A document discusses the creation of a Ka-band modulator developed specifically for the NASA/GSFC Solar Dynamics Observatory (SDO). This flight design consists of a high-bandwidth, Quadriphase Shift Keying (QPSK) vector modulator with radiation-hardened, high-rate driver circuitry that receives I and Q channel data. The radiation-hard design enables SDO’s Ka-band communications downlink system to transmit 130 Mbps (300 Msps after data encoding) of science instrument data to the ground system continuously throughout the mission’s minimum life of five years. The low error vector magnitude (EVM) of the modulator lowers the implementation loss of the transmitter in which it is used, thereby increasing the overall communication system link margin.
The modulator comprises a component within the SDO transmitter, and meets the following specifications over a 0 to 40 °C operational temperature range: QPSK/OQPSK modulator, 300-Msps symbol rate, 26.5-GHz center frequency, error vector magnitude ≤10 percent rms, and compliance with the NTIA (National Telecommunications and Information Administration) spectral mask.
This work was done by Jeffery M. Jaso of Goddard Space Flight Center. GSC-15217-1