Optical Interference Suppression via Bessel Function Zeros
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Solution Overview
Problem
Existing RF systems face challenges in receiving low-power signals in the presence of high-power interference, as they often saturate and generate third-order intermodulation distortion, which complicates the suppression of high-power signals while preserving low-power signals of interest.
Innovation Solution
The implementation of a Nonlinear Function Modification (NLFM) technique using a Mach-Zehnder modulator-based link architecture, which modifies the nonlinear function to suppress high-power interfering signals and reduce third-order intermodulation distortion products, allowing for simultaneous recovery of low-power signals without generating equally strong distortion products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional RF systems attempt to suppress high-power interfering signals, then the interference power is reduced, but the system generates third-order intermodulation distortion that complicates signal recovery
Solution Approach 1:
The patent replaces conventional electronic RF signal processing with an optical processing system. RF signals are converted to optical domain using electro-optic modulators, processed through optical components (Mach-Zehnder interferometers, optical filters), and then converted back to electrical signals. This substitution of the processing domain fundamentally changes how interference suppression is achieved, avoiding the intermodulation distortion problems inherent in electronic systems while maintaining the ability to suppress high-power interfering signals.
2Object-affected harmful factors
If photonic systems are used to suppress interference, then signal reception is improved, but the bandwidth and signal fidelity are still limited
Solution Approach 1:
The patent employs multiple parameter changes to enhance photonic system performance. This includes adjusting optical carrier frequencies, modifying modulation indices, changing optical path lengths, and tuning optical filter characteristics. These parameter adjustments enable the system to achieve broader bandwidth operation and improved signal fidelity while maintaining effective interference suppression. The ability to independently control multiple parameters provides fine-grained optimization of system performance.
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 effectively suppresses high-power interfering signals and minimizes third-order intermodulation distortion, preserving the low-power signal of interest, as demonstrated by experimental results showing significant suppression of both the interferer frequency and intermodulation distortion frequencies without compromising the signal fidelity.
Implementation Method 1
the RF signals, including both desired and undesired signals, are imposed on an optical signal using an optical modulator
Implementation Method 2
The modulated optical signal is then received at a photodetector to convert the signal back to an electronic signal
Implementation Method 3
Mach-Zehnder interferometric modulator link architecture that suppresses a high-power input signal at one frequency while recovering a low-power signal at a second frequency
Data Source
AI summary
A method of interference suppression with intermodulation distortion mitigation includes processing an RF signal comprising an RF signal of interest and an RF interfering signal to produce a first and second RF drive signal each with a desired RF interference signal power and having a 90 degree relative phase. The first RF drive signal is imposed onto a first optical signal with a modulator to generate a first modulated optical signal so that the modulator has a large-signal behavior that is characterized by a Bessel function of the first kind J1(ϕ), wherein the desired power at a frequency of the interference signal of the first drive signal is chosen to correspond to a zero of the Bessel function of the first kind J1(ϕ). The second RF drive signal is imposed onto a second optical signal with a modulator to generate a second modulated optical signal so that the modulator has a large-signal behavior that is characterized by a Bessel function of the first kind J1(ϕ), wherein the desired power at a frequency of the interference signal of the second drive signal is chosen to correspond to another zero of the Bessel function of the first kind J1(ϕ). The first and second modulated optical signal are combined with an optical power ratio that is selected to suppress third-order intermodulation distortion products in an electrical signal generated by detecting the optically combined first and second modulated optical signals.