Method and apparatus for VCO modulation in a communication system

A radio modem comprising:

• a VCO controller receptive to a data stream, said VCO controller developing a VCO control signal by GMSK waveform synthesis, wherein said VCO controller includes:
• ROM memory storing a plurality of waveform mass;
• a counter coupled to said ROM memory and capable of developing a sequence of ROM addresses to provide a sequence of ROM memory outputs;
• a temporal bit generator responsive to said data stream, said temporal bit generator developing a next bit Nb, a current bit Cb, and a past bit Pb from said data stream;
• control circuitry to develop a digital waveform signal from a selected waveform map in said ROM memory, said control circuitry being responsive to said Nb, Cb, and Pb bits and said sequence of ROM memory outputs;
• and
• a DAC responsive to said digital waveform signal and operative to output said VCO control signal that encodes said data stream;
• and
• a transmitter having a VCO portion, said VCO portion having an input responsive to said VCO control signal, said transmitter developing a modulated RF signal carrying said data stream in response to said VCO control signal.

A VCO modulator controller comprising:

• ROM memory storing a plurality of waveform maps;
• a counter coupled to said ROM memory and capable of developing a sequence of ROM addresses to provide a sequence of ROM memory outputs;
• a temporal bit generator responsive to a data stream, said temporal bit generator developing a next bit Nb, a current bit Cb, and a past bit Pb from said data stream;
• control circuitry to develop a digital waveform signal from a selected waveform map in said ROM memory, said control circuitry being responsive to said Nb, Cb, and Pb bits and said sequence of ROM memory outputs;
• and
• a DAC responsive to said digital waveform signal and operative to output a VCO control signal that encodes said data stream.

A VCO modulator controller comprising:

• storing means for storing a plurality of waveform maps;
• generating means for generating a plurality of temporal bits including a next bit Nb, a current bit Cb, and a past bit Pb from a data stream;
• addressing means for developing a series of addresses for said storing means to create a sequence of digital outputs from said storing means;
• developing means for developing a digital waveform signal from a selected waveform map of said storing means, said means for developing being responsive to said Nb, Cb, and Pb bits and said sequence of digital outputs of said storage means;
• and
• conversion means responsive to said digital waveform signal and operative to develop an analog VCO control signal that encodes said data stream.

A method for providing a modulated control voltage comprising the steps of:

• storing a plurality of waveform maps in a memory;
• generating a plurality of temporal bits including a next bit Nb, a current bit Cb, and a past bit Pb from a data stream;
• developing a series of addresses for said memory to create a sequence of digital outputs;
• developing a digital waveform signal utilizing said Nb, Cb, and Pb bits and said sequence of digital outputs of said memory;
• and
• converting said digital waveform signal to an analog VCO control signal that encodes said data stream.

A method for making a communications system comprising the steps of:

• providing a ROM memory on a semiconductor substrate that stores a plurality of waveform maps;
• providing a counter on said substrate that is coupled to said ROM memory and which is capable of developing a sequence of ROM addresses to provide a sequence of ROM memory outputs;
• providing a temporal bit generator on said substrate that is responsive to a data stream, said temporal bit generator developing a next bit Nb, a current bit Cb, and a past bit Pb from said data stream;
• providing control circuitry on said substrate to develop a digital waveform signal from a selected waveform map in said ROM memory, said control circuitry being responsive to said Nb, Cb, and Pb bits and said sequence of ROM memory outputs;
• and
• providing a DAC on said substrate that is responsive to said digital waveform signal and operative to output a VCO control signal that encodes said data stream.