Barcode technology is slowly being replaced with transponder tags that have many benefits over barcodes. Four issues with transponder tags are battery life, power requirement, range of communication, and physical size. Microwave backscatter modulation (MBM) is used throughout industry to reduce the power requirement and size on the transponder tags while compromising range. Researchers and designers of current transponder tags typically utilize a passive carrier-present carrier-absent (CPCA) reflection of the reader's carrier wave, or their transponder design uses an active backscatter system with an amplifier and circular polarization modulation. This research project develops a communication system that mixes a reader's carrier wave with an intermediate frequency (IF) at the active Probe in order to improve isolation of the data signal in a high-clutter environment. The design and testing of Probe and Reader concepts are discussed, and the advantages and weaknesses of each design are determined. The performance of the passive IF amplitude-modulated MBM system is analyzed. The passive-AM MBM system achieves better range than CPCA modulation, and does not require as many components and power as the active circular-polarization modulation system. With mid-level power usage and range, the proposed passive backscatter system is a compromise between the low-range passive CPCA system and the high-power high-range active circular-polarization modulation system.
Library of Congress Subject Headings
Microwave communication systems; Data transmission systems; Backscattering; Transponders
Department, Program, or Center
Electrical Engineering (KGCOE)
Thompson, Aaron, "Passive amplitude-modulated microwave backscatter modulation system" (2002). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus