September 7, 2012
The Honorable Julius Genachowski
Federal Communications Commission
445 12th Street, S.W.
Washington, D.C. 20554
The Honorable Lawrence E. Strickling
Assistant Secretary for Communications and Information
National Telecommunications & Information Administration
United States Department of Commerce
1401 Constitution Avenue, N.W.
Washington, D.C. 20230
Dear Chairman Genachowski and Assistant Secretary Strickling:
In this communication I want to inform you of the current status of technical possibilities in GNSS filter designs and components. I hope this will be helpful in establishing realistic guidelines for the characteristics of high precision GNSS receivers that will be used in critical applications.
We have improved our previous L1 filter and have extended the design to include all commercial GNSS bands.
Figure left above is our filter that protects GPS L1, Galileo L1 and GLONASS L1 bands. It brings in all the useful signals intact and rejects out of band signals with the slope of about 12 dB/Mhz. Similarly, Figure right above is our filter that protects GPS L2, GPS L5, GLONASS L2 and Galileo L5 and has slope of about 9 dB/Mhz.
These filters have been extensively tested with five different innovative tests and prove that the filters also improve the performance of GNSS receivers. These extensive innovative tests are embedded in the receivers that we mass-produce today and every user can test their receivers in all environments. These tests are much more extensive than those previously employed by PNT and other organizations. These embedded tests are not only much more extensive, but it takes only a few minutes to perform these by any novice user by clicking some receiver buttons. Compare that to the limited tests by PNT and others that took weeks to perform and needed experts with very expensive equipment in some laboratories to perform.
Attached is our 8-page commercial advertisement that has more details on filters and embedded test features.
These filters not only protect GNSS signals against all LightSquared signals (10L, 10H and 10R handsets) but also from all similar signals that may appear near all commercial GNSS bands in the future. We are proud that our filters help allow better usage of these precious bands, in particular for broadband wireless communication that our country desperately needs.
These filters apply to wideband high precision GNSS receivers and the cost is even less than earlier conventional filters. The case of narrow-band low precision receivers (e.g. Garmin) is much simpler, as has been demonstrated by GPS receivers in more than 300 million cell phones and mobile devices which are not affected by LightSquared signals. The low precision receivers (L1 C/A code only) require filter slopes 10 times less steep than those presented here and do not necessitate additional costs.
In summary, the technology exists today of improved filter design and better performing GNSS receivers and can actually be done at a cost lower than current conventional GNSS receiver filter designs. I trust that the information that I have presented can be used in establishing the performance guidelines and requirements for all GNSS receivers used in critical applications.
I also would like to invite your representatives to ION-2012 GNSS conference where we present details and answer questions at 2:00 PM on September 20.
Javad Ashjaee, Ph.D.
CEO, Javad GNSS
San Jose, California