High Sensitivity, High Dynamic Range, VLF Receiver Front End

ABSTRACT: Current and future VLF receiver technology for Emergency Action Message (EAM) reception must meet stringent reception capabilities in harsh environments. Existing receivers were designed in the 1970s and 1980s to accomplish this task in specific environment and against specific threats. Since that time, both the nature for the threat and existing VLF transmitter environment has changed and become more dynamic, requiring a higher performance, more adaptable receiver. Decreased numbers of USAF VLF transmitters covering the same geographic area means an overall weaker VLF signal which is driving the need for receivers with higher sensitivity. Other signals that from other DoD components or transmitters that will be deployed in the future can create"clutter"in the band. These, along with interference from the power grid, atmospheric effects ("spherics") and jammers make it difficult for present-day VLF receivers to maintain sensitivity on their intended target signals due to the adjacent strong interferers saturating the A/D converter and forcing the automatic gain control to attenuate the input signal on order to avoid overload. This attenuation effectively reduces the sensitivity for weak target echoes. What is therefore needed is a more advanced approach to increase the usable dynamic range of VLF receivers. BENEFIT: High dynamic range VLF signal detection Next generation EAM system