Wireless Relay Self-Interference Cancellation via Parasitic Echo
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Solution Overview
Problem
Conventional wireless communication relays face challenges in self-interference cancellation, particularly in small form factor designs with low isolation and adjacent channel operations, where reflections from transmitted signals interfere with receiver antennas, leading to noise and reduced throughput.
Innovation Solution
Incorporating a symmetric self-interference cancellation subsystem that generates a baseband approximation of self-interference, modulates it to the RF domain, and filters it using a band pass filter to extract frequency components overlapping with the receive band, thereby improving signal-to-noise ratio and reducing echo channel self-interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If physical isolation is used to separate transmit and receive antennas, then self-interference is reduced, but device size and complexity increase
Solution Approach 1:
The patent captures the harmful reflected signals using parasitic elements and converts them into useful information for self-interference cancellation. The parasitic elements receive reflected transmit signals that would otherwise be harmful, and this captured energy is processed to generate cancellation signals that subtract from the receive path, transforming the harmful reflection into a beneficial cancellation mechanism.
Solution Approach 2:
The patent introduces parasitic elements as intermediary components between the transmit and receive antennas. These parasitic elements act as mediators that capture reflected signals and transfer this information to the cancellation subsystem, enabling interference reduction without requiring direct physical isolation between transmit and receive paths.
2Object-affected harmful factors
If time division multiplexing is used to share spectrum, then interference is avoided, but throughput is reduced
Solution Approach 1:
The patent enables continuous simultaneous operation of transmit and receive functions by implementing self-interference cancellation. Unlike time division multiplexing that alternates between transmit and receive modes, this system maintains continuous receive operation while transmit occurs, eliminating the throughput penalty of time switching while continuously canceling interference through the parasitic element-based cancellation subsystem.
3Object-affected harmful factors
If RF domain self-interference cancellation is implemented, then cancellation performance is improved, but power consumption and manufacturing cost increase
Solution Approach 1:
The patent creates a copy of the reflected transmit signal path using parasitic elements that replicate the reflection characteristics. These parasitic elements generate a copied version of the interference signal that can be processed at lower frequencies and then subtracted from the receive path, avoiding the need for high-power RF domain processing while maintaining cancellation effectiveness.
Solution Approach 2:
The patent uses simple parasitic elements that are inexpensive to manufacture compared to complex RF domain cancellation hardware. These parasitic elements provide the necessary cancellation functionality through their passive electromagnetic characteristics, eliminating the need for expensive active RF components and reducing both manufacturing cost and power consumption.
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
This approach significantly enhances receive performance by effectively canceling self-interference, reducing noise, and maintaining power efficiency without the need for complex RF domain processing, allowing for deployment in environments with limited isolation.
Implementation Method 1
generates a baseband approximation of self-interference, modulates it to the RF domain
Implementation Method 2
filters it using a band pass filter to extract frequency components overlapping with the receive band
Data Source
AI summary
A wireless communications relay includes a first radio and a second radio operating over adjacent channels. A baseband signal to be transmitted (the “transmit signal”) from the first radio is split along two paths. A first path is delayed by a delay element and the second path is provided as input to a channel model configured to implement a transfer function approximating an echo channel of the local RF environment. The channel model outputs a baseband approximation of echo channel effects of the transmit signal, after which an RF chain modulates the echo channel approximation to the RF domain. This RF echo channel approximation is thereafter filtered by an RF band pass filter turned to an operating channel of the second radio. The filtered signal is thereafter combined with received signal to compensate for self-interference.