High performance miniaturized compact diplexer based on optimized integrated passive device fabrication technology

In this study, we proposed a compact miniaturized diplexer using 650 mu m polished gallium arsenide (GaAs) substrate via thin film integrated passive device (TF-IPD) fabrication technology. The introduction of the three-order elliptic function diplexer can achieve low insertion loss and high isolation between the two outputs with a dimension of 1.9 mm x 0.8 mm x 0.2 mm (0.0053 lambda(0) x 0.0023 lambda(0) x 0.0005 lambda(0)). The optimized IPD techniques for spiral inductor and metal-insulator-metal capacitor (MIMCAP) are discussed to achieve high Q-factor and excellent stability of the fabricated devices. Notably, the compact GaAs-based diplexer exhibits high performance with insertion loss of 0.5 dB and return loss larger than 16 dB. Besides, the isolation level between the two output ports is higher than 30 dB, which ensures the two ports can work independently without interference from each other. This study provides a facile fabrication approach for global system for mobile communications (GSM) and wideband code division multiple access (WCDMA) wireless communication systems.