GNSS Receiver Fast Search With Shared Correlation
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Solution Overview
Problem
Existing GNSS signal search methods require a large number of channels with dedicated correlators, code generators, and numerically-controlled oscillators, leading to inefficient and resource-intensive signal processing.
Innovation Solution
A receiver apparatus and method utilizing a fast search numerically controlled oscillator (FSNCO) and Doppler numerically controlled oscillator (DopNCO) to efficiently process GNSS signals, reducing the need for multiple channels by using a correlator that calculates and stores convolution values across multiple phases, allowing for faster signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of channels with dedicated correlators, code generators, and numerically-controlled oscillators are used to search for GNSS signals, then the signal detection capability is improved, but the device complexity and resource consumption increase significantly
Solution Approach 1:
The patent merges multiple dedicated channels into a single shared channel by time-multiplexing the correlator, code generator, and numerically-controlled oscillators. The correlator processes multiple code delays sequentially within a search window, allowing one physical channel to perform the work of multiple logical channels, thereby reducing hardware complexity while maintaining detection capability
Solution Approach 2:
The patent makes the correlator, code generator, and numerically-controlled oscillators universal components that can handle multiple functions. The correlator can process different code delays and Doppler offsets by reconfiguration, the code generator can produce different PRN codes by loading different seed values, and the NCO can generate different frequencies by changing control parameters, eliminating the need for dedicated components for each channel
2Measurement precision
If channels are re-started/reset to search for different Doppler offsets, then the signal search accuracy is improved, but the time required for signal acquisition increases
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing correlation results for multiple code delays within a search window before final signal acquisition. The system accumulates correlation metrics for different delays and Doppler offsets in advance, allowing faster final detection without requiring repeated channel resets, thus reducing acquisition time while maintaining precision
Solution Approach 2:
The patent maintains continuity of useful action by keeping the correlator running continuously through the search window without stopping or resetting between Doppler offsets. The system processes multiple delays and offsets in a continuous accumulation process, avoiding the time loss associated with channel re-starts while maintaining measurement precision through persistent correlation
3Measurement precision
If multiple numerically-controlled oscillators are used for each channel to handle different frequencies, then the frequency tracking accuracy is improved, but the use of energy and device complexity increase
Solution Approach 1:
The patent merges multiple numerically-controlled oscillators into a single shared NCO by time-multiplexing. The single NCO generates intermediate frequency signals for different Doppler offsets by being reconfigured between processing steps, eliminating the need for multiple parallel oscillators and significantly reducing energy consumption while maintaining frequency tracking accuracy through precise digital control
Data Source
AI summary
A method and apparatus for fast searching GNSS signals performed on a GNSS receiver includes the steps of receiving a signal having a known pseudo random noise code. State information of a code generator is stored when a pseudo random noise code is generated. Several NCO, including a Doppler NCO are used to search GNSS signal for several supposed Doppler's simultaneously. A search window associated with the received signal is reviewed a first time to identify a source of the received signal. After it is determined if a source of the received signal can be identified, the state information is loaded into the code generator prior to reviewing the search window a second time etc. Search windows is shifting by all length PRN Code. The loading of state information allows sequential review of the search window without re-adjustment of a fast search module which speeds the process of analyzing the received signals.