Current-Loop Signal Transmission for Long-Distance Low-Power Data
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Solution Overview
Problem
Existing signal transmission systems, particularly those conforming to the ANSI/TIA/EIA-644-1995 standard, are limited to transmission distances of a few meters due to power constraints, making it difficult to transmit digital data at high rates over longer distances while maintaining low power consumption.
Innovation Solution
A signal transmission system with a balanced and/or shielded signal cable, a transmitter circuit, and a receiver circuit with hysteresis, allowing for current loops with adjustable current intensities and directions to maintain voltage levels across a terminating resistor, enabling transmission over distances exceeding 30 meters with power consumption below 10 mW.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the transmission distance is extended beyond a few meters, then the operational range is improved, but the power consumption increases beyond the available power constraints
Solution Approach 1:
The transmitter circuit alternates between an active state with first current intensity for signal transmission and a low-power state with second current intensity for power saving. This periodic switching enables extended transmission distance while maintaining average power consumption within available power constraints
Solution Approach 2:
The transmitter circuit dynamically adjusts its current intensity based on operational requirements, switching between high current for active transmission and low current for power saving. This dynamic adaptation resolves the contradiction between transmission distance and power consumption
2Reliability
If the current intensity is increased to maintain voltage levels over long distances, then the signal quality is improved, but the power consumption exceeds the available power
Solution Approach 1:
The system uses periodic switching between high current intensity for signal quality and low current intensity for power saving. The transmitter activates with first current intensity only when signal transmission is required, then switches to second current intensity to conserve power, maintaining signal quality during active periods while staying within power constraints on average
3Length of stationary object
If the transmission distance is extended to more than 30 meters, then the operational range is improved, but the available power is insufficient to maintain signal levels
Solution Approach 1:
The transmitter circuit implements periodic operation with active transmission phases at first current intensity followed by low-power phases at second current intensity. This enables signal transmission over distances exceeding 30 meters during active phases while keeping average power consumption within the available power budget
Solution Approach 2:
The system changes the current intensity parameter dynamically, switching between first current intensity for extended range transmission and second current intensity for power conservation. This parameter modulation enables operation beyond 30 meters with limited available power
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
The system enables reliable digital data transmission at rates over 500 kbit/s over distances of more than 30 meters with reduced power consumption, enhancing the operational range and efficiency of industrial measurement and automation systems.
Implementation Method 1
a voltage which is proportional to the current strength and whose polarity depends on the current direction drops across the terminating resistor
Implementation Method 2
The receiver circuit has a hysteresis in such a manner that an output voltage having a first voltage level continues to have the first voltage level even with an input voltage with a voltage level falling below the first switching voltage threshold value
Data Source
AI summary
The signal transmission system comprises a transmitter circuit, a receiver circuit and a signal cable. A current divider is formed by a terminating resistor between the signal conductors of the signal cable. The transmitter circuit drives a loop current. When the receiver circuit input voltage has a voltage level above a first switching voltage threshold value, the output voltage assumes a first voltage level. The output voltage maintains the first voltage level when the input voltage is below the first switching voltage threshold value but above a second switching voltage threshold value. The transmitter circuit is configured to modulate the loop current with at least two different non-zero magnitudes at successive times. The first magnitude is greater than a first switching current threshold value and the second magnitude is less than the first switching current threshold value and greater than a second switching current threshold value.