Liquid crystalline polymer (LCP) based lumped-element bandpass filters for multiple wireless applications

This paper presents for the first time the design, implementation, measurements and reliability data of multiple RF filters on liquid crystalline polymer based substrates for different communication standards such as 802.11 a/b/g, LMDS/MMDS, cellular and Bluetooth applications. The first examples of this platform substrate technology are very compact 12 mm³ fully packaged SMT front-end filters with center frequencies of 2.45 and 5.775 GHz. One embodiment of the filter at 2.45 GHz, which is well suited for 802.11 b/g and Bluetooth type applications, provides a passband of 100 MHz with maximum inband insertion loss less than 2 dB at 25 °C, greater than 25 dB attenuation at 2700-2800 MHz, greater than 10 dB attenuation below 2.2 GHz, greater than 20 dB rejection at the seconds and third harmonic and inband VSWR less than 1.5 matched to 50 ohms at the input and output.