Coherent RF Photonic Link With Tunable OCSR Down-Conversion
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Solution Overview
Problem
Conventional RF photonic systems face challenges in capturing low-power broadband signals due to high system noise figures attributed to laser relative intensity noise and modulator half-wave voltage, and they often require large bandwidths that increase size, weight, and cost when using electronic down-conversion and filtering.
Innovation Solution
A tunable optical carrier-to-sideband ratio filtering and down-converting coherent RF photonic link system that integrates baseband down-conversion and filtering, utilizing photonic integrated circuits to achieve low noise figures and reduce size, weight, and cost, with features like tunable optical carrier-to-sideband ratio and balanced detection for RIN cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electronic down-conversion and filtering are used to achieve frequency conversion, then the system can process RF signals, but the size, weight, and cost increase due to large bandwidth requirements
Solution Approach 1:
The patent replaces electronic down-conversion and filtering systems with a photonic system that uses optical carriers and photodetectors. The optical frequency domain is used for signal modulation and processing, eliminating the need for large electronic bandwidth components. This substitution of electronic systems with photonic systems reduces the size and weight while maintaining frequency coverage capability.
2Productivity
If conventional RF photonic systems use laser relative intensity noise and modulator half-wave voltage, then the system can modulate and transmit signals, but the system noise figure increases
Solution Approach 1:
The patent extracts and eliminates the harmful laser relative intensity noise from the signal path by using a balanced detection configuration. The system separates the signal into two paths, detects them separately, and combines the outputs, which cancels out the RIN component. This extraction of the harmful noise element improves the noise figure while preserving signal transmission capability.
Solution Approach 2:
The patent converts the modulator half-wave voltage characteristic, which normally contributes to noise, into a beneficial effect by using it for carrier suppression. The carrier-suppressed single-sideband modulation technique transforms the modulator's inherent voltage-to-phase conversion into a mechanism that reduces noise figure while maintaining signal integrity.
3Object-affected harmful factors
If carrier-suppressed single sideband modulation is used to reduce noise, then the system noise figure improves, but the optical carrier-to-sideband ratio becomes difficult to control
Solution Approach 1:
The patent introduces dynamic control of the optical carrier-to-sideband ratio through a tunable optical filter. The filter's center frequency and bandwidth are dynamically adjusted to optimize the carrier-to-sideband ratio according to the specific operating conditions. This dynamic adaptability allows the system to maintain low noise figure while providing flexible control over the optical spectrum allocation.
Solution Approach 2:
The patent changes the operating parameters of the optical filter to control the carrier-to-sideband ratio. By adjusting the filter's center frequency offset and bandwidth, the system can optimize the suppression of the optical carrier while maintaining the single-sideband signal. This parameter adjustment provides a simple and effective method to control the OCSR without increasing device complexity.
4Weight of stationary object
If broadband frequency coverage is achieved using photonic integrated circuits, then the system size and cost are reduced, but the noise cancellation performance may be compromised
Solution Approach 1:
The patent merges multiple functions into a single photonic integrated circuit chip, including the optical modulator, optical filter, and photodetectors. This integration maintains the balanced detection configuration for noise cancellation while reducing the overall system size. The monolithic integration ensures that the noise cancellation performance is preserved through precise alignment and matching of the optical paths on the chip.
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
The system provides broadband frequency coverage with reduced size, weight, and cost, enhancing signal sensitivity and noise cancellation, suitable for applications in telecommunications, RF photonics, biology, cell sorting, spectroscopy, atomic physics, and precision navigation.
Implementation Method 1
modulating an RF input signal onto a portion of the first optical carrier signal to generate modulated optical signals
Implementation Method 2
optically filtering the carrier-suppressed single sideband signals to generate filtered carrier-suppressed single sideband signals
Implementation Method 3
generating an output RF signal based on the frequency-converted optical signals
Data Source
AI summary
A method includes generating first and second optical carrier signals having a specified frequency offset. The method also includes modulating an RF input signal onto a portion of the first optical carrier signal to generate modulated optical signals, where the modulated optical signals include the portion of the first optical carrier signal and sideband signals. The method further includes suppressing the portion of the first optical carrier signal in the modulated optical signals to generate carrier-suppressed single sideband signals. The method also includes optically filtering the carrier-suppressed single sideband signals to generate filtered carrier-suppressed single sideband signals. The method further includes combining the filtered carrier-suppressed single sideband signals with portions of the second optical carrier signal to generate frequency-converted optical signals. In addition, the method includes generating an output RF signal based on the frequency-converted optical signals. Each frequency-converted optical signal has an optical carrier-to-sideband ratio (OCSR) that is controllable.