A digital single sideband modulator for a digital radio frequency memory

The modulator is designed to use digital multiplying integrated circuits to produce the frequency shift rather than analog mixers. By replacement of the analog RF hardware with digital circuitry, the size and weight of an avionics device in an aircraft can be reduced. The circuit also employs a digital Hilbert transform filter to shift the phase of the incoming signal by 90 degrees. The circuit was tested with simulated S-band radar signals ranging from 3.012 to 3.038 GHz. The circuit, running in double-sideband mode, proved its ability to shift the frequencies of the radar signals by amounts in the range of -25 to +25 kHz. All spurious outputs of the system were found to be more than 28 dB below the carrier