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The 5.7 GHz band, while offering the greatest bandwidth, requires the use of much faster semiconductors and in general is too high in frequency for silicon to be employed. To date few RFICs have been developed for use in this band, limiting product offerings largely to discrete FETs and gain blocks for use as oscillators, gain stages, and active mixers, and diodes for use as passive mixers. The parasitics associated with most SOT low cost SMT packages used at lower frequencies create intolerable degradation at 5.7 GHz, so packaging is typically in more costly ceramic packages.
The higher component cost and limited IC availability make this the least-used of the three ISM bands. Solutions usually take the form of up- and down- converters and gain stages added on to lower frequency transceivers such as those discussed for the 900 MHz and 2.4 GHz bands. Applications are generally focused at the high-end "business" community rather than the cost-sensitive consumer, and include high data-rate LANs and PBX systems.
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