In this paper, a hexagonal split ring ultra-wideband absorber is proposed at THz frequency. The proposed structure consists of four graphene based hexagonal split rings, a dielectric substrate and graphene layer at the bottom. The proposed absorber achieves an ultra-wideband absorption characteristics from 0.95 THz to 2.96 THz with percentage bandwidth of 102.8% and bandwidth of 2.1THz with absorptivity beyond 90%. Also, 100% absorption is achieved from 2.07 to 2.33 THz making this unique feature for THz applications. Ultra-wideband response is mainly resulted because of overlapping of strong Electromagnetic (EM) resonance of the four split rings. The modes generated within the graphene split rings are merged for achieving ultra wide band response. Furthermore, the proposed absorber is polarization insensitive because of symmetry geometry and also exhibits absorption greater than 90% for incidence angle up to 75° for both TE and TM waves. In addition, tunability is achieved by varying the graphene chemical potential. These features make the proposed metal free absorber useful for terahertz applications and future nanoscale systems. The proposed absorber shows narrow absorption characteristics for higher graphene chemical potential values which can also be utilized for sensor applications.

Graphene-based ultra-wideband absorber for terahertz applications using hexagonal split ring resonators

Graphene-based metamaterials are gaining popularity for developing various reconfigurable and electrically tunable optical devices – especially in terahertz (THz) and infrared (IR) bands. Therefore, in this paper, we aim to investigate the broadband metamaterial-based absorber that efficiently absorbs the THz radiation ranging from 2.2 to 4.6 THz. The proposed absorber comprises a simple meta-square ring of graphene, which possesses different slots in its structure to induce multiple plasmonic resonances. It is observed that the proposed absorber manifests above 95% absorption for the normally incident THz waves, and it also maintains its absorption value over 80% for different obliquely incident operating conditions. Furthermore, the proposed absorber shows polarization-insensitive features. In addition, the absorption characteristics regulate from 95% to 15% by adjusting the chemical potential of graphene from 1 eV to 0.1 eV. Some of the salient features of the proposed absorber is largest reported bandwidth for single layer absorber with smallest footprint without sacrificing polarization insensitivity or amplitude tunability. From the application point of view, it could provide the pathway for implementing switching, cloaking, smart absorbers, and detection phenomena in the THz range. 

https://ieeexplore.ieee.org/ielx7/4563994/9999138/09994632.pdf

Polarization-Insensitive, Broadband, and Tunable Terahertz Absorber Using Slotted-Square Graphene Meta-Rings

In this paper, two identical Cylindrical Dielectric Resonator Antennas (CDRA) are stacked together to achieve Circular Polarization (CP). Ultra wideband impedance bandwidth and wide axial ratio bandwidth is achieved by three factors: stacking of similar DRs, stepped conformal microstrip feed line which will generate orthogonal modes and new partial ground plane with circular rings. Measurement results show that the proposed stacked Cylindrical CPDRA achieves an Impedance Bandwidth (IBW) of (S11 < −10 dB) of 72.48% (3.65–7.8 GHz) and Axial Ratio Bandwidth (ARBW) (AR <3 dB) of 44.12% (4.38–6.86 GHz), respectively. In addition, the proposed antenna shows dominant Left Hand CP with gain ranges from 1.4 to 6.5 dBic with maximum radiation efficiency of 93.3%. The advantages and novel points of proposed research work is as follows: (i) The novel configuration of stacking CDRA's along with stepped microstrip feed enhances ARBW, (ii) New proposed partial ground plane with two circular rings provides enhancement in IBW, (iii) Simple design and small height of DRs produces enhanced IBW, ARBW, Gain and Efficiency. Furthermore, by changing the position of circular rings on ground plane, the proposed antenna provides dominant LHCP to RHCP conversion and achieves polarization reconfigurability. The proposed antenna configuration covers the frequency range of applications of C‐band and military satellite communication.

A novel ultra wideband circularly polarized stacked cylindrical dielectric resonator antenna with modified ground plane

Our system proposes a wheelchair controlled by head gestures for people with quadriplegia paralysis (QP) or for those suffering from amputation of their hands and legs during the war in Iraq. The wheelchair design has an intelligent control that works with the movement of a patient‘s head in order to enable the patient to drive the wheelchair in the desired direction. The system consists of two main parts. The first is the transmitter in which sensing signals are transmitted to the second part and it consists of a 3-axes accelerometer (ADXL-345), a 433 MHz RF wireless receiver transmitter module, and Arduino UNO. The ADXL-345 sensor is placed in front of a hat that the patient wears. The system detects the direction of the patient's head movement then sends appropriate instructions to the wheelchair’s control part (receiving part). The receiving part is the wheelchair control system that consists of a 433 MHz RF wireless receiver transmitter module and an Arduino UNO. The Arduino processes the signals coming from the first part and moves the wheelchair accordingly in the desired direction. The research also provides an obstacle avoidance system with a range of 50 cm that prevents the wheelchair from colliding with objects. The head movement angles have been selected to be 40, 35 degree for vertical and horizontal movement respectively so that the QP patient feels comfortable to tilt his head in all directions and control the wheelchair easily. The system provides a very effective performance and accuracy.
ABSTRAK: Sistem ini bergantung kepada kerusi roda yang dikawal menggunakan isyarat kepala untuk mereka yang lumpuh kuadriplegia (QP) ataupun mereka yang dipotong tangan dan kaki semasa perang di Iraq. Ia merupakan reka bentuk pintar pada kerusi roda dan pesakit boleh mengawal pergerakan mereka dengan isyarat pada kepala. Sistem ini terdiri daripada dua bahagian utama iaitu yang pertama merupakan pemancar yang menghantar isyarat gerakan ke bahagian kedua dan ianya terdiri daripada 3 axis accelerometer (ADXL-345), modul penerima isyarat pemancar tanpa wayar 433 MHz RF dan Arduino UNO. Sensor ADXL-345 ini diletakkan di bahagian depan topi yang dipakai oleh pesakit. Sistem ini mengesan arah gerakan kepala pesakit dan kemudiannya arahan dihantar ke bahagian pengendali kerusi roda (bahagian penerimaan isyarat). Bahagian ini merupakan sistem pengendalian kerusi roda yang terdiri daripada modul pemancar penerimaan tanpa wayar 433 MHz RF dan Arduino UNO. Arduino memproses isyarat yang datang dari bahagian pertama bagi menggerakkan kerusi roda ke arah yang dikehendaki. Kajian ini turut menyediakan sistem mengelak halangan pada jarak 50 cm bagi menjauhi kerusi roda daripada melanggar objek. Sudut gerakan kepala telah dipilih pada 40, 35 darjah bagi gerakan menegak dan mendatar masing-masing, supaya pesakit QP merasa selesa bagi mengerakkan kepalanya ke semua arah dan mengawal kerusi roda dengan mudah. Sistem ini juga sangat cekap dan tepat dalam mengawal arah.

/pdf/intelligent-control-system-of-a-wheelchair-for-people-with-hafj1zsa4o.pdf

Intelligent control system of a wheelchair for people with quadriplegia paralysis

Graphene-based metamaterials are gaining popularity for developing various reconfigurable and electrically tunable optical devices – especially in terahertz (THz) and infrared (IR) bands. Therefore, in this paper, we aim to investigate the broadband metamaterial-based absorber that efficiently absorbs the THz radiation ranging from 2.2 to 4.6 THz. The proposed absorber comprises a simple meta-square ring of graphene, which possesses different slots in its structure to induce multiple plasmonic resonances. It is observed that the proposed absorber manifests above 95% absorption for the normally incident THz waves, and it also maintains its absorption value over 80% for different obliquely incident operating conditions. Furthermore, the proposed absorber shows polarization-insensitive features. In addition, the absorption characteristics regulate from 95% to 15% by adjusting the chemical potential of graphene from 1 eV to 0.1 eV. Some of the salient features of the proposed absorber is largest reported bandwidth for single layer absorber with smallest footprint without sacrificing polarization insensitivity or amplitude tunability. From the application point of view, it could provide the pathway for implementing switching, cloaking, smart absorbers, and detection phenomena in the THz range.

Abstract In this paper, a two port circularly polarized (CP) MIMO Cylindrical Dielectric Resonator Antenna (CDRA) with Quad-band response is designed for terahertz (THz) applications. This antenna is new since MIMO DRA antennas in the THz frequency range have never been described before. Also, by the varying graphene potential of the antenna, isolation between the two antennas is increased and CP tuning can be achieved which is another unique feature of this proposed antenna at THz region. The proposed DRA generates two higher order modes (HEM11δ and HEM12δ). The 3 dB Axial Ratio Bandwidth (ARBW) of 8.22, 2.48, 3.67 and 5.67% is achieved at four resonant frequencies. Various MIMO performance parameters are evaluated and these parameters are within acceptable limits. Advantages of the proposed design are quad response, higher order modes generation, CP tuning and good isolation between the ports. The tunability of graphene material allows it to provide CP responses in the frequency region that is most useful in biomedical applications. The use of a CP antenna in a THz biomedical application can improve system sensitivity by reducing polarisation losses and aligning them. All these features make the proposed MIMO DRA potentially suitable for THz applications.

HEM11δ and HEM12δ-based Quad band Quad Sense Circularly Polarized tunable Graphene-based MIMO Dielectric Resonator Antenna

Many people in the world today suffer from paralysis, physical illness, injury or any other disability. They have walking difficulties. A control system is developed with the aid of hand motion recognition for physically handicapped person with his gesture movement. The system is divided into unit for movement and wheelchair. This paper consists of gaining control of a wheel chair. This wheelchair can be operated by quick, joystick, hand movements. It consists of an accelerometer sensor that controls the users hand motion of the moving stools and clarifies the user movement and moves accordingly. When we changed the ways, the sensor registers values are changed & that values are given to atmega328p controller. Depending on the direction of the acceleration, Arduino controller controls the wheelchair ways like Left, Right, Forward, & Backward. This system also consists of ultrasonic sensor for obstacle avoidance. This program has the function of introducing control of Wheelchair direction reorganization of the hand gesture. For many applications the proposed wheelchair is used including schools, hospitals, old homes and airports. In addition, the SMS will be sent to the family members in case of emergency by pressing a single switch.

A Hand Gesture Based Wheelchair for Physically Handicapped Person with Emergency Alert System

A new ultrathin, ultra narrow band Dielectric based Metamaterial Absorber (DMMA) is designed for biosensing applications. The absorber provides dual-band response with perfect absorption with ultra-narrowband absorption characteristics with resonances at 5.98 THz and 6.72 THz. The absorber consists of a silicon based square split ring (SSSR) along with a graphene based circular split ring (GCSR) for the generation of perfect and ultra-narrow absorption characteristics. By varying the chemical potential of the graphene, the tunability and controllability is achieved for the proposed absorber. Due to its ultra narrow band absorption characteristics, the proposed absorber can be used for sensing cancer in various parts of the body, malaria, glucose in water and other chemicals. The unique features of the proposed absorber are its ultra-thin structure, simple design, tunability, polarization insensitivity, ultra narrow absorption bandwidth, high sensitivity, high Figure of Merit (FOM), and very high Quality factor (Q) values in a single device for detecting different diseases and chemicals.

Ultrathin, Ultra Narrow Band DMMA for Biosensing Applications

Soil moisture estimation has been an area of significant interest due to its widespread applications in the estimation and modeling of various large-scale ecological processes. Many approaches based on experimental observations and theoretical reasoning has been developed for soil moisture retrieval from SA systems. Among the major models developed, the empirical model proposed by Dubois et al. proves to be a good choice, because of its wide applicability and simplicity of implementation. Therefore to retrieve crop /vegetation covered soil moisture with SAR data is quite challenging. It is important point of research to minimize the use of apriori information while retrieving the parameters with SAR data. In this paper, two approaches have been selected for the retrieval of soil moisture and account for the vegetation effects. In the first approach, the water cloud model is used to introduce vegetation correction into the backscattering coefficients, which are then used in the inversion model to yield better soil moisture retrieval results. This requires apriori knowledge of several ground-measurable vegetation parameters. In the second approach, role of fusion of optical data into microwave synergistic model is applied where use of apriori information in minimizing the vegetation effects. First approach has been further modified in this paper to get good soil moisture estimation. The two approaches are applied to PALSAR data and MODIS data and its accuracy is estimated using Root Mean Square Error (RMSE) calculated between ground truth data and that measured using the two approaches. A quite good agreement between observed and retrieved soil moisture is observed from both the methods (water cloud & ground truth data.

P. Upender

Papers

Graphene-based ultra-wideband absorber for terahertz applications using hexagonal split ring resonators

HEM11δ and HEM12δ-based Quad band Quad Sense Circularly Polarized tunable Graphene-based MIMO Dielectric Resonator Antenna

A Hand Gesture Based Wheelchair for Physically Handicapped Person with Emergency Alert System

Ultrathin, Ultra Narrow Band DMMA for Biosensing Applications

Soil moisture estimation with PALSAR data near Roorkee region