# September 2009, Volume 18, Number 3

**B. Geiger, T. Gigl, J. Preishuber-Pfluegl, K. Witrisal**
[references] [full-text]

Experimental Characterization of System Parameters for Ranging in IEEE 802.15.4a using Energy Detectors

The IEEE 802.15.4a standard for impulse radio ultrawide band (IR-UWB) communication systems defines a ranging scheme which relies on the measurement of the round-trip propagation time of electromagnetic pulses. Accuracy is strongly dependent on the estimation of the timeof-arrival (TOA) of the pulse that is spread in time due to multipath propagation. The major concern therefore is the proper detection of the leading edge. In this work, the ranging capabilities of the standard are analyzed for an energy detector receiver. Emphasis is put on the influence of transmitter and receiver parameters, which are evaluated for a set of measured scenarios. It is shown that sub-meter ranging accuracy can be achieved with fixed parameter settings.

- EUROPEAN COMMISSION. Commission decision of 21 April 2009: On allowing the use of the radio spectrum for equipment using ultra-wideband technology. Official Journal of the European Union, L105/9, 2009.
- IEEEWORKING GROUP 802.15.4a. Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (WPANs): Alternate PHYs. NJ: IEEE, 2007.
- WITRISAL, K., LEUS, G., JANSSEN, G. J. M., PAUSINI, M., TROESCH, F., ZASOWSKI, T., ROMME, J.. Noncoherent ultrawideband systems. IEEE Signal Processing Magazine, 2009, vol. 26, no. 4, p. 48 - 66.
- DARDARI, D., CONTI, A., FERNER, U., GIORGETTI, A., WIN, M. Z. Ranging with ultrawide bandwidth signals in multipath environments. Proceedings of the IEEE, 2009, vol. 97, no. 2, p. 404 - 426.
- GUVENC, I., SAHINOGLU, Z. Threshold-based TOA estimation for impulse radio UWB systems. In IEEE Int. Conf. on Ultra- Wideband, ICU. 2005, p. 420 - 425.
- GUVENC, I., SAHINOGLU, Z., ORLIK, P. V. TOA estimation for IR-UWB systems with different transceiver types. IEEE Transactions on Microwave Theory and Techniques, 2006, vol. 54, no. 4, p. 1876 - 1886.
- XU, C., LAW, C. L. Experimental evaluation of UWB ranging performance for correlation and ED receivers in dense multipath environment. In Future Generation Communication and Networking. 2007, vol. 2, p. 186 - 192.
- GUVENC, I., SAHINOGLU, Z. Threshold selection for UWB TOA estimation based on kurtosis analysis. IEEE Communications Letters, 2005, vol. 9, no. 12, p. 1025 - 1027.
- LEI, Z., CHIN, F., KWOK, Y.-S. UWB ranging with energy detectors using ternary preamble sequences. In IEEE Wireless Communications & Networking Conf., WCNC. 2006, p. 872 - 877.
- KWOK, Y.-S., CHIN, F., PENG, X. Ranging mechanism, preamble generation, and performance with IEEE 802.15.4a low-rate lowpower UWB systems. In IEEE Ninth Symposium on Spread Spectrum Techniques and Applications. 2006, p. 525 - 530.
- CHIN, F., ZHI,W., KO, C.-C. System performance of IEEE 802.15.4 low rate wireless PAN using UWB as alternate-PHY layer. In IEEE Int. Symp. on Personal, Indoor and Mobile Radio Communications, PIMRC. 2003, p. 487 - 491.
- GEIGER, B. Ranging in the IEEE 802.15.4a standard using energy detectors. In IEEE EUROCON. St. Petersburg, 2009, p. 1948 - 1955.
- SAHINOGLU, Z., GEZICI, S. Ranging in the IEEE 802.15.4a standard. In Wireless and Microwave Technology Conf. 2006, p. 1 - 5.
- GIGL, T., PREISHUBER-PFLUEGL, J., WITRISAL, K. Statistical analysis of a UWB energy detector for ranging in IEEE 802.15.4a. In IEEE Int. Conf. on Ultra-Wideband, ICUWB. Vancover (Canada), 2009, in press.
- GUVENC, I., SAHINOGLU, Z. Multiscale energy products for TOA estimation in IR-UWB systems. In IEEE Global Communications Conf., GLOBECOM. St. Louis, 2005, p. 209 - 213.
- SAHINOGLU, Z., GEZICI, S., GUVENC, I. Ultra-wideband Positioning Systems – Theoretical Limits, Ranging Algorithms, and Protocols. Cambridge: Cambridge University Press, 2008.
- DIZDAREVIC, V., WITRISAL, K. Statistical UWB range error model for the threshold leading edge detector. In IEEE Int. Conf. on Information, Communications and Signal Processing, ICICS. Singapur, 2007, p. 1 - 5.
- GIGL, T., BUCHGRABER, T., ADALAN, A., PREISHUBERPFLUEGL, J., FISCHER, M., WITRISAL, K. UWB channel characterization using IEEE 802.15.4a demonstrator system. In IEEE Int. Conf. on Ultra-Wideband, ICUWB. Vancover (Canada), 2009, in press.
- GIGL, T., ARNITZ, D., PREISHUBER-PFLUEGL, J., WITRISAL, K. Experimental characterization of ranging in IEEE 802.15.4a using a coherent reference receiver. In IEEE Int. Symp. on Personal, Indoor and Mobile Radio Communications, PIMRC. Tokyo (Japan), 2009, in press.
- IRAHHAUTEN, Z., JANSSEN, G., HOMAYOUN, N., YAROVOY, A., LIGTHART, L. UWB channel measurements and results for office and industrial environments. In IEEE Int. Conf. on Ultra- Wideband, ICU. 2006, p. 225 - 230.

Keywords: Ultrawide band, IEEE 802.15.4a, energy detector, UWB measurements, ranging

**M. Aftanas, M. Drutarovsky**
[references] [full-text]

Imaging of the Building Contours with Through the Wall UWB Radar System

Any actual information about a building interior can be very useful before entering a dangerous area. It can be used to plan strategies in many rescue and security applications. The paper deals with imaging of the inner and outer building contours from the outside using through the wall UWB radar. The whole processing chain for obtaining the contours of a scanned building is explained. The image processing method of highlighting the building walls using Hough transform with assumed knowledge of the direction of walls is presented. The algorithm was tested on real measurement data acquired from a M-sequence UWB radar system.

- SACHS, J., AFTANAS, M., CRABBE, S., DRUTAROVSKY, M., KLUKAS, R., KOCUR, D., NGUYEN, T. T., PEYERL, P., ROVNAKOVA, J., ZAIKOV, E. Detection and tracking of moving or trapped people hidden by obstacles using ultra-wideband pseudonoise radar. In European Radar Conference EuRAD 2008, Amsterdam (The Netherlands), 2008, p. 408 - 411.
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- Camero. XaverTM800 - Through Wall Vision, one and two persons. [Online]. Available: http://www.camero-tech.com/xaver800.shtml.
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- AFTANAS, M. Through wall imaging using Msequence UWB radar system. Thesis to the dissertation examination, Technical University of Kosice, Department of Electronics and Multimedia Communications, Slovak Republic, Dec. 2007, p. 63.
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- CHENG-LI, J., KE-FENG, J., YONG-MEI, J., GANG-YAO, K. Road extraction from high-resolution SAR imagery using Hough transform. IEEE International Geoscience and Remote Sensing Symposium, Changsha (China), 2005, vol. 1, p. 336 - 339.
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- XU, F., JIN, Y. Automatic reconstruction of building objects from multiaspect meter-resolution SAR images. IEEE Transactions on Geoscience and Remote Sensing, 2007, vol. 45, p. 2336 - 2353.
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Keywords: UWB radar system, through the wall imaging, SAR scanning, Hough transform, highlighting the walls

**M. Herceg, T. Matic, T. Svedek**
[references] [full-text]

Performances of Hybrid Amplitude Shape Modulation for UWB Communications Systems over AWGN Channel in a Single and Multi-User Environment

This paper analyzes the performance of the hybrid Amplitude Shape Modulation (h-ASM) scheme for the time-hopping ultra-wideband (TH-UWB) communication systems in the single and multi-user environment. h-ASM is the combination of Pulse Amplitude Modulation (PAM) and Pulse Shape Modulation (PSM) based on modified Hermite pulses (MHP). This scheme is suitable for high rate data transmission applications because b = log_{2}(MN) bits can be mapped with one waveform. The channel capacity and error probability over AWGN channel are derived and compared with other modulation schemes.

- SCHOLTZ, R. A. Multiple access with time-hopping impulse modulation. In Proc. IEEE Military Commun. Conf., October. 1993, p. 11-14.
- FCC, Revision of part 15 of the commission’s rules regarding ultra-wideband transsmision systems. Federal Communications Commission, ET Docket, 2002, pp. 98-153.
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- ZHANG, H., LI, W., GULLIVER, T. A. Pulse Position Amplitude Modulation for time-hopping multiple-access UWB communications. IEEE Trans. on Comm., 2005, vol. 53, no. 8.
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- ELTAHER, A., KAISER, TH. Hybrid shape, amplitude, and position modulation for UWB communication systems. WSEAS Journal on Communications, July 2004.
- GHAVAMI, M., MICHAEL, L. B., HARUYAMA, S., KOHNO, R. A novel UWB pulse shape modulation system. Wireless Personal Communications, 2002, vol. 23, p. 105-120.
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- DURISI, G., ROMANO, G. On the validity of Gaussian approximation to characterize the multiuser capacity of UWB TH PPM. In Proc. IEEE Conf. Ultra Wideband Systems and Technology, 2002, pp. 157-161.
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Keywords: Ultra-Wideband, Pulse-Amplitude Modulation, Pulse-Shape Modulation

**S. Gona, V. Kresalek**
[references] [full-text]

Derivation of Equivalent Material Models for Composite Laminated Materials

In this paper, an original approach of derivation of equivalent electrical models for multilayer composite materials is presented. The purpose of the modeling is to approximate a given composite material by an equivalent dielectric slab or by a medium consisting from several dielectric layers. For each layer, an equivalent complex permittivity is set up by an optimization procedure in order to achieve the same values of reflection and transmission coefficients as are the measured values of reflection and transmission coefficients of the original composite material.

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- GONA, S., KRESALEK, V. Accuracy of multilayer equivalent models for composite laminated materials. Accepted for publication on the "International Conference of Applications of Advanced Electronics (ICEAA 09)". Torino (Italy), 2009, Sept 14-18.
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Keywords: Composite material, reflection and transmission coefficients, equivalent model, complex permittivity, numerical inversion

**R. Sotner, J. Petrzela, J. Slezak**
[references] [full-text]

Current-Controlled Current-Mode Universal Biquad Employing Multi-Output Transconductors

This paper deals with RC active biquad working in the so-called current mode (CM). The design approach uses only three transconductors (OTA) with the minimum necessary number of outputs and with only three passive grounded elements. The proposed filter has simple circuit configuration providing all standard transfer functions such as high-pass (HP), band-pass (BP), low-pass (LP), band-reject (BR) and all-pass (AP). Electronic tuning and independent adjusting of the quality factor and bandwidth of BP filter is possible. The presented circuits are verified by PSpice simulations utilizing OTAs on transistor level of abstraction. The linear parasitic effects of the real active elements in each suggested circuit are briefly discussed. Experimental verification is also given. Designed networks can be used in many applications such as antialiasing filters, in high-speed data telecommunication systems, for signal processing in the cable modems, in regulation and measurement techniques etc.

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Keywords: Current-mode, transconductor, electronic adjusting, universal filter

**M. Ma, C. Wang, S. Du**
[references] [full-text]

Low Voltage Current Mode Switched-Current-Mirror Mixer

A new CMOS active mixer topology can operate at 1 V supply voltage by use of SCM (switched currentmirror). Such current-mode mixer requires less voltage headroom with good linearization. Mixing is achieved with four improved current mirrors, which are alternatively activated. For ideal switching, the operation is equivalent to a conventional active mixer. This paper analyzes the performance of the SCM mixer, in comparison with the conventional mixer, demonstrating competitive performance at a lower supply voltage. Moreover, the new mixer’s die, without any passive components, is very small, and the conversion gain is easy to adjust. An experimental prototype was designed and simulated in standard chartered 0.18μm RF CMOS Process with Spectre in Cadence Design Systems. Experimental results show satisfactory mixer performance at 2.4 GHz.

- BRANDOLINI, G.D., ROSSI, P., MANSTRETTA, D., SVELTO, F. Toward multistandard mobile terminalsfully integrated receivers requirements and architectures. IEEE Trans. Microw. Theory and Tech., 2005, vol. 53, no 3, p 1026-1038.
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Keywords: Current mode, switched current mirror, mixer, low voltage, receiver, RF circuit

**A. Lahiri, A. Chowdhury**
[references] [full-text]

A Novel First-Order Current-Mode All-Pass Filter Using CDTA

This paper presents a new realization of a firstorder current-mode (CM) all-pass filter (APF) using the recently proposed modern active building block (ABB), namely the current differencing transconductance amplifier (CDTA). The CM APF is made using minimum number of components, namely a single CDTA and one grounded capacitor. The circuit does not use any external resistors and offers the advantages of current-tunable pole frequency, low input impedance and high output impedance. Non-ideal analysis and sensitivity analysis are provided and PSPICE simulation results are included to verify the workability of the circuit.

- BIOLEK, D. CDTA-Building block for current-mode analog signal processing. In Proc. ECCTD 03. Cracow (Poland), 2003, vol. III, p. 397-400.
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Keywords: Current-mode (CM), active building block (ABB), all-pass filter (APF), Current Differencing Transconductance Amplifier (CDTA)

**J. Silovsky, P. Cerva, J. Zdansky**
[references] [full-text]

Comparison of Generative and Discriminative Approaches for Speaker Recognition with Limited Data

This paper presents a comparison of three different speaker recognition methods deployed in a broadcast news processing system. We focus on how the generative and discriminative nature of these methods affects the speaker recognition framework and we also deal with intersession variability compensation techniques in more detail, which are of great interest in broadcast processing domain. Performed experiments are specific particularly for the very limited amount of data used for both speaker enrollment (typically ranging from 30 to 60 seconds) and recognition (typically ranging from 5 to 15 seconds). Our results show that the system based on Gaussian Mixture Models (GMMs) outperforms both systems based on Support Vector Machines (SVMs) but its drawback is higher computational cost.

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Keywords: Speaker recognition, Gaussian Mixture Models (GMM), Support Vector Machines (SVM), broadcast processing

**P. Foris, D. Levicky**
[references] [full-text]

Adaptive Digital Image Watermarking Based on Combination of HVS Models

In this paper two new blind adaptive digital watermarking methods of color images are presented. The adaptability is based on perceptual watermarking which exploits Human Visual System (HVS) models. The first method performs watermark embedding in transform domain of DCT and the second method is based on DWT. Watermark is embedded into transform domain of a chosen color image component in a selected color space. Both methods use a combination of HVS models to select perceptually significant transform coefficients and at the same time to determine the bounds of modification of selected coefficients. The final HVS model consists of three parts. The first part is the HVS model in DCT (DWT) domain. The second part is the HVS model based on Region of Interest and finally the third part is the HVS model based on Noise Visibility Function. Watermark has a form of a real number sequence with normal distribution.

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Keywords: Digital image watermarking, Human Visual System models, Discrete Cosine Transform, Discrete Wavelet Transform, Noise Visibility Function, color spaces, watermark embedding, watermark detection

**S. Tsakiris, A. Salis, N. Uzunoglu**
[references] [full-text]

FPGA Implementation of a Frame Synchronization Algorithm for Powerline Communications

This paper presents an FPGA implementation of a pilot–based time synchronization scheme employing orthogonal frequency division multiplexing for powerline communication channels. The functionality of the algorithm is analyzed and tested over a real powerline residential network. For this purpose, an appropriate transmitter circuit, implemented by an FPGA, and suitable coupling circuits are constructed. The system has been developed using VHDL language on Nallatech XtremeDSP development kits. The communication system operates in the baseband up to 30 MHz. Measurements of the algorithm's good performance in terms of the number of detected frames and timing offset error are taken and compared to simulations of existing algorithms.

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Keywords: Field Programmable Gate Arrays (FPGAs), frequency division multiplexing, power line communications, frame synchronization

**M. Prochazka**
[references] [full-text]

Reader’s Comment on: Application of the Global Optimization Approaches to Planar Near-Field Antenna Phaseless Measurements [1]

- PUSKELY, J., NOVACEK, Z. Application of the global optimization approaches to planar near-field antenna phaseless measurements. Radioengieering. 2009, vol. 18, no. 1, p. 9 - 17.
- BARTIK, H. Dept. of Electromagnetic Field, Czech Technical University in Prague.
- PUSKELY, J., NOVACEK, Z., POKORNY, M. Using global optimization approaches to reconstruct radiation patterns. In Proc. of the 14th Conference on Microwave Techniques. Prague (Czech Republic), April 23/24, 2008, p. 239-242.