RF Transceiver Cancellation for Simultaneous Spectrum Sensing
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Solution Overview
Problem
Conventional dynamic spectrum access systems face interference issues due to the inability to simultaneously transmit and sense the electromagnetic environment, leading to stale or inaccurate channel information, which can result in collisions and inefficient resource utilization.
Innovation Solution
The implementation of a multi-stage transmit signal cancellation approach using both analog and digital cancellation methods, allowing for simultaneous RF signal transmission and spectrum monitoring in a common frequency band, maintaining receiver linearity and enabling full-duplex operation in cognitive radio systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If spectral sensing and signal transmission are performed simultaneously from a common platform, then fresh channel information is available during transmission and system awareness is enhanced, but the transmitted RF signal leaks into the receiver front end and interferes with signal reception, significantly disrupting sensing accuracy
Solution Approach 1:
The patent extracts and removes the harmful transmit signal component from the received signal using analog RF cancellation circuitry. A cancellation signal is generated that mirrors the transmitted signal and is subtracted from the received signal, effectively taking out the self-interference before it corrupts the sensing information.
Solution Approach 2:
The patent introduces an intermediary cancellation signal that acts as a mediator between the transmitted signal and the received signal. This cancellation signal is generated through analog circuitry that replicates the transmit signal characteristics and is used to neutralize the harmful leakage, enabling simultaneous transmission and sensing.
2Measurement precision
If sensing is performed during idle periods when the RF transmitter is not transmitting, then receiver linearity is maintained and sensing accuracy is preserved, but channel information becomes stale after transmission periods and complex protocols are required to ensure fresh information availability
Solution Approach 1:
The patent enables continuous spectral sensing operation by removing the constraint that sensing must occur only during idle periods. Through analog RF cancellation, the system maintains continuous awareness of the electromagnetic environment, eliminating gaps in channel information and making the useful action of sensing continuous rather than intermittent.
3Stability of the object's composition
If the magnitude of the RF receive signal is reduced to maintain receiver linearity, then the receiver operates in a linear region enabling accurate signal processing, but the signal level becomes very low requiring sophisticated cancellation techniques
Solution Approach 1:
The patent applies preliminary action by performing analog RF cancellation before the signal enters the main receiver processing chain. By removing the dominant transmit signal component in advance, the receiver operates on a much lower residual signal level, maintaining linearity throughout the processing chain and enabling accurate detection of weak spectral signals.
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 solution ensures fresh and accurate channel information is available during transmission, enhancing system awareness and improving spectrum utilization efficiency by reducing interference and maintaining linear receiver operation.
Implementation Method 1
performing analog radio frequency (RF) cancellation to reduce a level of the RF multicarrier transmit signal component of the composite receive signal
Implementation Method 2
performing digital cancellation on the processed receive signal to remove remnants of the RF transmit signal therefrom
Data Source
AI summary
A multicarrier radio frequency (RF) transceiver implementing dynamic spectrum access (DSA) is capable of sensing a spectral environment and transmitting an RF signal at the same time. The transceiver can cancel an RF transmit signal component within a composite receive signal using a combination of analog and digital cancellation. In one embodiment, analog RF cancellation is performed to reduce the level of a transmit signal component of a composite receive signal before the signal reaches an RF receiver. The RF cancellation may be used to reduce the transmit signal component to a level that maintains the linear operation of the RF receiver. Digital cancellation may be performed to reduce transmit signal remnants within an output signal of the RF receiver. Digital cancellation may be performed on a subcarrier-by-subcarrier basis in some implementations.