Development of a Compact Low-Temperature Co-Fired Ceramic Antenna Front-End Module

This study proposes a compact 5-GHz front-end module with embedded antenna on a low-temperature co-fired ceramic substrate, which is to be used for the IEEE 802.11a wireless local area network applications. The module comprises an embedded inverted-F antenna, a bandpass filter, and a low-pass filter. Both the proposed filters possess transmission zeros at out band for suppressing unwanted signals. A double-pole double-throw bare die transmitting/receiving switch is mounted on the surface of the substrate. The interconnection between the bare die switch and the buried circuits is established by bond wires. The effect of the bond wire is considered by incorporating its equivalent inductance into the design of the filters. The overall size of the antenna front-end module is only 6.2 mm times 5.4 mm times 0.98 mm with most of the space (near two-thirds of the volume) reserved for the antenna so as to have a better radiation performance. Also, to avoid the potential close proximity coupling among the buried circuits and the antenna, numerous metal vias connecting the top and bottom grounds in the module are designed for shielding. Since the radiation of a small antenna is influenced by the nearby circuit ground due to induced ground current, the developed antenna front-end module is tested on two FR4 printed circuit boards (PCBs) with different sizes (i.e., 55 mm times 20 mm and 80 mm times 46 mm). It is demonstrated that the antenna module performs well on these two grounded PCBs. The achieved 10-dB return-loss bandwidths are near 900 MHz for the transmitting and receiving paths. The measured radiation patterns are quite omnidirectional with peak gains (including the losses of circuit components) at approximately 0 dBi for the transmitting path and -1.7 dBi for the receiving path.