Configurable Antenna System for Positive Train Control Fading
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Solution Overview
Problem
In wireless Positive Train Control systems, fast fading and weather/vandalism-induced antenna damage lead to communication link interruptions, with existing solutions like block-based channel coding and multiple parallel receivers either requiring large memory or increasing system cost.
Innovation Solution
A configurable multiple antenna system with a first and second antenna, connected through electrical paths with zero loss, and control circuits that allow switching between transmit, primary receive, and secondary receive modes, enabling the use of a TX antenna as a secondary RX antenna during deep fading without additional cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If block-based channel coding is used to correct burst errors, then error correction capability is improved, but block size must be large which increases latency and memory requirements
Solution Approach 1:
The system dynamically switches between different receive antennas based on signal quality conditions. When deep fading is detected on the primary antenna, the receiver transitions to using the secondary antenna, allowing adaptive response to changing channel conditions without requiring large fixed-size error correction blocks
Solution Approach 2:
The patent divides the receive antenna resources into primary and secondary paths, allowing the system to process smaller data blocks with reduced latency while maintaining error correction capability through antenna diversity rather than relying on large block-based forward error correction
2Reliability
If multiple parallel receivers are used to overcome deep fading, then reliability is improved, but system cost increases
Solution Approach 1:
The secondary antenna and its associated circuitry are designed to serve dual purposes: acting as a backup receive path during deep fading events and providing diversity reception to improve overall system reliability, rather than requiring completely separate parallel receiver systems
Solution Approach 2:
The patent combines the primary and secondary receive paths into a unified receiver architecture with switching capability, merging resources to achieve reliability improvement without the full cost of completely separate parallel receiver systems
3Reliability
If dual antennas are used with antenna splitter to overcome performance problems, then reliability is improved, but impedance matching issues cause performance degradation
Solution Approach 1:
The patent introduces specially designed coupling circuits as intermediary components between the antennas and the receiver, providing impedance transformation and matching functionality that eliminates the performance degradation caused by simple antenna splitters while maintaining service continuity
Data Source
AI summary
A configurable antenna arrangement is disclosed for wireless Positive Train Control system to overcome the deep fading and fast fading issue. The radio channel between a locomotive on-board radio unit and a base station is subject to fast and deep fading. The channel changes rapidly in a short time comparing to the length of the packet. The invention uses a TX antenna and a RX antenna in a time division multiple access (TDMA) radio system associated with control circuits to provide a configurable antenna sub-system. The antenna sub-system is configurable to provide a TX mode, a primary RX mode and a secondary RX mode. In both the TX mode and the primary RX mode, there is substantially no insertion loss. In the secondary RX mode, the TX antenna is used as the secondary RX antenna to overcome fading caused by Doppler shift.