Majlesi Journal of Telecommunication Devices
Volume:5 Issue: 2, Jun 2016

Orthogonal frequency division multiplexing (OFDM) is a multicarrier transmission technology in wireless environment that use a large number of orthogonal subcarriers to transmit information. In order to be able to demodulate OFDM signals accurately, channel estimation is needed for received signals. It is important to select a suitable interpolation method for estimation block. The goal of this paper is compering the methods of interpolation in OFDM system without using channel statistics information. Therefore, in this paper, we used pilots for obtaining the information of channel, and by the method of estimation without use of channel statistics information, the channel primary frequency response estimated in pilot’s frequencies. At the end, the whole channel frequency response estimated of pilot frequency response by the different interpolation methods. In this paper, different interpolation methods such as Linear, Second order, Spline, Cubic Hermite and Low pass interpolation are compared.

In this paper a novel MEMS capacitive pressure sensor with small size and high sensitivity is presented. This sensor has the separated clamped square diaphragm and movable plate. The diaphragm material is polysilicon. The movable and fixed plates are gold and the substrate is pyrex glass. The mechanical coupling is Si3N4. In capacitive sensor the sensitivity is proportional to deflection and capacitance changes with pressure for this reason with this design is improved the sensitivity with small size. The size of this sensor is 350×350 (µm2) and the thickness of diaphragm is 2µm with 1 air gap. This structure is designed by intellisuite software. In this simulation are shown the compare of polysilicon and polyimide diaphragms. Because in many previous works polysilicon and polyimide are used. In this MEMS capacitive pressure sensor the sensor sensitivity, diaphragm mechanical sensitivity for polysilicon(stress=100Mpa) diaphragm are 0.0074 (Pf/mmHg), 0.0042/mmHg), respectively and for polysilicon(stress=20Mpa) diaphragm are 0.0469(Pf/mmHg), 0.011/mmHg, respectively and polyimide diaphragm are 0.0226(pF/mmHg), 0.0091/mmHg), respectively. According to the simulating results for low pressure, the structure with polysilicon diaphragm has more change of the displacement and capacitance, this lead to high sensitivity than other diaphragms.

A novel CMOS wideband low-noise amplifier (LNA) with a new architecture of high gain, low NF and low power-consumption is proposed. This architecture consists of two non-uniform stages. In order to achieve high power gain (S21) and low power consumption, a current reused with resistive feedback based on an inverter-type amplifier is utilized at the first stage. The second stage of this circuit is used to increase the bandwidth and power gain. Simulation results show that the proposed LNA achieves a power gain between 19±.3 dB. The input return loss (s11) and output return loss (s22) are better than -10 dB. The noise figure (NF) of the proposed LNA is between 2~3.6 dB and reverse gain (S12) is below -30 dB for 3.1~10.6 GHz bandwidth. The input third-order intercept point (IIP3) and power consumption of the proposed LNA are -5 dBm and 13.6 mW, respectively.

Study on effects of changing the oxide thickness, can give us a view of the aspects of MOSFET, in field of design of the transistor elements. Changing the oxide thickness affects on both Cox and Vt. At first, in this paper, the relation between the threshold voltage and oxide thickness will be discussed. Then, the relation between the drain current and oxide thickness will be modeling. The result is a nonlinear and parabolic relationship between the drain current and oxide thickness. To ensure the authenticity of the obtained model, a MOSFET parameters, based on 5 µm CMOS technology was designed. This MOSFET was simulated with COMSOL software and obtained mathematical model analyzed with MATLAB. Finally, the data were compared, which confirmed the authenticity of the mathematical model.

in this paper we have presented the implementation of radar digital quadrature channel receivers in FPGA. Utilizing direct digitalization due to avoid improbable matching in producing in-phase (I) and quadrature (Q) signals, is greatly respecting in every modern system but this merit needs some considerations which are highlighted in the current paper. Two factors resource and maximum frequency for hardware implementation of proposed algorithm utilizing Virtex-5 ML506 are evaluated and compared with the customary algorithm of analog and digital receivers which generally utilize two mixers, lowpass filters and analog to digital converters for down converting signal from intermediate frequency to baseband. Also in this paper some simulations for different examples are illustrated.

This paper is focused on a novel design of stepped diaphragm for MEMS capacitive pressure sensor used in tire pressure monitoring system. The structure of sensor diaphragm plays a key role for determining the sensitivity of the sensor and the non-linearity of the output. First the structures of two capacitive pressure sensors with clamped square flat diaphragms, with different thicknesses are investigated and their sensitivity and non-linearity are compared together. Finally for increasing the sensitivity and linearity, a new capacitive pressure sensor with a stepped diaphragm is introduced. A numerical solution for determination of the accurate sensitivity of the sensor is presented. The results show that the sensitivity of the sensor is increased from 0.063 fF/KPa with flat diaphragm to 0.107 fF/KPa with stepped diaphragm and also the non-linearity is decreased from 2.37% to 1.857%. In this design, the sensor sensitivity and output linearity are increased simultaneously.