Light Grid Post-Amplifier Current Domain Signal Processing
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Solution Overview
Problem
The existing light grids face challenges with parasitic capacitance issues in their analog line buses, which affect signal processing due to varying lengths and parasitic capacitance values, leading to delayed pulse recognition and increased production costs.
Innovation Solution
The post-amplifier is designed to maintain both inputs at a constant potential, generating an output signal proportional to the current difference, effectively compensating for parasitic capacitance and operating in the current domain, thereby eliminating its impact on signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage evaluation is used with resistors to process differentially amplified received signals, then signal processing is achieved, but parasitic capacitance between line bus lines causes charging/discharging effects that delay pulse recognition and reduce reliability
Solution Approach 1:
The patent changes the evaluation parameter from voltage to current. Instead of measuring voltage differences that are affected by parasitic capacitance charging/discharging, the system directly measures currents from the differential amplifier. This parameter change eliminates the harmful capacitive effects while maintaining signal processing functionality.
Solution Approach 2:
The patent replaces the voltage-based evaluation mechanism (resistors converting current to voltage) with a direct current measurement mechanism. By using a current-to-voltage converter only at the final stage rather than throughout the signal path, the system avoids the harmful effects of parasitic capacitance on voltage signals.
2Adaptability or versatility
If the number of receivers connected in parallel is increased to support more light beams (up to 200), then the light grid can handle more beams, but the line bus becomes longer and parasitic capacitance increases significantly (up to 2.4 nF)
Solution Approach 1:
The patent changes the signal domain from voltage to current for the parallel receiver connections. By summing currents directly at the line bus rather than voltages, the system can accommodate many more parallel receivers without the parasitic capacitance problem that limits voltage-based systems to small numbers of receivers.
3Productivity
If more intelligent signal processing methods are implemented to handle higher frequencies and more light pulses per unit time, then productivity increases, but production costs increase due to more complex components
Solution Approach 1:
The patent changes the operating domain to current, which naturally handles high-frequency signals without the parasitic capacitance limitations of voltage-based systems. This allows high-speed signal processing using simpler, more cost-effective components rather than requiring complex expensive high-speed voltage amplifiers and filters.
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 significantly increases the cut-off frequency, allows for the use of less expensive components, and achieves a high bandwidth, enabling the transmission of shorter pulses at shorter intervals with reduced production costs.
Implementation Method 1
receiving circuits assigned to the receiving elements for differential amplification of the received signals
Implementation Method 2
the post-amplifier is designed in such a way that it generates an output signal proportional to the difference between the currents flowing from the two bus lines into the two post-amplifier inputs and constantly connects the two post-amplifier inputs at the same predetermined potential, so that the parasitic capacitance occurring between the two lines of the line bus is compensated for
Data Source
Figure 1
Figure 2
AI summary
The light grid (10) has optoelectronic receiver elements (18) and receiver circuits (20) assigned to the receiving elements for differential amplification of the received signals. The light grid has a line bus (46) with two lines (Ap,An) and a booster (48) for generating an output signal (54). The booster is so designed that it generates an output signal proportional to the difference of the current flowing from both bus lines in both the booster inlets (50,52). Both the booster inlets are held constant at same predetermined potential.