Antenna Characteristics and Ranging Robustness with Double Quadrature Receiver and UWB Impulse Radio Farid Bautista, Dominique Morche, Serge Bories, Gilles Masson CEA, LETI, MINATEC 17 rue des Martyrs 38054 Grenoble Cedex 9 FRANCE farid.bautista@cea.fr ; dominique.morche@cea.fr ; serge.bories@cea.fr Abstract— This paper analyzes the effect of the antenna characteristics on the ranging precision of UWB impulse radio receivers. It shows that the influence of the antenna highly depends on the chosen RF architecture. The single quadrature receiver architecture is first explained and analyzed. Then the double quadrature receiver is presented and its robustness is justified. A small size miniaturized ultra wideband antenna is then described. This antenna is exploited to validate the robustness thanks to link level simulations. Keywords-UWB, Antenna Effect, Impulse Radio, Ranging, RF Receiver Architecture I. INTRODUCTION Since ten years, UWB technology has received considerable attention for a wide range of applications since it has shown very interesting features [1]. Among them, the attractiveness of UWB for high accuracy indoor localization applications is well known and has justified a high number of studies [2], [3] to evaluate and to improve the performances of the technology with respect to the channel properties and to the signal to noise ratio. The UWB system noticeably outperformed the other technologies in terms of reliability and accuracy. However, the performances are also strongly linked with the characteristics of the RF receiver which are usually expressed in terms of ranging precision in Line Of Sight propagation conditions. During the last five years, the RF receiver architecture dedicated to ranging in impulse radio has greatly evolved. The first proposed solutions were based on energy detection [4] which has the advantage to offer low power consumption. Then, [5] has shown that coherent receiver architecture based on the classical quadrature receiver architecture was interesting to benefit from more processing gain in the receiver and to improve the robustness against out-of-band blockers. This architecture has then been judiciously exploited in [6] to reach centimetre ranging precision when using sub-GHz impulse radio signals. Later, double quadrature receiver architecture has been proposed to reach the same order of ranging precision but using the [3-5GHz] frequency band. The same ranging precision is reached by Continuous Wave Frequency Modulated UWB solutions. This means that nowadays, very high ranging precisions can be offered at a power consumption which is fully compatible (from 10 mW to 50 mW) with the integration of such circuits in mobile devices. The power consumption of the transmitter can be made much smaller [9]. This opens the door to a new kind of applications [10] where small RFID tag (with energy scavenging or remote power) can be precisely identified and localized. The development of such kind of applications requires really small tags and readers such that these equipments are not noticeable by the users. The bottleneck in size reduction is the antenna. Reducing its size far below the wavelength impacts its radiated efficiency and its strong integration on the device disturbs its omni-directionality in module and in phase. This may also impact the performances of the ranging system. We will show in this paper that the influence of the characteristics of small size antennas on ranging precision depends on the chosen RF receiver architecture. Firstly, we will describe the single quadrature receiver and explain how the antenna characteristics may modify the ranging precision. Then, the double quadrature receiver architecture will be presented as well as a new compact UWB antenna operating in the [3-5GHz] frequency band. The robustness of the proposed double quadrature receiver will be demonstrated thanks to link level simulations. It will be shown that both in azimuth and elevation, the ranging precision degradation is kept small. Then conclusion will be drawn. II. SINGLE QUADRATURE RECEIVER A. Architecture description In this paragraph, the single receiver architecture presented in [6] is explained. This paper has been selected as a reference because it offers one of the best ranging precision and is based on the extraction of the phase of the arriving signal. The architecture is presented in Fig. 1. The proposed system operates in the sub-GHz frequency band with 650 MHz center frequency and 500MHz signal bandwidth. The received pulse is first down-converted to baseband with two orthogonal sinusoids waves (625MHz) and then integrated in a window with a 2.5ns duration (Δ). Lastly, the signal is converted to the digital domain. 978-1-4577-2032-1/12/$26.00 © 2012 IEEE ICUWB 2012 173