Cellular Modem ADC Timing Synchronization for Accurate RF Sampling
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Solution Overview
Problem
Current wireless modems face uncertainty in Analog-to-Digital Converter (ADC) timing due to accumulated delay in the ADC input clock generation path, affecting the accuracy of RF signal measurements and positioning in cellular networks.
Innovation Solution
A method is introduced to determine ADC output timing by generating a start signal and synchronizing it with a system clock, then using a counter to calculate the time difference between the start and capturing sample clocks, allowing for accurate timing determination of ADC samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ADC input clock generation path is used to generate ADC samples, then the ADC sampling function is achieved, but accumulated delay causes timing uncertainty and reduces measurement precision
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing the start signal with the system clock before ADC sampling begins. The start signal is generated and synchronized in advance to establish a known timing reference, which eliminates accumulated delay effects during the actual sampling process. This advance synchronization ensures that the timing relationship between the system clock and ADC samples is predetermined and accurate.
Solution Approach 2:
The patent introduces an intermediary counter mechanism that mediates between the system clock and the ADC sampling process. The counter captures the time difference between the synchronized start signal and the actual ADC output timing, serving as an intermediary that translates and communicates the precise timing relationship. This intermediary structure allows accurate timing measurement without directly modifying the ADC input clock generation path.
2Measurement precision
If the ADC output clock timing is determined using traditional methods, then the sampling process is simple, but timing uncertainty negatively impacts positioning accuracy
Solution Approach 1:
The patent implements feedback by continuously monitoring and measuring the actual ADC output timing relative to the system clock using a counter. The measured time difference is fed back to the system to compensate for any timing deviations. This feedback mechanism ensures that timing accuracy is maintained and can be used to correct positioning calculations, thereby improving positioning accuracy despite the additional measurement step.
Solution Approach 2:
The patent replaces the traditional mechanical timing determination method with an electronic counter-based measurement system. Instead of relying on physical timing circuits or oscillators to determine ADC output timing, the system uses a digital counter to electronically measure the time difference between clock signals. This substitution provides higher precision and eliminates the accumulated delay issues inherent in traditional mechanical timing systems.
Data Source
AI summary
An analog-to-digital converter (ADC) has been disclosed. In some implementations, the ADC is configured to generate ADC samples based on input signals and an ADC input clock. The ADC is further configured to generate at a first time point a synchronized start signal indicating a starting point of capturing the ADC samples. The start signal and a system clock can be synchronized at a second time point. At a third time point, a capturing sample clock for capturing the ADC samples is generated. The synchronized start signal and the capturing sample clock can be input to a counter to determine a time difference between the second and third time points. An ADC output timing of the ADC samples can be determined based on the time difference.