Ka-band I/Q modulator Multi-Chip Module for high data rate communications

This paper describes the development and test results of a flight qualified, hermetic I/Q modulator Multi-Chip Module (MCM) with X-band input and Ka-band output for either Tracking and Data Relay Satellite System (TDRSS) or Deep Space Network (DSN) high data rate communications applications. The module is 0.9″ wide by 1.7″ long without the attachable coaxial connector. It draws <500 mW of DC power. A Ka-band modulator MMIC previously developed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) provides the direct I/Q modulating function in the module. A Commercial Off The Shelf (COTS) MMIC frequency multiplier provides either a multiply-by-three or a multiply-by-four function for the upconversion of the X-band carrier to one of the Ka-band output frequencies of choice. The multi-chip module is configurable for the desired frequency band during fabrication by installing the corresponding band-pass filter. This filter, along with the biasing of the multiplier MMIC, passes the upconverted carrier to the I/Q modulator. A COTS MMIC broadband amplifier is used following the modulator to boost the output signal level to approximately +10dBm range, suitable for driving an external SSPA or TWTA. Chip attenuators are located between each function block for level setting as well as temperature compensation. An innovative package was designed to house the circuits described. Both the TDRSS and DSN versions of this upconverting direct modulation module have been fully tested and successfully implemented in the Ka-band Exciter of both the S/Ka-band and X/Ka-band Frontier Radio developed by JHU/APL for NASA. A data rate of up to 200 Mbps has been demonstrated during radio test, with current efforts targeting beyond 300 Mbps. 1 2