In the present study, a pencil beam pattern synthesis of uniformly excited large thinned planar antenna (LTPA) arrays is proposed. The aim is to find out the best positions of ‘ON’ and ‘OFF’ elements in the antenna array corresponding to the lowest possible peak side lobe level (PSLL). Modified binary coded genetic algorithm (MBC-GA) is utilized to determine the optimum solution with less computational cost. In order to evaluate the performance of proposed method, a 32∗48-element LTPA array is considered for numerical analysis.
In this paper, synthesis of Ni0.5Zn0.5Fe2O4 nanoparticles via sol-gel process followed by fabrication of ultra-thin layer (90 μm) of ferrite-polymer nanocomposite on an aluminum (Al) substrate is carried out. The structural characterizations show that pure Ni-Zn ferrite phase formation occurred with average particles size of ∼ 19 nm. The nanocomposite coating shows excellent broadband absorption properties over the frequency range 4–15 GHz with absorptivity of greater than 85%. Simulations were performed for obtaining the optimum film-thickness of ferrite-nanocomposite and found that the return loss for varying thickness of ferrite layer was minimum for 5 μm thickness.
In this paper, a planar, compact, single-substrate, multiband 2 sets of 2-elements each multiple-input multiple-output (MIMO) antenna system is presented. The MIMO antenna system consists of a tunable 2 - element meandered and folded MIMO antenna to cover the LTE Band (698 MHz - 813 MHz) and a compact 2-element modified truncated cube wideband antenna to cover 754 MHz-971 MHz, 1.65-1.83 GHz and 2-3.66 GHz, respectively. The ground plane of this antenna behaves as a sensing antenna operating in 0.76-1.92 GHz, and 3.0-5.2 GHz. The upper band antennas operate in 0.728-1.08 GHz, 1.64-1.84 GHz, 2.1-3.69 GHz, and 5.01-5.55 GHz range to develop a complete antenna platform for cognitive radios (CR) and Internet of Things (IoT) applications. The antenna is fabricated on a low cost FR-4 substrate (epsilon(r)=4.4 tan delta=0.02) of dimensions 65 x 120 x 1.56 mm(3).
In this paper, design of a dielectric polarizer based potter horn antenna for providing circular polarization with good beam symmetry along with ±25° coverage is discussed. This is designed for deep space satellite TTC uplink application and frequency of operation is 7.15GHz-7.25GHz. The design aspects and the simulation results of antenna elements are presented. This antenna finds application in many future ISRO missions.
In this paper, the design of sheet-beam Extended Interaction Klystron (SBEIK) is discussed. The SBEIK is initially designed by implementing the preliminary equations and then modelled using CST-Microwave Studio (MWS) to obtain the dispersion characteristics by the Eigen-mode solver. The coupler design is carried out with stepped impedance transformer approach and is optimised to get a return loss of −54 dB. Particle-in-cell (PIC) simulation is carried out in CST-PIC solver indicated an RF output power of 7 kW and a gain of 28.4 dB.
This paper demonstrates the graphene as a competitive alternative to metals for antenna application. A conductive layer is developed by printing the cotton fabric by a commercially available graphene nanoparticle based ink and utilized to fabricate a rectangular patch antenna. It is shown that the patch antenna performance enhancement methods are likely applicable for graphene based conductive sheets over metal microstrip. The −6 dB impedance bandwidth of the antenna (24.2%) is enhanced by exciting the higher order TM02 mode and radiation efficiency (above 74% in the operating band) is improved using a low dielectric constant foam substrate. The prototype of the proposed design is fabricated showing excellent agreement between simulated and measured results.
This paper introduces a new concept where antenna engineering is explored as an 8-ary polarization shift keying (POLSK) technique. A multi-fed circular patch antenna has been used as POLSK modulator/demodulator with 8 polarization transmit/receive states. A full system has been designed, characterized, and successfully demonstrated. The antenna engineering would replace the complex electronic circuitry and make the system less expensive and less noisy. This technique is free from bandwidth limitation and should be attractive for high data rate communications.
A quantitative comparison is carried out between various transformations for evaluating the finite region of Sommerfeld Integral (SI). These transformations deform the integration path into upper half plane (u.h.p) and avoids location of pole singularities. Results are shown for the case of Horizontal Electric Dipole (HED) located in the superstate of a two-layer microstrip configuration backed by a perfect electric conductor (PEC). Comparisons suggests that the semi-elliptic contour for finite part of SI, and the weighted averages method (WAM) for SI tail is the best approach for small and large lateral electrical separation (ρ/λ).
In this paper, design of Substrate Integrated Coaxial Line (SICL) fed printed dipole antenna for Ka band application is demonstrated. The proposed antenna efficiently utilizes the out of phase surface current in the central and outer conductor of the SICL to excite the dipole antenna. The use of SICL removes the need of using balun to feed the dipole antenna and makes the feeding network simpler. The metal plate at the top layer acts as reflector for the dipole antenna which helps to enhance the gain of the antenna upto 5.38 dBi with a broad bandwidth of 2.37 GHz. The antenna is implemented in low profile planar substrate making it suitable for practical application in Ka band.
In this work, a high gain circular patch antenna has been proposed for X-band applications. 6.43 dB gain enhancement, compared to a circular patch, has been achieved in the broadside direction by loading the circular patch with a double layered superstrate. Simulation and optimization have been carried out using Ansys HFSS v.15. Measured results have been taken to validate the simulation result.
A single feed dual band dual circular polarized (CP) slotted loop antenna at C band communication for low cost application is presented in this paper. This antenna uses a microstrip transmission line to feed a ‘C’ shaped slot, on the opposite side of the substrate, two rectangular slotted stubs are placed across the diagonal line of the square loop to enhance the axial ratio bandwidth. Simulated results show that the antenna can used at 6.63 GHz centre frequency. The simulated impedance bandwidth is 3.7183 GHz i.e. 70.05% and axial ratio bandwidth are 125.8 MHz and 577.4 MHz, respectively. The measured return loss are from 4.4 GHz–5.41 GHz and 6.29 GHz–7.1 GHz. Simulated peak gain is 3.96 dBi at 5.08 GHz.
A Substrate Integrated Waveguide (SIW) based patch antenna with improved performance in terms of impedance bandwidth, radiation efficiency, gain, reduced cross-polarization level and harmonic suppression is proposed in this paper. In addition to the SIW technique, the reason of this improved performance is the use of a modified proximity microstrip feed line consisting of a stepped transformer followed by a pair of λ g /4 microstrip-line resonators. The designed antenna has a gain of 8.90 dBi, impedance bandwidth of 34.3% and radiation efficiency of 87.13% at 7.14GHz that are much higher compared to values reported in the literature for single layer patch antennas.
In this paper, a 3dB ultra-wideband (UWB) power divider has been designed using three wide-band coupled resonators. The resonator unit which consists of symmetric interdigital coupled input/output lines, resonates in two basic for broadening the operating bandwidth. Output ports maintains equal distance from the input in order to achieve in-phase power divisions. The prototype structure provides an equal magnitude, in-phase power division and adequate isolation at outputs from 3.82 to 10.2 GHz, which almost complies the FCC defined UWB frequency range. It has advantages like single layer, via free and compact in size.
Advanced communication systems require antennas with more bandwidth and smaller dimensions compare to conventional antenna. There have been increasing demands for antenna design that possess features such as size, low profile, multiband, broadband, low cost etc. Fractal antennas have entered the view of many as a very promising solution. Fractals were the term originally defined by Mandelbrot to describe the family of complex structures, which means broken or irregular fragments that possess an inherent similarity in their geometrical structure. In this paper, we have proposed a crown fractal antenna. It has been observed that simulated and experimental results of the proposed antenna have shown dual band behavior. The same geometry had proposed initially, but the substrate material used was RT-DUROID while we used FR-4 substrate here, which reduces the cost.
This paper presents the digital transmitter architecture using Class S power amplifier (PA) based on GaN HEMT transistor. In order to overcome the efficiency degradation problem in amplification of envelope varying signal, delta-sigma modulation scheme is used along with Class S power amplifier. The proposed Class S architecture is based on current switching Class D power amplifier which is designed and fabricated at 2 GHz. The result shows that the drain efficiency of 71.5% and gain of 11.6 dB is obtained at peak output power. LTE signal of 5 MHz band is used as an input to delta-sigma modulator for validating the functionality of Class S PA design.
A compact Multiband Microstrip Patch Antenna with V cut connected to U slot on patch for super high frequencies (SHF) in C band and X band applications is proposed. The proposed antenna fabricated on a FR-4 substrate with dimensions 40 mm (L) × 40 mm (W) × 1.6 mm (h), relative permittivity εr =4.4 and loss tangent δ = 0.025. The proposed antenna is designed by etching V cut connected to U slot on a rectangular patch(0.2473λ×0.3092λ) with inset feed. CST microwave studio suite software used to simulate and measurement is done on VNA. The proposed multiband antenna can be used for Satellite Communications, Citizens Broadband, IEEE 802.11a system, ISM Equipment, Amateur Radio, Aeronautical Radio navigation and Maritime applications.
In this paper, a simple and fast time domain technique is proposed to determine simultaneously the complex permittivity and thickness of the material under test (MUT) for future 5G applications. The proposed free space time domain technique is calibration independent, noninvasive and uses only the magnitude of power corresponding to the reflected multiple signals from the MUT. The method is validated experimentally for various samples under different background materials and the error in the extracted permittivity and thickness is found less than 5%.
A quad-band polarization independent metamaterial absorber have been presented and discussed in this paper. The proposed unit cell structure consists of meander line type structure surrounded by a square ring printed on FR4 substrate backed by copper ground. The proposed structure displays three diverse absorption peaks 3.2 GHz, 6.25 GHz, 8.23 GHz and 9.60 GHz with absorpties of 97.7%, 97.6%, 93.1% and 99.6% respectively. It is symmetrical in nature and makes the structure polarization independent. Surface current have been analyzed to visualize the absorption at different absorption peaks of the proposed unit.
In this paper a low profile ultra thin miniaturized wide band reflection type metamaterial surface is proposed. The measured 3 dB stop band of bandwidth 3.98 GHz from 8.02 GHz to 12.00 GHz is obtained. The wide band reflection characteristic is obtained by using modified circular split ring resonator as meta-surface unit cell. The proposed unit cells dimension is 0.25 λ × 0.25 λ × 0.025 λ making the proposed design low profile and ultra thin. The prototype meta-surface is fabricated and measured. A bandwidth enhancement of 50 % with electrical size reduction of 53.64 % is achieved. Miniaturized meta-surface with wide band characteristic have high value practical applications.
This paper presents a method for measurement of dielectric permittivity of different liquid chemicals. The experiment is carried out by using a homocentric resonator made up of steel. The experimental setup consists of Agilent N9320B RF spectrum analyzer with internally connected frequency generator. Spectrum analyzer and resonator connected with each other by a power line. A resonator has inlet and outlet for continuous flow of liquid chemical which acts as a dielectric material. When the liquid flows through the resonator an amplitude verses frequency graph is obtained on the spectrum analyzer. By observing A-F plot on the screen, a resonant frequency for various peaks is measured. By using resonant frequency, dielectric permittivity of various liquids is measured. The results of experimentation have shown that the variations in dielectric permittivity for different liquid chemicals are in the range of 0.59% to 7.82% which is acceptable. Thus, it is proved that the homocentric resonator system can be used efficiently for the measurement of the dielectric constant of liquid chemicals.
