GPS PNT Flexible Satellite

ABSTRACT: The objective of this effort is to investigate designs and possible options for a PNT Flexible satellite for GPS to enhance position, navigation, and timing (PNT) capabilities at a low cost using small augmentation satellites with limited payload. A desired feature to help overcome GPS coverage issues due to terrain, spoofing, jamming and interference is to broadcast military signals at a higher power than the civilian signals. When operating using a saturated traveling wave tube amplifier (TWTA), for example, the behavior of this amplifier very nearly approaches an ideal limiting amplifier. Due to the suppression characteristics of the amplifier, input signals have to be amplitude-balanced in order to prevent the loss of signal on weaker signals. Under this SBIR effort we propose to develop an enhanced constant envelope modulation technology for flex-power operation that will provide improved power efficiency using a digital waveform generator and state of the art L-band high power amplifiers (HPA). We shall assemble a lab test environment including digital waveform generation, RF modulation with HPA and GPS UE signal reception to compare the flex-power performance and power savings of this enhanced modulation method with the conventional interplex modulation method currently used by the GPS satellites. BENEFIT: The ability to deliver configurable flex power to GPS signals on-board NavSat or similar GPS satellite vehicles would enable constellation managers the capability to serve the GPS user community with improved signal quality and navigation precision at a fraction of the cost compared to traditional solutions. The ability to adapt to changing requirements and situations with the flex power solution is a dramatic improvement over current capabilities. Due to the cost effectiveness of this solution and the significant improvements this capability would provide, it is anticipated that significant interest will be garnered for this technology and an accelerated transition path toward implementation on future GNSS satellites will be desired.