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1

Noncircularity of Demodulated Radar Signal

Rytel-Andrianik R.

International Journal of Electronics and Telecommunications

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2013

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Vol. 59, No. 3

301-306

EN

The output of the quadrature demodulator is generally regarded as a complex signal that is circular if only the demodulator is well balanced. In the paper we analyze properties of quadrature demodulators, particularly digital one, and show that the output is noncircular also if the input signal is nonstationary. Then we find sources of this noncircularity and show that they stem from transients of the low-pass demodulator filter. This is quite important because nonstationary inputs are quite typical in radar where power of echoes depends strongly on range. In the first sections we also review complex random signals and properties of circularity and properness.

2

Estimation of Two Sinusoids in a Very Short Signal

Rytel-Andrianik R.

International Journal of Electronics and Telecommunications

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2012

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Vol. 58, No. 2

123-128

EN

In the paper, the estimation of the parameters (frequency, amplitude, phase) of two complex-valued sinusoids embedded in a white gaussian circular additive noise is considered. In this context, it is answered what is the minimal necessary number of signal samples needed to reliably estimate all the parameters of both sinusoids. The Cramer-Rao bounds and maximum likelihood estimator are used in the analysis. The answer to the posed question is not straightforward. It is shown that three signal samples are enough only if the difference of phases between both sinusoids meets certain condition, otherwise estimation results are ambiguous. The use of four signal samples has the advantage that reliable estimates can be obtained irrespectively of this phase difference.

3

System przetwarzania sygnałów w radarze MTD

Nałęcz M., Rytel-Andrianik R., Rupniewski M.

Elektronika : konstrukcje, technologie, zastosowania

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2009

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Vol. 50, nr 8

38-44

PL

W artykule przedstawiono zarys koncepcji systemu przetwarzania sygnałów w radarze średniego zasięgu wykorzystującym filtrację MTD (ang. Moving Target Detector). System tego typu wdrożono do produkcji w Centrum Naukowo-Produkcyjnym Elektroniki Profesjonalnej RADWAR S.A. w 2008 roku. Omówiono zalety stosowania przyjętego rozwiązania i opisano specyfikę projektowania odpowiedniego banku filtrów. Zaprezentowano oryginalne podejście do problemu uogólniania informacji pochodzących z wielu kanałów przetwarzania.

EN

The fundamentals of signal processing in MTD (Moving Target Detector) medium range radar system are presented. Similar system has been successfully implemented in the Scientific-Industrial Centre of Professional Electronics RADWAR S.A. in year 2008. The paper presents advantages of the proposed solution and describes the specific problems related to the design of the filter bank. The original approach to the problem of the data merging from multiple processing channels is also discussed.

4

Detekcja i estymacja parametrów przyspieszającego obiektu przez radar z liniowo modulowaną falą ciągłą

Rytel-Andrianik R.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2007

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nr 1

7-12

PL

Opisano problem obserwacji przyspieszającego obiektu przez radar z częstotliwościowo modulowaną falą ciągłą. Przedstawiono modele analizowanych sygnałów; spełniający kryterium optymainości Neymana-Pearsona test decyzyjny do stwierdzenia obecności obiektu oraz estymator największej wiarygodności odległości i parametrów ruchu wykrytego obiektu. Zamieszczono również przykłady wykorzystania opisanych metod do analizy rzeczywistych sygnałów radarowych.

EN

In the paper, the problem of a frequency modulated continuous wa-ve (FMCW) radar observing an accelerating target was described. Analyzed radar signal model was given and procedures for target Neyman-Pearson detection and maximum likelihood estimation of its motion parameters were presented. The described methods were used to analyze motion of real targets whose echo was recorded by an FMCW radar. The paper is based on the author's PhD thesis.

5

On the ambiguity function for accelerating target in FMCW radar

Rytel-Andrianik R.

Journal of Telecommunications and Information Technology

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2007

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nr 1

40-44

EN

In the paper, we are concerned with FMCWradar detection of an accelerating target, echo of which is buried in an additive white Gaussian noise. We derive and analyze three-dimensional generalized ambiguity function for target range, velocity and acceleration. We interpret known properties of this function and obtain new ones, which allows us to specify resolutions and regions of unambiguity for range, velocity and acceleration. The obtained resolutions we express in terms of corresponding Cramer-Rao bounds.

6

Exact Cramer-Rao Bounds for Signals with Constant Amplitude and Polynomial Phase

Rytel-Andrianik R.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2003

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Vol. 51, nr 4

421-433

EN

Exact and closed-form Cramer-Rao bounds (CRBs) are derived for parameters of a continuous-time complex signal [formula] with constant amplitude and polynomial phase of arbitrary degree. The signal is measured in additive Gaussian noise over arbitrary time interval [T1, T2]. The influence of changes in the measurement interval center of CRBs is analysed and two special cases of [formula] and [formula] are considered in more detail. It is shown that the latter case, though less often used, gives lower CRBs for phase parameters.

7

A Novel Approach to Signal Processing in FMCW Radar

Wojtkiewicz A., Nałęcz M., Kulpa K., Rytel-Andrianik R.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2002

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Vol. 50, Nr 4

347--359

EN

New possibilities of Digital Signal Processing (DSP) in Frequency Modulated Continuous Wave (FMCW) radar are presented. By the use of a transformation belonging to the class of higher-order bilinear time-frequency transforms (such as Polynomial Phase Transform PPT, Generalized Ambiguity Function GAF or Generalized Wigner-Ville Distribution GWVD) one can estimate coefficients of polynomial phase of the intermediate frequency (IF) signal. Two practical cases with non-negligible higher order coefficients are considered: compensation of nonlinear modulator and estimation of moving target acceleration, velocity and range. In the latter case, target velocity introduces to the processed signal a linear phase shift that can be measured using Fourier transform. Similarly, target acceleration introduces parabolic shift to the signal phase, which in turn enables the estimation of the acceleration. The article includes the description of a relationship between quadratic coefficient and object acceleration as well as estimation methods for this coefficient. Examples based on recorded signals from working FMCW radar prove usefulness of proposed methods.