSPP TL (spoof surface plasmon polariton transmission line) based on a Minkowski fractal geometric structure. Theoretical analysis indicates that transmission lines with Minkowski fractal structures exhibit lower dispersion cutoff frequencies compared to conventional transmission lines. Additionally, the dispersion characteristics of fractal transmission lines can be adjusted by varying the indentation depth and iteration count of the fractal design. Based on this concept, both a conventional transmission line and a fractal transmission line were fabricated. Test results show that the dispersion cutoff frequency of the fractal transmission line is 31 % lower than that of a conventional transmission line of the same width. Measurements conducted on different body parts, combined with SAR (Specific Absorption Rate) analysis, further demonstrate that the proposed transmission line can be safely and efficiently applied in human-body wearable systems.

An ultra-compact diplexer using a half-mode substrate integrated waveguide (HMSIW) structure loaded by the miniaturized metamaterial unit cell is offered in this paper. The evanescent mode technique, the half-mode technique, and the meander technique have been employed, simultaneously to miniaturize the total dimension of the proposed diplexer. In the modified metamaterial unit cell, which is called the meander complementary split-ring resonator (MCSRR) unit cell, the meander slot line is etched inside the interior space of the ring instead of the conventional slot line in the traditional complementary split-ring resonator (CSRR) unit cell. Accordingly, the electrical size of the MCSRR unit cell is smaller than the conventional CSRR unit cell with the same physical size. By loading the introduced MCSRR unit cell on the HMSIW structure, a miniaturized diplexer has been designed and simulated. To verify the performance of the proposed component, the designed HMSIW-MCSRR diplexer has been fabricated and measured. A reasonable agreement between simulated and measured results has been achieved. The fractional 3-dB bandwidths of the up and down channels are 3.3 % and 2.8 % at 2.45 GHz and 3.55 GHz, respectively. The total size of the proposed diplexer is about 0.25 λ g  × 0.08 λ g .

A new N -way reconfigurable power divider with path switching and frequency tuning functions is proposed. The divider successfully realizes flexible path switching and frequency adjustment by using the innovative design of PIN diodes, reconfigurable parallel coupling lines and reconfigurable short-circuit branches. By dynamically adjusting the state of the PIN diode, the port connection and disconnection functions can be realized, and an advanced isolation network is introduced to ensure excellent port isolation performance during port switching. In addition, by embedding a varactor diode ( C v 2 ) between the coupling lines of the input port, the impedance matching during port switching is effectively guaranteed. Furthermore, by loading a reconfigurable short-circuit branch containing a varactor diode ( C v 1 ) on one side of the input port coupling line, the frequency adjustment function is realized. Finally, N transmission modes with 2 N  − 1 operating states can be realized. For verification, a four-way reconfigurable power divider is designed and fabricated, and 15 states of four transmission modes of the power divider are realized, each state enabling frequency tuning capability. The results facilitate the potential application of the proposed power divider in wireless communication systems.

In this manuscript, a dualband bandpass filter is designed and fabricated in X and K frequency bands. The proposed filter is implemented based on the half mode substrate integrated waveguide technology. Two resonant slots and a complementary split ring resonator are etched on the top metallic layer of the proposed structure. Therefore, the proposed filter can be easily integrated to other lateral components. Moreover, an efficient method is presented to extract the equivalent circuit model of the dual band filter. The proposed model is investigated in four separate stages to considerably reduce the encountered complexity. A theoretical background is utilized to provide the primary values of the circuit elements. These circuit elements are further modified using an optimization algorithm to provide best matching with full wave simulations. Finally, the designed filter is fabricated to validate the simulation and equivalent circuit results. The operational frequencies and fractional bandwidths of the dual band filter are 9.9 GHz/48 % and 20.75 GHz/20 %, respectively. The simulation, measurements, and equivalent circuit results are in good agreement together.

A square octagon split ring resonator (SOSRR) based six-band polarization-insensitive metamaterial absorber (MMA) with a high effective medium ratio (EMR), and excellent absorption is proposed in this study. It can be utilized as an S, C, X, and Ku band frequency absorber and as a sensor at 3.34 GHz (S-band). A unique patch has been introduced in the proposed unit cell to achieve high polarization insensitive properties with excellent absorption of 76 %, 82 %, 92 %, 99 %, 98 %, and 98 % respectively under S, C, X, and Ku band frequency spectrum. The distinctive features of this proposed SOSRR unit cell are its simple, unique structure with a high EMR value of 11.12, and polarization-insensitive up to 90° at 3.34, 5.08, 7.95, 11.68, 14.26, and 15.89 GHz respectively. The designed MMA unit cell is fabricated on a loss FR-4 dielectric substrate with an electrical dimension of 0.089 λ 0  × 0.089 λ 0 . Measurement of absorption value for the unit cell and array structure performance verified by experiment with excellent agreement. The suggested MMA is very attractive for refractive index sensing applications due to several features, including its low profile, excellent angular stability, polarization insensitivity, sensitivity (S), quality factor (QF), and EMR value.

In this paper, a metamaterial-based Multiple-Input Multiple-Output (MIMO) antenna structure with high isolation at the N257 Band (from 26.5 to 29.5 GHz), of the 5G millimeter-wave applications is presented. A resonator structure based on a metamaterial (MTM) cell exhibiting low values of constitutive parameters and achieving a Near-Zero-Index (NZI) at the targeted frequency band is investigated by leveraging the Epsilon-Near-Zero (ENZ) principles. This MTM cell serves as the radiating element of our proposed antenna, placed at the end of a 50 microstrip feed line. A 50 dB isolation between a two elements antenna array is achieved through an isolation technique that combines the characteristics of the MTM cell with a modified ground plane. Furthermore, our antenna exhibits desirable performance metrics, including lower Envelope Correlation Coefficient (ECC < 0.0007) values, high diversity gain (DG > 9.99 dB) and lower Channel Capacity Loss (CCL < 0.4 bits/s/Hz), making it a promising candidate for 5G MIMO applications in the millimeter-wave range.

Design of end-fire circularly polarized (CP) antennas on metal-bezel mobile terminals for satellite direct link poses considerable challenges. To address this challenge, we propose an end-fire CP antenna for metal-bezel mobile terminals. A metal rectangular loop antenna is placed at the top of the structure to create CP radiation. A T-shaped capacitive coupling structure is employed to improve the axial ratio (AR), while a concave slot is integrated into the T-shaped feeding network to form a matching circuit, thereby enhancing impedance matching. A prototype antenna is fabricated to validate the design. Measured results demonstrate that the antenna provides a −6 dB impedance bandwidth of 0.52 % (2,484–2,497 MHz), a 3 dB AR bandwidth of 0.85 % (2,474–2,495 MHz), and a peak gain of 2.3 dBic. Its end-fire radiation has a wide coverage beamwidth up to 103° and 44° for two principal cuts, making it suitable for the S-band of the BeiDou Satellite Navigation System (BDS). The proposed antenna features a compact design, provides ample space for future MIMO systems, and is an ideal candidate for metal-bezel mobile terminals to provide satellite direct link.

This paper presents a novel 3D-printed microstrip patch antenna designed to enhance bandwidth and gain for X-band applications. The proposed antenna features an innovative open book shape (OBS) structure formed by two triangular prism-shaped substrates symmetrically positioned above a planar substrate. The 3-D structure of the antenna increases the substrate thickness to improve the gain and bandwidth. The substrate is fabricated by employing a 3-D printing technique. Later, a copper plate is pasted on the substrate to realise the radiating patch. The proposed antenna has dimensions of 33 × 30.4 mm 2 , achieves a gain of 10.7 dBi and a return loss bandwidth of 31 %, covering the 8.2 GHz–11.3 GHz frequency range. The proposed OBS antenna demonstrates significant performance enhancements compared to existing designs, establishing it as a high-performance solution for X-band applications.

Two important performance measures in wireless communication are data rate and bandwidth. It is necessary to adjust wireless technology to achieve the highest possible data rate. Terahertz (THz) frequency is increasingly being used in a variety of applications because to its non-ionizing properties. THz technology can achieve high data rates of up to Tera bits per second (Tbps). The proposed antenna incorporates THz technology as well as a photonic crystal (PhC) structure to improve antenna performance. This work introduces a unique Double Pie Drilled Patch antenna (DPDPA) and investigates its characteristics using the antenna tool. This study optimizes the suggested antennas by adjusting the PhC air hole shapes, lattice value, and hole dimensions. The optimized DPDPA based on the rectangular air hole PhC model, produces −78.41 dB return loss (RL), 1.0002 VSWR, and 23.5 dBi gain at 2.10 THz frequency. Delivering a rapid data rate in wireless connections and other diverse streams is aided by the suggested patch antenna.