Same-Aperture STAR System Signal Isolation
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Solution Overview
Problem
Current technologies face limitations in achieving sufficient transmit-to-receive (T/R) isolation over a wide bandwidth for same-aperture simultaneous transmit and receive (STAR) systems, particularly due to the narrow bandwidth of ferrite circulators and the physical realizability of impedance matching for antenna return loss, which restricts the ability to simultaneously transmit and receive in the same frequency band.
Innovation Solution
The implementation of a three-port signal connector with a signal isolator and a differencing device that subtracts the transmit signal from the receive path, combined with various impedance matching and signal processing techniques, including photonic and electronic differencing devices, to enhance T/R isolation and enable STAR operations across a broader bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrite circulators are used for T/R isolation, then isolation performance is improved, but bandwidth is limited
Solution Approach 1:
The patent introduces a differencing device as an intermediary component that subtracts the transmit signal from the receive path. This mediator actively cancels the harmful transmit signal leakage, enabling wideband operation without being constrained by the narrow bandwidth of ferrite circulators while maintaining high T/R isolation performance
Solution Approach 2:
The patent changes the operational parameters by using signal processing techniques that adapt to different frequency conditions. The differencing device dynamically adjusts the subtraction operation across the entire bandwidth, allowing the system to maintain isolation performance across wide frequency ranges rather than being fixed at a narrow band
2Measurement precision
If impedance matching is optimized for antenna return loss, then signal quality is improved, but T/R isolation performance deteriorates
Solution Approach 1:
The patent converts the harmful effect of impedance matching limitations into a benefit by using the differencing device to cancel the transmit signal. The system accepts that impedance matching cannot simultaneously optimize both signal quality and isolation, but uses signal subtraction to turn this limitation into an opportunity to actively manage and cancel interference, achieving both goals through a different mechanism
Solution Approach 2:
The patent implements a feedback mechanism where the transmit signal is monitored and fed back through the differencing device to be subtracted from the receive path. This closed-loop feedback approach continuously compensates for impedance matching imperfections, maintaining both signal quality and T/R isolation by dynamically adjusting the cancellation based on actual transmit signal conditions
3Reliability
If multiple antenna elements are arranged to place receive antenna in null of transmit pattern, then T/R isolation is improved, but device complexity increases
Solution Approach 1:
The patent extracts the isolation function from the physical antenna arrangement and relocates it to a signal processing domain. Instead of relying on complex spatial positioning of multiple antenna elements to achieve isolation through pattern nulls, the system uses a differencing device to extract and cancel the transmit signal from the receive path, simplifying the antenna configuration while maintaining isolation 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 significantly improves T/R isolation beyond traditional methods, allowing for effective simultaneous transmission and reception in the same frequency band, even when the transmit signal strength is comparable to or weaker than the receive signal, and effectively mitigates co-site interference.
Implementation Method 1
a differencing device that subtracts the transmit signal from the receive path
Implementation Method 2
with a signal isolator and a differencing device that subtracts the transmit signal from the receive path
Data Source
AI summary
A same-aperture any-frequency simultaneously transmit and receive (STAR) system includes a signal connector having a first port electrically coupled to an antenna, a second port electrically coupled to a transmit signal path, and a third port electrically coupled to receive signal path. The signal connector passes a transmit signal in the transmit signal path to the antenna and a receive signal in the receive signal path. A signal isolator is positioned in the transmit signal path to remove a residual portion of the receive signal from transmit signal path. An output of the signal isolator provides a portion of the transmit signal with the residual portion of the receive signal removed. A signal differencing device having a first input electrically coupled to the output of the signal isolator and a second input electrically coupled to the third port of the signal connector subtracts a portion of the transmit signal in the receive signal path thereby providing a more accurate receive signal.