Flexible microwave filters on ultra thin Liquid Crystal Polymer substrate

In this paper, investigations about the applications of ultra thin Liquid Crystal Polymer (LCP) in flexible microwave filters are carried out. The LCP substrate of 50μm substrate thickness was offered as a double copper clad laminate with 18μm copper laminate thickness. First, a microstrip line are fabricated and measured to show the microwave transmission characterization at flat and bending condition. Then, for demonstration purpose, a X band band-pass filter and a stepped impedance low pass filter were designed and tested with overall LCP dimensions of 5.4 × 3.2 mm² and 15.7×2 mm²,respectively. For the filters, good agreement between the simulated and measured S-parameters and compact sizes are obtained. The bending effects of the microstrip line and the band-pass filter are also measured and the measured data shows a very low susceptibility to the S-parameters due to bending behavior. The results show that ultrathin LCP substrate is a promising candidate for the miniaturization and flexibility applications in microwave devices.