DAS Remote Oscillator Synchronization Using Digital Pulse Timing
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Solution Overview
Problem
Distributed antenna systems (DASs) face challenges in synchronizing local oscillators across remote units due to limited bandwidth capabilities and interference, requiring precise bandpass filters that can be expensive and large.
Innovation Solution
A method for frequency synchronizing local oscillators in remote units of DASs using a received digital pulse signal from a central unit, which includes a time difference unit to calculate the frequency difference between the reference oscillator and the local oscillator, and a frequency adjustment unit to provide a signal to synchronize them, thereby reducing the need for expensive filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precise bandpass filters are used to synchronize local oscillators in DAS, then frequency synchronization accuracy is improved, but device cost and size increase
Solution Approach 1:
The patent replaces the mechanical/electronic bandpass filter system with a digital signal processing system. A time difference unit calculates frequency differences by comparing zero-crossing points or peak points of reference and local oscillator signals, eliminating the need for physical filters. This substitution achieves precise frequency synchronization without the cost and size penalties of precise bandpass filters.
2Device complexity
If digital pulse signal processing is used for frequency synchronization, then device cost is reduced, but measurement precision may be affected
Solution Approach 1:
The patent creates multiple copies of the digital pulse signal at different frequencies (reference oscillator signal and local oscillator signal) and processes them through identical time difference calculation algorithms. This allows comparison of corresponding features (zero-crossings or peaks) to determine frequency differences with high precision using simple digital logic rather than expensive analog components.
Solution Approach 2:
The time difference unit continuously calculates the frequency difference between reference and local oscillator signals and feeds this information back to adjust the local oscillator frequency. This closed-loop feedback mechanism ensures continuous frequency synchronization while using only simple digital processing components, maintaining high precision at low cost.
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 allows for precise synchronization of local oscillators in remote units, improving frequency accuracy and reducing the need for costly bandpass filters, enhancing the efficiency of frequency shifting communications signals within DASs.
Implementation Method 1
a local oscillator configured to generate a mixing frequency signal
Implementation Method 2
The remote unit mixes the frequency shifted downlink communications signal with a mixing frequency signal generated by a local oscillator
Data Source
AI summary
Frequency synchronizing a local oscillator in a remote unit in a distributed antenna system (DAS) used for frequency shifting communications signals based on a received digital pulse signal from a central unit. A remote unit receives a frequency shifted downlink communications signal and a reference pulse signal indicative of a frequency of a reference oscillator from a central unit. To recover the original signal, a mixing frequency signal generated by a local oscillator is used. To recover a signal having the same frequency as the original signal, the local oscillator should be the same or substantially the same frequency as the frequency used to create the frequency shifted version. A time difference signal indicating the frequency difference between the oscillators is calculated. A frequency adjustment signal is provided to the local oscillator based on the time difference signal to decrease the frequency difference between the oscillators.