Efficient methods for generating chirp spread spectrum signals

A method comprising:

• repetitively accumulating an input word to produce a frequency ramp;
• receiving symbols and adding to the frequency ramp frequency offsets representative of the symbols, to produce a modulated frequency ramp for a modulated chirp;
• controlling a roll-over rate of the modulated frequency ramp responsive to a spreading factor control signal and a frequency bandwidth control signal, to control a spreading factor and a frequency bandwidth of the modulated chirp;
• controlling a center frequency of the modulated frequency ramp and, correspondingly, the modulated chirp, responsive to a center frequency control signal;
• accumulating frequency samples of the modulated frequency ramp to produce phase samples corresponding to the modulated chirp;
• and
• rotating the phase samples based on an input vector to produce the modulated chirp with the spreading factor, the frequency bandwidth, and the center frequency.

An apparatus comprising:

• an input to receive a modulated chirp including a repeating frequency ramp that has frequency offsets representative of symbols added to the frequency ramp at symbol boundaries, the modulated chirp having a known spreading factor, a known center frequency, and a known bandwidth;
• a frequency accumulator to repetitively accumulate an input word to produce a frequency ramp;
• a spreading factor controller to control a roll-over rate of the frequency ramp responsive to a spreading factor control signal representative of the known spreading factor and a frequency bandwidth control signal representative of the known bandwidth;
• a center frequency controller to control a center frequency of the frequency ramp responsive to a center frequency control signal representative of a negative of the known center frequency;
• a phase accumulator to accumulate frequency samples of the frequency ramp with the controlled roll-over rate and the controlled center frequency, to produce phase samples;
• and
• a vector rotator to rotate the phase samples based on the modulated chirp, to produce a de-chirped signal including the symbols.