Monobit Cross-Spectral SIC Circuit for Antenna Self-Interference
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Solution Overview
Problem
Wideband RF systems face challenges in simultaneously transmitting and receiving radio signals due to self-interference, which can damage receivers and obscure low-power signals of interest, particularly in small form factor platforms with close antennas and complex multipath scenarios.
Innovation Solution
A self-interference cancellation (SIC) circuit using a cross power spectral density measurement system with a 1-bit cross-correlator to estimate signal similarity and generate a cancellation signal, controlled by an FPGA-based software model to adjust phase and amplitude, reducing the need for numerous components and enabling efficient cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-power transmit signals are used, then transmission power is improved, but self-interference increases causing receiver damage or saturation
Solution Approach 1:
The patent applies preliminary anti-action by generating a cancellation signal that is the inverse of the self-interference signal before it reaches the receiver. The cancellation signal is created by sampling the transmit signal, processing it through a cancellation circuit with adjustable phase and amplitude, and subtracting it from the received signal, thereby preemptively neutralizing the harmful self-interference effect.
Solution Approach 2:
The patent uses an intermediary approach by introducing a cancellation signal as a mediator between the transmit signal and the receiver. This cancellation signal acts as an intermediate element that counteracts the self-interference, allowing the receiver to process the desired signal without being overwhelmed by the high-power transmit signal leakage.
2Volume of moving object
If spatial isolation between antennas is reduced to save space, then device size is improved, but self-interference increases obscuring low-power signals
Solution Approach 1:
The patent applies copying by creating a replica of the self-interference signal through the cancellation circuit. By sampling the transmit signal and generating a corresponding cancellation signal that mirrors the characteristics of the self-interference, the system can accurately replicate and neutralize the interference without requiring physical separation between antennas.
3Object-affected harmful factors
If traditional SIC circuits are used, then self-interference cancellation is achieved, but device complexity increases due to numerous components required for multipath scenarios
Solution Approach 1:
The patent applies dynamics by making the cancellation circuit adjustable and adaptive. The phase and amplitude of the cancellation signal can be dynamically modified to match varying self-interference conditions, including multipath scenarios. This dynamic adjustment capability allows a single circuit to handle multiple interference patterns without requiring numerous fixed components for each scenario.
Solution Approach 2:
The patent implements universality by designing a cancellation circuit that can handle multiple types of self-interference scenarios through a single unified approach. The circuit can process direct coupling, reflected signals, and multipath interference using the same fundamental mechanism, eliminating the need for separate dedicated circuits for each interference type.
Data Source
AI summary
Techniques are disclosed for self-interference signal cancellation. A self-interference cancellation method includes measuring an error between an output of a hardware cancellation circuit and an output of a software model of the hardware cancellation circuit. The method further includes estimating an amplitude error, a phase error, and a delay error based on the measured error and the output of the hardware cancellation circuit, and locating a largest frequency domain error peak in the measured error. The method further includes applying an all-pass filter to the estimated and measured signals at the peak error frequency to produce a filtered estimated signal and a filtered measured signal and optimizing the filtered estimated signal and the filtered measured signal to obtain an optimized canceller setting. The optimized canceller setting is provided to the hardware cancellation circuit.