Development of a flight qualified Ka-band multi-chip module for the solar probe plus mission

Abstract

The Johns Hopkins University Applied Physics Lab (JHU/APL) has developed a flight qualified, hermetically sealed, I/Q modulator Ka-band Multi-chip Module (MCM). Prototypes of this device have been developed over the years, but Solar Probe Plus (SPP) will be the first mission to use a flight qualified version of the MCM. This MCM enables a first for a deep-space mission: primary science data downlink with simultaneous data and navigation over Ka-band. SPP will also be the first JHU/APL mission to use Ka-band for downlink. The MCM contains three gallium arsenide (GaAs) monolithic microwave integrated circuit (MMIC) die, two of which are commercial off the shelf (COTS) parts, and the third is a custom die designed at JHU/APL. The MCM takes an X-band input, multiplies the signal up to Ka-band, modulates I/Q data directly onto the Ka-band carrier and outputs a signal in the +10dBm range, capable of driving an external SSPA or TWTA. Improvements made over previous prototype designs include a revision of the custom I/Q modulator MMIC on a different foundry process, development of automatic wire-bonding for large quantity (>30) flight unit assembly, test automation, and a novel calibration routine to create a linear I/Q space. All flight units went through a NASA approved screening and qualification process. A full lot of 30 MCM units were screened and qualified, producing 12 usable flight units, of which 2 were selected to be used in the 2 flight Frontier Radios on the Solar Probe Plus mission.