Ranging Method Resolving Carrier Phase Ambiguity
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Solution Overview
Problem
Current ranging technologies face challenges in achieving high accuracy due to the ambiguity in carrier phase measurements, which limits precise delay estimation in radio signal propagation, especially in satellite navigation and radar systems.
Innovation Solution
The method involves modeling the noise-free part of the receive signal as a function of propagation delay, using a statistical model to align a tracking algorithm with the delay parameter grid, and constructing a long integration ambiguity histogram to resolve ambiguity and provide precise delay measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase measurements are used for ranging, then measurement precision is improved, but ambiguity in delay estimation occurs
Solution Approach 1:
The patent segments the delay estimation problem into two parts: coarse delay estimation using baseband signal processing and fine delay estimation using carrier phase measurements. The coarse estimate resolves the integer ambiguity of the carrier phase cycles, while the fine estimate provides high precision. This segmentation allows both accuracy and unambiguous delay estimation.
Solution Approach 2:
The patent introduces an intermediary variable - the coarse delay estimate from baseband processing - that mediates between the ambiguous carrier phase measurements and the true delay. This intermediary resolves the integer cycle ambiguity by providing a reference frame against which the precise carrier phase measurements can be interpreted.
2Measurement precision
If multiple transmitters and time instances are combined to resolve carrier phase ambiguity, then ranging accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the complexity by separating ambiguity resolution from precision measurement. The baseband processing handles the complex task of resolving integer ambiguities using multiple transmitters and time instances, while the carrier phase processing focuses on precise fractional cycle measurement. This segmentation simplifies the overall system architecture.
Solution Approach 2:
The patent performs preliminary action by obtaining coarse delay estimates from baseband processing before performing the precise carrier phase measurements. This preliminary estimation of integer cycles simplifies subsequent processing by providing a reference frame, reducing the computational complexity of resolving ambiguities in later stages.
3Ease of operation
If DLL and PLL control loops are used for tracking, then ease of operation is improved, but manufacturing precision of delay measurement is limited
Solution Approach 1:
The patent merges the outputs of two control loops - the delay-locked loop (DLL) providing coarse delay estimates and the phase-locked loop (PLL) providing precise carrier phase measurements. By combining these two measurement streams with different precision characteristics, the system achieves both ease of operation through standard tracking loops and high precision delay measurement.
Solution Approach 2:
The patent creates a composite measurement approach by combining coarse delay measurements from baseband processing with fine delay measurements from carrier phase processing. This composite measurement strategy leverages the strengths of both methods - the robustness and ease of tracking of baseband processing and the high precision of carrier phase measurements - to achieve superior overall performance.
Data Source
AI summary
The present invention relates to a method of determining a distance or location of a remote device or reflector, the method comprising: receiving a signal from a remote signal transmitter associated with or contained in or attached to the remote device; estimating a first propagation delay associated with the received signal, wherein the first propagation delay represents a first candidate for a correct propagation delay; deriving a relationship between the first candidate and one or more other candidates for a correct propagation delay from the received signal; determining a plurality of other candidates for a correct propagation delay based on said relationship; generating a likelihood histogram based on said candidates for a correct propagation delay; selecting a propagation delay from said candidates based on the likelihood histogram; and determining a distance or location of the remote device or reflector using the selected propagation delay.