PSSR Detect-and-Avoid via SSR Pulse Reflection
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Solution Overview
Problem
Current Passive Secondary Surveillance Radar (PSSR) systems face challenges in accurately detecting and tracking aircraft without transponders, especially in crowded airspace, due to limitations in omni-directional antenna coverage and signal strength, which can lead to increased risks of mid-air collisions.
Innovation Solution
A method and system that determine the position of a target object using a PSSR system by analyzing pulse repetition frequency patterns of Secondary Surveillance Radar (SSR) signals, even when the target is outside the main antenna beam, by forming a time-ordered sequence of intervals and identifying congruent segments to derive the pulse repetition frequency pattern, allowing for accurate detection and avoidance of targets with or without transponders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PSSR systems use conventional SSR with omni-directional antenna, then aircraft with transponders can be tracked, but aircraft without transponders cannot be detected
Solution Approach 1:
The patent uses reflected interrogation signals as an intermediary to detect aircraft without transponders. The PSSR receives SSR interrogation signals that reflect off the target aircraft's body (without requiring transponder reply), enabling detection of non-cooperative targets while maintaining compatibility with existing SSR infrastructure
Solution Approach 2:
Instead of relying on active transponder replies from targets, the system inverts the approach by detecting the reflected interrogation signals themselves. This passive detection method allows tracking of aircraft without transponders by observing how they reflect the SSR's own signals
2Area of stationary object
If PSSR operates outside main antenna beam coverage, then detection coverage is improved, but signal strength and detection accuracy deteriorate
Solution Approach 1:
The system performs preliminary analysis of pulse repetition frequency patterns to identify congruent segments before attempting position determination. By pre-processing the signal intervals to establish the PRF pattern, the system can accurately detect targets even when signals are weak or intermittent outside the main beam coverage
Solution Approach 2:
The patent changes the detection parameter from relying on continuous strong signals to analyzing temporal patterns of pulse intervals. By examining the pulse repetition frequency pattern and identifying congruent segments in the time-ordered sequence of intervals, the system maintains detection accuracy despite varying signal strength across different coverage areas
3Measurement precision
If PSSR uses staggered interrogation pattern analysis, then detection accuracy in crowded airspace is improved, but system complexity increases
Solution Approach 1:
The patent segments the complex staggered interrogation pattern analysis into manageable steps: forming a time-ordered sequence of intervals, identifying congruent segments within that sequence, and deriving the PRF pattern from those segments. This segmentation simplifies the processing of crowded airspace signals by breaking down the pattern recognition task into discrete, executable operations
Data Source
AI summary
A detect-and-avoid system for an ownship aircraft is disclosed. The system has a control station in communication with an ownship aircraft, and a Passive Secondary Surveillance Radar (PSSR) system at the ownship aircraft. The PSSR is equipped to receive a reply from a target object, in response to an interrogation signal of staggered P1 and P3 pulses sent by a narrow-beam antenna of a Secondary Surveillance Radar (SSR) to the target object, and also to receive P2 pulses transmitted by a wide-beam antenna of the SSR. A pulse repetition frequency (PRF) pattern for the staggered interrogation signal is determined, followed by estimating a transmit time of the interrogation signal, and determining a position of the target object. A corresponding detect-and-avoid method is also disclosed.