An LTCC-Based Wireless Transceiver for Radio-Over-Fiber Applications

This paper describes the realization of a low-temperature co-fired ceramic (LTCC)-based wireless transceiver with optical interface for radio-over-fiber applications involving several standards. The RF front-end including an antenna is fabricated in LTCC technology, while the optical transceiver with a single-mode optical interface is built on a silicon motherboard. The front-end operates in the 5-6-GHz band, while the modulated optical carrier is transmitted at 1.55-$\mu{\hbox {m}}$ wavelength. The front-end module is an attractive solution for wireless local area network applications such as IEEE 802.11a or HIPERLAN2 requiring a direct link to an optical backbone.

I. Introduction

Radio-Over-Fiber applications are of growing interest to a number of outdoor and indoor applications. The basic idea consists of employing several base stations connected to a single central unit by means of a fiber-optic backbone. Such a setup is also generally referred to as a distributed antenna system. The RF base stations and the central unit are either linked through baseband-modulated optical carriers or by subcarrier multiplexing the optical carrier with the RF signal. The benefits in using such a distributed antenna system are twofold: great versatility and potentially large cost effectiveness. Using subcarrier-multiplexed radio-over-fiber is versatile in several ways. First of all, changes in the transmission standards and protocols can easily be implemented by reprogramming or substituting the central unit instead of the transceivers. Secondly, the transceiver architecture can be kept simple and, thus, small and cost effective.