Three dimensional tracking by array doppler radar

• US 5,570,094 A
• Filed: 10/10/1995
• Issued: 10/29/1996
• Est. Priority Date: 10/10/1995
• Status: Expired due to Fees

• Current Assignee: Board of Regents of The University of Wisconsin (University of Wisconsin System)
• Original Assignee: Board of Regents of The University of Wisconsin (University of Wisconsin System)
• Inventors: Armstrong, Brian S. R.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/541,413
• Time in Patent Office: 385 Days
• Field of Search: 342/90, 342/97, 342/95, 342/106, 342/107, 342/108, 342/115, 342/140, 342/195
• US Class Current: 342/107
• CPC Class Codes: G01S 13/584 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/66 Radar-tracking systems; Analogous systems
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 15/66 Sonar tracking systems

Abstract

A moving target which is reflecting waves will give rise to the well known Doppler frequency shift. When the reflected signal can be compared with the transmitted signal in homodyne detection, the resulting signal is called the Doppler signal. Both frequency and phase of the Doppler signal carry information about the motion of the target.

By observing a Doppler signal at several points in space, it is possible to determine the position, velocity and acceleration of a moving target. Systems employing this principle are-used to track acoustic emitters with sonar, as well as radio emitters with radar. While the prior an has relied on analyzing the Doppler shift frequency, the present invention introduces a method employing the analysis of the phase of the Doppler signal. The phase-based algorithm shows a better signal to noise ratio in applications where the ratio of velocity and distance to the point of closest approach is large. The improved signal to noise ratio translates to lower power and lower cost for Doppler based three dimensional tracking.

Claims

1. A method of determining position, velocity, and acceleration of a moving target consisting of analyzing the phase angle of Doppler signals detected at three or more distinct points in space comprising:

a. Representing the target motion in the velocity plus parallel acceleration plus perpendicular acceleration (VAA) model;

b. Performing a search in the three dimensional space of possible velocities and parallel and perpendicular accelerations for the parameters which best fit the detected phase angles;

c. Transforming the VAA model representation into a position, velocity, and acceleration model representation; and

d. Determining the position, velocity, and acceleration of the moving target by optimizing the position velocity and acceleration model parameters to best fit the motion model to the detected phase angles.

2. A method of determining position, velocity, and acceleration of a moving target consisting of analyzing the phase angle of Doppler signals detected at three or more distinct points in space comprising:

a. Representing the target motion in the velocity plus parallel acceleration plus perpendicular acceleration (VAA) model;

b. Using an aerodynamic model of the target to express velocity plus parallel acceleration plus perpendicular acceleration in terms of the velocity and the angle and between the velocity vector and direction of gravity, and performing a search in the two-dimensional space of possible velocities and possible angles between the velocity vector and direction of gravity for the parameters which best fit the detected phase angles;

c. Transforming the velocity and angle parameters into the VAA model parameters, and then transforming the VAA model representation into a position, velocity, and acceleration model representation; and

d. Determining the position, velocity, and acceleration of the moving target by optimizing the position velocity and acceleration model parameters to best fit the motion model to the detected phase angles.

3. A device for determining the position, velocity, and acceleration of a moving target consisting of:

a. three (3) or more Doppler radars comprising a transmitter, a receiver, and homodyne detector;

b. a data acquisition system for converting the Doppler signals generated by the Doppler radars into a digital format;

c. a computing machine for analyzing the phase angle of the Doppler signals; and

,

d. software for analyzing the phase angle for the Doppler signals and determining the position, velocity, and acceleration for the moving target whereby said software further comprising a method for establishing an initial estimate of the target motion parameters;

said method employing a search of the space of possible VAA model parameters.