24-GHz CW radar front-ends on cellulose-based substrates: A new technology for low-cost applications

This paper presents, for the first time, a 24-GHz Continuous Wave (CW) radar front-end, entirely realized on a cellulose-based (i.e. paper) substrate. The front-end uses a microstrip circuitry that is fabricated using a copper adhesive laminate to have low conductor losses. A single dielectric layer is adopted to reduce complexity and, in perspective, costs. The radar exploits an external oscillator and transmits a power of about 2 mW. The antenna has a gain of 7 dBi and features an half-power beam width of 42 degrees. Its efficiency is 25%, including the feeding line. A singly-balanced diode mixer is adopted in the receiver chain. The mixer conversion loss is 11 dB with a local oscillator driving level of 0 dBm. In Doppler mode, the radar is able to detect a small fan (i.e. the movement of its rotor) at 1 m distance from the antenna. This contribution demonstrates that circuits on cellulose are capable to operate up to the boundary between microwave and millimeter-waves.