A compact LTCC Bluetooth system module with an integrated antenna

In this article, a system-on-package (SoP) approach for Bluetooth system module applications using low-temperature co-fired ceramic (LTCC) technology is presented. The developed LTCC integrated substrate for our Bluetooth module application is overall 12 × 12 × 1 mm3 in size, with integration of two originally proposed components, a balanced-to-unbalanced bandpass filter and a folded meander-line inverted-F antenna, as well as other passive circuitries. The embedded balanced-to-unbalanced filter, which is derived from the basic center-tapped transformer circuit, works simultaneously as a balun and a bandpass filter, thus leading to a significant amount of size reduction for the overall module. Likewise, comparing to the usual quarter-wavelength inverted-F antennas, our proposed antenna is only one-tenth of a wavelength in length—but no sacrificing of antenna efficiency. Consequently, couplings among different functional blocks of this highly integrated module are crucial to its performance and the resulting effects are discussed. A fully functional prototype is successfully fabricated and tested, demonstrating a promising solution for Bluetooth applications.