An active transmitter antenna with beam scanning and beam shaping capability for 60GHz application

摘要

For 60GHz indoor communication systems [1], there is a remarkably large range of frequency allocated for unlicensed wireless telecommunications around 60 GHz (typically 59–66GHz). In Europe, the frequency ranges 62–63 GHz and 65–66 GHz are reserved for wideband mobile networks (Mobile Broadband System). In Japan, the 59–67 GHz band is reserved for wireless communications. In indoor operation, as the link between transmitter and receiver can be shadowed because of human body interposition for example, implementing beam-scanning antennas is needed to carry out high bite rate communications. Some solutions are conceivable to achieve beam-scanning antennas, for example phased arrays [2] but it does not allow for scanning the beam over a large angle and it induces losses due to phase shifters. It is the same limitation for switched antenna arrays based on a Butler matrix [3]. Homogeneous lenses may allow the obtention of a wide scan antenna [4] but bring about a problem of retro-diffusion from the lenses to the sources. Lüneburg lens avoids this problem because it presents a dielectric gradient index lens whose relative permittivity εT varies radially according to the law given by [5]. Moreover, this inhomogeneous lens offers the particularity to have infinity of focus points. So, it becomes possible to achieve a very wide scan antenna. Practically, inhomogeneous lens can be manufactured either from materials with varying effective dielectric permittivity [6] or by assembling a finite number of concentric homogeneous dielectric shells [7]. This kind of inhomogeneous spherical lens antenna has demonstrated off-axis performances by moving one source around the lens [8] and a beam shaping capability by associating several sources below the lens [9]. In this paper, we study a plate Luneburg lens to obtain a narrow beam (10°) for azimuth plane and a wide beam (70°) for elevation plane. First, a new mi- ed solution is chosen to manufacture the lens by using holes in a Teflon sheet (εT=2.04) and external foam crowns (εT=1.45 and εT=1.25). Secondly, the principle of the beam-scanning and beam-shaping antenna is matched by using one MMIC power amplifier behind each ridged source waveguide. Finally, a transmitter active reconfigurable antenna at 60 GHz is tested by measuring the received power and the radiation patterns for different configurations.