RF performance of ink-jet printed microstrip lines on rigid and flexible substrates

In this paper, microstrip lines that are directly patterned by Ag ink-jet printing are discussed and their RF performance is investigated on both rigid and flexible substrates, which are FR-4 and polyimide (PI) film substrates, respectively. Microstrip lines are designed by computational simulation, and the simulated results are compared with the measured RF results of the fabricated microstrip lines. The measured transmission losses of the microstrip lines are 0.24 dB/cm for the FR-4 substrate and 0.66 dB/cm for the PI film substrate at 3 GHz. To measure the RF performance of the printed microstrip lines undergoing bending tests, the distances between the ends of the bended microstrip line are varied from 5 cm to 9.2 cm. The microstrip lines are twisted by torsion angles in the range of 0–40°. The RF performance and characteristics remain nearly unchanged under bending and torsion tests except for negligible variation caused by impedance mismatching occurred during the measurement process. The measured RF performance demonstrates that the printed Ag conductive lines can be utilized in RF application such as wearable and flexible systems, which require low-cost and low-end antennae at low frequencies.