Flexible bandpass filter on polyimide substrate

A polyimide (PI)-based flexible bandpass filter is fabricated by self-metallization technology, which covers Wireless Local Area Network (WLAN) of 5.15—5.875 GHz. The measured characteristics indicate the flexible filter under flat state has the return loss of better than 20 dB, the minimum insertion loss of 0.83 dB, a 3 dB bandwidth of 0.725 GHz, and the central frequency of 5.5 GHz. At the same time, the designed filter is measured in different bending and folding conditions. Simulated and measured results are similar whether the filter is under flatting, bending, or folding conditions. Fatigue test and timeliness test are studied to confirm that the filter has stable chemical and mechanical properties. The formed silver layers fabricated by self-metallization technology have good mechanical and electrical flexibility. The designed flexible filter is promised for integration within future flexible electronics.