A modulator utilizing the Ku-band instead of the usual S-band has been developed to improve transmission rates for suborbital platforms. The unit operates in the 14.5–15.5-GHz band and supports data rates up to 200 Mbps. In order to keep the modulator costs low, the modulator is based on the LCT2 [Low Cost TDRSS (Tracking and Data Relay Satellite System)] Transceiver design, which utilizes a single-board modulator incorporating an Analog Devices quadrature modulator IC, with I&Q [inphase (I) and quadrature (Q)] bandwidths of 70 MHz. A pin-compatible version of the chips with I&Q bandwidths of up to 160 MHz is used to achieve the higher data rates. To support the higher data rate, an LVDS (low-voltage differential signaling) user interface will be incorporated into the modulator board. The LCT2 configuration uses a 1×4 in. (≈2.5×10.2 cm) high-power S-band amplifier module. The new amplifier printed circuit board (PCB) module is replaced with a compact S-band to Ku-band upconverter, with an RF output of +5 dBm.
A key feature is the unit’s small form factor of 4×5×1.5 in. (≈10.2×12.7×3.8 cm). It has a low complexity, consisting of two PCBs and a DC/DC converter. This keeps the cost down, which is an important feasibility issue for the types of missions that it is designed for — low-cost suborbital. This modulator is useful for any suborbital platform such as sounding rockets, balloons, unmanned aerial vehicles (UAVs), and expendable launch vehicles.
This work was done by Steven Bundick of Goddard Space Flight Center and Jim Bishop, David Newman, and Nazrul Zaki of LJT & Associates. For further information, contact the Goddard Innovative Partnerships Office at (301) 286-5810. GSC-15456-1