Transmitter Interference Mitigation via Offset Local Oscillator
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Solution Overview
Problem
Existing radio transmission systems face interference issues due to spurious signals, particularly intermodulation spurs, which can exceed desired energy levels and interfere with other devices, and reducing transmitted power to mitigate this problem reduces the range of the desired signal.
Innovation Solution
A method and apparatus that generate an offset local oscillator signal and configured information signal, using a spurious mitigation offset to shift spurious frequencies away from receive frequency ranges, allowing simultaneous transmission without reducing transmit power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If transmitted power is reduced to mitigate spurious signals, then interference with other devices is reduced, but the range of the desired signal is reduced
Solution Approach 1:
The patent changes the frequency parameter of the transmitted signal by applying frequency offset techniques. This shifts the spurious signals to different frequency locations where they do not interfere with other devices, while maintaining the original transmit power level and thus preserving the desired signal range.
Solution Approach 2:
The patent addresses the interference problem by moving from the time/power domain to the frequency domain. Instead of reducing power in the time domain, the solution operates in the frequency domain by applying frequency offsets and using frequency selective filtering to separate desired signals from spurious signals.
2Object-affected harmful factors
If frequency offset is applied to move spurious signals away from receive frequency ranges, then interference is mitigated, but device complexity increases
Solution Approach 1:
The patent applies frequency offset in advance during the signal generation stage, before transmission. This preliminary frequency shifting prevents spurious signals from falling into receive frequency ranges in the first place, eliminating the need for complex real-time interference cancellation systems.
Solution Approach 2:
The patent introduces frequency offset as an intermediary parameter that mediates between the transmit signal and the receive frequency ranges. This intermediary frequency shift acts as a buffer that separates the desired signal from potential interference without requiring direct manipulation of the interfering 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
Effectively mitigates spurious frequencies without reducing transmit power by moving them outside the receive frequency ranges of other devices, enabling multiple devices to transmit simultaneously within the same channel without interference.
Implementation Method 1
The offset local oscillator signal and the configured offset information signal are combined using a mixing technique
Data Source
AI summary
A method and apparatus mitigates spurious transmissions. An offset local oscillator signal is generated that is at a frequency that is offset from a nominal transmit channel carrier frequency by a spurious mitigation offset. An information signal is generated that comprises a series of modulation symbols and has a transmission bandwidth at baseband. A configured offset information signal is generated from the information signal, wherein the spectrum of the configured offset information signal is offset from DC by a channel configuration offset, and is further offset by a negative of the spurious mitigation offset. The offset local oscillator signal and the configured offset information signal are combined using a mixing technique. The spurious mitigation offset is zero when a spurious condition does not exist and is non-zero when the spurious condition does exist.