This paper presents an innovative coupling design for a bandpass substrate integrated waveguide (SIW) filter, enabling high selectivity and facilitating flexible design. The proposed filter design has two parts: one is a mixed coupling structure, and the second part is a cross-coupling path. Both parts contribute to transmission zero (TZ) near the passband. Cross-coupling creates TZ, while mixed-coupling offers TZ and filter design flexibility. The cross-coupled path is analyzed in three configurations: without a load, with an inductive load, and with a capacitive load. To demonstrate this, three filter designs are simulated and fabricated based on the type of path load. The filter achieves center frequencies near 27 GHz with a fractional bandwidth exceeding 3%. Four to five TZs are introduced to enhance selectivity. Key performance metrics include a return loss exceeding 15 dB within the passband and an insertion loss between 1.65 and 2.1 dB. The measured results align with the simulated results, validating the structure and theory of the cross-coupled load.

The growing global population and rising food demand, coupled with environmental challenges, call for advanced agricultural technologies. Plant body communication (PBC) is an emerging approach that utilizes intrinsic plant tissues for signal transmission, enabling seamless integration of plant sensors via a unified gateway for real-time monitoring and controlled magnetic and/or electric stimuli across growth stages. Realizing PBC requires precise characterization of the electrical and magnetic properties of plant tissues. In this work, the M - H characteristics of different types of Mangifera indica L. tissues were measured across different seasons using a vibrating sample magnetometer under magnetic fields up to 1.8 x10(4) Oe at room temperature. The measured data were analyzed using an arctan-based multicomponent nonlinear model, with parameters extracted via nonlinear least-squares optimization, capturing seasonal and tissue-specific variations. The reliability of the extracted magnetic parameters was validated using the coefficient of determination (R-2). These findings provide new insights into plant-based biomagnetism and support the development of robust PBC systems (for continuous monitoring and nutrient diagnostics) in precision agriculture.

This paper presents a novel design of an electric coupling structure for a substrate-integrated waveguide (SIW) bandpass filter, which exhibits flexible characteristics, sharp roll-off, and high out-of-band rejection, making it suitable for 5G applications. The filter structure is designed with a rectangular slot with a metallic cylindrical via and a narrow propagating path. The proposed design creates a transmission zero (TZ) and shows flexibility in terms of TZ and bandwidth. This structure can be used for both inline and cross-line SIW topologies. Two filters are simulated and fabricated to validate the design. The first filter is designed at 27.12 GHz frequency with 4.98% fractional bandwidth (FBW) and one TZ at a higher stopband using an inline filter topology. The second filter is centered at 27.46 GHz frequency and 4.11% FBW with two TZ at both sides of the passband in crossline topology.

ABSTRACT In this paper, a wide band tapered rod two‐element MIMO antenna system is designed using a perforated H‐guide section for W‐band applications. The antenna system comprises of a metallic housing and a perforated H‐guide section with tapered input/output dielectric sections. The dielectric section is sandwiched between the two halves of the metallic housing. The designed MIMO antenna is fed by a pair of WR‐10 rectangular waveguides. The perforations in the dielectric section not only provide the mechanical stability to the structure but also facilitate high inter‐port isolation. The MIMO performance of the designed antenna system is calculated with reference to envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL). These parameters are below the satisfactory range of 0.5, 10 dB, and 0.4 bit/s/Hz. High gain (> 12 dBi), high port‐to‐port isolation (> 28 dB), and end‐fire radiation characteristics of the designed antenna system, make it a potential candidate for W‐band communication systems.

In this paper, a perforated H-guide based directional coupler is designed and developed for the W-band frequency spectrum (75-90 GHz). It is fed by the rectangular waveguide WR-10. The designed directional coupler utilises two perforated H-guide sections that are connected through a dielectric bridge. This bridge not only provides mechanical stability between the perforated H-guide sections but also improves its coupling performance. The directional coupler with different couplings (15, 20 and 25 dB) are designed in this paper. To verify the proposed design approach, a directional coupler with 20 dB coupling with a bandwidth of 18.18% (75-90 GHz), is fabricated, and its characteristics are measured. The measured results agree well with the simulated ones.

The rapid global population growth is driving increased food demand, requiring innovative agricultural solutions amid limited resources. A key advancement in smart agriculture is directly monitoring plants and crops instead of their environment. Plant body communication (PBC) is a novel and innovative technique that uses a plant's biological tissue to transmit signals, enabling seamless integration of sensors on, in, and/or near the plant with a single gateway. This gateway supports real-time plant monitoring and delivers essential electric and/or magnetic signals at any growth stage. This comprehensive process is grounded in the accurate measurement of dielectric properties, their characterization, and the equivalent electrical circuit modeling of plant tissues-a crucial aspect of this research that is instrumental in implementing the PBC technique. This article reports the measurement of the dielectric properties of Mangifera indica L. stem tissue using a Physical Property Measurement System instrument incorporated with an LCR meter from 4 Hz to 4 MHz. Furthermore, the parametric modeling of the dielectric spectrum, based on a multiple Cole-Cole model with up to two poles, is derived using the nonlinear least-squares method to represent the frequency-dependent variations of permittivity up to two relaxation processes. Additionally, complex impedance spectroscopy is presented and analyzed with the plant tissue's biological analogy to develop an equivalent circuit model (ECM) with parameter values fit to the measured data. PBC shows promise as a future agricultural method in precision agriculture (PA) for year-round plant growth monitoring and nutrient deficiency diagnosis, paving the way for efficient and sustainable farming.

In this letter, a wideband high-gain dielectric lens integrated with a tapered rod antenna using a perforated H-guide is presented for the W-band [(75 to 110) GHz] applications. The designed antenna is fed through a rectangular waveguide WR-10. The antenna can be divided into three sections: metallic housing, perforated H-guided-based tapered dielectric sections, and extended hemisphere dielectric lens. The tapered dielectric section has three parts: tapered feed, perforated H-guide, and radiating tapered end. Further, to enhance the gain, an extended hemisphere dielectric lens is integrated with the radiating tapered end. The proposed antenna shows endfire radiation characteristics with a substantial gain of around 23.9 dBi and excellent cross-polarization (x-pol) levels in both the E- and H-planes. The mechanical stability, wide impedance bandwidth, better radiation efficiency, and high gain of the designed antenna make it a suitable candidate for W-band applications.

This paper introduces a bandpass filter (BPF) designed using the substrate integrated waveguide (SIW) technique, targeting the 5G upper band frequency range. The filter is designed based on cross-coupled structure. The filter have mainly two part of consideration, one is novel proposed mixed coupling design loaded cavity and second part is cross-coupling cavities. Both part of design contribute transmission zero's (TZ) formation to improve the stopband performance and selectivity of the filter. Proposed filter design simulated and fabricated for the validation of the concept. The filter center frequency is 26 GHz with 930 MHz bandwidth along five TZ's. The measured minimum insertion loss (IL) is 1.9 dB, and return loss (RL) is better than 18 dB. The filter model demonstration use PCB fabrication process and due to this it is cost-effective and suitable for large production of 5G application.

A novel diagonal coupling structure on substrate integrated waveguide (SIW) bandpass filter is proposed. The diagonal coupling design is formed in a manner that introduces the cross-coupled path without any addition of a cavity. So, the proposed design reduces the number of cavities to create multiple paths for the formation of cross-coupling. The diagonal coupling and cavity-loaded mixed-coupling structure suppressed the higher mode of the filter, and it further improved the stopband performance. The design is used as universally applicable to any of the bandpass filter topologies. Here, inline, cross line on a single layer and one multilayer topology based on three filters designed and fabricated to prove the universal use of proposed diagonal coupling. The testing results agree well with the simulated response.

A novel mixed-coupling substrate integrated waveguide (SIW) filter design of a dual-band response with improved selectivity has been proposed in this paper. A mixed-coupling structure is formed using a slot line with inductive load and an iris window is introduced to couple cavities on a single-layer substrate. The proposed design is highly flexible, with three independent coupling parameters. It shows passband and transmission zero (TZ) tuning and efficiently produces three TZs. The TZs are positioned at the lower and upper edges of each passband. The fabricated model is presented for the validation of the proposed filter model. The measured results are closely aligned with the simulated data. This SIW filter is cost-effective, high-performance, and suitable for large-scale production for 5G applications.

This paper describes the development of an RF resonator based tilt sensor. The sensor is designed using 3D printing and metallization. It operates in the frequency range of 1 to 2 GHz. The essential parameter to detect the change in the tilt or inclination of the surface is variation in resonant frequency. The RF-based 3D printed tilt sensor consists of two parts. One is a semi-circular fixed hollow RF resonator and the other is a semi-circular pendulum. Due to the inclination of the surface, the pendulum will move inside the hollow RF resonator which results in change in relative permittivity and consequently to the variation in resonant frequency. Using an RF resonator and pendulum-based structure with 3D printing makes it applicable for a wide range, low cost and accurate. This sensing system provides a linear correlation and resolution of 2 MHz.

We present an analysis of the thin film Nd0.5Dy0.5FeO3/Si, focusing on its spin reorientation, dielectric, and magnetic characteristics. Exploring spin reorientation involves assessing dielectric and magnetic attributes across temperatures ranging from 2 to 300 K, at different applied frequencies. At temperatures between 34 and 24 K, a spin reorientation phenomenon is observed at a frequency of 10 kHz. As the applied frequency increases, the region of spin reorientation shifts towards higher temperatures. At 2 MHz, this region shifts to the temperature range from 30 to 45 K. This behaviour of the spin reorientation and shift in the spin reorientation region is further validated by AC Susceptibility data. By examining the magnetic order within the antiferromagnetic thin film, this study introduces an innovative approach to magnetic order investigation using dielectric properties.

This study explores the room-temperature magnetodielectric (MD) and magnetoresistance (MR) properties of Nd0.5Dy0.5FeO3 thin films on n-type silicon substrates from 4 Hz to 2 MHz. The observed MD effect registers a change of similar to 23 %, and the MR effect manifests a change of similar to 11 % when subjected to an applied magnetic field of 2.5 T at a frequency of 177 Hz. Interestingly, the MD effect was absent at 1 T across all frequencies. However, we observed an MR of 6 % at 1 T, implying the possibility of an intrinsic MD effect or the co-existence of both intrinsic and extrinsic contributions to the MD effect. To comprehensively gauge the dielectric properties of the thin film at higher frequencies, a 5-GHz microstripline resonator was fabricated. Coupled with experimental data and simulations, this study reveals a dielectric constant of similar to 56 for the Nd0.5Dy0.5FeO3 thin film at 5 GHz and 300 K.

This paper presents a novel coupling design for substrate integrated waveguide (SIW) bandpass filter. The coupling structure is formed by a rectangular slot cut on the top metal surface and inductive post. This design is based on the mixed coupling structure, where magnetic and electrical coupling play the filter formation with two transmission zeros at both sides of the pass band. For the validation, fabrication, and testing of the model is performed.

This paper presents a Band Pass Filter (BPF) using substrate integrated waveguide (SIW) technique in the Ka-band frequency range. The device model is designed with an inductive post in a single layer of substrate, which is compact and easy to fabricate. Filter have a center frequency around 31.5 GHz, B.W. = 2 GHz, fractional B.W. = 6.29%, Insertion loss at center frequency is around 0.6 dB & Return loss is better than 22 dB, Stop Band rejection is better than 15 dB at both side of Pass Band. A fabricated model is presented for validation of the simulated filter design. The measured result is in good agreement with the simulated result. The proposed Filter can be used in 5G applications with good performance.

Abstract In this paper, a frequency reconfigurable, circularly polarized graphene-based antenna has been designed. The antenna consists of a truncated graphene patch and single series cross-aperture coupled feeding. Two orthogonal modes are generated by the sequential rotation of the electromagnetic signal on the graphene patch through the cross aperture in ground plane. The frequency reconfigurability can be achieved by varying the external dc bias voltage at the graphene patch. The proposed antenna can resonate in the broad range of frequencies from 1.22 to 1.44 THz at chemical potential from 0.5 to 1.0 eV. In this range of chemical potential, the axial ratio of the antenna is less than 3 dB. The maximum gain of antenna has been achieved up to 4.6 dBi with 62% radiation efficiency at the chemical potential of 1 eV.

As compared to the current 4G mobile technology, a higher bandwidth and a lower latency will be provided by 5G and beyond technologies, which is planned to be deployed in 2020-2030, providing connectivity to billions of devices and enabling bandwidth with more than hundreds of megabits per second and very low latency less than 1 millisecond (ms). The tunable wideband RF system is essential part for realization of above mentioned technology in which tunable Band Pass Filter (BPF) is important microwave component. The tunable filter with variable frequency response is designed by altering of the electrical path of the mode current. Spoof surface Plasmon Polaritons (SSPPs) based BPF structure are the artificial engineered material-based design. This is trend towards of Microwave Photonics or Metamaterial Physics to application of tunable Bandpass Filter at Microwave Frequency. The paper comprises of corrugated ring resonator SSPP structure with tuning capability using novel approach at Microwave Frequency.The corrugated ring resonator-based bandpass filter show octave bandwidth i.e. the 3 dB passband is achieved between 3. 5-7.0 GHz. The varactor tuned corrugated ring resonator is shown to achieve electronically tunable BPF.

In this paper, we designed and analysed the broadside coupled H guide based directional coupler for the Sub-THz frequency range. The designed broadside directional coupler is fabricated using the Form Lab SLA (stereolithography) based 3D printer. In this technique, Grey resin material is used which acts as a polymer material. To excite the LSM mode firstly we designed the broadband transition from rectangular waveguide to H-guide which is fed by the rectangular waveguide WR-2.8. The even and odd mode properties of the broadside coupled H-guide have been studied. The proposed broadside coupler has a 24dB coupling at a frequency of 330GHz. To enhance the mechanical stability we introduced the bridge between the broadside coupled guides. In addition to the bridge and altering the gap between the waveguide, the coupling is varied with respect to the frequency.

Nd 0.5 Dy 0.5 FeO 3 epitaxial thin film grown on LaAlO 3 (001) substrate by pulsed laser deposition technique shows a significant magnetodielectric effect. At 100 K, a variation of around 13% in relative permittivity is observed at frequencies higher than 2 MHz in the presence of 5 T. This variation in relative permittivity (ε΄) increases to about 50% at 2 K. To utilize the observed magnetodielectric effect, we have designed the microstripline based resonator circuit using High-Frequency Structure Simulator (HFSS). Simulations are performed for the two values of the real part of permittivity (in the absence and presence of an external magnetic field) to observe the magnetic field tunability of the resonance frequency. A shift of 27% is observed in the resonant frequency of the microstripline based resonator on Nd 0.5 Dy 0.5 FeO 3 epitaxial thin film.

Human Body Communication (HBC) technique uses human body as communication channel for transferring various physiological data. Like humans, plants are also composed of different types of tissues with highly specialized functions. For feasibility study of electrical signal transmission through plant body; two pair of electrodes viz. one pair for the transmitter and one pair for the receiver involving stem of full Mangifera Indica plant by using capacitive coupling has been setup. The signal transmission through the different parts of stem of different thickness has been analyzed in time domain at 100 kHz. Different channel lengths have been used for capacitive coupling and different electrode distance has been used for galvanic coupling under similar environmental conditions at room temperature. Effect of positioning the ground electrode in both longitudinal and transverse directions with respect to signal electrode in galvanic coupling has also been investigated and reported in this paper.