Method and system for securely communicating information using multiple rf carriers

A transponder system wherein information is communicated from a first location to a second location using a plurality of RF frequencies based on a first pulse train having a first pulse width representing a first data value and a second pulse train having a second pulse width representing a second data value, comprising:

• a base station located at said first location, said base station being adapted to:
• (a) selectively transmit a first combined RF signal from said first location by generating a plurality of first RF signals and combining said first RF signals to form said first combined RF signal, wherein each respective first RF signal has a frequency equal to a respective one of said RF frequencies and is generated having a respective first transmission power level, and
• (b) selectively transmit a second combined RF signal from said first location by generating a plurality of second RF signals and combining said second RF signals to form said second combined RF signal, wherein each respective second RF signal has a frequency equal to a respective one of said RF frequencies and is generated having a respective second transmission power level;
• and
• a transponder adapted to receive, as appropriate, said first combined RF signal and said second combined RF signal at said second location, wherein the first transmission power levels are chosen so that as a result of attenuation of the first combined RF signal between said first location and said second location, said first pulse train may be reconstructed from the received first combined RF signal, and wherein the second transmission power levels are chosen so that as a result of attenuation of the second combined RF signal between said first location and said second location, said second pulse train may be reconstructed from the received second combined RF signal.

A method of communicating information from a first location to a second location based on a first pulse train having a first pulse width representing a first data value and a second pulse train having a second pulse width representing a second data value, said method comprising:

• choosing a plurality of RF frequencies;
• selectively generating a first amplitude modulated RF signal corresponding to said first pulse train using said RF frequencies and transmitting said first amplitude modulated RF signal from said first location, said first amplitude modulated RF signal being generated using a respective first transmission power level for each RF frequency;
• selectively generating a second amplitude modulated RF signal corresponding to said second pulse train using said RF frequencies and transmitting said second amplitude modulated RF signal from said first location, said second amplitude modulated RF signal being generated using a respective second transmission power level for each RF frequency;
• receiving said first amplitude modulated RF signal at said second location, wherein the first transmission power levels are chosen so that as a result of attenuation of said first amplitude modulated RF signal between said first location and said second location, said first data value may be detected from the received first amplitude modulated RF signal;
• and
• receiving said second amplitude modulated RF signal at said second location, wherein the second transmission power levels are chosen so that as a result of attenuation of said second amplitude modulated RF signal between said first location and said second location, said second data value may be detected from the received second amplitude modulated RF signal.

A transponder system wherein information is communicated from a first location to a second location using a plurality of RF frequencies based on a first pulse train having a first pulse width representing a first data value and a second pulse train having a second pulse width representing a second data value, comprising:

• a base station located at said first location, said base station being adapted to:
• (a) selectively generate a first amplitude modulated RF signal corresponding to said first pulse train using said RF frequencies and transmit said first amplitude modulated RF signal from said first location, said first amplitude modulated RF signal being generated using a respective first transmission power level for each RF frequency, and
• (b) selectively generate a second amplitude modulated RF signal corresponding to said second pulse train using said RF frequencies and transmit said second amplitude modulated RF signal from said first location, said second amplitude modulated RF signal being generated using a respective second transmission power level for each RF frequency;
• and
• a transponder adapted to receive, as appropriate, said first amplitude modulated RF signal and said second amplitude modulated RF signal at said second location, wherein the first transmission power levels are chosen so that as a result of attenuation of said first amplitude modulated RF signal between said first location and said second location, said first data value may be detected from the received first amplitude modulated RF signal, and wherein the second transmission power levels are chosen so that as a result of attenuation of said second amplitude modulated RF signal between said first location and said second location, said second data value may be detected from the received second amplitude modulated RF signal.

A method of communicating information from a first location to a second location based on a first pulse train having a first pulse width representing a first data value and a second pulse train having a second pulse width representing a second data value, said method comprising:

• selectively amplitude modulating a plurality of RF carrier signals to generate a first amplitude modulated RF signal corresponding to said first pulse train and transmitting said first amplitude modulated RF signal from said first location;
• and
• selectively amplitude modulating said plurality of RF carrier signals to generate a second amplitude modulated RF signal corresponding to said second pulse train and transmitting said second amplitude modulated RF signal from said first location;
• wherein remote from said first location said first data value may be detected from said first amplitude modulated RF signal only when received at said second location, and wherein remote from said first location said second data value may be detected from said second amplitude modulated RF signal only when received at said second location.