A lightweight fast hopping synthesizer for EHF satellite applications

A 15-watt, 6-lb dual fast hopping synthesizer has been developed at Lincoln Laboratory as a technology prototype for potential use in spread spectrum EHF satellite applications. The dual unit provides a pair of independently controllable hopping outputs with sub-microsecond phase-settling times. The low DC power consumption is achieved mainly through the use of a 40-MHz radiation hardened CMOS direct digital synthesizer (DDS). The small available bandwidth from this DDS is expanded to 540 MHz centered near 10 GHz using a single, fast-settling phase locked loop (PLL). A novel adaptive pre-tune approach has been implemented to enable the PLL to maintain its fast-settling characteristics over a -40°C to +60°C temperature range and mitigate the effects of component aging. This design has made extensive use of chip and wire hybridization to achieve the small size despite the relative complexity of the PLL circuitry. To provide a convincing demonstration that the design is suitable for on-orbit usage, parts selection was appropriately limited and a flight qualifiable packaging strategy was adopted. The performance of this synthesizer design was validated in a system context through the incorporation of two prototype units into a laboratory based spread spectrum EHF communications system simulator