Control system for a QPSK burst modem used for ACTS satellite testing

A test system was designed to determine the performance a QPSK satellite burst modem when using the Ka band link of the Advanced Communications Technology Satellite. Interface circuitry, largely based on the 22V10 programmable logic device, was designed to allow the modem to be controlled by a personal computer. Communication between the interface and the computer was accomplished through the computer's parallel port. TDMA frame timing was automatically controlled by the interface. A C language program provided operator control of the interface itself. Tests using this system showed that a severe night-time fading problem is experienced at the FAU receiver site. Very low error rates were recorded by this system in a loop-back transmission at the NASA satellite control terminal.