Directional Coupler Multi-Drop Bus Impedance Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multi-drop bus technologies face limitations in increasing transfer speed due to signal reflection and distortion at branch points, impedance mismatch, and poor coupling efficiency, which restricts high-speed data transfer between processors and memory modules.
Innovation Solution
A directional coupling-type multi-drop bus design where coupler ends on the main board and child board are aligned to form directional couplers with adjustable coupling degrees and line widths, ensuring impedance matching and optimal signal propagation by varying the distance and thickness of insulating films, and using a multilayer wiring structure to adjust coupling impedances within a specific range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a multi-drop bus is used to reduce the number of transmission lines, then the number of transmission lines is reduced, but the transfer speed cannot be increased due to signal reflection and impedance discontinuity at branch points
Solution Approach 1:
The patent applies parameter changes by varying the line widths of the first and second connection lines in the directional coupler to precisely control the coupling impedance. By adjusting the line width parameters, the coupling impedance is matched to the differential impedance of the transmission lines, eliminating signal reflection and enabling high-speed data transfer while maintaining the multi-drop bus structure's advantage of reduced transmission lines
Solution Approach 2:
The patent introduces a directional coupler as an intermediary component between the transmission line and the stub. This directional coupler acts as a mediator that enables signal coupling to the stub while maintaining impedance matching on the main transmission line, thus preventing signal reflection and distortion. The directional coupler structure includes first and second connection lines with specific line widths that are calculated to achieve the desired coupling impedance matching
2Reliability
If the characteristic impedance is matched at branch points to prevent signal reflection, then signal distortion is reduced, but the input capacitance of modules attached to stubs still lowers the impedance at branch points
Solution Approach 1:
The patent extracts the impedance-matching function from the branch point itself and relocates it to the directional coupler structure. By placing the impedance-matching mechanism in the directional coupler (through carefully designed connection line widths) rather than at the branch point, the patent isolates the impedance control function from the module attachment points. This allows the stub and its input capacitance to be separated from the main transmission line's impedance characteristics, preventing the stub's capacitance from affecting the main line's impedance
Solution Approach 2:
The patent applies local quality by creating different geometric characteristics (different line widths) in different parts of the directional coupler. The first connection line has a specific width optimized for coupling to the stub, while the second connection line has a different width optimized for maintaining impedance matching with the main transmission line. This localized differentiation of line widths enables simultaneous optimization of coupling efficiency and impedance matching
3Adaptability or versatility
If connectors are used to exchange or add modules in stubs, then module flexibility is improved, but parasitic capacitance and inductance of connectors cause signal reflection and distortion
Solution Approach 1:
The directional coupler serves as an intermediary that electrically isolates the stub (and its connector) from the main transmission line. The coupling mechanism through the directional coupler allows signal transfer to the stub while preventing the parasitic effects of the connector from propagating back to the main line. This intermediary structure enables module exchangeability through connectors while maintaining signal integrity on the main bus
4Productivity
If directional couplers with different coupling degrees are used to optimize signal distribution, then coupling efficiency is improved, but the impedance matching becomes more difficult to maintain
Solution Approach 1:
The patent systematically varies the line width parameters of the connection lines to simultaneously achieve both optimal coupling degree and impedance matching. By changing the geometric parameters (line widths) of the first and second connection lines, the patent optimizes the coupling impedance to match the differential impedance of the transmission line. This parameter optimization enables efficient signal distribution to multiple stubs while maintaining impedance matching, resolving the contradiction between coupling efficiency and impedance matching precision
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 design enhances signal transfer speed, reduces power consumption, and maintains performance even with positional shifts between boards, achieving reliable and efficient data transfer by matching impedance and optimizing coupling efficiency.
Implementation Method 1
directional coupler, where two parallel lines formed as printed wires on the same board are sandwiched between two grounded conductive plates
Implementation Method 2
the input capacitance of the module attached to a small transmission line (stub) at the end of a branch
Data Source
AI summary
The invention relates to a directional coupling-type multi-drop bus of which the impedance is matched with the bus at the time of coupling so that the speed is increased. A directional coupler is formed when a second module provided with a second coupler end is mounted on a first module provided with a first coupler end, and as a result, the coupling impedance where the proximity effects in the coupling state of the directional coupler are reflected is matched with the impedance of the bus.