Analog RF Interference Cancellation for Full Duplex Systems
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Solution Overview
Problem
Conventional interference cancellation methods in wireless full duplex systems are limited by the dynamic range of ADC/DAC, making it difficult to effectively cancel the second-type self-interference component, which has a power 60 dB higher than the wanted signal.
Innovation Solution
An interference cancellation apparatus and method that uses a radio frequency reference signal to cancel the first-type self-interference component and a reconstructed self-interference signal, estimated through self-interference channel parameters, to cancel the second-type self-interference component directly in the analog domain, avoiding the limitations of ADC/DAC dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional digital baseband self-interference cancellation is used, then the system can operate in full duplex mode, but the cancellation performance is limited by the ADC/DAC dynamic range of about 60 dB
Solution Approach 1:
The patent segments the self-interference cancellation into two distinct parts: first-type self-interference cancellation handled by conventional digital baseband methods, and second-type self-interference cancellation handled by a new analog RF reconstruction method. This segmentation allows each method to address its specific interference type optimally, with the analog method handling the high-power second-type interference that exceeds ADC/DAC dynamic range.
Solution Approach 2:
The patent introduces an intermediate analog processing stage between the RF receiver and the digital baseband processor. A self-interference signal generator reconstructs the second-type self-interference signal in analog form at RF frequencies, and this reconstructed signal is subtracted from the received signal before ADC conversion. This intermediary analog cancellation stage prevents the high-power interference from saturating the ADC, enabling subsequent digital processing to effectively handle the remaining first-type interference.
2Ease of manufacture
If digital baseband self-interference cancellation is used, then implementation is simplified, but it cannot effectively cancel the second-type self-interference component with power 60 dB higher than the wanted signal
Solution Approach 1:
The patent applies preliminary action by canceling the second-type self-interference component in the analog domain before the signal enters the digital baseband processor. The self-interference signal generator uses channel state information to reconstruct and subtract the high-power second-type interference from the received signal at RF frequencies, prior to ADC conversion. This preliminary analog cancellation removes the problematic interference component that would otherwise overwhelm the digital processor and prevent effective cancellation of the remaining first-type interference.
3Productivity
If wireless full duplex technology is implemented, then spectral efficiency is doubled, but self-interference from transmit signal to receive signal must be avoided or canceled
Solution Approach 1:
The patent converts the harmful self-interference signal into a beneficial cancellation mechanism. By using channel state information and a self-interference signal generator, the system reconstructs the second-type self-interference signal and subtracts it from the received signal. This transforms the originally harmful high-power interference into a controlled cancellation process, enabling full duplex operation where transmit and receive occur simultaneously on the same frequency without mutual interference.
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AI summary
Embodiments of the present invention relate to the field of communications technologies, and provide an interference cancellation apparatus and method, which can avoid being limited by a dynamic range of an ADC/DAC and can cancel a second-type self-interference component effectively. The method includes: acquiring a radio frequency reference signal; receiving a radio frequency receive signal by using a main receive antenna; canceling a first-type self-interference component in the radio frequency receive signal according to the radio frequency reference signal, to generate a first processed signal; acquiring the reconstructed self-interference signal according to a self-interference channel parameter and the radio frequency reference signal; canceling a second-type self-interference signal in the first processed signal according to the reconstructed self-interference signal to generate a second processed signal; performing down-conversion processing on the second processed signal to generate a third processed signal; performing analog to digital conversion on the third processed signal to generate a digital signal; and acquiring a digital baseband reference signal, and performing self-interference channel estimation according to the digital baseband reference signal and the digital signal to acquire the self-interference channel parameter. The present invention is used for interference cancellation.