Deepti Das Krishna

Novel Millimeter-Wave Antenna Array Using Half Mode Substrate Integrated Waveguide (HMSIW)

A millimeter wave antenna using Half Mode Substrate Integrated Waveguide (HMSIW) is presented. Narrow rectangular patch is used as radiating element fed by the open end of the HMSIW. Simulation results are presented for antenna array designed on Alumina substrate for 24GHz and 60GHz band.

Circularly polarized square patch antenna with improved axial ratio bandwidth

This paper proposes and analyses a circularly polarized square patch antenna with an improved axial ratio bandwidth covering a frequency of 1.665GHz to 1.845GHz. The antenna attains circular polarization using the perturbations — truncated corners and well-shaped slots embedded on the patch. The results indicate that the antenna attains desirable axial ratio (below 3dB) for a wide elevation range of −134° to 47°. When compared to conventional truncated corner circularly polarized square patch antenna, the axial ratio bandwidth of the proposed antenna is increased by 30MHz. The antenna model is fabricated, tested and the measured results show a high correlation with the predicted ones.

Specific Absorption Rate Reduced (SAR) Mobile Phone Antenna Designs

In this work, we have presented a study of various antennas used in mobile phones in terms of their Specific Absorption Rates (SARs). Conventional antennas such as a half wavelength dipole antenna (0.835 GHz), rectangular patch antenna (0.8 GHz) and Planar Inverted F Antenna (PIFA) (0.8 GHz) are designed and simulated. In order to reduce their SAR values, Electromagnetic Band Gap (EBG) structure is placed near the dipole antenna. The various plots such as the S-parameter, radiation patterns and SAR values are generated to investigate results. The human head model with six layers having the appropriate material properties is designed to have a realistic approach in the detailed study on the SAR. All simulations are done in Ansys HFSS.

On the Visualization of the Weaver's “Third Method” for SSB Generation

ABSTRACT The Weaver technique or the third method of generation of single sideband modulation with suppressed carrier (SSB-SC) amplitude modulation (AM) signals is one such algorithm which looks deceptively simple when compared with the more analytically tractable phase-shift method. With the advent of digital signal processing (DSP) techniques such as the CORDIC (coordinate rotation digital computer) algorithm, an elegant low-complex implementation of the Weaver technique is now feasible, which necessitates a better understanding of the underlying principle. However, despite its popularity, it is not explained in detail in conventional text books on communication engineering and in general literature. Using the background theory of complex signals (I and Q), in this paper, we have depicted the entire operation graphically. Combined with necessary mathematics and implementation ideas, this will be a comprehensive tutorial on the third method of SSB-SC generation and should motivate students to look at the underlying mathematical theory of problems in the area of communications and signal processing for similar interpretations.

Miniaturization of Square Patch Antenna using Complementary Split Ring Resonators

In this paper, a novel compact micro strip antenna, designed on FR4 substrate, is proposed. Here, a compact square patch antenna is designed in such a way that the radiating patch is loaded by a layer of metal between the patch and the ground which makes the antenna operate at a lower frequency. The antenna design is optimized to obtain a resonant frequency of 2.45GHz. Miniaturization of the antenna is obtained by using meta-material based structures inscribed on the metal layer. The meta-material structure used here is a square-shaped complementary split ring resonator (CSRR). On varying the number and size of inclusions, high levels of miniaturization are observed.

Frequency and polarization reconfigurable fractal microstrip antenna

A compact fractal antenna which is both frequency and polarization reconfigurable is presented in this paper. The proposed paper presents a Minkowski fractal microstrip antenna loaded with slots operating at a frequency of 1.7GHz. Frequency and polarization re-configurability is achieved by introducing four slots on the fractal shaped patch with PIN didoes as switches across them. By varying the ON and OFF conditions of PIN diodes, the antenna is able to operate in 5 different frequencies and as well as for two different polarization.

Analysis of coaxial stub type balun fed dipole antenna

Analysis of a series-parallel coaxial stub type balun having a wider operating bandwidth is discussed in this paper. The balun, operating for a frequency range of 180 to 400MHz, is made using a pair of RG58C/U coaxial cables and is integrated with a simple dipole antenna. Simulations are done in ANSYS HFSS and the results of coax fed dipole with and without balun are compared. Results show that the balun is successful in cancelling or choking off the imbalance current. The SPCS type balun fed dipole antenna is fabricated at 180MHz and measurements are carried out.

A planar UWB antenna design with triple band-notches for WiMAX, WLAN and downlink of X-band satellite communications system

A printed ultrawideband (UWB) monopole antenna with an overall size of 32x26mm2 with triple band-notches is presented in this paper. The antenna has an inverted T-shaped stub introduced in the monopole patch, two C-shaped parasitic strips and a pair of rectangular split-ring resonators close to the feed line and patch junction to introduce the desired frequency notches. The ground plane is beveled for wideband performance. The three band notches are 3.3-3.6 GHz, 5.05-5.90 GHz and 7.25-7.75 GHz for IEEE 802.16 (WiMAX) band, the wireless area network (WLAN) band and the downlink of X-band satellite communication systems respectively. The frequency band over which the antenna radiates is between 2.8 and 11.8GHz with a VSWR<;2 and in the stop bands it has high rejection level. The antenna is simulated using both frequency domain based solver and a time domain based solver and the results are found comparable, which proves that the antenna with the notches shows good performance for various UWB applications.

A Cost Effective Hybrid-Log Periodic Dipole Antenna (H-LPDA)

This paper presents a hybrid-log periodic dipole antenna (H-LPDA) which is a cost effective alternative to the regular planar-log periodic dipole antenna (PLPDA) . In case of a PLPDA, required substrate dimensions increases with bandwidth as we have to accommodate dipoles of shortest dimensions to the longest. In order to make the antenna more cost effective in terms of the high frequency substrates used, a 3D structure is incorporated with the PLPDA while keeping the overall dimension as well as the performance same as the original PLPDA. In this paper, a PLPDA designed to operate over 700MHz - 4.5GHz is replaced by the proposed H-LPDA design. The design is simulated, fabricated and measured. The antenna is found to have performance similar to that of the original PLPDA antenna with good impedance matching (VSWR<;2) and a stable radiation pattern with a gain of 6.5dB over the desired operating band.

Compact CPW Fed Band-Notched Antenna for Portable UWB Applications

A compact band-notched CPW fed Ultra Wideband (UWB) antenna for portable UWB applications is proposed. The antenna is designed with the intention of reducing the dimensions of the radiating element without deteriorating its performance over the UWB range so that it can be incorporated within the physical limit specification of the USB plug footprint of Type-A. Also an electronically switchable quarter-wavelength notch filter designed for IEEE 802.11a has been incorporated into the system to avoid interference with existing WLAN communication. The antenna, fabricated on FR4 substrate (εr=4.4, thickness=1.6 mm) with a compact physical dimension of 9×30mm2, offers a good impedance bandwidth from 3.0 to 11.4GHz. The radiation patterns were found to be omnidirectional. The gain and efficiency of the antenna are also reported. The antenna was looked upon for its behavior at the notch frequency (5.45GHz) which showed a good VSWR ≫2 affirming excellent filtering of the WLAN band starting from 5.1-5.8GHz.