Suppression and IMD generation in a hard limiter transponder

Small terminal communications experiments that use the Advanced Communications Technology Satellite (ACTS), such as the Mini-Terminal Test Bed (MTTB) experiment, and that will send two narrowband signals through the hard-limited transponder are described. The suppression of a weaker signal in a hard limited transponder and the generation of intermodulation distortion (IMD) products are discussed. Simulations for CW signals of various signal levels were performed, and the maximum suppression was found to be 6 dB. IMD products generated include a pair of equal-amplitude signals symmetrically centered in frequency on the stronger signal and additional unequal-amplitude products that correspond to third and higher order products.