wireless transreceivers
with the wireless industry striving to offer customers better connectivity and functionality. Users are promised ubiquitous wireless access to digital voice, the Internet, and many other sources of information. In order to incorporate in a small form-factor the different modes of access required to achieve ubiquitous connections between users and service providers adopting different radio technologies, future PCS devices are expected to be highly integrated and multi-standard in nature [1]. In fact, according to the IMT-2000 specifications, the next generation “phones”, or information appliances, potentially need to be compatible with up to five disparate radio standards for high-speed data access. In addition, “accessory” radios such as GPS and Bluetooth may also be incorporated for location sensing and short-range cable replacement. One approach to providing multi-standard connectivity would be to simply incorporate independent transceivers for each standard targeted. However, traditional transceiver designs rely heavily on multiple semiconductor technologies and discrete components, and by incorporating multiple transceivers, this situation is compounded and becomes cumbersome with the multiplicity of components needed. It is clear that for multi-standard transceivers to be practical, higher levels of integration will be necessary.
Current transceiver solutions often use low cost CMOS for digital and baseband circuitry, while reserving silicon bipolar or GaAs for critical RF circuits. While this is good for optimizing the performance of individual subsystems, it is costly and makes full transceiver integration very difficult. Discrete passive components commonly used in today’s transceivers (e.g. SAW filters and high-Q resonators) enable excellent filtering and ease generation of spectral pure signals, but they are often bulky and expensive. In addition, while the fixed frequency characteristics of these components are ideal for single-standard transceivers, they are inflexible and generally not as well suited for systems requiring multi-standard adaptation.