Compact superposed modulated signal generator

A compact superposed modulated signal generator for use in a digital signal transmission system for transmitting digital information, said generator comprising:

• a first filter for converting an input non-return-to-zero (NRZ) digital data signal to a double interval raised cosine pulse signal;
• a second filter for converting said input NRZ digital data signal to a single interval raised cosine pulse signal;
• an attenuator for attenuating a signal output from said second filter;
• an adder/subtracter for superposing a signal generated by said first filter on a signal attenuated by said attenuator;
• a memory for storing a digitized waveform comprising previously sampled and quantized signals generated by said first filter, said second filter, said attenuator, said adder/subtracter, and said input NRZ digital data signal, and for outputting the digitized waveform responsive to an input data pattern and a clock signal;
• a D/A converter for converting the digitized waveform output from the memory into an analog signal;
• and
• a third filter for controlling the bandwidth of a signal superposed by said adder/subtracter and for eliminating unnecessary frequency components generated by the D/A converter.

A compact superposed modulated signal generator for use in a digital signal transmission system for transmission for transmit digital information, said generator comprising:

• a memory for storing a digitized waveform which corresponds to a digital signal formed by superposing a double interval raised cosine signal with an attenuated single interval raised cosine signal, and for outputting the digitized waveform responsive to an input data pattern;
• a D/A converter for converting the digitized waveform output from the memory into an analog signal;
• and
• a filter for controlling the bandwidth of the analog signal.