Virtual Hybrid Coupler Circuit for Low-Voltage Full Duplex Cancellation
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Solution Overview
Problem
Conventional full duplex transmission systems face challenges in canceling transmitted signals at the receiver input due to low voltage power supply constraints in modern CMOS technologies, making standard resistive bridge architectures impractical and transform-based hybrid solutions bulky and inefficient at high speeds.
Innovation Solution
A circuit architecture utilizing a first and second feedback resistor, along with sets of M and N transistors, configured to cancel transmitted signals based on resistance ratios, allowing for signal cancellation without exceeding maximum amplitude requirements, suitable for low voltage conditions in CMOS technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard resistive bridge hybrid coupler is used to cancel transmitted signals, then signal cancellation is achieved, but internal node voltage swing exceeds the available power supply voltage
Solution Approach 1:
The patent changes the operating parameters by using transistor-based variable resistance elements instead of fixed resistive bridge components. The transistors are biased to provide equivalent resistance ratios while operating within the available voltage supply, thereby achieving signal cancellation without requiring excessive voltage swing at internal nodes
Solution Approach 2:
The patent substitutes the traditional resistive bridge hardware architecture with a transistor-based active circuit implementation. This replacement allows the system to achieve the same signal cancellation function while adapting to low-voltage CMOS operating conditions through electronic control rather than passive component ratios
2Temperature
If transform-based hybrid solution is employed to achieve signal cancellation, then voltage constraints are satisfied, but device size increases and cancellation performance deteriorates
Solution Approach 1:
The patent segments the signal cancellation function into separate transistor stages that can be integrated within the CMOS process. By dividing the cancellation function across multiple transistor pairs with specific resistance ratios, the system achieves the required voltage compatibility without requiring a single large transform-based component
Solution Approach 2:
The transistor-based circuit serves multiple functions: it provides signal cancellation, maintains voltage compatibility, and integrates within standard CMOS fabrication processes. This multi-functionality eliminates the need for separate bulky transform-based hybrid components while achieving all required performance targets
Data Source
AI summary
Various transmission systems may benefit from techniques to improve the quality of the transmission. For example, certain full duplex transmission systems may include a virtual hybrid coupler. A circuit can include a first feedback resistor. The circuit can also include a second feedback resistor coupled to the first feedback resistor. The circuit can further include a first set of M transistors coupled to the first feedback resistor. The circuit can additionally include a second set of N transistors coupled to the second feedback resistor and to the first set of M transistors. The circuit can be configured to cancel a transmitted signal at a receiver input based on a ratio of resistance values of the first feedback resistor and the second feedback resistor, and based on a ratio of M to N.