Design of a radio front-end module at 5 GHz

A radio frequency (RF) front-end module at 5 GHz has been designed. The module consists of two switches, two bandpass filters, a balun, a low noise amplifier (LNA) and a power amplifier (PA). The top-down design methodology is used in our design. Firstly, the module function is specified with input and output (I/O) ports. Secondly, the RF front-end is partitioned into functional blocks. High-level simulations can be done with block parameters. Thirdly, each block is implemented into a schematic circuit and simulated. Fourthly, the schematic is implemented into a layout. Finally, simulation and optimization are done on the layout level. It is shown that the conventional design methodology with lumped element models has difficulty in meeting the requirement at a frequency of above 5 GHz. Distributed components and sub-circuits based upon the transmission line theory must be utilized. In the paper, designed filters, switches and baluns at 5 GHz using microstrip lines are presented. The whole design is finally implemented into a module form. The CAD (computer aided design) tool used is ADS (advanced design systems) from Agilent Technologies Inc.