Methods and apparatus for narrowband ranging systems using coarse and fine delay estimation

An apparatus comprising:

• receiver circuitry including a low-pass filter;
• analog front end circuitry coupled to the receiver circuitry, the analog front end circuitry including analog-to-digital circuitry;
• a processor coupled to the analog front end circuitry, the processor configured to:
• high-pass filter low-pass reference signal samples to generate band-pass reference signal samples;
• high-pass filter low-pass reflected signal samples to generate band-pass reflected signal samples, the low-pass reference signal samples generated by the analog-to-digital circuitry from a reference signal received and low-pass filtered by the receiver, and the low-pass reflected signal samples generated by the analog-to-digital circuitry from the reference signal reflected off a target and then received and low-pass filtered by the receiver;
• generate a first correlation based on the low-pass reference signal samples and the low-pass reflected signal samples;
• correlate the band-pass reference signal samples with the band-pass reflected signal samples to generate a second correlation;
• determine a first time sample at which a first peak of the first correlation occurs, the first peak having a highest intensity value;
• determine, based on the first time sample, a second time sample at which a second peak of the second correlation occurs;
• and
• determine a distance to the target based on the second time sample.

A non-transitory computer readable medium storing instructions that are executable by a processor to cause the processor to perform a method comprising:

• generating band-pass reference signal samples using reference signal samples;
• generating band-pass reflected signal samples using reflected signal samples;
• generating a first correlation based on the reference signal samples and the reflected signal samples;
• correlating the band-pass reference signal samples with the band-pass reflected signal samples to generate a second correlation;
• determining a first time sample at which a first peak of the first correlation occurs;
• determining, based on the first time sample, a second time sample at which a second peak of the second correlation occurs;
• and
• determining a distance to a target based on the second time sample.