April 2006, Volume 15, Number 1
This paper deals with a design method of the analog all-pass filter designated for equalization of the group delay frequency response of the analog filter. This method is based on usage of evolutionary algorithm, the Differential Evolution algorithm in particular. We are able to design such equalizers to be obtained equal-ripple group delay frequency response in the pass-band of the low-pass filter. The procedure works automatically without an input estimation. The method is presented on solving practical examples.
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- MARTINEK, P., VONDRAS, J. Multi-criterion filter design via Differential Evolution method for function minimization. In 1st IEEE Int. Conf. on Circuits and Systems for Communications ICCSC'02 Proceedings. St. Petersburg (Russia): Saint-Petersburg State Technical University, 2002, vol. 1, p. 106-109.
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Keywords: Analog all-pass filters, group delay frequency response, Differential Evolution algorithm
This paper shows the circuitry implementation and practical verification of the autonomous nonlinear oscillator. Since it is described by a single third-order differential equation, its state variables can be considered as the position, velocity and acceleration and thus have direct connection to a real physical system. Moreover, for some specific configurations of internal system parameters, it can exhibit a period doubling bifurcation leading to chaos. Two different structures of the nonlinear element were verified by a comparison of numerically integrated trajectory with the oscilloscope screenshots .
- CHUA, L. O., KOMURO, M., MATSUMOTO, T. The double scroll family. IEEE Trans. on CAS I, 1986, vol. 33, no. 11, p. 1073 - 1117.
- POSPISIL, J., KOLKA, Z., HORSKA, J., BRZOBOHATY, J. New reference state model of the third-order piecewise-linear dynamical system. Radioengineering, 2000, vol. 9, no. 3, p. 1 - 4.
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Keywords: Nonlinear oscillator, chaos, Lyapunov exponents, circuit realization, measurement
This paper deals with design and realization of a PLL synthesizer for the microwave X−band. The synthesizer is intended for use as a local oscillator in a K−band downconverter. The design goal was to achieve very low phase noise and spurious free signal with a sufficient power level. For that purpose a low phase noise MMIC VCO was used in phase locked loop. The PLL works at half the output frequency, therefore there is a frequency doubler at the output of the PLL. The output signal from the frequency doubler is filtered by a band-pass filter and finally amplified by a single stage amplifier.
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- GRAVEL, J-F., WIGHT, J. S. On the conception and analysis of a 12-GHz push-push phase-locked DRO. IEEE Transactions on Microwave Theory and Techniques, vol. 54, no. 1, January 2006.
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- VAGNER, P. Kmitoctovy syntezator v pasmu X (X-Band PLL Synthesizer). Diploma thesis. Brno: VUT. 2005 (in Czech).
- HEWLETT-PACKARD COMPANY HP E7404A Specifications and Characteristics. Reference Guide. 1999.
Keywords: Microwave PLL synthesizer, phase locked loop, low phase noise, local oscillator, X-band
The propagation of ultra wide band (UWB) signals through walls is analyzed. For this propagation studies, it is necessary to consider not only propagation at a single frequency but in the whole band. The UWB radar output signal is formed by both transmitter and antenna. The effects of antenna receiving and transmitting responses for various antenna types (such as small and aperture antennas) are studied in the frequency as well as time domain. Moreover, UWB radar output signals can be substantially affected due to electromagnetic wave propagation through walls and multipath effects.
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- SCHEJBAL, V. et al. UWB radar signal propagation through walls and multipath effects. IEEE Aerospace & Electronic Systems Magazine. Submitted to publication.
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- PENA, D., FEICK, R., HRISTOV, H. D., GROTE, W. Measurement and modeling of propagation losses in brick and concrete walls for the 900-MHz band. IEEE Transactions on Antennas and Propagation, 2003, vol. 51, no. 1, p. 31 - 39.
- SOUTSOS, M. N., BUNGEY, J. H., MILLARD, S. G., SHAW, M. R., PATTERSON, A. Dielectric properties of concrete and their influence on radar testing. NDT&E International, 2001, vol. 34, p. 419 - 425.
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Keywords: Ultra wide band, UWB antennas, UWB propagation, multipath effects
The paper presents the modification of lattice RLS adaptive filtering algorithms for the case of nonstationary signal processing. The modification includes the using of sliding window and dynamic regularization in the adaptive filter correlation matrix estimation. The algorithms can be implemented by means of sequential or parallel computations. Based on sequential computations, 30 regularized prewindowed, sliding widow and regularized sliding window lattice RLS algorithms were developed. A family of the same algorithms with parallel computations includes 21 units. Lattice algorithms are developed for the application in single-channel adaptive filters with complex-valued weights. Some computation procedures of the algorithms are listed. The results of the algorithm simulation are also presented.
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- DJIGAN, V. I. RLS adaptive filtering algorithms based on parallel computations. Radioengineering: Proceedings of Czech and Slovak Technical Universities and URSI Committees, 2005, vol. 14, no. 3, p. 28 - 36.
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- DJIGAN, V. I. Lattice RLS adaptive filtering algorithms diversity. Digital Signal Processing, 2005, no. 3, p. 2 -12 (in Russian).
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- DJIGAN, V. I. Sliding window in lattice RLS algorithms of adaptive filtering. In Proceedings of the 13-th International Conference on Information Systems and Technologies. Moscow (Russia), 2005, vol. 1, p. 151 - 154 (in Russian).
- DJIGAN, V. I. Regularization of lattice RLS algorithms. In Proceedings of the 5-th International Scientific-Technical Conference on Electronics and Informatics 2005. Moscow (Russia), 2005, vol. 2, p. 131 - 132 (in Russian).
- DJIGAN, V. I. A family of lattice adaptive filtering algorithms with parallel computations. In Proceedings of the 14-th International Scientific and Technical Conference on Problem of Information Transmitting and Processing in Telecommunication Networks and Systems. Ryazan (Russia), 2005, p. 203 - 204 (in Russian).
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Keywords: Adaptive filtering, RLS, fast RLS, lattice RLS
Averaging techniques as temporal averaging and space averaging have been successfully used in many applications for attenuating interference , , , , . In this paper we introduce interference removing of the ECG signal by polynomial approximation, with smoothing discrete dependencies, to make up for averaging methods. The method is suitable for low-level signals of the electrical activity of the heart often less than 10 m V. Most low-level signals arising from PR, ST and TP segments which can be detected eventually and their physiologic meaning can be appreciated. Of special importance for the diagnostic of the electrical activity of the heart is the activity bundle of His between P and R waveforms. We have established an artificial sine wave to ECG signal between P and R wave. The aim focus is to verify the smoothing method by polynomial approximation if the SNR (signal-to-noise ratio) is negative (i.e. a signal is lower than noise).
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Keywords: Polynomial approximation, electrocardiogram ECG, high resolution of the ECG, low-level signals, interference
A test module for serial links is described. In the link transmitter, one module generates pseudorandom pulse signal that is transmitted by the link. Second module located in the link receiver generates the same signal and compares it to the received signal. Errors caused by the signal transmission can be then detected and results sent to a master computer for further processing like statistical evaluation. The module can be used for long-term error monitoring without need for human operator presence.
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Keywords: Serial link, bit error rate, LFSR counter, free-space optical link, FPGA
The following paper introduces a low bitrate video coding method on the basis of 3D motion compensated wavelet transform and SPIHT algorithm. In contrast to the conventional algorithms applying motion compensation and differential coding, here wavelet transform is used to exploit the opportunities of time redundancy. For coefficient collection, the 3D version of SPIHT algorithm was selected from the various procedures developed for wavelet transform. Motion vectors are compressed, too (also by wavelet transform), therefore the time and spatial redundancy of coding is exploited here as well. These procedures result in effective video compressing and can easily be aligned to the MPEG4 standard.
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Keywords: Video coding, 3D wavelet transform, SPIHT, motion compensation, MPEG-4, motion vector compression
A novel GPS satellite signal acquisition scheme that utilizes lifting wavelet to improve acquisition performance is proposed. Acquisition in GPS system is used to calculate the code phase (or shift) and find the pseudo-range, which is used to calculate the position. The performance of a GPS receiver is assessed by its ability to precisely measure the pseudo-range, which depends on noise linked to the signals in the receiver’s tracking loops. The level of GPS receiving equipment system noise determines in part how precisely pseudo-range can be measured.
Our objective, in this paper, is to achieve robust real-time positioning with maximum of accuracy in the presence of noise. Robust positioning describes a positioning system\'s ability to maintain position data continuity and accuracy through most or all anticipated operational conditions. In order to carry out a robust less complex GPS signals acquisition system and to facilitate its implementation, a substitute algorithm for calculating the convolution by using lifting wavelet decomposition is proposed.
Simulation is used for verifying the performance which shows that the proposed scheme based lifting wavelet transform outperforms both FFT search and signal decimation schemes in the presence of a hostile environment.
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Keywords: GPS, acquisition, convolution, FFT, decimation, lifting wavelet