Optical Feed Signal Generator for Phased Array Antennas
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Solution Overview
Problem
Phased array antennas face challenges in efficiently generating feed signals with controlled phase and amplitude for beamforming, particularly in minimizing interference in densely populated areas, due to the high cost and space requirements of existing optical solutions like wavelength selective switches and the limitations of chromatic dispersion in optical fibers and micro ring resonators.
Innovation Solution
A feed signal generator comprising a wavelength selective separator, an optical time delay element, and an optical amplitude control apparatus, where only one optical signal is delayed, allowing the other to compensate for losses and maintain constant amplitude, thereby generating a feed signal with a preselected power and phase for phased array antennas, potentially using optical ring resonators or chirped Bragg gratings for time delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wavelength selective switches are used to select spectral components, then the desired time delay and phase control are achieved, but the cost and device size become prohibitive
Solution Approach 1:
The patent extracts only the necessary spectral components (first and second spectral components) from the optical spectrum using a wavelength selective separator, rather than using complex wavelength selective switches to control all spectral components. This extraction approach reduces device complexity while maintaining the required time delay precision through chromatic dispersion.
Solution Approach 2:
The patent replaces the mechanical/electronic wavelength selective switches with an optical-based solution using chromatic dispersion in optical fiber. The time delay is achieved optically through the wavelength-dependent group velocity in the dispersive medium, eliminating the need for complex electronic switching mechanisms.
2Loss of time
If optical fiber chromatic dispersion is used to introduce time delay, then the desired phase control is achieved, but the total delta delay and delay resolution are limited
Solution Approach 1:
The patent changes the operating parameters by selecting specific spectral components with a frequency difference that optimizes the time delay achieved through chromatic dispersion. By carefully selecting the first and second spectral components, the system achieves the required time delay and resolution without needing excessively long fiber lengths or complex cascaded structures.
Solution Approach 2:
The patent segments the optical spectrum into specific first and second spectral components that are then processed through the chromatic dispersion medium. This segmentation allows the system to achieve the desired time delay with a single optical fiber rather than requiring cascaded segments, improving both delay range and resolution.
3Area of stationary object
If micro ring resonators are used to introduce time delay, then space occupancy is reduced, but the group delay is substantially lower and cascaded structures are required
Solution Approach 1:
The patent uses an optical fiber as a copy or alternative implementation of the time delay function provided by micro ring resonators. The optical fiber achieves the same time delay effect through chromatic dispersion but with significantly higher group delay values, eliminating the need for cascaded resonator structures while maintaining compact form factor.
4Loss of energy
If ring resonators operate far from resonance frequency to minimize optical loss, then transmission efficiency is improved, but the group delay generated is substantially lower
Solution Approach 1:
The patent converts the typically harmful effect of chromatic dispersion (which causes pulse broadening and signal degradation) into a beneficial time delay mechanism. By intentionally exploiting the wavelength-dependent group velocity in the optical fiber, the system achieves high group delay while maintaining low optical loss, turning a potential disadvantage into the core functional mechanism.
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 solution reduces the need for expensive wavelength selective switches and cascaded optical components, enabling higher time delay and improved beam pointing resolution while maintaining consistent signal power and minimizing interference, making it suitable for pico and nano cell networks.
Implementation Method 1
The wavelength selective separator apparatus is arranged to separate the optical spectrum into a first optical signal being the first spectral component and a second optical signal being the second spectral component
Implementation Method 2
a pair of time delayed optical signals are generated by subjecting the optical spectrum generated by a mode-locking laser, MLL, to chromatic dispersion by transmitting it through an optical fibre. Due to their different wavelengths, the various spectral components in the MLL spectrum experience different delays
Implementation Method 3
The heterodyning device is arranged to heterodyne the delayed optical signal and the second optical signal to generate a feed signal for the phased array antenna at the preselected frequency difference
Data Source
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Figure 5
AI summary
A feed signal generator (10) for a phased array antenna, comprising: an input (12) to receive an optical spectrum having first and second phase-locked spectral components, respectively having first and second optical frequencies; wavelength selective separator apparatus (14) to separate the optical spectrum into a first optical signal being the first spectral component and a second optical signal being the second spectral component; an optical time delay element (16) to apply a time delay to the first optical signal to form a delayed optical signal; a heterodyning device (20) to heterodyne the delayed optical signal and the second optical signal to generate a feed signal (22) having a power proportional to a product of the amplitudes of the second and delayed optical signals and a phase proportional to the time delay; and optical amplitude control apparatus (18) to set an amplitude of the delayed optical signal such that the product of said amplitudes causes the power of the feed signal to have a preselected value.