Design of Compact Stacked-Patch Antennas on LTCC Technology for Wireless Communication Applications

The exploding growth of wireless communications systems leads to an increasing demand for integrated compact low-cost antennas. As a result, LTCC (Low Temperature Co-fired Ceramics) multilayer technology is becoming more and more popular for the production of highly integrated, complex multilayer modules and antennas. This technology is appreciated for its flexibility in realizing an arbitrary number of layers. However, LTCC materials typically possess a high dielectric constant. On one hand, this helps reduce the antenna size, but on the other hand also reduces the bandwidth of planar patch antennas, thus making the design for practical wireless communication systems more difficult and therefore more challenging. A common approach for improving the bandwidth performance of a patch antenna is to add parasitic elements to the antenna structure, e.g., a stacked patch [1]. This reduces the impedance variation of the antenna with frequency, thus enhancing bandwidth performance. Various arrangements of stacked structures have been investigated in [2][3]. Typically a foam and low dielectric constant substrate stacked configuration or a high and low dielectric constant material combination is used to achieve a broad bandwidth. These structures require a thicker substrate (typically the total antenna thickness=~0.1λ0, λ0=wavelength in free space) and different materials. This is not suitable for the compact antenna requirement and LTCC technology. In addition a tedious procedure may be required in the design of such a different-substrate-stacked patch antenna. There are many parameters that need to be adjusted for an optimized bandwidth performance, such as the length and width of each patch, the thickness of each substrate, as well as the position of the feed point. In practice it is very difficult to adjust every parameter for optimal performance. In this paper, a simple design method is presented for compact stacked-patch antennas based on LTCC multi-layer structures. It is found that an optimal bandwidth performance always can be obtained by changing only the number of the LTCC layers. The design methodology is presented first followed by its applications to three emerging wireless communication systems. It will be shown that the stacked-patch antenna on LTCC multilayers can achieve a bandwidth of as much as twice of that for a single-patch antenna with the same substrate. Such a bandwidth may meet the requirements of several wireless communication systems, such as Bluetooth, IEEE 802.11a, as well as the broadband LMDS (Local Multi-point Distribution System).