Distributed Antenna Interface Tray for PIM-Free High-Power BTS Signals
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Solution Overview
Problem
Existing interface systems between base transceiver stations (BTS) and distributed antenna systems (DAS) face issues with high-power signal attenuation, leading to poor call quality due to passive intermodulation (PIM) noise, especially when handling high-power downlink signals.
Innovation Solution
A distributed antenna system interface tray (DIT) that performs gain control and monitoring, separating and adjusting both downlink and uplink signals to prevent PIM, using a combination of cavity duplexers, variable attenuators, and a management system to ensure optimal signal levels and quality across multiple carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high-power attenuator is used to connect DAS to BTS, then the DAS can receive high-power downlink signals from BTS, but passive intermodulation noise deteriorates call quality
Solution Approach 1:
The system segments the signal path by separating downlink and uplink signals through cavity duplexers for each carrier, allowing independent optimization of each path to prevent PIM noise while maintaining high power handling capability
Solution Approach 2:
The patent employs variable attenuators controlled by a management system to dynamically adjust signal levels based on real-time conditions, replacing static high-power attenuators with adaptive components that maintain optimal performance without PIM degradation
2Power
If high-power attenuator is used to attenuate signal level, then DAS is protected from high-power input, but PIM characteristic degrades signal quality
Solution Approach 1:
The cavity duplexer acts as an intermediary component between the high-power attenuator and subsequent circuitry, providing isolation and filtering that prevents PIM noise generation while maintaining the signal level attenuation function
Solution Approach 2:
The system changes the operating parameters by using multiple per-carrier cavity duplexers with specific Q factors and coupling coefficients, transforming the static attenuation approach into a frequency-selective, carrier-specific parameter optimization that eliminates PIM while maintaining signal integrity
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
Enables the connection of high-power BTS signals to DAS without PIM interference, optimizing signal levels for each carrier and improving the efficiency of installation and operation, thereby enhancing call quality and data transmission.
Implementation Method 1
a cavity duplexer (DUP) connected directly to an antenna port of a BTS and configured to separate a DL path and a UL path
Implementation Method 2
a fixed attenuator (F ATT) configured to reduce a level of a high-power DL signal input from the BTS by a designated amount
Implementation Method 3
a DL variable attenuator (DL V ATT) provided on the DL path and configured to adjust a signal to an appropriate level
Implementation Method 4
a combiner configured to combine signals input from multiple per-carrier POIs and transmit a combined signal to the DAS
Implementation Method 5
a fan unit (FU) configured to cool down heat emitted from the DIT and control temperature of the entire system
Data Source
AI summary
A distributed antenna system interface tray (DIT) includes a plurality of per-carrier points of interface (POIs), a combiner, and a DIT management system (DMS). Each of the plurality of POIs may be configured to couple with a corresponding per-carrier base transceiver station (BTS), receive a per-carrier downlink (DL) signal from the corresponding BTS, filter the DL signal through a duplexer, adjust the filtered DL signal based on a designated level, output the filtered DL signal to a combiner, receive an uplink (UL) signal from the combiner, adjust the UL signal based on a designated gain, and transmit the UL signal to the corresponding BTS. The combiner may be configured to combine a plurality of DL signals received from the plurality of POIs into a combined DL signal, transmit the combined DL signal to a distributed antenna system, receive a UL signal from the distributed antenna system, and distribute the UL signal to the plurality of POIs.