M. V. Kartikeyan

Defected Ground Structure in the perspective of Microstrip Antennas: A Review

Defected ground structures (DGS) have been developed to improve characteristics of many microwave devices. Although the DGS has advantages in the area of themicrowave filter design, microwave oscillators, microwave couplers to increase the coupling, microwave amplifiers, etc., it is also used in the microstrip antenna design for different applications such as antenna size reduction, cross polarization reduction,mutual coupling reduction in antenna arrays, harmonic suppression etc., TheDGS ismotivated by a study of Photonic/Electromagnetic Band gap structures. The etching of one or more PBG element creates defect in the ground plane and used for the same purpose. The DGS is easy to be an equivalent L-C resonator circuit. The value of the inductance and capacitance depends on the area and size of the defect. By varying the various dimensions of the defect, the desired resonance frequency can be achieved. In this paper the effect of DGS, to the different antenna parameter enhancement is studied. Index Terms – Defected Ground Structure, Microstrip Antennas.

165-GHz coaxial cavity gyrotron

The basic investigations on a coaxial cavity gyrotron operating at 165 GHz have been accomplished and the feasibility of manufacturing a 2-MW continuous-wave coaxial cavity gyrotron at 170 GHz has been demonstrated. In the last measurements, the data required for fabrication of an industrial tube have been completed. The influence of misalignment of the insert on gyrotron operation has been investigated. The limitation of the high-voltage performance of the electron gun due to buildup of a Penning discharge has been suppressed and the leakage current to the insert has been measured as a function of the retarding collector voltage.

MICROSTRIP PATCH ANTENNA WITH SKEW-F SHAPED DGS FOR DUAL BAND OPERATION

The goal of this paper is to use defected ground structure (DGS) in microstrip antennas for dual band operation at microwave frequencies. The soft nature of the DGS facilitates improvement in the performance of microstrip antennas. A design study on microstrip patch antenna with speciflc DGS slot has been presented in the proposed work. In this paper, a stacked microstrip patch antenna (SMPA) has been designed for broadband behavior, and then skew- F shaped DGS has been integrated with a detailed study of possible DGS slots in a small area for dual band operation. The design and optimization of both the SMPA and DGS structures along with the parametric study were carried out using CST Microwave Studio V.9. Further, the dual band antenna, i.e., the SMPA with skew-F shaped DGS, has been fabricated, and the experimental results have shown a good agreement with the simulation ones.

Efficiency enhancement of microstrip patch antenna with defected ground structure

Defected ground structures (DGS) have been developed to improve characteristics of many microwave devices. Although the DGS has advantages in the area of the microwave filter design, microstrip antenna design for different applications such as cross polarization reduction and mutual coupling reduction etc., it can also be used for the antenna size reduction. The etching of a defect in the ground plane is a unique technique for the antenna size reduction. The DGS is easy to be an equivalent LC resonator circuit. The value of the inductance and capacitance depends on the area and size of the defect. By varying the various dimensions of the defect, the desired resonance frequency can be achieved. In this paper the effect of dumbbell shaped DGS, to the size reduction of a microstrip patch antenna is investigated. Then a cavity backed structure is used to increase the efficiency of the microstrip patch antenna, in which the electric walls are placed surrounding the patch. The simulation is carried out with IE3D full wave EM simulator.

METAMATERIAL INSPIRED PATCH ANTENNA WITH L-SHAPE SLOT LOADED GROUND PLANE FOR DUAL BAND (WIMAX/WLAN) APPLICATIONS

Due to the integration of difierent wireless applications at difierent bands on a single device, multi-band microstrip patch antenna is the best solution keeping the overall size of the device small. In the present work, a metamaterial-inspired antenna is proposed for WiMAX/WLAN applications. Design studies, parametric analysis, simulation results along with measurements for a L-shape slotted ground microstrip patch antenna with CSRR (Complementary Split Ring Resonator) embedded on patch structure operating simultaneously at WiMAX (3.5GHz) and WLAN (5.8GHz) are presented. The metamaterial-inspired loading is exploited to create resonance for upper WLAN band while an L-shape slot on the ground plane resonates at the WiMAX band, maintaining the antennas overall small form-factor. The measured S-parameter and radiation patterns of fabricated prototype show that the proposed design is suitable for emerging WiMAX/WLAN applications.

Possible operation of a 1.5-2-MW, CW conventional cavity gyrotron at 140 GHz

We present a study of the feasibility of continuous wave (CW) operation of a 140-GHz conventional cavity gyrotron at high power levels operating in the TE/sub 31,8/- and TE/sub 25,10/-modes. The question of mode selection is discussed, and a possible design of such a gyrotron with beam energy up to 90 keV and a current of 60-70 A is given. We find that it should be possible to operate a 140-GHz gyrotron at power up to 2 MW if a sufficiently high-order mode is used, although CW power may be somewhat lower.

Novel Printed MIMO Antenna With Pattern and Polarization Diversity

In this letter, a novel compact antenna system for diversity/multiple-input-multiple-output (MIMO) application is proposed for WLAN (5.8 GHz) band with good isolation between the two input ports. The novelty of the proposed MIMO antenna system is, though the resonators are physically separated by a distance of 0.029λ ( λ is the free-space wavelength at 5.8 GHz) equal to the thickness of the substrate (1.524 mm) used for the fabrication of the antenna system, the isolation between them is enough for practical application of the antenna for MIMO. The MIMO system possesses good pattern diversity and polarization diversity with good isolation without the use of any isolation enhancement techniques. Moreover, the concept can be extended to the realization of an MIMO antenna system to operate at other frequencies with suitable scaling and optimization of geometrical parameters of the antenna topology.

A Compact Dual-Band Antenna With Omnidirectional Radiation Pattern

In this letter, a low-profile planar microstrip antenna is proposed to operate at lower WLAN (2.4 GHz) and WiMAX (3.5 GHz) frequency bands. The antenna has good omnidirectional radiation pattern for both the bands with compact form-factor. The obtained result shows that the proposed dual-band omnidirectional microstrip antenna has better impedance bandwidth and high radiation efficiency while maintaining the structural compactness. The electromagnetic model of the proposed antenna is developed in CST Microwave Studio for analysis and optimization. The fabricated antenna and measured results are presented.

Design of a 42-GHz 200-kW gyrotron operating at the second harmonic

The design of a 42-GHz 200-kW continuous-wave gyrotron operating in the TE/sub 4,2/ mode at the second cyclotron harmonic is presented. This study includes mode selection, cavity design, and interaction calculations for power and efficiency as a function of various parameters, as well as preliminary design of the beam optical system, launcher, and window. This device is intended to serve as a heating source for a small experimental steady-state Tokamak, which requires microwave power, preferably in the form of a Gaussian beam.

RF Behavior of a 200-kW CW Gyrotron

The RF behavior of a 42-GHz 200-kW continuous-wave (CW) gyrotron for plasma heating in a small experimental tokamak is presented in this paper. The operating mode, as a matter of technical convenience, is the mode, as is required by the end user. Design constraints are carefully investigated, and starting currents are computed. Cold-cavity and self-consistent calculations are carried out; power and efficiencies are computed for a typical set of beam parameters. In addition, a triode-type magnetron injection gun (MIG) has been designed, and the realistic beam parameters obtained from these MIG calculations are used in time-dependent self-consistent calculations which are carried out before and after space-charge neutralization. These studies on RF behavior suggest that it is feasible to realize CW powers in excess of 200 kW at 42 GHz with as the operating cavity mode.