Optical Fiber Beamforming via Phase Adjustment
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Solution Overview
Problem
Current wireless communication systems using millimeter wave bands face challenges in long-distance transmission due to high propagation loss, and existing beamforming techniques require complex control of optical demultiplexers and accurate fiber length measurements, limiting wavelength utilization efficiency and increasing costs.
Innovation Solution
A wireless communication system that adjusts the phases of optically modulated signals with fixed wavelengths, allowing for beamforming of both transmitting and receiving antennas without requiring base station control or optical fiber distance information, by using a configuration where wavelengths are fixed and phase adjustments are made to equalize phase rotations across multiple antenna elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beamforming is performed using variable wavelengths and fixed dispersion, then directivity can be formed, but wavelength utilization efficiency deteriorates and the wavelength band must be greatly expanded
Solution Approach 1:
The patent inverts the conventional beamforming approach by using fixed wavelengths instead of variable wavelengths, and variable dispersion instead of fixed dispersion. This inversion resolves the contradiction by maintaining directivity formation capability while improving wavelength utilization efficiency, as the fixed wavelengths can be continuously reused without requiring broad wavelength band expansion.
Solution Approach 2:
The patent changes the controllable parameter from wavelength to dispersion. By keeping wavelengths fixed and adjusting dispersion values dynamically, the system maintains beamforming functionality while eliminating the need to expand wavelength bands, thereby improving wavelength utilization efficiency.
2Reliability
If chromatic dispersion is used to cause delay differences between optical signals, then beamforming can be achieved, but accurate fiber length measurement is required which increases system complexity
Solution Approach 1:
The patent enables the system to automatically determine optimal dispersion values without requiring external fiber length measurement equipment. The base station self-adjusts dispersion parameters based on feedback from the accommodation station, eliminating the need for complex external measurement systems while maintaining beamforming capability.
3Measurement precision
If base station control is implemented for wavelength adjustment, then beamforming precision is improved, but system complexity and cost increase
Solution Approach 1:
The patent introduces the optical fiber dispersion characteristic as an intermediary that naturally provides the necessary phase differences for beamforming. Instead of complex base station control systems actively adjusting wavelengths, the system utilizes the passive chromatic dispersion property of optical fibers to achieve precise beamforming, thereby reducing control system complexity.
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 enables efficient beamforming while maintaining wavelength utilization efficiency and avoiding cost increases, without the need for complex control systems or accurate fiber length measurements.
Implementation Method 1
an accommodation station (a master station) modulates the intensity of an optical carrier with a radio frequency (RF) signal to be transmitted
Implementation Method 2
delay differences occur between optical signals of wavelengths due to chromatic dispersion during transmission through an optical fiber
Implementation Method 3
A base station (a slave station) reconverts the optical signal received through the optical fiber to the RF signal
Implementation Method 4
radiates the reconverted RF signal through an antenna as a radio wave
Data Source
AI summary
To n antenna elements of the base station, n wavelengths set at predetermined intervals in a range in which chromatic dispersion in an optical fiber between accommodation and base stations can be regarded as constant are assigned. The accommodation station adjusts the phases of optical signals of the wavelengths or modulated signals that modulate the optical signals such that the amounts of phase shift of their RF signals are at predetermined intervals. The accommodation station transmits beacon signals multiple times while varying a transmission phase shift interval α1 and the terminal transmits beacon number information of a beacon signal selected based on received power multiple times. The accommodation station varies a reception phase shift interval α2 for each piece of beacon number information to determine a reception phase shift interval α2 which maximizes the received power and determines the transmission phase shift interval α1 based on the beacon number information received from the terminal.