Secondary Radar Signal Receiver Phase Correlation Timing
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Solution Overview
Problem
Current multilateration systems face significant measurement uncertainty in determining the reception times of secondary radar signals, particularly due to noise and multipath propagation, which affects the accuracy of aircraft location in air traffic control, especially in wide-area multilateration where clock synchronization is challenging and requires extensive effort.
Innovation Solution
The method involves converting intermediate frequency signals of secondary radar signals into binary phase signals, correlating them with a sample phase code sequence to determine the best match, and assigning a reception time to a reference point based on the overlap of the pattern phase code sequence with the phase signal, thereby reducing the scattering of reception times by evaluating phase information rather than solely relying on amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amplitude-based pulse shape evaluation is used to determine reception times, then the method is simple to implement, but measurement uncertainty increases to the order of 100ns due to noise and multipath propagation
Solution Approach 1:
The patent changes the evaluation parameter from amplitude-based pulse shape to phase information. By extracting and evaluating the phase of the intermediate frequency signal, the system achieves reception time accuracy in the order of 10ns or better, overcoming the 100ns uncertainty limitation of amplitude-based methods while maintaining implementation feasibility through standard signal processing techniques.
2Measurement precision
If clock synchronization infrastructure is implemented to improve location accuracy, then measurement precision improves, but device complexity and synchronization effort increase considerably
Solution Approach 1:
The patent enables each multilateration sensor to independently determine precise reception times by evaluating phase information from received signals. This self-service approach eliminates the need for complex inter-sensor clock synchronization infrastructure, as each sensor autonomously achieves high-precision timing through phase-based evaluation of the intermediate frequency signal.
3Measurement precision
If the number of multilateration sensors is increased to compensate for measurement uncertainty, then location accuracy improves, but device complexity and system cost increase
Solution Approach 1:
By changing from amplitude-based to phase-based signal evaluation, the patent reduces measurement uncertainty per sensor from 100ns to 10ns or better. This tenfold improvement in individual sensor precision reduces the number of sensors required to achieve a given location accuracy, thereby simplifying the overall system while maintaining or improving performance.
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 approach significantly reduces the measurement uncertainty of reception times, enhancing the accuracy of aircraft location in multilateration systems without the need for complex clock synchronization infrastructure, by leveraging coherent phase information from Mode S interrogation signals.
Implementation Method 1
a high-frequency signal receiving part with an antenna input, a useful signal output for a baseband secondary radar signal and a binary phase information output with phase information of the secondary radar signal, the high-frequency signal receiving part being set up for receiving, filtering and amplifying a high-frequency signal
Implementation Method 2
characteristic phase information of a received secondary radar signal is determined by converting an intermediate frequency signal of the received secondary radar signal into a binary phase signal; correlating the binary phase signal with a sample phase code sequence
Data Source
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AI summary
The method involves determining characteristic phase information of a received radar signal, by transferring an intermediate frequency signal of the received radar signal into a binary phase signal. The binary phase signals are correlated with a sample phase code sequence by calculation of the hamming distances between the phase information of a section of a received radar signal packet and a sample phase code sequence under relative displacement of the sample phase code sequence regarding the radar signal packet. An independent claim is also included for a secondary radar signal receiver, which has a high frequency signal receiving element.