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by mandvi mandvi, Mandvi Mandvi
3 Views, 3 PDF Downloads

To achieve high data rate we are mapping higher Order modulation technique with OFDM in wireless mobile communication. Higher Order modulation means more number of bits is mapped to each symbol. To achieve high data rate, we are transmitting more number of symbols. These symbols are modulated on the subcarriers using IFFT process. At the output of IFFT, these symbols are added up resulting in high PAPR. A high PAPR causes undesirable distortion in the system (because we have limited linear range power amplifier and A/D, D/A Converter). In this paper, a Hybrid RCF+ Companding (tanhR) technique is proposed for reducing PAPR in OFDM system.

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by Haobo Yuan, Hongwei Liu, Xinxin Dong, Jiansheng Jia, Hongguang Zhou
8 Views, 4 PDF Downloads

Abstract:Planar near-field to far-field transform (NF-FF) by the Fast Fourier Transform (FFT) in antenna measurement is often insufficiently accurate, especially for low side-lobe antennas. This paper presents a new highly accurate FFT based on Gaussian Quadrature, and applies it to discretize the double integrals in NF-FF. The proposed method needs much less sampling points on the scanning plane. An example of the low side-lobe antennas show that although the proposed method is several times slower than the conventional method, it obtains a much more accurate pattern than the latter does.

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by Dr Suraya mubeen
0 Views, 2 PDF Downloads
Multiple antennas can be arranged in various geometrical configurations to form antenna array with high directive radiation pattern. Linear antennas are limited in their steering capability. The circular arrays ar   more popular in recent years over other array geometries because they have the capability to perform the scan in all the directions and considerable change in the beam pattern which provide 3600 total coverage. Circular arrays are less sensitive to mutual coupling as compared to linear and rectangular arrays since they do not have edge elements. They can be used for beam forming in the azimuth plane for example at the base stations of the mobile radio communication systems as the components for signal processing. FFA design method of circular apertures for narrow beam width and low side lobes has been reported by Taylor. It includes the development of continuous circular aperture distributions, which contain only two independent parameters, A & , where A is related to the design of side lobe level and  is a number controlling the degree of uniformity of the side lobes.
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by Frederick Ray Gomez
19 Views, 5 PDF Downloads

Differential implementation is becoming highly favoured in RFIC (radio frequency integrated circuit) design, notably its high immunity to common-mode noises, acceptable rejection of parasitic coupling, and increased dynamic range. One specific RF front-end building block that is usually designed as a differential circuit is the mixer.  This technical paper presents a study of a differential mixer, notably the double-balanced mixer implemented on a direct-conversion architecture in a standard 90nm CMOS (complementary metal-oxide semiconductor) process.  Operating frequency is set at 5GHz, which is a typical frequency for RF (radio frequency) receiver.   Impedance matching was essential to fully optimize the mixer design.  The direct-conversion double-balance mixer design eventually achieved conversion gain of 11.463dB and noise figure of 16.529dB, comparable to mixer designs from past research and studies.

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