RF Signal Isolation via Optical Single Side Band Modulation
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Solution Overview
Problem
Traditional electronic techniques for isolating RF signals in the microwave frequency range and higher are limited in terms of bandwidth and isolation, and there is a need for improved methods to effectively separate RF signals using photonic techniques.
Innovation Solution
The method employs optical single-side-band modulation combined with optical filtering, where RF signals are upconverted to an optical carrier frequency and then processed using 90-degree hybrids and optical notch filters to isolate and separate the signals, allowing for high isolation between counter-propagating signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electronic techniques are used for RF signal isolation, then the isolation can be achieved, but the bandwidth is limited and isolation performance is insufficient
Solution Approach 1:
The patent replaces traditional electronic isolation techniques with photonic techniques. Specifically, it uses optical modulators to convert RF signals to optical domain, enabling much larger instantaneous bandwidths and higher isolation levels compared to electronic circulators and filters. The optical domain processing allows for isolation performance that electronic systems cannot achieve while simultaneously providing extended bandwidth capability.
Solution Approach 2:
The patent changes the operating domain from electronic to photonic, utilizing optical carrier frequencies instead of electronic frequencies. This parameter change enables the system to achieve both high isolation and large bandwidth simultaneously, as optical systems operate at frequencies orders of magnitude higher than electronic systems, providing access to much wider available bandwidth while maintaining excellent isolation characteristics through optical filtering and modulation techniques.
2Reliability
If multiple circulators or matched pairs of circulators are used to improve isolation, then isolation performance increases, but device complexity increases
Solution Approach 1:
The patent substitutes complex electronic circulator-based isolation systems with a photonic system using optical modulators and optical filters. This replacement achieves the required isolation performance with fewer and simpler components. The optical modulator approach provides high isolation through the inherent properties of optical modulation and filtering, eliminating the need for multiple expensive and complex electronic circulators.
3Reliability
If photonic techniques are used for RF isolation, then bandwidth and isolation are improved, but system complexity increases
Solution Approach 1:
The patent implements photonic techniques by replacing electronic signal processing components with optical counterparts. The system uses optical modulators to convert RF signals to optical domain, where signal processing and isolation are achieved through optical filtering and modulation techniques. This substitution provides superior bandwidth and isolation performance while managing system complexity through the use of integrated photonic components and standardized optical interfaces.
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 significantly increases RF isolation between signals, enabling better separation and handling of simultaneous transmit and receive operations, with improved bandwidth and protection from damaging RF powers, such as lightning strikes.
Implementation Method 1
The optical modulator is biased to produce single side band optical outputs of the first and second RF signals
Implementation Method 2
The optical single side band optical outputs of the first and second RF signals may then be passed to an optical notch filter to remove one of the single side band optical outputs
Implementation Method 3
The remaining single side band optical output of the first and second RF signals may then be to an electrical signal
Data Source
AI summary
A method and apparatus for isolating an RF signal are provided. A first RF signal is received and passed to an input of a 90 degree hybrid. An output of the 90 degree hybrid is connected to a first waveguide and a second output is connected to a second waveguide of an optical modulator. A second RF signal is received and passed to an input of a second 90 degree hybrid. An output of the second 90 degree hybrid is connected to the second waveguide and a second output is connected to the first waveguide of the optical modulator. The optical modulator is biased to produce single side band optical outputs of the RF signals. The single side band optical outputs are passed to an optical notch filter to remove one of the side band outputs. The other of the side band optical outputs is converted to an electrical signal.