This paper proposes an architecture of an interference canceller for satellite communications with super-posed transmission, which is applicable not only to QPSK but also to 16QAM transmission to get higher satellite capacity. We implement it as an FPGA-based prototype and verify its performance. We propose here to use a new method to measure the satellite round-trip delay using an extended matched filter (EMF), which can work in low C/N conditions such as 0 dB and under. Given this performance, our canceller can work in a network in which forward and reverse links have the same power level. The results of the laboratory tests for QPSK show that interference can be suppressed by about 30 dB and that the BER degradation due to the canceller was small enough for operation.