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Majlesi Journal of Telecommunication Devices - Volume:6 Issue: 3, Sep 2017

Majlesi Journal of Telecommunication Devices
Volume:6 Issue: 3, Sep 2017

  • تاریخ انتشار: 1396/08/29
  • تعداد عناوین: 6
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  • Sara Hassani * Pages 59-62
    This paper presents an ultra-low-voltage ultra-low-power CMOS Operational Transconductance Amplifier (OTA), using a novel feed-forward technique. The proposed topology is based on a bulk driven input differential pair, and inclusion of a gain-stage in the Miller capacitor feedback path to enhance the pole-splitting effect. The main objective of the proposed OTA is to utilize idle current source devices in small signal paths to improve the OTA performance. Not only the DC gain of the proposed OTA is enhanced by 10dB, its unity gain bandwidth (UGB) is also increased by factor of 3 with no extra power dissipation. The proposed OTA is designed and simulated in 180nm CMOS technology consuming only 386nW under the supply voltage of 400mV.
    Keywords: OTA, low-power design, bulk driven transistor, pole splitting, feedforward
  • Jahangir Bagheri, S.Narges Mahdian Zadeh Pages 63-68
    One of the most important features of the defense systems in each country is the abilities and capabilities of deceiving the other side(enemy) and reducing or increasing the target recognition by them. "Radar" is one of the most important tools for target detection. The effective Radar Cross Section (RCS) of each body (which is also unique) effects on distincting the speed, direction and distance of the targets(by means of Radar). Therefore, by changing the quantity of RCS,it is possible to involve the Radar to make a mistake in target acquaintance. This paper, while making clear some of the most important features of RCS and the particulars of therelated structure and function, analyzes the current mechanisms and presents a particular technique concerning the reduction or increment of the effective RCS of the targets,with the aim of utilizing it in Electronic Warfare(EW). In the meantime some other items nomely:parameters and factors in RCS, Rayleigh curve, Corner reflectors, Dihedral and Trihedral corner reflectors, The effect of angle of exposure of radiation on the target in the above mentioned corner reflectors. Drawing the related conclusion, etc. are being analyzed and examined minutely, in this paper.
    Keywords: Radar Cross Section (RCS), Effective RCS- Corner reflectors, Dihedral reflectors- Trihedral reflectors, Electronic Warfare(EW)- Electromagnetic waves
  • Majid Malekian, Hossein Emami, Mohsen Ashourian Pages 69-72
    One of the structures made of photonic crystal is all-optic filter which these filters are widely used in optic telecommunications systems and networks. In this paper, a method has been presented to design an optic filter based on two-dimensional photonic crystals. The crystal which we suggested, was obtained by FDTD and PWE numeric methods, that influenced different parameters of output wavelength of filter. The result showed that increase of refraction index of Dielectric, leads information in output wavelength of filter.
    Keywords: All- optic filter, photonic crystal, FDTD, PWE
  • Alireza Bagherzadeh, Mostafa Yargholi Pages 73-77
    This paper presents an integrated phase-locked loop (PLL) frequency synthesizer for wireless communication application in standard 0.18 µm CMOS process. Delta sigma modulator used for reducing phase noise. The use of modulation concepts results in a beneficial noise shaping of the phase noise (jitter) introduced by fractional-N division. The this technique has the potential to provide low phase noise, fast settling time, and reduced impact of spurious frequencies when compared with existing fractionalPLL techniques. Simulation results show that the phase noise of frequency synthesizer is -108 @1MHz offset, and the PLL synthesizer provides output frequencies 880-915 MHz in uplink and 925-960 MHz in downlink. Fref is 26 MHz and channel spicing is 700 KHz. Moreover, benefiting from the combination of current-mode-logic (CML) the PLL consumes a total power dissipation of only 24.35 mW with a single 1.8 V supply including all the buffers. Although prescaler increases settling time (ts), it decreases power consumptions. Settling time in uplink is 425 ns and in downlink about 475 ns.
    Keywords: Frequency Synthesizer, Sigma-Delta, Phase noise, settling time, GSM-E, PLL
  • Mohsen Beiranvand, Ebrahim Rahimi, Gholamreza Babaabasi Pages 79-84
    A sigma-delta modulator designed as part of a complete GSM (enhanced data rate for GSM evolution) transceiver is described. High-resolution wide-band analog-to-digital converters enable the receiver to rely on digital processing, rather than analog filtering, to extract the desired signal from blocking channels. High linearity and High SNR are the most stringent requirements for the converters in this wireless application. In this paper a second-order modulator with feed forward structure in order to cover bandwidth correspond to GSM telecommunication standards is designed and simulated. In this modulator, low distortion structure and according to the relevant standard bandwidth is used. In order to provide minimum GSM standard requirement parameters, a second – order modulator is used and by an oversampling rate of 120 and bandwidth of 200 KHZ, SNR, 98 dB and the accuracy of 15.5 bits is achieved. Also its circuit structure by using capacitance switch method with 0.13 micron technology and 1.8 volt power supply has been implemented.
    Keywords: Analog to Digital converter_Sigma – Delta modulator_low – power components_low voltage
  • Ali Farmani *, Mohammad Hossein Sheikhi Pages 85-89
    We proposed a novel structure of ultrafast all optical Feynman logic gate based on the cross-phase modulation that is principle nonlinear effect in a quantum dot semiconductor optical amplifier assisted with a Mach-Zehnder interferometer at the wavelength of 1.55 µm. To realize ultrafast mechanism, an active layer with a thickness of 1.7-µm, and the confinement factor of 0.75 and 0.7 respectively for both TE0 and TM0 modes, are provided. By solving the rate equations, a gain difference up to 0.1 dB has been obtained. The proposed structure has the potential application in advanced optical devices such as optical memristors.
    Keywords: Semiconductor Optical Amplifier, Optical Logic gate, Cross-Phase Modulation, Mach-Zehnder Interferometer