Augmented Passive Tracking of Moving Emitters

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional bearings-only passive emitter tracking systems face challenges in initializing and maintaining accurate target tracking due to the requirement for observer maneuvers and high error rates, especially when targets are not flying at constant velocities, leading to frequent failures in convergence and track divergence.

Innovation Solution

The integration of infrequently scheduled radar range information with ESM azimuth measurements to form an augmented measurement sequence input to the tracking filter, allowing for improved kinematic estimation and prediction of target emitters without the need for observer acceleration, thereby creating a low-probability-of-intercept (LPI) radar track mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional bearings-only passive emitter tracking is used, then the system can operate passively without emitting radar signals, but the tracking accuracy deteriorates and convergence fails when targets do not fly at constant velocities

Engineering Contradiction:

Improvetracking convergence reliabilityVSAvoidtarget position estimation accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent merges active radar range measurements with passive ESM azimuth measurements into a unified tracking filter. The radar provides range and range rate data while the ESM system provides azimuth information, and these are combined in an integrated estimator that produces accurate target position and velocity estimates even during maneuvers without requiring observer acceleration

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces a measurement controller as an intermediary that selectively gates radar measurements into the passive tracking filter based on target maneuver detection. When maneuvers are detected, the controller activates radar measurements to augment the passive ESM data, allowing the system to maintain tracking accuracy during dynamic conditions while primarily operating in passive mode

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If observer maneuvers are performed to achieve observability in bearings-only tracking, then target position can be estimated, but the system complexity and operational constraints increase

Engineering Contradiction:

Improveemitter position and velocity estimationVSAvoidobserver maneuver requirement

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent performs preliminary action by detecting target maneuvers before they cause tracking failure. The system continuously monitors for maneuver conditions and proactively activates radar measurements in advance, preventing the need for observer maneuvers to restore observability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical solution of observer maneuvers with an information-based solution using radar range measurements. Instead of physically maneuvering the platform to achieve observability, the system substitutes mechanical motion with electromagnetic measurement data that provides the necessary geometric information for accurate tracking

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If radar is used for active detection and tracking, then accurate target kinematics can be obtained, but the radar may be detected by threat ESM or RWR systems

Engineering Contradiction:

Improvetarget range and velocity measurementVSAvoidradar detection by threat systems

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic action by using infrequent, intermittent radar measurements rather than continuous active tracking. The radar gates measurements into the passive filter only when maneuvers are detected, creating sparse periodic updates that maintain accuracy while minimizing the radar's electromagnetic signature and reducing detection probability by threat systems

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent creates a multi-functional tracking system that can operate in multiple modes: primarily passive bearings-only mode for low observability, and augmented mode with radar measurements for high-accuracy tracking during maneuvers. This universal system adapts its function based on operational conditions, providing both stealth and accuracy as needed

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS7626538B2Augmented passive tracking of moving emitter

Publication Date: 2009.12.01 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

In one embodiment, the disclosure relates to a method for estimating and predicting a target emitter's kinematics, the method including the steps of: (a) passively sampling, at a first sampling rate, an emitter signal to obtain at least one passively measured signal attribute for estimating the target kinematics; (b) inputting the passively measured signal attribute to an estimator at a first sampling rate; (c) determining a radar duty cycle for active radar measurements as a multiple of the first sampling rate, the multiple defining a duration between radar transmissions; (d) directing a radar system to make active target measurements at the determined duty cycle; (e) inputting to the estimator the active target measurements at the determined duty cycle, while continuously inputting the passively measured signal attributes.