GNSS Signal Search With Time-Multiplexed Correlator Resources
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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 acquisition processes.
Innovation Solution
A receiver apparatus and method utilizing a fast search numerically controlled oscillator (FSNCO) and Doppler numerically controlled oscillator (DopNCO) to efficiently search for GNSS signals by correlating shifted and non-shifted PRN code elements, storing convolution results, and determining signal availability through metric comparison, allowing for faster and more efficient signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple channels with dedicated correlators, code generators, and NCOs are used to search for different Doppler offsets, then signal search coverage is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple dedicated channels into a single shared channel by time-multiplexing the correlator, code generator, and NCO resources. The correlator processes different Doppler offsets sequentially by reloading code delays between measurements, allowing one physical channel to perform the function of multiple dedicated channels, thereby reducing device complexity while maintaining signal search coverage
Solution Approach 2:
The patent makes the correlator, code generator, and NCO universal resources that can serve multiple Doppler offset searches. By clearing and reloading code delays dynamically, these components can be reconfigured for different search channels, enabling one set of hardware to perform multiple functions that previously required separate dedicated components for each channel
2Measurement precision
If channels are restarted or reset to search for different Doppler offsets, then signal search accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary setup by pre-calculating and storing code delays in memory before the actual signal search begins. During the search process, the correlator can quickly reload pre-computed code delays for different Doppler offsets without performing time-consuming calculations during the measurement itself, thereby maintaining accuracy while reducing processing time
Solution Approach 2:
The patent enables continuous signal search by eliminating the need to stop and reset channels between Doppler offset measurements. The correlator continuously processes signals by dynamically reloading code delays for different offsets, maintaining uninterrupted measurement flow and avoiding the time losses associated with channel restarts and resets
3Reliability
If a large number of channels are configured for signal searching, then signal detection capability is improved, but resource efficiency deteriorates
Solution Approach 1:
The patent combines multiple virtual search channels into a single physical channel implementation. By time-multiplexing the correlator, code generator, and NCO, the system achieves the signal detection capability of multiple channels while using only one physical set of hardware resources, thereby dramatically improving resource efficiency without sacrificing detection capability
Solution Approach 2:
The patent implements a self-service mechanism where the single correlator automatically manages its own code delay configuration for different Doppler offsets. The system dynamically reloads appropriate code delays from memory based on the current measurement requirements, eliminating the need for external control of multiple separate channels and improving resource utilization efficiency
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.