LOW POWER ASYNCHRONOUS GPS BASEBAND PROCESSOR

• US 20190317222A1
• Filed: 11/13/2018
• Published: 10/17/2019
• Est. Priority Date: 02/23/2012
• Status: Active Grant

• Current Assignee: Cornell University
• Original Assignee: Cornell University
• Inventors: Manohar, Rajit, Tang, Benjamin, Longfield, Stephen, Bhave, Sunil A.
• Granted Patent: US 10,705,223 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

Asynchronous Global Positioning System (GPS) baseband processor architectures with a focus on minimizing power consumption. All subsystems run at their natural frequency without clocking and all signal processing is done on-the-fly.

Claims

1-25. -25. (canceled)

26. A method for clockless GPS baseband processing, the method comprising:

a) receiving an input signal for one channel from an RF front and;

b) providing the input signal to a code numerically controlled oscillator (NCO) and a carrier NCO;

c) using overflows in the code NCO to mark a predetermined code period, thereby forming an accumulation interval and referencing time to sampling in the input signal;

d) obtaining, from output of the carrier NCO and the code NCO, early, prompt and late phase and quadrature accumulations;

e) obtaining code offset and Doppler frequency estimates for the one channel;

f) tracking deviations in code offset and Doppler frequency for the one channel, using the early, prompt and late phase and quadrature accumulations;

g) obtaining GPS satellite time and code start time from code offset and Doppler frequency information and the input signal; and

h) repeating steps (a)-(g) until all channels have been processed;

wherein all steps are performed asynchronously.

27. The method of claim 26 wherein steps (b)-(g) are performed without clocking, and predetermined frequency ratios are preserved.

28. The method of claim 26 wherein the input signal includes a satellite number and a candidate Doppler frequency.

29. The method of claim 26 wherein the obtaining code offset and Doppler frequency estimates for the one channel comprises:

determining a correlation power estimate; and

acquiring the code offset and Doppler frequency estimates when the correlation power estimate is greater than a predetermined threshold.

30. The method of claim 29, wherein the correlation power estimate is given by I²+Q², where

31. The method of claim 26, wherein calculations in the steps (a)-(g) are performed using fixed point arithmetic.