Driver Circuit Pre-Emphasis for Long Test Signal Lines
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Solution Overview
Problem
In test apparatuses, long transmission lines cause test signals to be faded or lost, making it difficult to increase test rates by simply speeding up the driver circuit.
Innovation Solution
A driver circuit comprising a main driver, sub-driver, differentiating circuit, and adding section that enhances the drive signal by adding differentiated signals, with optional delay, amplitude compensation, and impedance matching to maintain signal integrity over long transmission lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the driver circuit is speeded up to increase test rate, then test speed is improved, but signal integrity deteriorates due to fading and loss in long transmission lines
Solution Approach 1:
The differentiating circuit performs preliminary differentiation on the drive signal before transmission, pre-emphasizing high-frequency components that will be attenuated during transmission. This preliminary action compensates for expected signal degradation, ensuring that the signal arrives at the device under test with adequate integrity even at high test rates
Solution Approach 2:
The circuit changes the frequency characteristics of the drive signal by differentiating it, transforming the signal waveform to have enhanced high-frequency content. This parameter change in the signal spectrum compensates for the frequency-dependent attenuation in the transmission line, maintaining signal integrity at higher test rates
2Adaptability or versatility
If the physical length of transmission line is increased to connect driver circuit to device under test, then device connectivity is improved, but signal loss increases causing fading and loss of test signals
Solution Approach 1:
The differentiating circuit transforms the signal waveform by emphasizing high-frequency components, changing the spectral parameters of the transmitted signal. This compensation technique counteracts the frequency-dependent loss in long transmission lines, enabling reliable transmission over extended distances
Solution Approach 2:
The circuit applies preliminary anti-action by pre-emphasizing frequencies that will be attenuated during transmission. The differentiating circuit intentionally boosts high-frequency content before transmission to counteract the expected signal loss, effectively compensating for the adverse effects of long transmission lines
Data Source
AI summary
A test apparatus for testing a device under test is provided. The test apparatus includes a test signal generating section for generating a test signal to be provided to the device under test, a driver circuit for providing the test signal to the device under test and a determination section for determining whether is good or bad of the device under test based on the output signal outputted by the device under test according to the test signal. The driver circuit includes a main driver and a sub-driver for outputting drive signals according to the test signal, respectively, a differentiating circuit for outputting a differentiated signal obtained by differentiating the drive signal outputted by the sub-driver and an adding section for providing a signal having the waveform according to the test signal which is obtained by adding the differentiated signal to the drive signal outputted by the main driver to the device under test.