Broadband Spatio-Temporal Channel Sounder for the 2.4 GHz ISM Band

Abstract

This report documents the continuing research efforts of the Propagation Group at Georgia Tech towards the construction of a broadband spatio-temporal channel sounder for the Aerospace Corp. The channel sounder, a valuable research tool in radio frequency (RF) channel and direction finding (DF) measurement, was constructed from the 8-element antenna array receiver setup on loan from Aerospace Corporation to support this collaborative project. Upon completion of the 2006 portion of this on-going collaboration, the following contributions were made to the system: The broadband pseudo-random noise generator was modified for improved operation and wider bandwidth. The vector RF signal generator was improved to be cleaner, more stable, and include onboard programming firmware, obviating the need for an external computer and allowing better transmitter portability. An autonomous self-powered transmitter platform was constructed. Extensive improvements were made to the RF receiver signal chain in order to compensate for near out-of-band interference and amplifier noise. Software improvements included an SQL database interface for captured data and associated metadata in order to facilitate storage and retrieval. In addition to these improvements, field measurements were taken to demonstrate channel sounding operation and direction finding in environments with copious noise and interference. Collectively, these outputs fulfill the research deliverables for the year 2006 collaborative project between Aerospace Corporation and Georgia Tech. Future work for this ongoing collaboration will likely involve more measurements and further miniaturization of the array channel sounder. The ultimate goal of the research should be a single compact receiver box containing all RF components and analog-to-digital conversion hardware. This box could then be plugged into a network or laptop computer and an arbitrary array manifold for portable direction-finding and channel measurement. When coupled with the array processing software developed during the 2004 and 2005 phase of this collaborative project, the end result will be a dynamic, portable unit capable of both spatio-temporal channel sounding and/or accurate DF location of 2.4 GHz radios in a complicated radioscape. Temporal and spatial analysis of the measurements should be able to yield detailed data to assist in detailed channel characterization.