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Redundant Time and Frequency Reference Units for Satellite Applications
FREQUENCY ELECTRONICS INC MITCHEL FIELD NY
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A class of multiple input and output redundant frequency generators is described which provide extremely low noise reference signals to satellite subsystems. The frequency distribution units are designed to survive the hostile environments of space over a ten year mission life. In addition, these systems must maintain frequency accuracies under all conditions and provide for periodic fine frequency tuning adjustments with resolutions of better than 3 x 10-12 in response to external digital tuning commands. To meet these requirements, multiple frequency sources, either quartz, Rubidium, or Cesium are used. Only one of the sources is on line at any given time with a second source powered up in the hot standby mode and additional sources unpowered. Hence, overall emission reliability is maximized and power consumption is reduced. Isolation at the RF outputs between the on-line and the hot standby oscillator exceeds -120 dB. Many of the distribution systems receive DC power from the spacecraft bus and incorporate high efficiency DCDC converters and low noise linear regulators to provide proper operating voltages for the reference sources and distribution networks. Additionally, a high degree of RFI filtering is included to minimize conducted emissions and susceptibility on the power lines.
APPROVED FOR PUBLIC RELEASE