DESIGN AND IMPLEMENTATION OF AN FPGA TRANSPONDER

This paper describes the design and implementation of a transponder on a field programmable gate array (FPGA). The function of the transpond er is to decode the interrogation pulses from the ground station and r eturn a reply corresponding to the type of interrogation. The function s performed by the transponder include, but are not limited to, the de coding of the timing characteristics of the two modes of operation (Mo des A and C), suppression of reply when necessary, encoding of the ser ial pulse train output for either mode, and suppression of all replies for a 47 s period upon power-up. The design was thoroughly simulated before implementing on an FPGA.