Cross-phase Noise Compensation in Dual Polarized Microwave Transceivers
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Solution Overview
Problem
Dual polarized microwave transceivers face significant cross-polarization interference due to frequency offset and phase noise from independently operated local oscillators, which complicates communication link performance and reduces channel capacity.
Innovation Solution
A method for cross-phase noise compensation is implemented by receiving pilot symbols and estimating cross-phase noise to determine a compensation factor, which is then applied to the signal to mitigate interference, allowing independent operation of transmitters without synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If independent local oscillators are used in dual polarized transceivers, then device complexity and synchronization requirements are reduced, but cross-phase interference and phase noise between polarizations increase
Solution Approach 1:
The patent converts the harmful cross-phase interference into a measurable parameter by using pilot symbols to estimate the interference characteristics. The system then uses this estimated interference information to compensate and cancel the cross-phase noise, transforming the harmful effect into a manageable parameter that can be corrected through signal processing.
Solution Approach 2:
The patent implements a feedback mechanism where the receiver estimates cross-phase interference from received pilot symbols and feeds this information back to compensate for the interference. This closed-loop approach continuously monitors and corrects the cross-phase noise, allowing independent oscillators to operate without degrading system performance.
2Productivity
If separate transmitters with independent local oscillators are used for orthogonal polarizations, then channel capacity is doubled, but frequency offset and phase noise between channels increase
Solution Approach 1:
The patent introduces pilot symbols as an intermediary element that mediates between the independent transmitters and the receiver. These known reference symbols allow the receiver to estimate and measure the frequency offset and phase noise between channels, providing the information needed to compensate for these impairments and maintain signal quality.
Solution Approach 2:
The patent changes the approach from attempting to maintain constant phase relationships to dynamically estimating and compensating for phase variations. By using pilot symbols to continuously measure and correct phase noise and frequency offset, the system adapts to the actual conditions rather than relying on perfect synchronization.
3Reliability
If cross-phase noise compensation is implemented, then signal quality and error rates improve, but processing complexity and computational requirements increase
Solution Approach 1:
The patent applies partial compensation by focusing on compensating for cross-phase interference using only the essential pilot symbol information. Rather than attempting to correct all possible signal impairments, the system selectively addresses the dominant cross-phase noise component, achieving significant improvement with moderate processing complexity.
Data Source
AI summary
Cross-phase interference occurs in dual polarized or orthogonal polarized microwave links when independent local oscillators (LOs) are utilized in each outdoor unit (ODU) transceiver operating on the same frequency channel. If the cross-phase noise is not compensated the performance of the microwave link will be degraded. In order to reduce cross-phase noise two or more pilot symbols are utilized to enable cross-phase noise estimates to be determined at the receiver of the microwave link. The pilot symbols enable a cross-phase noise compensation factor to be determined for the signal from the one or more cross-phase noise estimates. The received signal can then be compensated using the estimated cross-phase noise compensation factor.