An antipodal Vivaldi antenna operates simultaneously for telemetry and sensing when placed conformally onto PVC pipes. Good radiation efficiency is realised and the antenna impedance matching remains stable when a pipe is empty or contains water. The fidelity factor performance based on an input Ultra-Wideband Gaussian pulse is a suitable figure of merit to detect water presence. Different water levels and pipe conditions correspond to fidelity factors between 90% and 96%, which are a suitable dynamic range for sensing and the appropriate quality for pulse communications for remote monitoring. 1. Introduction Monitoring pipe systems represents a major problem where continuous information on the liquid content must be constantly provided. This is the case for water leakage sensor networks or for stormwater detection in critical drainage system. Several technologies were proposed in the literature for these applications such as tracer gases and thermography [1]. Furthermore, ultrasound sensors have been proposed for accurate detection and localisation of leakages in buried water pipes [2, 3]. Acoustic wave monitoring is widely used in leak detection but they are concerns in terms of time response, robustness, reliability, accuracy, and costs. Radio-frequency telemetry has been more recently introduced to localize leaks and malfunctioning pipelines. In particular, Ground Penetrating Radar (GPR) systems can be efficiently designed to image subsurface scattering leaks by using low-frequency electromagnetic (EM) waves [4, 5]. However, due to their cost and characteristics, GPR is suitable for extraordinary maintenance. EM sensors revealing wave propagation distortion inside metallic pipes have been recently proposed [6]. Although reflections coming from leaks/cracks can be promptly identified by EM propagating mode monitoring, this technique is restricted to a limited number of applications and scenarios. High data rates and low-power requirements make Ultra-Wideband (UWB) technology largely used for short-range wireless communication and sensor systems. With a large operating spectrum, short pulses can be generated. UWB sensors can then monitor pulse distortion and identify the associated environmental changes. Operating in the time domain implies the design of novel figures of merit to characterize UWB impulse radio systems. The signal purity in particular can be used to assess the time domain performance of the UWB front-end for antenna and sensor operative scenarios. This can be measured in terms of fidelity factor, which estimates the distortion of the
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