8-PSK transmit filtering using reduced look up tables

A method for generating a modulation waveform for transmitting data symbols, the modulation waveform comprising a real part and an imaginary part comprising:

• inputting data symbols to a logic unit over a plurality of successive symbol periods, wherein each data symbol comprises a plurality of information bits:
• forming in the logic unit at least two derived bits during each symbol period by combining selected information bits;
• forming, during each symbol period, a plurality of bit sequences, each bit sequence containing bits input or derived over a plurality of symbol periods;
• generating, during each symbol period, a plurality of filtered waveform segments using the bit sequences;
• combining, during each symbol period, at least two of the filtered waveform segments to obtain a segment of the imaginary waveform part;
• combining, during each symbol period, at least two of the filtered waveform segments to obtain a segment of the real waveform part,
• wherein the modulation waveform is generated in balanced form on two outputs for each of the real and imaginary parts.

A waveform generator for generating, from sequence of data symbol each having a plurality of information bits, a modulation waveform having a real part and an imaginary part, said waveform generator comprising:

• a logic unit having an input for receiving said data symbols and an output, wherein the logic unit combines, during each symbol period, selected information bits comprising the data symbol to produce two or more derived bits, and wherein selected information bits and the derived bits are presented at the output of the logic unit;
• a delay register connected to the output of the logic unit for storing a plurality of bit sequences, wherein each bit sequence comprises bits selected from the information bits and the derived bits over a plurality of symbol periods;
• a filter generating a filtered waveform segment during each symbol period from the bit sequences;
• a first combiner combining, during each symbol period, at least two of the filtered waveform segments to obtain a segment of the imaginary part of the modulation waveform;
• and
• a second combiner combining, during each symbol period, at least two of the filtered waveform segments to obtain a segment of said real part of the modulation waveform,
• wherein the first and second combiners comprise first and second two-wire resistive combining networks for generating respectively the real and imaginary part of the modulation waveform in balanced form.

A method of generating filtered modulation signals, comprising:

• receiving over a plurality of symbol periods successive data symbols to be transmitted, each data symbol comprising a plurality of input bits;
• combining the input bits in said data symbols to generate derived bits;
• bitwise filtering selected input bits and derived bits to generate component waveforms;
• generating a filtered quadrature modulation waveform signal having a real part and an imaginary part by selectively combining the component waveforms using weighting factors selected to produce a desired signal constellation, wherein the modulation waveform is generated in balanced form on two outputs for each of the real and imaginary parts.

A waveform generator for generating, from sequence of data symbol each having a plurality of information bits, a modulation waveform having a real part and an imaginary part, said waveform generator comprising:

• a logic unit to combine input bits comprising the data symbols during each symbol period to generate derived bits;
• a filter to generate component waveforms during each symbol period by bitwise filtering selected input bits and the derived bits;
• a first combiner combining, during each symbol period, at least two of the component waveforms to generate the imaginary part of the modulation waveform,
• a second combiner combining, during each symbol period, at least two of the component waveforms to generate the real part of the modulation waveform, and
• wherein said first and second combiners use weighting factors to combine said component waveforms selected to produce a desired signal constellation, and
• wherein the first and second combiners comprise first and second resistive combining networks for generating respectively the real and imaginary part of the modulation waveform in balanced form.