“Digital
Signal Processing” No. 42013
In
the issue:

superRayleigh signal resolution;
 digital processing of radar pulsetrain
waveforms;

optimization processing systems of signals;
 algorithms of stochastic signal processing;
 reducing complex noises in speech;
 segmentation of earth surface hyperspectral imagery;
 method of finding probability characteristics;
 methods synthesis of aperiodic binary sequences;
 method for pitch estimation.


POTENTIAL LIMIT AND QUALITY INDICATORS OF SUPERRAYLEIGH SIGNAL RESOLUTION
Klimov S.A., zuk_house@rambler.ru
In this article the directions of search for potential limit of superRayleigh
resolution are systematized. The simple and convenient resolution quality
indicator system for performance evaluation of full signal resolution
is established. The question of existence of superRayleigh resolution
potential limit in solving radar detectionresolution problem is answered.
It is shown, that resolving curves of single signals are determined rigidly
and they cannot be exceeded if priori statistical information is given.
Then full resolution probability curves determine the limit of resolution
for fixed false alarm probability and coefficient of correlation of signals.
The degree of approximation to potential limit of superRayleigh resolution
for a large number of digital spectral analyses algorithms is evaluated
by using simulation modeling.
Keywords: resolution, superRayleigh resolution, resolution limit,
quality indicators of signal resolution, digital spectral analyses.
DIGITAL PROCESSING OF RADAR PULSETRAIN WAVEFORMS USING LOWORDER WEIGHT
FUNCTIONS
Zaytsev G.V., gennadyzaytsev@yandex.ru
The paper analyzes
processing algorithm of pulsetrain waveforms in digital radar receiver.
The algorithm consists of range gating and dopplerfilterbank calculation
in each range gate. Filter bank is realized by spectral analysis with
preliminary weighting to reduce filter sidelobes. Several versions of
spectrum calculations are discussed.
Each waveform with specific duration requires specific weight function.
So for radars with wide set of pulse trains the number of weighting coefficients
to be stored becomes unacceptable. Main part of the paper tackles this
problem. To simplify implementation the paper suggests using synthesized
by the author weight functions with simple cosinesum representation,
given rolloff rate, and minimum sidelobe level for the given width of
the main lobe. Simple representation allows calculating weights in real
time during processing instead of their storage. Any of these functions
proved to be nearoptimal for wide set of waveform parameters. For further
simplification, step weight function are examined with step length being
equal to pulse repetition period. It is shown that for suggested functions
with large rolloff rate transition to step functions leads to insignificant
performance degradation.
Keywords: quasicontinuous signal, optimum filtering, weight function,
digital signal processing.
OPTIMIZATION OF COHERENTWEIGHT PROCESSING SYSTEMS OF MULTIFREQUENCY
SIGNALS
Popov D.I., adop@mail.ru
The methods of optimization of coherentweight processing systems of multifrequency
radar signals on probabilistic criterion are considered. The block diagrams
of adaptive processing systems at continuous and discrete modes are given.
The analysis of processing systems of multifrequency signals is carried
out.
Keywords: adaptation, probabilistic criterion, moving targets,
multifrequency signals, optimization, clutter, processing systems, blind
speeds.
IMPLEMENTATION OF STOCHASTIC SIGNAL PROCESSING ALGORITHMS IN REAL ARITHMETIC
Ratynsky M.V., Petrov S.V., m3v5r7@inbox.ru,
petrovsv@lest.ru
Four problems of stochastic signal processing in receiving system with
antenna array are discussed: detection, enumeration and arrival direction
estimation of signal sources and adaptive space filtering. The solution
of the problems is implemented generally in complex arithmetic. It is
proved that solution of all the problems can be implemented in real arithmetic
when antenna array has central symmetric structure. The results of complex
and real solutions are really identical for all cases, but in the second
case (real arithmetic) the amount of computations is four times less as
compared with the first one (complex arithmetic).
Keywords: signal processing algorithms, stochastic signals, signal
detection, sources enumeration, arrival direction estimation, adaptive
space filtering, real arithmetic.
A NEW METHOD OF FINDING PROBABILITY CHARACTERISTICS IN THE OUTPUT OF NONLINEAR
SYSTEMS
Bartenev V.G., Bartenev M.V., syntaltechno@mail.ru
The paper presents a new method of finding probability characteristics
in the output of nonlinear systems using elliptical properties of some
distributions. Elliptically symmetric distributions are secondorder distributions
with probability densities whose contours of equal height are ellipses.
This class includes the Gaussian, Laplace distributions and others which
can be generated from certain firstorder distributions. Such desirable
features for the description of the secondorder statistics may be used
in the transformation analysis of a random signal by the nonlinear devices.
These elliptically symmetric distributions simplify the evaluation of
the output probability characteristics. That is the base of the suggested
method in this paper which is illustrated by real losses of detection
with analytically developed low false alarm rate of nonlinear multiplier
with small integrated samples when the output distribution differs substantially
from Gaussian.
Keywords: Elliptically symmetric are secondorder distributions,
the output probability characteristics of the nonlinear devices, detection
probability, false alarm probability, multiplier  integrator.
METHODS AND RESULTS SYNTHESIS OF APERIODIC BINARY SEQUENCES AND POLYPHASE
BARKER SEQUENCES
Potekhin E., Shuvalov A., Leukhin N., potegor@yandex.ru,
shuvalov.as@gmail.com
The article provides information about the methods of generation, building
and searching for optimal binary sequences till length 76 and multiphase
Barker sequence till length 52. Search algorithms and analytical conclusions
are described in detail. Examples of sequences and their basic characteristics
such as merit factor and linear complexity are given.
Keywords:
binary sequences, Barker code, the autocorrelation function, the side
lobes, multiphase sequences.
REDUCING COMPLEX NOISES IN SPEECH USING FILTERING IN MODULATION DOMAIN
Azarov I.S., Vashkevich M.I., Lihachev D.S., Petrovsky A.A., azarov@bsuir.by,
vashkevich@bsuir.by,
palex@bsuir.by
The paper presents a method for noise reduction which is capable of handling
noises of different nature such as white, colored quasiperiodicor reverberation.
This allpurpose method is based on filtration in modulation domain. In
order to obtain modulation signals source speech is decomposed into overlapping
analytical subband signals using a filter bank. Then each analytical signal
is parametrized in terms of instantaneous amplitude and frequency. Subchannel
samples are grouped by instantaneous frequency values and their overall
intensity envelopes are evaluated. Envelopes are filtered with a bandpass
filter which retains speech modulations and attenuates noise modulations.
Finally subband gains are calculated and applied to subchannel signals
and the cleared speech signal is reconstructed. The paper contains experimental
results that show that the proposed method has a better performance than
its known counterpart based on RASTA (RelAtive SpecTrA).
Keywords: speech signal, filtering, modulation area, noise reduction,
synthesis, evaluation of quality.
SOME ISSUES OF SPECTRAL EFFICIENCY INCREASING OF COMMUNICATION SYSTEMS:
NONORTHOGONAL TRANSMISSION
Bakulin M.G, Kreindelin V.B., Shumov A.P., m.g.bakulin@gmail.com,
vikrend@gmail.com,
magnit2250@mail.ru
Extension of Mazo's concept of fasterthanNyquist (FTN) signaling to
pulse trains that modulate a bank of subcarriers is considered. This method
corresponds to two dimensional FTN signaling. The signal processing is
similar to orthogonal frequency division multiplex (OFDM) transmission
but the subchannels are not orthogonal. Despite nonorthogonal pulses and
subcarriers, the method achieves the isolatedpulse error performance
and it does so in as little as half the bandwidth of ordinary OFDM system.
Keywords: wireless systems, nonorthogonal transmission, spectral
efficiency, OFDM, subcarriers bank, Mazo concept.
THE METHOD FOR
PITCH FREQUENCY ESTIMATION IN PRESENCE OF NOISE
Gai V.E., iamuser@inbox.ru
A pitch frequency estimation algorithm in presence of noise is proposed.
The algorithm can be used in the development of speaker identification
systems. Results of research proving the effectiveness of the proposed
algorithm are presented.
Keywords: speaker identification, speech signal, pitch frequency,
active perception theory, interference, frequency estimate.
ADAPTIVE ALGORITHM OF RECURSIVE DIGITAL FILTER PARAMETER DETERMINING
FOR ACOUSTIC FEEDBACK COMPENSATION
Kondratyev K.V., Uglev V.A., Nepomnyaschy O.V., Sergeevich V.N., kondratyev37@mail.ru,
uglevv@yandex.ru
This article considers
the question of the audio signal adaptive filtering with a digital filter
that suppresses acoustic feedback. The algorithm for adjusting the parameters
of the recursive digital filter is put forward, this algorithm allows
to take into account the changing dynamics of the acoustic environment
in the room. Filter characterization is realized each time while in the
acoustic path information gap lasting of the order of 12 seconds is changing
wanted signal. The results of testing the algorithm for signal processing
with a loudspeaker system showed that high efficiency of acoustic feedback
suppression (up to 93%). It is also considered the prospect of the proposed
filter application for the advanced systems of manmachine interaction.
Keywords: audio, sound pressure, an adaptive filter, a recursive
algorithm, noise compensation, correlation function.
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