60 GHz tapered-helix antenna for WPAN applications

Figure 1: The average atmospheric absorption in the range 10 to 400 GHz (fig. 1 in [2]) without the contribution of fog and rain at sea level and 9150 m of altitude. The most prominent application of MMW communications is data transfer between personal digital devices (smartphones, personal digital assistant, mobile computing devices, etc.). The term personal area network (PAN) has been coined to describe this kind of communications. Devices in a PAN typically use short-range, high-bandwidth links to exchange data between them (i.e., multimedia file transfer between mobile devices) and medium
60 GHz Tapered-Helix Antenna for Байду номын сангаасPAN Applications
Paolo Nenzi, Francesco Tripaldi, Frank Silvio Marzano, Fabrizio Palma and Marco Balucani University of Roma “Sapienza” - DIET Via Eudossiana, 18 – 00184 Roma (Italy) nenzi@diet.uniroma1.it, phone: +39-0644585433 Abstract In this work the design of a broadband, high gain conical helical antenna is presented. The antenna is realized using a MEMS process that guarantees the high repeatability and throughput necessary for industrial applications. The designed antenna works in the 55GHz to 85GHz frequency range and has a gain greater than 8 dBi. This antenna presents potential applications in the emerging 60GHz communication band (assigned to WPAN) and in 76GHz RADAR applications for the automotive industry. The design procedure, mechanical and electromagnetic simulations are presented. Introduction The recent availability of CMOS processes that allows the realization of transistors with transit frequencies of hundreds of gigahertz [1] makes possible the production of siliconbased analog microwave circuits operating in the millimeterwave (MMW) frequency range. The advantage of using digital compatible, silicon-based, CMOS processes, for the realization of radio-frequency circuits, is the possibility to integrate on the same IC (integrated circuit) the entire communication system, reducing design and manufacturing costs. The type of communication systems developed in this frequency range are mostly dictated by the propagation characteristics of the atmosphere, that presents several absorption peaks, due to the molecular oxygen and water, as shown in figure 1. range links to transfer data to remote sites via a central infrastructure. The atmospheric propagation limits the interdevice communications to a few tens of meters and the device-infrastructure communication to few-hundreds. This is not a drawback in PAN as the concept of “personal area” suggests that communications should occur in an area under the control of the single person. For such applications, carrier frequency should be centered on absorption peaks to reduce interferences from nearby devices and, to provide some form of security against eavesdropping. The second application by importance is short-range RADARs, mainly collision avoidance radars for the automotive industry. Automotive RADARs are studied since the 70s of the past century [3] and only recently have been installed on high-end cars, and their general deployment is not yet foreseeable. On board millimeter-wave RADARs are used to inform the driver about potential collision risk with the preceding vehicle, to reduce the braking time by pretensioning brakes, to deploy the passive restraint systems, to reduce the risk associated to blind-spots in lane change and to provide information to station-keeping for automatic cruisecontrol. Automotive RADARs should operate under all atmospheric conditions (e.g., heavy rain or fog) when severe additional absorption (with respect to the values shown in figure 1) is present, therefore the operating frequencies should be chosen around the absorption minima. The contrasting needs of the two different applications (communications and ranging) imply that they cannot share the same frequencies. Regulatory agencies share at least 5GHz of continuous unlicensed bandwidth between 56 GHz and 66 GHz, assigned to WPAN (Wireless Personal Area Network) applications, centered on the O2 absorption peak. All share the 76 GHz - 77 GHz band for the automotive RADARs, near the minimum of absorption. ITU and MPT (Japan) have assigned the 60 GHz - 61 GHz band to RADAR service and FCC the 46.7 GHz – 46-9 GHz band, where absorption is lower. It is evident that there exists a continuous frequency range of 21 GHz bandwidth (i.e. from 56 GHz to 77 GHz) that can be exploited for combining communication and ranging systems in automotive applications. Such combination is the essence of the ITS (Intelligent Transportation Systems) applications, in which the vehicle is required to react to stimuli coming from the environment, co-operate with its neighboring vehicles and with the road traffic-control systems. In this view the concept of WPAN can be extended to include the car in the “personal digital devices” in the network and the traffic-control systems in the infrastructures. In this work we present a high gain antenna that can operate across the entire (21 GHz) bandwidth and can be integrated into the package of an IC. The antenna can be used