Flexible Thin Film Multi-antenna Integrated Backscatter Device

In the ambient backscatter communication (AmBC) system, a backscatter device (BD) transmits its messages to receivers by modulating and reflecting incident radio frequency (RF) signals from ambient RF emitters. Most existing studies investigate single-antenna BDs and fabricate them using the conventional printed circuit board (PCB) method. In this paper, we propose flexible inkjet-printed integrated backscatter devices (IBDs) for indoor backscatter radios. We investigate and fabricate both single-antenna and multi-antenna IBDs using the inkjet printing technique. Since the commonly used substrate polyethylene terephthalate (PET) for inkjet-printed electronics has highly lossy properties, the printed feeding lines in the RF become inefficient. We propose to overcome this problem by positioning the backscatter switch next to each antenna and controlling them simultaneously with the baseband backscatter signal. Attenuation of the baseband control signal in printed lines is low leading to increase in overall efficiency of the proposed system. We validate the prototypes with received backscatter signal strength measurements in an anechoic chamber. The result shows that the printed four-antenna IBD can benefit approximately 9 dB diversity gain compared with the single-antenna version.