**1. Introduction**

26 UKoLoS

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54(4): 1647 – 1655.

Ultra-Wideband (UWB) sensors exploit very weak electromagnetic waves within the lower microwave range for sounding the objects or processes of interest. The interaction of electromagnetic waves with matter provides interesting options to gain information from a great deal of different scenarios. To mention only a few, it enables the assessment of the state of building materials and constructions, the investigation of biological tissue, the detection and localization of persons buried by rubble after an earthquake or unauthorized people hidden behind walls, and much more [1]. The advantage of such methods consists in their non-destructive and continuously running measurement procedure which may work at high speed and in contactless fashion.

Sensors applying electromagnetic interactions with the test object have been in use for a long time. However, most of such sensors are restricted to a relatively narrow bandwidth and, consequently, they can provide only a small amount of information about the test object. Sophisticated data processing supposed, UWB sensors may be able to provide more information and, therefore, to reduce ambiguities which are inherently part of indirect measurement methods such as electromagnetic sensing.

Depending on the actual tasks, the requirements on the sensing system may be quite different, such as the optimum operational frequency band, measurement speed, sensitivity, system costs, reliability, power consumption etc. There are several UWB sensing principles known, each having specific advantages and disadvantages. Generally, one can state that the usability of UWB-sensors will be largely improved with increasing degree of system

© 2013 Sachs 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 Sachs 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.

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

integration regardless of the sensor principle. The HaLoS-project addresses this topic by investigating general purpose UWB sub-modules like amplifiers, ADCs, fast processing units etc. as well as an integration-friendly sensor concept based on ultra-wideband pseudonoise codes.

HaLoS – Integrated RF-Hardware Components for Ultra-Wideband Localization and Sensing 371

*f* of a periodic sounding signal ( *Pt* - period duration) or via the Fourier

of the impulse response *gt* of a scenario under

<sup>2</sup> *ua P r tc* (4)

<sup>2</sup> *R SC T B* (5)

is the coherence time of a random or

(2)

, i.e. the capability of the radar to

(3)

 periodic signal non-periodic signal

pseudo-random signal (i.e. the width of the auto-correlation function). The occupation density of the frequency band is given by the line spacing *f* which is either determined by

As non-periodic signals are quite unusual in UWB sensing, we will avoid discussing them. The line spacing *f* gives the frequency resolution of the sensor or it determines the

In the case of UWB radar sensing, we can convert (1) and (2) into corresponding spatial

separate two close point targets of identical reflectivity. We will refer to the usual relation

1 for time stretched signal <sup>2</sup>

<sup>2</sup> 1 for pulse shaped signal 2

even if it should be considered with care. The relation originates from narrowband radar whose sounding signal suffers not from signal deformation neither by reflection at small bodies nor by antenna transmission. In contrast to that, a UWB signal bouncing a point scatterer will sustain a twofold differentiation and further deformations due to the antennas.

1

*Recording time*: UWB sensors provide, depending on their principle of work, either the impulse response function (IRF) or the frequency response function (FRF) of the scenario under test. The time needed to collect all data for one IRF or FRF (including synchronous averaging of repetitive measurements) we call recording time *RT* . Non-stationary test

1

1

test. If *g t* does not settle down within *w P T t* , we have to anticipate time aliasing.

*coh*

*c*

*w*

The unambiguous rage *ua r* of the UWB radar relates to the signal repetition by:

*<sup>B</sup> t c*

 


0 1

 

*<sup>P</sup> f t <sup>f</sup> <sup>T</sup>*

Here, *wt* represents the width of a pulse, and *coh*

maximum observable length <sup>1</sup> *T f <sup>W</sup>*

Transform by the observation interval *T* of non-periodic signals:

parameters. One of them assigns the range resolution *<sup>r</sup>*

*c*

*r*

scenarios limit the recording time either to

*SC B*

the repetition rate 0

( *c* - wave velocity):

The chapter is organized as follows. First, the most important performance figures of UWB sensors are introduced. Second, we give an overview of various UWB-sensor principles recently in use and explain the UWB pseudo-noise concept. Then, we address some specific topics like wideband receiver circuits, transmitter circuits and high-speed data capture. Finally, some aspects of monolithically integrated UWB-sensors are discussed.
