Negative Feedback Impedance Matching for On-Chip Transmission Lines
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Solution Overview
Problem
Existing impedance matching solutions for transmission lines require frequent selection of terminating resistors, leading to high costs, low reliability, and poor operability due to the use of multiple off-chip discrete devices and switches.
Innovation Solution
A negative feedback circuit with a reference resistor, variable resistors, a voltage follower, proportional current mirror, and a comparison arbiter is used to dynamically regulate resistances on-chip, allowing for real-time impedance matching without the need for frequent resistor switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple off-chip discrete terminating resistors and switches are used to achieve impedance matching for different transmission line impedances, then the circuit can be compatible with different impedance transmission lines, but the cost increases and reliability decreases
Solution Approach 1:
The patent implements a negative feedback circuit that continuously monitors the voltage at node A (reference voltage) and compares it with the voltage at node B (output voltage). The comparison result feeds back to dynamically adjust the resistance of the variable resistor, ensuring precise impedance matching without requiring multiple discrete resistors or switches. This closed-loop feedback mechanism maintains high reliability while achieving adaptability to different transmission line impedances.
Solution Approach 2:
The patent replaces static discrete resistors and switches with a dynamic variable resistor whose resistance can be continuously adjusted based on feedback signals. The variable resistor's resistance changes dynamically to match different transmission line impedances, eliminating the need for manual switching between multiple fixed resistors and improving both reliability and adaptability.
2Adaptability or versatility
If multiple off-chip discrete terminating resistors and switches are used for impedance matching, then the circuit can accommodate different transmission line impedances, but the operability becomes poor
Solution Approach 1:
The patent implements a self-adjusting impedance matching system where the circuit automatically regulates its own resistance through the negative feedback mechanism. The comparison arbiter continuously compares voltages and generates feedback signals that automatically adjust the variable resistor's resistance, eliminating the need for manual intervention or complex switching operations by the user, thus greatly improving operability.
Solution Approach 2:
The automatic feedback control system eliminates manual switching operations entirely. The circuit self-regulates by continuously monitoring voltage differences and adjusting the variable resistor accordingly, making the system easy to operate while maintaining compatibility with different transmission line impedances.
3Adaptability or versatility
If multiple off-chip discrete terminating resistors are used for impedance matching, then the circuit can match different transmission line impedances, but the cost increases
Solution Approach 1:
The patent merges multiple discrete components (multiple terminating resistors and switches) into a single integrated variable resistor implemented on-chip. This consolidation reduces the total component count, eliminates the need for external discrete devices, simplifies the circuit structure, and significantly reduces manufacturing cost while maintaining the ability to match different transmission line impedances through electronic control.
Solution Approach 2:
The patent uses a reference voltage (copied from a stable reference source) to generate the feedback signal that controls the variable resistor. This copying mechanism allows the circuit to achieve precise impedance matching without requiring multiple precision discrete resistors, reducing cost while maintaining adaptability.
4Adaptability or versatility
If switches are used to select different terminating resistors for impedance matching, then the circuit can be compatible with different transmission line impedances, but the reliability and operability deteriorate due to switch problems
Solution Approach 1:
The patent eliminates switches entirely by using a feedback-controlled variable resistor. The negative feedback circuit continuously adjusts the resistor's resistance based on voltage comparison, providing a reliable switchless solution that maintains adaptability to different transmission line impedances without the reliability issues associated with mechanical or electronic switches.
Solution Approach 2:
The patent replaces static switching between discrete resistors with dynamic continuous adjustment of a single variable resistor. This dynamic approach eliminates the reliability problems of switches while maintaining the ability to match different impedances through electronic control signals.
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 reduces costs, enhances reliability, and improves operability by enabling flexible and precise impedance matching directly on the chip, eliminating the need for multiple off-chip resistors and switches.
Implementation Method 1
a voltage follower (308) having a first end, a second end and a third end, the first end of the voltage follower (308) being connected to the first end of the reference resistor (302) at node A; the voltage follower (308) being configured to make voltage at node A, VA, follow a reference voltage inputted to the third end of the voltage follower (308)
Implementation Method 2
a proportional current mirror (310) having an input end and an output end; the input end of the proportional current mirror (310) being connected to the second end of the voltage follower (308) and the output end of the proportional current mirror (310) being connected to the first end of the first variable resistor (304) at node B; the proportional current mirror (310) being configured to output a current of the output end of the proportional current mirror (310) in proportion to a current of the input end of the proportional current mirror (310)
Data Source
AI summary
A negative feedback circuit including: a voltage follower for making the output voltage follow a reference voltage, a proportional current mirror for outputting a current in proportion to a reference current via a reference resistor as a input current of the proportional current mirror, a comparison arbiter for comparing the voltage across the reference resistor and the voltage across a first variable resistor to acquire a regulating signal, inputting the regulating signal to the third regulating end of the first variable resistor and inputting the regulating signal to the third regulating end of a second variable resistor to synchronously regulate the resistances of the first and second variable resistors and thus make the resistances of the first and second variable resistors equal to the desired terminating resistance. The present invention also discloses a method and apparatus for performing on-chip impedance matching for a transmission line.