Wireless Innovation Forum Top Ten Most Wanted Innovations

Innovation #4: Low Cost Wide Spectral Range RF Front-End (Multi-octave Contiguous) (Tx,Rx)

4.1 Executive Summary

Small, low cost transmit and receiver front-ends are critical to enable viable wireless solutions in spectrum that is being opened by regulatory bodies to improve spectrum utilization and meet the broadband needs of their citizens. Generally, such front-ends are limited in tunable range.  It is desirable to make available front-ends that cover extended frequency range; easily in excess of one decade, while retaining necessary performance criteria such as tunable selectivity, blocking dynamic range, IM performance, noise figure, and phase noise floor.  Out of Band Emissions, frequency stability and tolerance, and low phase noise are some of the critical criteria of the transmitter section of the desired wide band or wide tuning range RF front-end.

4.2 Application

AThis innovation supports applications that require an RF front-end, capable of transmitting and receiving over a very wide spectral range. For example, a front-end capable of operating in TV Whitespace in a continuously-tuned fashion.  This includes operation over all TV channels, 2-51 (54-698MHz), while retaining the ability to operate in the presence of strong adjacent and alternate TV transmitters.  An additional example would be a continuously-tuned front-end that could take advantage of licensed broadband / LTE services as well as unlicensed, lightly-licensed, and leased spectrum.  Such a device might conceivably operate from below 400MHz through 4GHz or higher.  An upper limit of 6GHz is easily justified today.

4.3 Qualifiers

The innovation includes transmit and receive subsystems, should be low cost and small in physical size, with acceptable power consumption, multi-octave operation, and high linearity on receive and transmit.

4.4 Description

Regulatory bodies around the world are looking for opportunities to improve spectrum utilization and provide more broadband service for their constituencies. Often, the spectrum “white-spaces” that are becoming available are not contiguous and are located in harsh RF environments. Noted above is TV whitespace where there could be one or more unoccupied 6MHz channels from 54-698MHz.  Such whitespace would be shouldered by strong adjacent or alternate TV transmitters.  A viable product solution using this spectrum needs to be producible at low cost, operate over this broad frequency range because the unoccupied channels vary by geographical area, and have a receiver that can tolerate a high power TV broadcast signal on  adjacent or alternate channels. Design of receivers involve high linearity front ends coupled with tunable pre-selection or its equivalence. For reference information, see section 6 on TVWS in “Public Safety Interference Environment – Raising Receiver Performance Requirements” http://groups.winnforum.org/p/cm/ld/fid=88, December 3, 2009, Session 3.2) 

Another example is that of opportunistic and as-needed broadband spectrum access.  Devices are generally designed to operate on several pre-determined bands.  These bands are generally described within 3GPP documents and are standardized.  In general, devices are regionalized; they are populated to operate on regional bands with sufficient overlap so that some world-wide access is guaranteed.  Private networks, extensions of public carrier networks, and device to device communications may utilize additional spectrum, such as shared use-cases contemplated at 3.5GHz and unlicensed spectrum at 5GHz, to accomplish one or more of these goals.  Additional spectrum will also likely be identified that can be used for similar needs or to further augment capacity through discontiguous bonding.  To that end, front-ends of the future should evolve towards continuous spectrum use ability.  Substantial challenges must be overcome to ensure that performance criteria, noted above, are sufficiently met.