**1. Introduction**

438 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications

2002

Released 22 April 2002

, vol. 50, 2005, 4245-4258

*and Propagation*, vol. 57, 2009, 1692-1704

*Propagation,* Prague, March 2012

no.12, pp.2109-2138, Dec. 2006

(ISMRM), Montreal, Canada, ISSN 1545-4428, p.1804, (2011)

[63] S.M. Sze, *Physics of Semiconductor Devices 2nd edn*, New York, Wiley, 1981

circuits," in Proc. *IEEE Custom Integrated Circuits Conf.*, 1987, pp. 659-662

pp. 48–56, Mar. 2002

[51] R. Herrmann, J. Sachs, K. Schilling, and F. Bonitz, "New extended M-sequence ultra wideband radar and its application to the disaggregation zone in salt rock," Proc. *12th*

[53] FCC 02-48, "Revision of Part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems", First Report & Order, Washington DC, Adopted 14 Feb 2002,

[54] Electronic Communication Committee, "ECC Decision of 24 March 2006 amended 6 July 2007 at Constanta on the harmonized conditions for devices using Ultra

[55] M. Kmec, J. Sachs, P. Peyerl, P. Rauschenbach, R. Thomä, R. Zetik, "A Novel Ultra-Wideband Real-Time MIMO Channel Sounder Architecture," *XXVIIIth URSI General* 

[56] M. Helbig, I. Hilger, M. Kmec, G. Rimkus, J. Sachs, "Experimental phantom trials for UWB breast cancer detection," *German Microwave Conference*, GeMiC 2012, Ilmenau [57] M. Lazebnik, E.L. Madsen, G.R. Frank et al.: "Tissue-mimicking phantom materials for narrowband and ultrawideband microwave applications" *Physics in medicine and biology*

[58] E. C. Fear, S. C. Hagness, P. M. Meaney, M. Okoniewski, and M. A. Stuchly, "Enhancing breast tumor detection with near-field imaging," *IEEE Microwave Magazine*, vol. 3, no. 1,

[59] I.J. Klemm J.A. Craddock, A. Leendertz et al.: "Radar-based breast cancer detection using a hemispherical antenna array – experimental results," *IEEE Trans on Antennas* 

[60] Kosch O., Thiel F., Ittermann B., and Seifert F., "Non-contact cardiac gating with ultrawideband radar sensors for high field MRI", *Proc. Intl. Soc. Mag. Reson. Med. 19*,

[61] M. Helbig, M. Kmec, J. Sachs, C. Geyer, I. Hilger, G. Rimkus, "Aspects of antenna array configuration for UWB breast imaging Brust", *6th European Conference on Antennas and* 

[62] Afzali-Kusha, A.; Nagata, M.; Verghese, N.K.; Allstot, D.J.; , "Substrate Noise Coupling in SoC Design: Modeling, Avoidance, and Validation," *Proceedings of the IEEE* , vol.94,

[64] J.A. Olmstead and S. Vulih, "Noise problems in mixed analog-digital integrated

�Wideband (UWB) technology in bands below 10.6 GHz, " July, 6, 2007

*Assembly 2005,* Oct. 23-29, New Delhi, October 2005.

*International Conference on Ground Penetrating Radar*. Birmingham, UK, Jun. 2008. [52] FCC News Release, "New Public Safety Applications and Broadband Internet Access Among Uses Envisioned by FCC Authorization of Ultra-Wideband Technology", 14 Feb

> This chapter presents scientific achievements in the field of UWB radar and communication systems for biomedical applications. These contributions focus on low-power MMIC designs, novel antenna structures and competitive approaches for communication and imaging.

> The first section describes components for UWB radar sensors and communication systems, namely antennas and integrated circuits. Novel broadband antenna concepts for UWB radar and communication applications are presented. Symmetrical UWB antenna structures for free space propagation with improved performance compared to existing antennas regarding radiation pattern stability over frequency are designed, realized and successfully characterized. Novel differential feeding concepts are applied, suppressing parasitic radiation by cable currents on feed lines. For applications such as communication with implants and catheter localization, a miniaturized antenna optimized for radiation in human tissue is designed. The radiation characteristics of the antenna are measured using an automated setup embedded in a liquid consisting of sugar and water, mimicking the dielectric properties of biological tissue. For UWB radar transmitters, a differential and low-power impulse generator IC is realized addressing the FCC spectral mask based on a quenched cross-coupled LC oscillator. The total power consumption is only 6 mW at an impulse repetition rate of 100 MHz. By adding a simple phase control circuit setting the start-up phase condition of the LC oscillator, an impulse generator with a bi-phase modulation scheme is achieved. A further modification introduces a variable width of the pulse envelope as well as a variable oscillation frequency. The corresponding spectra have controllable 10 dB bandwidths and center frequencies fitting the different spectral allocations in the USA, Europe and Japan. On the receiver side, both a fully differential correlation-based and an energy detection receiver for the 3.1-10.6 GHz band are designed. Monostatic UWB radar systems require

©2013 Mirbach et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ©2013 Mirbach et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### 2 Will-be-set-by-IN-TECH 440 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications UWB in Medicine – High Performance UWB Systems for Biomedical Diagnostics and Short Range Communications <sup>3</sup>

transmit/receive turn-around times in the nanosecond regime. Integrated front-ends which successfully address this issue are presented here for the first time.

*2.1.1. Circular slot antenna excited with a dipole element*

Planar broad monpoles or dipoles are favored UWB antennas for communication systems with high data rates, e. g. potentially used in base stations for patient monitoring. However, broad monopoles fed single-endedly are prone to cable currents on the feeding line disturbing the radiation characteristic in the lower frequency range [15], while dipoles behave like a *λ*-radiator with a zero in main beam direction in the upper frequency range. Both effects lead to an undesired change of the radiation pattern in the operational frequency range reducing the effective bandwidth. For the widely-used impulse based UWB systems, this leads to a

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UWB in Medicine – High Performance UWB Systems for Biomedical Diagnostics and Short Range Communications

A practical solution to overcome the described parasitic radiation pattern performance is the combination of a circular slot antenna with a dipole feeding element as depicted in Fig. 1. The circular slot behaves like a broad monopole according to Babinet's principle. A broad dipole located in the center of the circular slot and consisting of two circular segments excites the slot antenna. The inherent symmetrical feeding of the dipole avoids the propagation of cable currents due to the virtual ground plane in between the transmission lines and results in an

The length of the exciting dipole is designed to be *λ*/2 at the center of the FCC UWB frequency range. Therefore, the dipole is smaller than pure UWB dipole antennas with a typical length of *λ*/2 at the lower edge of the FCC UWB frequency range. The perimeter of the circular slot is about *λ* at the lower edge of the FCC UWB frequency range leading to a resonance at 4.3 GHz (see simulation result for |*S*11| in Fig. 2(a)), and hence, to a return loss better than 10 dB at 3.1 GHz. Additional resonances with a low qualtiy factor are arising if the perimeter of the slot is a multiple of the wavelength (see at 6.9 GHz and 9.8 GHz in Fig. 2(a)). Therefore,

In order to characterize the dipole slot antenna with a single-ended coaxial line, a common UWB planar transition from coplanar stripline to a microstrip line based on [32] is used. A metallic shielding around this balun suppresses any parasitic radiation (see Fig. 1). The

broadening of the impulse and consequently to a degraded system performance.

uniform radiation characteristic over the UWB frequency range.

a UWB behavior regarding return loss is achieved.

**Figure 1.** Dipole slot antenna.

The second section deals with signal processing. As, due to the large RF bandwidth, direct analog to digital conversion and digital signal processing are not feasible (at least not at reasonable power consumption), analog signal processing is one focus. For communication, detection methods based on analog correlation require channel estimation, storing of impulse responses and also precise time synchronization. Therefore methods based on energy detection are developed which require no or little channel knowledge, having low complexity, robustness to multipath propagation and high resistance to synchronization and symbol clock errors. New modulation techniques are described, which can cope with interchip and intersymbol interference. Also a novel support by a comb filter resulting in significant SNR improvements in interference and multiuser scenarios is presented. The methods developed for communication applications can also be used in the radar context. For detection and tracking of moving targets (e.g. heart in the body) new algorithms based on particle filtering are developed for the digital signal processing part. It is shown that the accuracy, the resolution and robustness can be improved compared to conventional methods. For the objective of catheter localization, the knowledge of the shape and position of the human body surface is inevitable. A UWB imaging algorithm for the detection and estimation of this surface has been developed based on trilateration and is also described in this second section. Furthermore, building on this surface estimation algorithm, a new method for the localization of transmitters in dielectric media is presented. Taking into account the refraction effects on the boundary surface, the algorithm uses the impulse time of arrival to determine the transmitter position inside of the dielectric medium.

The third section finally describes the design of bistatic UWB radar systems using the components presented in the first section. Single-ended and differential radar demonstrators are developed, with which the potential of impulse-radio UWB sensing is evaluated. Measurements aimed at applications of the developed hardware such as vital sign monitoring and communication with implants are presented. Further measurements are performed to prove the functionality of the imaging algorithms derived in the second section. For surface estimation, a single radar sensor is moved around a highly reflective target in order to emulate a whole sensor array. For the verification of subsurface transmitter localization, a transmitter is placed inside of a container filled with tissue mimicking liquid, and its position is visualized with respect to the estimated container surface.
