A Compact LTCC Bluetooth System Module with an Integrated Antenna Lap K. Yeung, 1 Jie Wang, 1 Yong Huang, 1 Shu-Chuen Lee, 2 Ke-Li Wu 1 1 Dept. of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong 2 AvantWave Limited, Hong Kong Recieved 18 July 2005; accepted 25 August 2005 ABSTRACT: 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 mm 3 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. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE 16: 238 –244, 2006. Keywords: antenna; balun; Bluetooth; filter; LTCC; system-on-package I. INTRODUCTION There is an ever-increasing demand for fast and reli- able ad-hoc wireless data transfer between two or more consumer electronic devices. Typical applica- tions include mobile phones, PDAs, portable comput- ers, cameras, and printers. Currently, a common so- lution for such demand is the Bluetooth protocol for ad-hoc networks operating at 2.45 GHz. Under this scenario, each member in the network, namely, a consumer electronic device, should be equipped with a Bluetooth module [1] in order to enable standard- ized data transfer. Undoubtedly, this Bluetooth-based communication capability will be playing an impor- tant role in current and future consumer electronics. For an attractive implementation of such modules, cost and compactness are the two most fundamental concerns. Low-temperature co-fired ceramic (LTCC) tech- nology, due to its attributes of low volume production cost, multilayered 3D configuration, and low RF loss, has been widely used in various integrated micro- wave/RF front-end modules and discrete RF func- tional components. For various applications, a multi- layered LTCC SoP implementation with integrated passive functional components, which otherwise have to be acquired in discrete form as part of the package substrate, would be a very desirable goal. Further- more, the use of on-package components can elimi- nate the need for discrete components and therefore reduce the cost. Various LTCC-based front-end mod- ules have been reported recently [2– 4]. Some LTCC- Correspondence to: K.-L. Wu; email: klwu@ee.cuhk.edu.hk. DOI 10.1002/mmce.20147 Published online 3 February 2006 in Wiley InterScience (www. interscience.wiley.com). © 2006 Wiley Periodicals, Inc. 238