Optical Phased Array RF Beamforming Without Bandwidth-Limited ESAs
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Solution Overview
Problem
Current electrically scanned arrays (ESAs) are limited by bandwidth and operating frequency due to beam forming electronics, and optically controlled RF phased arrays face challenges in large-scale implementation and cost due to difficulties in co-packaging optics with antenna elements.
Innovation Solution
An optical phased array system that includes a photodiode array and an RF antenna element array, where the optical phased array receives a laser signal and outputs an optical beam, and each photodiode mixes this with an optical plane wave beam from a phase-locked local oscillator laser to generate electronic signals for the RF antenna elements, allowing for RF beam formation without mechanical movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If beam forming electronics are used to control individual antenna elements in electrically scanned arrays, then phase control for beam steering is achieved, but bandwidth and operating frequency are limited
Solution Approach 1:
The patent replaces traditional electrical beam forming electronics with an optical control system. An optical phased array modulates the phase of RF signals by converting optical phase modulation to electrical domain through photodetectors, thereby achieving phase control without bandwidth-limited electronics in the RF path
Solution Approach 2:
The optical carrier wave serves multiple functions simultaneously: it carries phase modulation information, provides high-frequency operation capability, and enables broadband operation. This multi-functional approach allows the system to achieve both phase control and high bandwidth that were previously contradictory
2Productivity
If optically controlled RF phased arrays are implemented, then bandwidth is improved, but device complexity increases due to difficulties in co-packaging optics with antenna elements
Solution Approach 1:
The patent integrates the optical phased array and RF antenna array into a unified structure where optical components and antenna elements are co-packaged on a common substrate. The optical modulators are positioned in direct correspondence with antenna elements, enabling compact integration while maintaining optical control benefits
Solution Approach 2:
The patent introduces optical fibers or waveguides as intermediary elements to connect the optical phased array with the RF antenna elements. These intermediaries enable the transmission of optical control signals to modulate RF signals without requiring direct physical integration of complex opto-electronic components at each antenna element
3Productivity
If optically controlled RF phased arrays are implemented, then bandwidth is improved, but cost increases
Solution Approach 1:
The patent uses optical copying techniques where a single optical source is replicated across multiple channels through optical beam splitting and phase modulation. This allows phase control for multiple antenna elements to be achieved by modulating a single optical carrier, significantly reducing the cost compared to having independent optical sources for each element
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 the operation of RF phased arrays with large bandwidth, reducing size, weight, and power consumption, while maintaining phase control for steerable RF beams, thus overcoming the limitations of traditional ESAs and optically controlled phased arrays.
Implementation Method 1
Each photodiode may be configured to: receive at least a portion of the optical beam and at least a portion of an optical plane wave beam... and output an electronic signal based on the at least the portion of the optical beam and the at least a portion of the optical plane wave beam
Data Source
AI summary
A system may include an optical phased array, a photodiode array, and a radiofrequency (RF) antenna element array. The optical phased array may be configured to: receive a laser signal from a signal laser; and output an optical beam. Each photodiode may be configured to: receive at least a portion of the optical beam and at least a portion of an optical plane wave beam, wherein the optical plane wave beam is formed based at least on a local oscillator (LO) laser that outputs a laser beam having a different wavelength from the signal laser; and output an electronic signal based on the at least the portion of the optical beam and the at least a portion of the optical plane wave beam. The RF antenna element array may be configured to output an RF beam based on received electronic signals from the photodiode array.