Interface Circuit Masking Reflected Waves via Timing Control
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Solution Overview
Problem
Conventional techniques for reducing reflected waves in communication interfaces, such as USB, are limited by the assumption of equal impedances between transmission and dummy lines, leading to impedance mismatches and persistent reflected waves when devices with non-standard impedances are used.
Innovation Solution
An interface circuit that masks reflected waves using a masking means triggered by a transmission timing notification signal, ensuring only signals from the communication party are received, thereby preventing erroneous operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If output impedance is adjusted to eliminate impedance mismatch, then reflected waves are reduced, but the technique fails when actual transmission line impedance differs from dummy transmission line impedance
Solution Approach 1:
A masking circuit is introduced as an intermediary component between the reception circuit and the transmission line. This masking circuit temporarily masks (blocks) the reception circuit from receiving reflected waves during the transmission period, preventing the harmful effect without requiring impedance matching. The masking circuit operates independently of impedance conditions, providing universal protection against reflected waves regardless of actual transmission line impedance values.
2Reliability
If impedance adjustment is used to address reflected waves, then communication stability improves, but the solution is limited by assumption of equal impedances between transmission lines
Solution Approach 1:
The invention extracts the reflected wave problem from the impedance matching framework and addresses it separately through temporal masking. Instead of trying to eliminate reflected waves through complex impedance adjustment mechanisms, the solution simply extracts the harmful reflected waves in time domain by masking the reception circuit during the transmission period. This separation simplifies the overall system while maintaining reliability.
3Object-affected harmful factors
If conventional impedance adjustment techniques are used, then reflected waves are reduced under ideal conditions, but reflected waves persist when devices with non-standard impedances are connected
Solution Approach 1:
The masking circuit performs preliminary action by blocking the reception circuit from receiving any signals during the transmission period, before the reflected waves can be processed. This preliminary masking action prevents the reception circuit from being affected by reflected waves regardless of the actual impedance conditions, providing universal protection across all device types and cable configurations.
Data Source
AI summary
A transmission circuit (101) for transmitting data onto a transmission line, and a mask circuit (102) for generating a mask signal (105) for removing a reflected wave based on a transmission timing notification signal (104) supplied form the transmission circuit (101) are provided. For example, a timer circuit (301) causes the mask signal (105) to be effective only for a predetermined time immediately after transmission. A logic circuit (302) is used to remove a reflected wave from the received signal (106) based on the mask signal (105), and a resultant masked received signal (107) is input to a reception circuit (103).