Manchester-Coded Signal Transmission for DC Offset-Free Data Detection
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Solution Overview
Problem
Conventional signal transmission systems experience DC offset in PWM signals due to varying pulse widths, leading to malfunction in data detection and incorrect data reception.
Innovation Solution
A signal transmission system utilizing a modulation signal generating unit that produces Manchester codes with a 50% duty ratio, combined with a clock generating unit that introduces a delay, ensuring the modulation signal remains free of DC offset and allowing accurate data detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pulse width modulation is used to transmit data, then data transmission capability is improved, but DC offset occurs in the received signal causing detection malfunction
Solution Approach 1:
The patent changes the modulation method from pulse width modulation to Manchester code modulation with fixed 50% duty ratio. This parameter change ensures that the modulation signal maintains a constant average level regardless of data content, eliminating DC offset while preserving data transmission capability through the inherent transition properties of Manchester encoding
Solution Approach 2:
The patent converts the potential harm of fixed duty ratio limitation into a benefit by using Manchester code's mandatory transitions at bit boundaries. These transitions, which might seem restrictive, actually provide automatic clock recovery and eliminate DC offset simultaneously, turning a constraint into a solution for both synchronization and DC offset elimination
2Object-generated harmful factors
If Manchester code with fixed duty ratio is used, then DC offset is eliminated, but compatibility with conventional PWM-based systems is reduced
Solution Approach 1:
The patent changes the fundamental modulation parameter from variable pulse width to fixed 50% duty ratio Manchester code. This parameter change eliminates DC offset by ensuring equal high and low time proportions in each bit period, while the self-synchronizing transitions of Manchester code maintain compatibility with standard digital communication interfaces and receivers
3Adaptability or versatility
If variable pulse width is used for data encoding, then data representation flexibility is improved, but signal stability deteriorates due to DC offset
Solution Approach 1:
The patent changes the encoding approach from variable pulse width to fixed width Manchester transitions. Data is represented by the pattern of transitions rather than pulse duration, maintaining data representation flexibility through the two-state nature of Manchester encoding (rising edge for 0, falling edge for 1) while achieving signal stability through constant duty ratio
Solution Approach 2:
The patent employs periodic transitions at regular intervals corresponding to bit periods in Manchester encoding. This periodic structure ensures that transitions occur at predictable intervals regardless of data content, providing signal stability and enabling easy synchronization while still encoding variable data through the direction and pattern of these periodic transitions
Data Source
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AI summary
A signal transmission system has a modulation signal converter 1 that generates a modulation signal using a Manchester code with a duty ratio of 50% in accordance with transmission data; a clock generator 6 that generates a clock with the amount of delay with respect to the rising or falling edge of the modulation signal; and a data detector 5 that generates received data by sampling the modulation signal in synchronization with the clock. Since the modulation signal converter 1 generates the modulation signal by combining the Manchester code with the duty ratio of 50%, its duty ratio is always 50% independently of the transmission data, thereby preventing the DC offset of the modulation signal on the receiving side. Accordingly, it offers an advantage of achieving good communication quality with a simple circuit configuration without producing the DC offset in the modulation signal on the receiving side.