Mode A/C/S Transponder Positioning Using Phase Difference and Time of Flight

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Solution Overview

Problem

Current mode A/C/S transponder positioning systems face challenges in determining the position of aircraft outside the range of Secondary Surveillance Radar (SSR) coverage and lack full 360-degree coverage, especially in small airports without SSR installations, posing hazards to aviation.

Innovation Solution

A system comprising three antennas, with one antenna sending an interrogation signal and the other two receiving reply signals, uses GPS to measure transit times and distances to determine possible locations of an intruder, and discriminates between these using phase differences to pinpoint the aircraft's position, enabling operation outside SSR range with full coverage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If three omnidirectional antennas are used to measure distance separately, then positioning can be achieved outside SSR range, but the system complexity and transmission time control difficulty increase

Engineering Contradiction:

Improvepositioning capability outside SSR rangeVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines distance measurement and bearing determination functions into a single antenna system. By using an array of antennas with phase difference measurement, the system simultaneously obtains both range and angular information, eliminating the need for separate omnidirectional measurement systems and reducing overall complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from measuring only distance (1D) to measuring both distance and bearing angle (2D) by utilizing the spatial arrangement of multiple antennas. The phase difference between antenna elements provides angular information, adding a dimensional aspect to the positioning measurement.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If TCAS is used for positioning, then operation outside SSR range is enabled, but coverage is limited to certain angles and cannot be used on ground

Engineering Contradiction:

Improveoperation outside SSR rangeVSAvoidcoverage range and ground operation capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal positioning system that functions both in air and on ground, unlike TCAS which is air-only. The antenna array configuration and signal processing method are adaptable to various operational environments, providing full 360-degree coverage regardless of whether the system is mounted on an aircraft or ground station.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system dynamically adjusts its operation based on environmental conditions and mounting configuration. The antenna array can be deployed in different geometries and the signal processing adapts to distinguish between aerial and ground-based operations, enabling versatile multi-environment functionality.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If phase difference measurement is used to discriminate between two possible locations, then full 360 degree coverage is achieved, but measurement precision requirements increase

Engineering Contradiction:

Improvefull 360 degree coverageVSAvoidphase difference measurement precision

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent segments the bearing determination into discrete phase difference measurements between antenna pairs. By dividing the 360-degree coverage into multiple angular sectors corresponding to different antenna element pairs, the system achieves comprehensive coverage while managing measurement precision requirements through segmented analysis.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively determines the location of aircraft outside SSR coverage with high accuracy and full 360-degree coverage, enhancing aviation safety by providing a reliable positioning system that can be used both on the ground and in the air.

Implementation Method 1

measure a first phase of the reply signal received by the antenna two, and a second phase of the reply signal received by the antenna three, and determine a phase difference between the first phase and the second phase

Methodology Applied

Scientific EffectPhase difference: Phase Modulation

Implementation Method 2

measure a first transit time and a second sum time representing times of transit of the reply signal from the intruder to the station one, and the sum time the signal transmit from station one to the intruder and from the intruder to the station two

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS11480671B1Mode A/C/S transponder positioning system and method for using the same

Publication Date: 2022.10.25 SEAMATICA AEROSPACE LTD

AI summary

The present invention provides a low-cost and low-volume mode A/C/S transponder positioning system to detect the position of a target aircraft, or intruder, outside the range of a secondary surveillance radar system. The system uses a signal of the intruder to pinpoint the location of the intruder. The system can be used on both the ground and on an aircraft in a full 360 degree range around the system.