High Frequency Approaches for LTCC Based Sensors

Abstract

Low temperature co-fired ceramics (LTCC) have been developed for RF and microwave circuits for a number of applications (i.e. cell phones and wireless systems). The same attributes that make LTCC an important technology for telecommunications are also important for sensors. Compact three-dimensional architectures with low dielectric loss materials are available with LTCC technology. The underlying electric and magnetic responses of materials in the RF and microwave frequency ranges will be discussed and these unique responses can be exploited in a sensor system. Gases, liquids and solids have unique dipolar responses in the RF and microwave ranges. For example, the dielectric relaxation of water has been investigated in water/starch mixtures. Classic dipolar relaxation of water occurs at 30GHz and additional relaxation mechanisms have been found in the 1–10 GHz range because of the starch gelation process. These relaxations could be the basis for a sensor system to monitor the gelation of food starches. In addition, miniature coil assemblies for magnetic resonance imaging (MRI) systems with operation in the 300 MHz to 850 MHz range will be presented. These types of coils with additional passive components are envisioned in a LTCC-based circuit topology.