Design of quasi-lumped element diplexers for multiple wireless applications using liquid Crystalline Polymer (LCP) based substrates

This paper presents the design of compact diplexers for applications such as dualband WLAN (802.11 a/b/g), and Satellite TV applications in organic laminates based multilayer substrates that use materials such as Liquid Crystalline Polymer (LCP). LCP based devices such as filters, baluns and diplexers have been demonstrated by the authors in [1, 2]. This paper focuses on the design of various diplexers. The first examples of diplexers using this platform substrate technology are very compact 3.5×2.2×0.75mm ³ and 2.2×1.5×0.75mm³ fully packaged SMT diplexers with passbands suitable for 802.11 a/b/g namely 2.4-2.5, and 4.9-5.9 GHz. The larger embodiment of the diplexer provides greater than 30dB isolation between the bands and greater than 40dB rejection of the second harmonics and greater than 30 dB rejection of the third harmonic of each band while guaranteeing less than 1.5dB insertion loss and VSWR < 2 from -25°C to 85°C. The paper is organized as follows: section I discusses the process technology and its advantages over commonly used ceramic technologies followed by section II which discusses the design of diplexers using embedded inductors and capacitors. Section in concludes the paper with a discussion on the various functions available with this substrate technology.