Downlink calibration requirements for the TSUNAMI (II) adaptive antenna testbed

The TSUNAMI (II) project is an investigation into the use of adaptive antenna technology. The field trial system has been developed for the purposes of investigating the feasibility of implementing such a system using a GSM-1800 base station system. The field trial system uses a digital baseband beamforming technique (DBF) which, like all DBF systems, relies on the accurate transfer of weighted signals to and from the antenna array elements. As such, an accurate and reliable calibration system is required to combat effects arch as temperature and humidity on the individual antenna array paths. In this paper, results are presented of studies made on the field trial system, with regard to the operational temperature variations over an extended period of time. Investigations are presented of the TSUNAMI (II) downlink calibration technique and the implications for future adaptive antenna array calibration systems.