ODU XPIC System I/Q Mismatch Compensation
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Solution Overview
Problem
Conventional all outdoor unit (ODU) microwave backhaul systems face challenges in high capacity communications due to I/Q mismatches, noise floors, and increased power consumption, particularly with the transition from superheterodyne to direct conversion architectures, which can lead to operational limitations at high quadrature amplitude modulation (QAM) levels.
Innovation Solution
Implementing a dual channel all ODU microwave backhaul system with a direct conversion architecture and cross polarization interference cancellation (XPIC) using interconnects like Ethernet or IF cables to share and cancel out noise between ODUs, reducing I/Q mismatches and enabling higher capacity communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct conversion architecture is used in all ODU configurations, then device complexity and power consumption are reduced, but I/Q mismatches and noise floors increase
Solution Approach 1:
The patent combines multiple ODUs into a coordinated system where I/Q mismatch compensation is performed across ODU pairs. By merging the processing capabilities and sharing calibration data between ODUs, the system achieves better signal quality while maintaining the simplicity of direct conversion architecture in each individual ODU.
Solution Approach 2:
The patent implements feedback mechanisms where I/Q mismatch parameters are measured and compensated through coordinated processing between ODU pairs. The system continuously monitors and adjusts for I/Q mismatches, noise floors, and group delays by exchanging calibration information between paired ODUs, thereby maintaining signal quality without increasing individual ODU complexity.
2Productivity
If multiple all ODU receivers are used for high capacity communications, then communication capacity increases, but I/Q mismatches and noise floors worsen
Solution Approach 1:
The patent merges multiple ODU receivers into coordinated pairs that perform joint signal processing. By combining the received signals from both ODUs in the pair and applying I/Q mismatch compensation algorithms, the system achieves high communication capacity while maintaining signal quality through diversified reception paths.
Solution Approach 2:
The patent uses paired ODUs where each ODU in the pair performs similar functions but with complementary signal processing. The calibration and compensation mechanisms create a form of redundancy where each ODU copy can verify and correct the other's signal processing, thereby maintaining quality while increasing capacity.
3Reliability
If I/Q mismatch compensation is performed, then signal quality improves, but device complexity increases
Solution Approach 1:
The patent segments the I/Q mismatch compensation process into distinct calibration and execution phases. During initial calibration, mismatch parameters are measured and stored. During normal operation, these pre-determined parameters are applied without requiring real-time complex processing, thereby improving signal quality while minimizing ongoing processing complexity.
Solution Approach 2:
The patent performs I/Q mismatch calibration and compensation parameter determination in advance before actual signal reception. By pre-characterizing the I/Q mismatches, group delays, and noise floors of each ODU pair during calibration, the system eliminates the need for complex real-time compensation processing during high-capacity communication operations.
Data Source
AI summary
An all outdoor unit communication system, for performing cross polarization interference cancellation, is provided. The system includes a first outdoor unit (ODU) configured to receive a first directionally polarized signal, a first RF module configured to convert the first directionally polarized signal into a first in-phase (I) component and a first quadrature (Q) component, and a first modem configured to up-convert the first I and Q components from baseband into a first directionally polarized intermediate frequency (IF) signal. The system being configured to communicate, via an interconnect coupled to the first ODU, a second directionally polarized IF signal to the first ODU, and where the first modem is further configured to utilize the second directionally polarized IF signal to cancel out at least a portion of a first cross-polarization leakage at the first ODU.