Diode-switched thermal-transfer printed antenna on flexible substrate

Diode-switching that can be used to introduce frequency agility into antennas produced by thermal transfer printing is demonstrated. The particular example is a triangular Sierpinski fractal pattern with two PIN diodes to switch between operation optimised for the 800 MHz ultra-high frequency (UHF) band (diodes on) and 2400 MHz ISM band (diodes off). Our measured results show an improvement in S 11 in the UHF band from −2 to −28 dB and from −7 to −30 dB at 2400 MHz, when switching the diodes appropriately. The measured bandwidth is 200 (1000) MHz, and the measured directivity is 3.1 dB (5.2 dB) while the measured gain is −5.2 dB (6.7 dB) for the diodes on (off).