Railway Track Circuit Using PN Code Spread Spectrum
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Solution Overview
Problem
Conventional track circuit apparatuses for railways face challenges in maintaining communication reliability due to signal interference, fading, and noise from adjacent block sections, which complicates error correction and data encryption, leading to high costs and difficulties in ensuring data integrity.
Innovation Solution
A track circuit apparatus that uses a ground-based transmitter to digitally modulate data with a common carrier frequency and assigns different pseudo random noise (PN) codes to adjacent block sections, enabling reliable data transmission and reception through direct-sequence spread-spectrum processing, and includes error correction and encryption processors to ensure data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional track circuit apparatus uses audio frequency modulation for data transmission between block sections, then data communication can be established, but signal interference, fading, and noise from adjacent block sections occur leading to poor communication reliability
Solution Approach 1:
The patent replaces the conventional audio frequency modulation system with a spread spectrum communication system using pseudo-random noise codes. This substitution transforms the communication method from narrowband FM to wideband direct-sequence spread spectrum, fundamentally changing how data is transmitted and making it resistant to interference, fading, and noise that plague conventional systems.
Solution Approach 2:
The patent changes key communication parameters by assigning different pseudo-random noise codes to different block sections and using a common carrier frequency for all sections. This parameter change enables the system to distinguish between signals from different block sections while maintaining resistance to interference and noise, directly improving communication reliability.
2Object-affected harmful factors
If conventional track circuit apparatus uses multiple carrier frequencies for adjacent block sections to prevent interference, then signal interference between block sections is reduced, but device complexity and cost increase due to requiring multiple transmitters and receivers
Solution Approach 1:
The patent makes the carrier frequency universal across all block sections by using a common carrier frequency for data transmission. The distinction between different block sections is achieved not through different frequencies but through unique pseudo-random noise codes assigned to each section, thereby reducing device complexity while preventing interference.
Solution Approach 2:
The patent introduces pseudo-random noise codes as an intermediary element that mediates between the common carrier frequency and the need to distinguish different block sections. These codes act as unique identifiers for each block section while allowing all sections to operate on the same frequency, thereby reducing the number of transmitters and receivers needed.
3Loss of information
If conventional track circuit apparatus uses FM modulation for data transmission, then data can be transmitted between ground-based and on-train controllers, but error correction and data encryption become complex and costly
Solution Approach 1:
The patent substitutes the conventional FM modulation system with direct-sequence spread spectrum modulation using pseudo-random noise codes. This substitution inherently provides better resistance to errors and interference, simplifying the requirements for error correction and encryption systems while maintaining data integrity.
Solution Approach 2:
The patent changes the modulation approach from FM to direct-sequence spread spectrum, which fundamentally alters how data is encoded and transmitted. This parameter change makes the system inherently more robust against errors and interference, reducing the complexity of error correction mechanisms needed to maintain data integrity.
Data Source
AI summary
A track circuit apparatus for a train, the track circuit apparatus includes: a ground-based transmitter that is installed corresponding to each of a plurality of block sections divided from a track circuit formed by rails, digitally modulates transmission data by a carrier frequency predetermined and common for each of the block sections, assigns different pseudo random noise (PN) codes to adjacent block sections, and modulates and transmits the data; and a ground-based receiver or an on-train receiver that demodulates received data corresponding to a block section based on the carrier frequency of one of reception signals received from the block section and the PN code assigned to the block section.