*2.3.1. Introduction*

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

**Figure 1.** M-sequence based impedance spectroscopy (bandwidth 17 MHz – 4 GHz; 9th order Msequence). Left: Device implementation with external coupler. Right: M-sequence device with internal

Figure 4 of Chapter 14 (HaLoS-project) relates to the basic structure which can be found in all device modifications. Such device configurations were applied in an early project state for microwave imaging and organ motion tracking experiments. Involving a directional coupler, it is further used for impedance spectroscopy as exemplified in Fig. 1. Multichannel systems and MIMO-arrays are based on the device philosophy as illustrated in Fig.

**Figure 2.** M-sequence two-port network analyzer (operational band 40 MHz – 8 GHz, 9th order Msequence, USB2 interface). It can be extended by an RF-switch matrix for MIMO-radar imaging.

coupler and rigid probe connection to improve measurement reliability.

6 of Chapter 14. Implemented examples are depicted in Fig. 2 to Fig. 4.

The exploitation of UWB microwave technologies for biomedical diagnostics requires the development of antennas and sensors tailored to this application. The integration of the antennas as a part of a complex system leads to serious compatibility and functionality constraints, which must be properly addressed for high system performance. Within ultraMEDIS, two goals were pursued: Firstly, the detection of early stage breast cancer and secondly, the development of a magnetic resonance imaging (MRI) compatible navigator

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

system (Section 4). These two goals provide different challenges in terms of antenna design, implementation, and experimental evaluation, both with respect to mechanical and electrical constraints [10]. As both applications involve different approaches, they will be treated separately.

ultraMEDIS – Ultra-Wideband Sensing in Medicine 265

**Figure 5.** Simulated scenarios to investigate the effective radiation of electromagnetic energy into the body (on the left). The antenna used is a bow-tie excited by a Gaussian pulse of a duration of around 80 ps FWHM. The *Phantom* material is a homogenous dispersive material simulating the dielectric behavior of the human body tissues. The results (on the right) represent the time-dependent co-polar component of the electric field evaluated at a distance of 44.5 mm from the phantom interface (the green spot in the figure). The examined cases are, from top to bottom: the antenna in direct contact with the phantom; with the implementation of a thin dielectric layer; with the implementation of a matching

ε = 4

ε = 4

0.5 mm

antenna

0.5 mm 2 mm

antenna

antenna

layer plus a thin dielectric layer, respectively.

Phantom

Phantom

d = 44.5 mm

Phantom

d = 44.5 mm

d = 44.5 mm
