2011/4

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    Realization of Resistorless Wave Active Filter using Differential Voltage Current Controlled Conveyor Transconductance Amplifier
    (Společnost pro radioelektronické inženýrství, 2011-12) Pandey, Neeta; Kumar, Praveen
    In this paper, a resistorless realization of high order voltage mode wave active filter based on Differential Voltage current controlled conveyor transconductance amplifier (DVCCCTA) is presented. The wave method is used for simulating reflected and incident wave for basic building block i.e. series inductor and configuring it for other passive element realization by making appropriate connection. The proposed structure uses grounded capacitors and possesses electronic tunability of cutoff frequency. The proposed approach is verified for a 4th order low pass filter through SPICE simulation using 0.25µm TSMC CMOS technology parameters.
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    Energy Analysis of Received Signal Strength Localization in Wireless Sensor Networks
    (Společnost pro radioelektronické inženýrství, 2011-12) Moravek, Patrik; Komosny, Dan; Simek, Milan; Girbau, David; Lazaro, Antonio
    This paper presents the investigation of energy demands during localization of wireless nodes in ad-hoc networks. We focus on the method based on the received signal strength (RSS) to estimate the distances between the nodes. To deal with the uncertainty of this technique, statistical methods are used. It implies more measurement samples to be taken and consequently more energy to be spent. Therefore, we investigate the accuracy of localization and the consumed energy in the relation to the number of measurement samples. The experimental measurements were conducted with IRIS sensor motes and their results related to the proposed energy model. The results show that the expended energy is not related linearly to the localization error. First, improvement of the accuracy rises fast with more measurement samples. Then, adding more samples, the accuracy increase is moderate, which means that the marginal energy cost of the additional improvement is higher.
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    OFDM Signal Detector Based on Cyclic Autocorrelation Function and its Properties
    (Společnost pro radioelektronické inženýrství, 2011-12) Sebesta, Vladimir; Marsalek, Roman; Fedra, Zbynek
    This paper is devoted to research of the general and particular properties of the OFDM signal detector based on the cyclic autocorrelation function. The cyclic autocorrelation function is estimated using DFT. The parameters of the testing signal have been chosen according to 802.11g WLAN. Some properties are described analytically; all events are examined via computer simulations. It is shown that the detector is able to detect an OFDM signal in the case of multipath propagation, inexact frequency synchronization and without time synchronization. The sensitivity of the detector could be decreased in the above cases. An important condition for proper value of the detector sampling interval was derived. Three types of the channels were studied and compared. Detection threshold SNR=-9 dB was found for the signal under consideration and for two-way propagation.
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    Digitally Programmable Fully Differential Filter
    (Společnost pro radioelektronické inženýrství, 2011-12) Beg, Parveen; Khan, Iqbal A.; Maheshwari, Sudhanshu; Siddiqi, Muzaffer A.
    In this paper a new digitally programmable voltage mode fully differential Kerwin-Huelsman-Newcomb(KHN) filter is realized using digitally controlled CMOS fully balanced output transconductor (DCBOTA). The realized filter uses five DCBOTAs, a single resistor and two capacitors. The filter provides low-pass, high-pass and band-pass responses simultaneously. The pole-frequency of all the responses is controlled by externally applying an 8- bit digital control word. All the responses exhibit independent digital control for pole-ω0 and pole-Q. The proposed filter also offers low passive sensitivities. Non-ideal gain and parasitic associated with the actual DCBOTA is also discussed. The CMMR results for low-pass response are also included which highlight the advantage of a fully-differential operation. Exhaustive PSPICE simulation is carried out using 0.5µ technology which may be further scaled to explore state-of-the-art applications of the proposed circuit.
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    A High Accurate and Low Bias SNR Estimator: Algorithm and Implementation
    (Společnost pro radioelektronické inženýrství, 2011-12) Gong, Chao; Zhang, Bangning; Liu, Aijun; Guo, Daoxing
    Signal to noise ratio (SNR) estimators are required for many radio engineering applications. In this paper, a SNR estimator based on the first and second order moments is derived and examined for constant envelop modulations over additive white Gaussian noise (AWGN) channel. In the first, a modification method is proposed to reduce the bias of conventional first and second order moments based SNR estimator. Then, in order to reduce hardware implementation complicity, multi segments of cubic polynomial are adopted to approximate the expression of the proposed SNR estimator which doesn’t have a close form solution. The approximate expression is very precise in the SNR range -10dB ~ 20 dB as illustrated by numerical simulation. Besides, practical hardware circuit is proposed for FPGA implementation. Simulation results show that the proposed SNR estimator has the lowest normalized bias and variance when compared with two other classic estimators.