On the design of satellite transponder receive chain gain distribution for efficient wideband channel utilization

As the warfighter becomes mobile and beyond line-of-sight (BLOS) information exchange provides essential capabilities, satellite transmission systems arrive as a critical communications component. Receive chain gain characteristics drive the wideband satellite system noise performance. These characteristics must be carefully considered in regard to communication link closure. This paper presents solid evidence that not only must the low noise amplifier (LNA) noise characteristics be optimized, the entire receive gain/loss structure must be crafted to compensate for overall transponder gain distributions. In particular, the variable and cascaded gain or loss of each controlling the overall transponder transfer function must be properly designed. This paper highlights results showing the cascading of LNAs and attenuators in a fashion to accommodate large effective isotropic radiated powers (EIRP) as well as the generally smaller EIRP available from the warfighter´s mobile terminals. The paper presents transponder gains for various cases of power and/or bandwidth limited terminals. Graphs and figures detail the overall satellite transfer characteristics as well. From these canonical cases, we explore different operational effects and the resulting communication link parameters. Combinations of large and small ground terminal EIRPs define useful transponder gain operating ranges as well as non-desirable regions. The paper further provides results of such operational conditions and how they can best be accommodated in MILSATCOM systems such as the wideband gapfiller satellite (WGS). Conclusions on reliable gain/loss combinations and channel utilization round out the paper. Overall, the paper presents various methods of achieving suitable satellite transponder transfer characteristics through careful satellite receive chain design.