Multi-Gigabit, MMW Point-To-Point Radios: Propagation Considerations And Case Studies

By Tom Rosa, HXI, LLC

Military surveillance and commercial high-definition TV have joined carrier "backhaul" to drive development of lower cost, multi-gigabit millimeter-wave (mmW) radios, and the wildly differing system requirements, while challenging, are being met right now.

This article provides a basic overview of the unique benefits provided by mmW radios at V-Band (57-64 GHz) and E-Band (71-76/81-86 GHz) followed by a discussion of the severe operating challenges presented by two radically different deployments (high resolution airborne surveillance video and carrier/enterprise "backhaul") and two case studies of how those challenges were met. Typical system performance, as well as some performance vs. cost trade-offs, will also be presented.

Unique Issues for MMW Radios

Communications at mmW frequencies offers several unique and very potent advantages as well as some sizable disadvantages. In order to develop cost-effective, high performance links a solid understanding of the issues and in particular how to benefit from the advantages while mitigating the disadvantages is crucial. Reduced hardware size and wider bandwidths are among the leading advantages for radios operating at mmW frequencies. For instance, mmW radios utilize smaller high gain antennas, waveguide and RF front ends than do their lower frequency counterparts. Reasonably priced mmW MMICs are readily available for all the small signal active functions - LNAs, mixers, LO multipliers, etc. The availability of very wide, contiguous bandwidth (7 GHz in V-band, two 5 GHz bands in E-band) allows low cost modulation/demodulation architectures for multi-gigabit data rates.