M.M. Sharma

Compact Planar Monopole UWB Antenna with Quadruple Band-Notched Characteristics

A compact planar monopole UWB antenna with quadruple band-notched characteristics is analyzed and presented. By introducing a C-shaped slot, nested C-shaped slot in the radiating patch and U-shaped slot in the feed line, quadruple band-notched characteristics are achieved at frequencies of 2.5, 3.7, 5.8 and 8.2GHz. The proposed antenna has been fabricated and tested. Measured impedance bandwidth of the antenna is 2.35{12GHz, which covers Bluetooth and UWB band, for VSWR 2, for rejecting 2.5/3.5GHz WiMAX, WLAN and ITU 8GHz band signals, respectively. The average gain of this antenna is 4.30dBi with a variation of §1:8dBi over the whole impedance bandwidth. Signiflcant gain reduction over the rejected band is also observed. The antenna shows good omnidirectional radiation patterns in the passband with a compact size of 40mm £ 34mm.

Digital image authentication system based on digital watermarking

In these days, people are using social networking sites for sharing their life moments as images. And another side other users can access or even download those digital images. Faker can exploits by editing and modifying the original image. Modify images can then be upload and share. The illegal use of personal image comes under copyright law. This research paper introduces a prototype for Digital Image Authentication System (DIAS). This system can perform visible and invisible watermarking on image. DIAS is applicable for color and gray images. The input image could be of any size, and the resultant image size would be same as input image. DIAS identifies the ownership of digital image using Digital Watermarking. The Digital watermarking concept is used to hide and detect information from image. It is the best way to copyright protection of the user. By the use of digital watermarking, user can blame on faker for ownership. This is known as an Authentication System for ownership identification. The complete system consists of two functions, one for hiding information inside image and other for detecting information from image. In this approach, digital watermarking performed using Discrete Wavelet Transform (DWT) and analyzed its results.

Ultra-wideband truncated rectangular monopole antenna with band-notched characteristics

Design and performance of an ultra-wide band truncated rectangular monopole antenna with band-notched characteristics is presented in this paper. In the proposed antenna, split ring resonator (SRR) is etched inside the truncated rectangular patch of the monopole antenna to achieve band-notch operation. The achieved impedance bandwidth of antenna is from 2.43 GHz to 13.30 GHz, for VSWR <; 2. With the insertion of SRR in truncated rectangular patch band-notched characteristic from 5.04 GHz to 6.09 GHz (VSWR >; 2) suitable for IEEE 802.11a WLAN band (5.15 - 5.35 GHz and 5.725 - 5.875 GHz) and HIPERLAN/2 band (5.45 - 5.725 GHz) is achieved. The proposed antenna shows average antenna gain of 4.35 dBi with a variation of ± 1.7 dBi over the impedance bandwidth. In the notched band, the antenna gain falls down to 3.45 dBi as compared to truncated rectangular monopole antenna gain of 5.65 dBi.

Printed fractal elliptical monopole antenna for UWB application

A new elliptical ultra-wideband fractal antenna with elliptical iterations is presented in this paper. The proposed antenna is based on Descartes Circle Theorem (DCT). The proposed structure is fed by the 50 Omega microstrip line. The antenna is fabricated on a 1.59 mm thick FR-4 (relative permittivity of 4.4) substrate. The antenna structure is analyzed using a transmission line matrix (TLM) method based CST Microstripes. The simulated impedance bandwidth ratio 18.31:1 shows good agreement with the experimental results for VSWR<2. The fabricated antenna exhibits omni-directional radiation pattern and the measured results show a good agreement with the simulated one. It has been demonstrated numerically and experimentally that this antenna is suitable for ultra-wideband (UWB) applications.

Full Composite Fractal Antenna with Dual Band used for Wireless Applications

In this paper a full composite fractal antenna, having a modified Sierpinski fractal antenna with 50-Ω microstrip line, used for dual band wireless applications. The S11 parameter and radiation characteristics of the antenna design indicate that a Sierpinski fractal antenna with circular slot having Dual Band frequency bandwidth from 3.8 GHz to 4.4 GHz and 4.8 GHz to 5.4 GHz to covering 5.2 GHz for C-Band and X-Band wireless applications in 3.8 GHz- 14 GHz frequency range. The proposed antenna is fed by a 50-Ω microstrip line and designed on a low cost FR4 substrate having dimensions 96 (L) ×72 (W) × 1.5 (t) mm3 with □r=4.9 and tan δ= 0.025. The antenna shows acceptable gain with nearly omni-directional radiation patterns in the frequency band.

An extremely wideband printed antenna for wireless communication systems

A coplanar waveguide (CPW) fed semi circular disc antenna with a modified ground plane is presented. The proposed antenna consists of a semicircular radiating patch and semicircular arc-shaped ground plane. To achieve extremely wideband, two modifications are introduced. The first one is to modify the ground plane, and the second one is to insert slits near the feed point. Theoretical results show that the proposed antenna operates over 3.0 to 40 GHz for VSWR < 2. Details of the proposed antenna are presented, and simulated results show that the antenna has stable radiation patterns and good gain over its whole frequency band.

Admittance analysis of nonuniformly spaced phased arrays of waveguide apertures in a ground plane

A general formulation for the analysis of a phased array of waveguide apertures in a common ground plane has been given for finite number of elements and nonuniform spacings based on network representation of the system. The analysis yields the radiation pattern, reflection coefficient, and aperture field in each waveguide. The pattern of an array of physically identical elements is expressed as superposition of patterns of infinite number of arrays. The formulation, when applied to single and two aperture cases, confirms the known results. It is then applied to investigate the properties of the element position modulated phased array of 15 rectangular waveguide apertures excited by uniform incident waves. Uniformly spaced arrays are also analyzed for comparison. The dominant mode and one higher order evanescent mode are included in the computations. The results show that the overall power reflection coefficient of the nonuniform array does not undergo any peaks over a wide scan range. It is concluded that the advantages of nonuniformly spaced arrays in suppressing grating lobes and eliminating blind spots are physically realizable.

A Compact Frequency Selective Surface Based Band-Stop Filter for WLAN Applications

This paper presents a compact frequency selective surface (FSS) based band-stop spatial filter for WLAN application which can be useful for modern communication system. The proposed structure is designed on PTFE substrate which have exceptional weather and heat resistance with excellent insulator characteristics. It is a single sided metallic square patch FSS which give 10-dB insertion loss bandwidth from 5 to 6 GHZ and resonated at 5.5 GHZ. The unit cell has the aspect dimension of 0.302λ×0.302λ×0.0366λ millimeter cube. The proposed design has been simulated using CST Microwave studio. CST microwave studio is based on finite difference time domain method (FDTD).

A novel ultra-wide band antenna design using notches and stairs

This paper describes the parametric study of a novel rectangular planar ultra-wide band antenna (UWB). The proposed design exploits U and T-shaped notches with stairs at two corners on the radiating patch along with stepped microstrip feed. The stairs are also used at the corners of the partial ground plane with a rectangular notch and an electromagnetically coupled stepped rectangular strip. The proposed UWB antenna is designed and simulated using Computer Simulation Technology Microwave Studio (CST-MWS). This antenna operates in a frequency band ranging from 3.0985 to 10.666 GHz with the overall dimensions of 34 mm (L), 37.5 mm (W) and 1.7 mm (H). The VSWR is less than 2 for entire operating frequency range. The impedance bandwidth of the proposed design is nearly 7.5675 GHz. This antenna finds its applications in 5.2/5.8 GHz WLAN, 3.5/5.5 GHz WiMAX, 4 GHz C band and lower frequencies of X band. The effect of the stepped ground plane and the dimensions of U, T and rectangular shaped notches on the optimization of the return loss is parameterized and discussed in detail.

A quad-band reconfigurable microstrip-fed circular disc monopole antenna for multiradio wireless systems

A quad-band reconfigurable monopole antenna for multiradio wireless systems is presented and designed on Rogers 5880 substrate. The quad-band antenna comprised of circular patch, parasitic double T-stub, two inverted L-stubs. Single diode is employed between stubs to make antenna reconfigurable and obtained four resonance at 2.3/3.89/4.96/5.70 GHz. Impedance bandwidth of antenna are 350/410/110/650 MHz for LTE 2300 and 2.4 GHz WLAN, C-band, 4.9 GHz WLAN, 5.5 GHz WiMAX and 5.8 GHz WLAN bands.