Planar architecture for microstrip interfaced packaging of coplanar-waveguide-based radio frequency microelectromechanical system switches

Abstract

This paper describes the architecture of microstrip (MS) interfaced packaging of a coplanar-waveguide (CPW)-based radio frequency microelectromechanical systems (RF MEMS) switch in a hermetic metalceramic RF package. The switch is integrated along with CPW to MS (CPW-MS) transitions within the package itself. This makes the MS interfaced packaged switch module readily mountable on MS based RF boards and subsystems. The CPW-MS transition for the package was designed as a separate off-chip entity on an alumina substrate and utilizes via hole. The integrated three-dimensional model of the package consisting of the RF MEMS switch and the transitions was simulated using high frequency structure simulator. The realized module shows an insertion loss of 0.2 and 1.1 dB at 100 MHz and 7 GHz, respectively. The measured isolation is better than 60 dB at 100 MHz and 30 dB at 7 GHz. The return loss is better than 15 dB up to 7 GHz. The estimated packaging and transitioning loss is 0.5 dB at 5 GHz. This packaging architecture is a planar solution for the MS interfaced packaging of CPW based RF MEMS switches for designers who do not have access to high-end technologies, such as zero-level packaging, through silicon via or low temperature co-fired ceramics. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)1 Introduction Radio frequency microelectromechanical systems (RF MEMS) switches exhibit unprecedented low insertion loss and wideband performance. These switches are generally realized in a shunt or series configuration using microstrip (MS) line or coplanar waveguide (CPW) transmission lines. 1 Designers prefer CPW-based RF MEMS switches over MS ones as CPW transmission lines incorporate the availability of an adjacent ground path along with the signal line and support a higher frequency of operation. 1 On the other hand, realization of the majority of planar RF individual modules and their integration is carried out in MS transmission line technology. This is because of the inherent advantages of MS transmission lines, such as ease of interconnects, adjustments, compact size, ease of fabrication, and low cost. 2-6 Due to the different modes of electromagnetic signal propagation, CPWbased RF modules cannot be directly integrated to MS based RF modules. Likewise, CPW-based RF MEMS switches cannot be readily integrated on MS based RF boards or subsystems. A CPW to MS (CPW-MS) transition would be required at both ends of the CPW RF MEMS switch for the integration. 5,6 Reference 7 discusses a frequency tunable MS patch antenna using CPW based RF MEMS capacitors wherein CPW-MS transitions have been utilized.The published datasheets and references of commercially available surface mountable packaged RF MEMS switches, such as Omron and DelfMEMS, show CPW input-output RF

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