We present a concept, developed at the National Astronomy and Ionosphere Center (NAIC) at Arecibo, Puerto Rico, for active suppression of Global Positioning System (GPS) signals in the 305 m dish radio receiver path prior to backend processing. The subsystem does not require an auxiliary antenna and is intended for easy integration with radio telescope systems with a goal of being a turnkey addition to virtually any facility. Working with actual sampled signal data, we have focused on the detection and cancellation of the GPS L3 signal at 1381.05 MHz which, during periodic test modes and particularly during system-wide tests, interfere with observations of objects in a range of redshifts that includes the Coma supercluster, for example. This signal can dynamically change modulation modes and our scheme is capable of detecting these changes and applying cancellation or sending a blanking signal, as appropriate. The subsystem can also be adapted to GPS L1 (1575.42 MHz), L2C (1227.6 MHz), and others. A follow-up is underway to develop a prototype to deploy and evaluate at NAIC. RFI mitigation workshop

The growing international user base for the Global Positioning System, coupled with the increasing number of critical applications, is fostering the development of ground and satellite based augmentations. There is a concern that those augmentations that share the registered GPS band, especially using code division multiple access in a fashion similar to GPS, may cause harmful interference.In this paper, the impact of both cochannel and adjacent channel interference from these proposed services to the signals in the GPS LI band is analyzed. Laboratory test results are also presented to support the results obtained through analysis. The carrier-to-noise spectral density ratio (C/N 0 ) degradation and excess tracking error due to cochannel interference are used as performance metrics. The analysis and test results indicate that under certain conditions, when the Interference-toSignal Ratio (ISR) is greater than 10 dB, the C/N 0 degradation could be as high as 7 to 9 dB and the excess tracking error as high as 2 to 3 meters rms. The loss of C/N 0 could mean the loss of significant interference margin for safety-of-life applications. The resultant degradation in tracking error will exceed the error budget of the GPS receiver specification for aviation applications. To be certain that this level of degradation is not experienced by the GPS receiver in critical applications, it is suggested that the proposed services not operate in the GPS LI band. For the services in adjacent bands fo LI, it is recommended to use appropriate emission limits obtained on the basis of total interference, from all the proposed services.

We present a concept, developed at the National Astronomy and Ionosphere Center (NAIC) at Arecibo, Puerto Rico, for active suppression of Global Positioning System (GPS) signals in the 305 m dish radio receiver path prior to backend processing. The subsystem does not require an auxiliary antenna and is intended for easy integration with radio telescope systems with a goal * Speaker.