Bidirectional Differential Interface Test Apparatus with Transmitter Cancellation
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Solution Overview
Problem
Existing test apparatuses for devices with bidirectional differential interfaces face challenges in accurately measuring differential signal amplitudes without being affected by the transmitter's output, requiring complex differential amplifiers that are difficult to design for high-speed and high-linearity applications.
Innovation Solution
A test apparatus design that includes a main current driver amplifier and a cancel driver amplifier, along with a level shift circuit and comparator circuit, which cancels out the effects of the transmitter's output on the receiver, allowing for amplitude judgment without the need for a differential amplifier, using resistors and current sources to manage signal levels and comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a differential amplifier is used to measure differential signal amplitude, then measurement precision is improved, but device complexity increases and high-speed performance becomes difficult to achieve
Solution Approach 1:
The patent extracts and removes the differential amplifier from the test apparatus configuration. Instead of using a differential amplifier to measure the differential signal amplitude, the invention uses a single-ended measurement approach where the differential signal is converted to a single-ended signal through a resistor network, and then measured by a standard comparator. This eliminates the need for a complex high-speed differential amplifier while maintaining measurement capability.
Solution Approach 2:
The patent creates a simplified copy of the differential signal measurement function using resistive dividers and a single-ended comparator. Rather than directly measuring the differential voltage with a complex amplifier, the invention copies the measurement function through a resistor network that converts the differential signal into proportional single-ended voltages that can be measured by simpler circuitry.
2Productivity
If a bidirectional differential interface is used for high-speed signal transmission, then productivity is improved, but the receiver is affected by the transmitter's output signal
Solution Approach 1:
The patent applies preliminary anti-action by using a hybrid circuit configuration that preemptively cancels out the transmitter's output signal before it can interfere with the receiver. The hybrid circuit is designed to generate an equal and opposite signal that nullifies the transmitter's output, effectively preventing the interference from reaching the receiver input. This allows the bidirectional interface to operate at high speeds without the receiver being affected by the transmitter's driving signal.
3Object-generated harmful factors
If a hybrid circuit is used to cancel transmitter output, then harmful factors are reduced, but device complexity increases
Solution Approach 1:
The patent merges the hybrid circuit functionality directly into the receiver input stage, combining the interference cancellation function with the signal reception function in a single integrated configuration. Rather than adding a separate hybrid circuit module, the invention integrates the canceling function into the existing receiver architecture, using shared resistors and circuit elements to achieve both signal reception and transmitter output cancellation simultaneously.
Data Source
AI summary
First and second resistors are provided between a first input/output terminal and a power supply terminal, and between a second input/output terminal and the power supply terminal, respectively. Third and fourth resistors are connected to the second and first input/output terminals, respectively. First and second current-switching switches couple either the first input/output terminal side or the second input/output terminal side with a first current source and a second current source, respectively, according to the value of pattern data. A level shift circuit shifts the electric potentials at the second terminals of the third and forth resistors by a predetermined level. A comparator circuit compares the electric potentials at the second terminals of the third and fourth resistors level-shifted by the level shift circuit with those at the second terminals of the fourth and third resistors, respectively, and generates first and second comparison signals according to the comparison results.