Photonic Signal Cancellation Using Dual-Drive Modulators
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Solution Overview
Problem
In wireless RF systems, undesired electrical signals with significant power levels often interfere with desired signals, particularly in co-located platforms like ships or airplanes, where traditional cancellation methods are limited by signal path delays and narrow bandwidth, leading to incomplete signal suppression and increased system costs.
Innovation Solution
The use of a photonic subtractor with a dual-drive electro-optic modulator and an adaptive signal processor to cancel undesired signals over wide bandwidths without physical time delay, allowing for simultaneous adjustment of signal amplitude, phase, and time delay to achieve more complete signal cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional signal cancellation methods are used, then signal cancellation is achieved, but bandwidth is limited and signal path delays cause incomplete suppression
Solution Approach 1:
The patent replaces traditional electrical signal cancellation systems with a photonic system using optical modulators and photodetectors. This substitution eliminates electrical signal path delays and enables wide-bandwidth operation while maintaining complete signal suppression, as the photonic domain operates independently from the RF electrical domain that suffers from bandwidth limitations and delay issues.
Solution Approach 2:
The patent changes the operational domain from electrical to optical by using optical modulators to impose RF signals onto optical carriers. This parameter change enables the system to handle wide bandwidths without the limitations of electrical systems, as the optical domain provides superior bandwidth capabilities while the photodetector converts the optical signal back to electrical for cancellation.
2Adaptability or versatility
If dynamic range of components is increased to handle both desired and undesired signals, then signal processing capability is improved, but system cost and size increase
Solution Approach 1:
The patent uses photonic substitution to avoid the need for high dynamic range electrical components. By converting RF signals to optical domain for processing and then back to electrical, the system achieves high dynamic range capability without requiring expensive, large-scale electrical components with extended dynamic range, thus reducing system cost and size.
Solution Approach 2:
The patent introduces an optical intermediary (optical carrier and photodetector) between the RF signal sources and the cancellation process. This intermediary enables the system to handle large dynamic ranges by operating in the optical domain during signal combination, avoiding the need for electrical components to directly handle the full dynamic range, thereby reducing cost and complexity.
3Reliability
If physical time delay is used for signal cancellation, then cancellation is achieved for narrowband signals, but bandwidth is limited and overlapping signals cannot be fully suppressed
Solution Approach 1:
The patent replaces electrical time delay mechanisms with photonic processing that operates without the bandwidth limitations of electrical systems. The optical modulator can impose signals with different time delays onto the optical carrier simultaneously, enabling effective cancellation across wide bandwidths without the narrowband constraints of traditional electrical delay lines.
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 undesired signals even when they overlap with desired signals in time and frequency, enhancing signal quality and reducing system complexity and cost by enabling cancellation across multiple decades of bandwidth.
Implementation Method 1
an optical beam is generated that propagates from the optical input to an optical output of the electro-optic modulator. The optical beam is modulated with the first and second portions of the first signal and with the second signal
Data Source
AI summary
A signal canceller includes a dual-drive electro-optic modulator having separate first and second electrical inputs. The first electrical input is coupled to a first portion of a first signal and the second electrical input is coupled to a second signal and to a second portion of the first signal. A laser generates an optical beam that propagates from the optical input to an optical output of the electro-optic modulator. The dual-drive electro-optic modulator modulates the optical beam with the first and second portions of the first signal and with the second signal. The modulation cancels at least some the first signal and generates a modulation signal with reduced first signal modulation component.