Receiver Sensitivity via PIM Reference Signal Cancellation
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Solution Overview
Problem
Receiver sensitivity in communication systems is compromised by transmitter-induced passive intermodulation products (PIM) due to the parallel operation of receiver and transmitter systems, which conventional filter techniques cannot effectively address, especially in broadband multicarrier FDD systems.
Innovation Solution
A method and apparatus that generate a reference signal to cancel PIM distortions by modeling and subtracting the intermodulation effects from the received signal, using non-linear filtering and feedback mechanisms to improve receiver sensitivity, applicable to both hardware and software solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transmitter and receiver operate in parallel in broadband multicarrier FDD systems, then system functionality and bandwidth are improved, but receiver sensitivity deteriorates due to transmitter-induced passive intermodulation products
Solution Approach 1:
The patent captures the harmful PIM distortion signal and uses it as a reference input to a non-linear model. By feeding the PIM signal itself into the model, the system generates an accurate reproduction of the distortion that can then be subtracted from the received signal, effectively converting the harmful distortion into a useful reference for cancellation.
Solution Approach 2:
The patent introduces a non-linear model as an intermediary component between the PIM distortion source and the received signal. This model acts as a mediator that processes the captured PIM signal and generates a compensated version that can be subtracted from the main received signal, enabling clean separation of the desired signal from the distortion.
2Ease of manufacture
If conventional filter techniques are used to remove PIM distortions, then implementation simplicity is maintained, but effectiveness deteriorates because PIM products fall within the receive band
Solution Approach 1:
The patent replaces conventional mechanical/electronic filter techniques with a signal processing approach using non-linear modeling and digital subtraction. Instead of using physical filters that cannot distinguish in-band PIM from desired signals, the system uses computational methods to identify and remove distortions based on their non-linear relationship with the transmitted signal.
Solution Approach 2:
The patent changes the approach from frequency-based filtering to parameter-based distortion characterization. By modeling the non-linear parameters that define PIM generation and applying these same parameters to the captured transmitted signal, the system generates a distortion model that accurately reflects the actual PIM present in the received signal for precise removal.
3Reliability
If non-linear modeling and reference signal generation are implemented, then receiver sensitivity is improved by canceling PIM distortions, but device complexity increases
Solution Approach 1:
The patent performs preliminary action by capturing and storing the transmitted signal before it is modulated and amplified, and by pre-characterizing the non-linear parameters of the system. This advance preparation allows the non-linear model to be built beforehand, enabling real-time PIM cancellation without requiring complex real-time analysis of the distortion mechanism during signal reception.
Solution Approach 2:
The patent creates a simplified copy or model of the complex non-linear PIM distortion process. By developing a non-linear model that replicates the distortion characteristics using captured transmitted signals and characterized parameters, the system produces an accurate replica of the PIM distortion that can be subtracted without needing to implement the full complexity of the actual distortion-generating hardware.
Data Source
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AI summary
A method comprising capturing a signaling on a transmission path conveying a signal to be transmitted and on a reception path conveying a signal being received, setting model parameters related to a distortion effect on the basis of the captured signaling, the distortion effect being caused by the signal to be transmitted on the signal being received due to passive intermodulation between the transmission path and the reception path, generating a reference signal being related to a predetermined frequency spectrum part used by the signal being received by applying the model parameters on a captured signaling on the transmission path, and correcting the signal being received by using the generated reference signal.