Performance Analysis of Associate Radix-2, Radix- 4 and Radix-8 based FFT using Folding Technique

: In recent years, as a result of advancing VLSI technology, Orthogonal Frequency Division Multiplexing (OFDM) has received a great deal of attention and has been adopted in many new generation wideband data communication systems such as IEEE 802.11a, IEEE 802.16e, HiPerLAN/2, Digital Audio/Video Broadcasting (DAB/DVB), and for 4G Radio mobile communications. This is because of its high bandwidth efficiency as the use of orthogonal waveforms with overlapping spectra. The immunity to multipath fading channel and the capability for parallel signal processing make it a promising candidate for the next generation mobile communication systems. The modulation and demodulation of OFDM based communication systems can be efficiently implemented with an FFT and IFFT, which has made the FFT valuable for those communication systems. The complexity of an OFDM system highly depends upon the computation of Fast Fourier Transform (FFT) algorithm. With the advent of new technology in the fields of VLSI and communication, there is also an ever growing demand for high speed processing and low area design. It is also a well-known fact that the multiplier unit forms an integral part of processor design. Due to this regard, high speed multiplier architectures become the need of the day.

A Compact Sequentially Rotated Circularly Polarized Dielectric Resonator Antenna Array

In this study, a compact 2 × 2 circularly polarized (CP) sequentially rotated (SR) dielectric resonator antenna (DRA) array operating in the IEEE 802.11a band is presented. To acquire the CP radiation, an elliptical slot (ES) was introduced to couple a rectangular dielectric resonator (RDR). The ES generates two resonant frequencies corresponding to the dominant even and odd modes. The SR feeder is made of four quarter-wavelength microstrip transformers to reduce the input impedance of the elements and, consequently, maximize the power transferred to each element. Experimental and simulation verifications were conducted on a 54 × 50 × 0.813 mm3 prototype to evaluate the performance of the proposed antenna array, which achieved a VSWR < −10 dB bandwidth of 1 GHz (5.1–6.05 GHz) and axial ratio (AR) < 3 dB of 0.95 GHz (5.1–5.85 GHz). The agreement between the simulated and measured results confirmed the validity of the proposed design.

Design and Impedance Modeling of a Compact Sequentially Rotated Quasi-Lumped Antenna Array for Wi-Fi Applications

In this study, a miniaturized 2 × 2 sequentially rotated (SR), circularly polarized (CP), and quasi-lumped antenna array that resonates in the IEEE 802.11a band is introduced. The shorting pins technique is implemented to achieve circular radiation patterns, and the resonating elements are excited using a SR quarter-wavelength feeding network. A resonance model of the four radiating elements array is postulated to give a physical insight into the relative dimensions and to allow for a study of the resonance characteristics and the effect of the shorting pins. An antenna model is simulated, fabricated, and measured to authenticate this arrangement, giving results of |S11| < −10 dB and axial ratio (AR) < 3 dB for bandwidths of 3.85% (5.645–5.867 GHz) and 1.54% (5.77–5.86 GHz) for right-hand circular polarization (RHCP). The size of the antenna array structure is 0.696 λ 0 × 0.599 λ 0 × 0.0157 λ 0 at a center frequency of 5.8 GHz.

PENGGUNAAN TEKNOLOGI NFC-RFID DAN VANETS-DSRC DI SISTEM GERBANG TOL OTOMATIS UNTUK MENGURANGI KEMACETAN PADA PINTU TOL

Konsep E-Tol menjadi sebuah solusi yang memungkinkan pengurangan kemacetan yang terdapat di pintu tol karena sehinggadapat mengurangi intensitas penumpukan kendaraan di pintu Tol, ada beberapa solusi yang ditawarkan yaitu dengan sistem pintu tolotomasi yang berdasarkan Menempelkan Kartu yang menggunakan Teknologi Near Fear Communication (NFC) berbasis Radio Frequency Identifikasi (RFID) dan Teknologi otomatis berbasis Vehicle Ad-Hoc Networks (VANETS) yang memanfaatkan teknologi Dedicated Short Range Comunication (DSRC) Near Fear Communication (NFC) yang berbasis pada berbasis RFID pada frekuensi 13.56 MHz, dengan jarak hingga 10 cm. Kecepatan pertukaran data mencapai 42 kilobits/s. Communication (NFC) Standarisasi komunikasi protocol dan pertukaran data NFC, yaitu berdasarkan standar indentifikasi frekuensi radio (RFID), termasuk ISO/IEC 14443 dan DSRC mempunyai frekuensi operasi di 5,9 GHz (5850-5925 MHz) dengan bandwidth yaitu 75Mhz, dengan standarisasi teknologi menurut IEEE 802.11a yang menggunakan modulasi Orthogonal frequency-division multiplexing (OFDM).

Signal processing for transmitted-reference ultra wideband system

This thesis focuses on transmitted-reference ultra wideband (TR-UWB) systems coexistence with IEEE802.11a WLAN systems. TR-UWB systems can relax the difficult synchronization requirements and can provide a simple receiver architecture that gathers the energy from many resolvable multipath components. However, UWB TR systems are susceptible to interference which comes from other wireless systems. In this thesis, TR-UWB system performance is studied in the presence of strong IEEE 802.11a WLAN interference in both AWGN and IEEE channel model. In order to reduce both the effects of interference by and into UWB signals, we propose a new method in conjunction with a multi-carrier type transmission pulse using wavelet analysis and notch filtering. Using wavelet analysis, spectral density of the transmitted UWB signal around the interfering band is reduced by 60 dB lower than the peak. With the modified TR-UWB receiver, the TR-UWB system shows performance improvement in the presence of strong IEEE 8-2.11a interference in both AWGN and IEEE channel models. The proposed method can be used for the coexistence of different wireless systems with UWB system.

Signal processing for transmitted-reference ultra wideband system

This thesis focuses on transmitted-reference ultra wideband (TR-UWB) systems coexistence with IEEE802.11a WLAN systems. TR-UWB systems can relax the difficult synchronization requirements and can provide a simple receiver architecture that gathers the energy from many resolvable multipath components. However, UWB TR systems are susceptible to interference which comes from other wireless systems. In this thesis, TR-UWB system performance is studied in the presence of strong IEEE 802.11a WLAN interference in both AWGN and IEEE channel model. In order to reduce both the effects of interference by and into UWB signals, we propose a new method in conjunction with a multi-carrier type transmission pulse using wavelet analysis and notch filtering. Using wavelet analysis, spectral density of the transmitted UWB signal around the interfering band is reduced by 60 dB lower than the peak. With the modified TR-UWB receiver, the TR-UWB system shows performance improvement in the presence of strong IEEE 8-2.11a interference in both AWGN and IEEE channel models. The proposed method can be used for the coexistence of different wireless systems with UWB system.

A Broadband Circularly Polarized Antenna with Low-Profile and Wide Axial Ratio Beamwidth

In this work, the design and the characterization of a broadband circular polarized monopole having low-profile and wide axial ratio beamwidth were presented. The antenna was designed on readily available, inexpensive glass-reinforced epoxy substrate having an overall size of 0.56λ0×0.50λ0×0.029λ0 (at center frequency 5.5 GHz). The proposed antenna was a modification of a square-shaped monopole antenna, which incorporates a pair of peripheral slits and an off-center slot for a elliptical polarized radiation. A v-shaped notch below the feed line was introduced and extended as antenna ground to generate broadband circular polarization characteristics. The −10 dB reflection coefficient bandwidth and 3-dB axial-ratio bandwidth of the proposed antenna were measured to be of 47.6 and 27 %, respectively. The 3-dB axial ratio beamwidth of the antenna was 93.5°. The antenna proposed in this work covers multiple application frequency bands including HiperLAN/2 IEEE 802.11a (5.15 - 5.35 GHz / 5.47 - 5.725 GHz) band, WLAN frequency band (5.1 - 5.9 GHz), C-band uplink (5.925 - 6.325 GHz) and part of military application band (4.75 - 4.99 GHz). HIGHLIGHTS Design and characterization of a broadband circular polarized monopole having low-profile and wide axial ratio beamwidth Proposed antenna covers multiple application frequency bands including HiperLAN/2 IEEE 802.11a, WLAN, C-band uplink and part of military application bands Proposed antenna is compact, low-profile and exhibits good polarization purity GRAPHICAL ABSTRACT