RF Mixer Spurious Signal Cancellation via Baseband Compensation
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Solution Overview
Problem
Radio frequency (RF) transmitters often generate spurious signal replicas due to imperfect devices like RF mixers, leading to spurious signal interference and degradation of transmission signal quality.
Innovation Solution
A method and system for cancelling spurious signals in RF transmitters by measuring RF spurious signals, generating baseband compensation signals based on these measurements, and modifying the baseband signal to be fed back into the RF mixer for upconversion, thereby eliminating the spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If RF mixers are used for frequency translation, then carrier signal upconversion is achieved, but spurious signal replicas are generated causing interference
Solution Approach 1:
The patent measures the spurious signals generated by the RF mixer and creates compensation signals that replicate the spurious components. By subtracting these compensation signals from the baseband signal, the harmful spurious replicas are cancelled at the output, converting the harmful effect into a controllable and eliminable artifact
Solution Approach 2:
The system implements a feedback mechanism where spurious signals are measured at the RF mixer output, processed to generate compensation signals, and fed back to the baseband input. This closed-loop feedback continuously cancels spurious components, maintaining signal quality despite mixer imperfections
2Manufacturing precision
If spurious signal cancellation is implemented, then transmission signal quality is improved, but device complexity increases
Solution Approach 1:
The patent introduces intermediate processing stages including spurious signal measurement circuits, compensation signal generation circuits, and signal combination circuits. These intermediary components facilitate the cancellation process by breaking down the complex task into manageable stages, making the overall system more implementable despite increased complexity
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 effectively cancels spurious signals, improving transmission signal quality and facilitating efficient high-speed wireless communication by mitigating interference caused by undesired signal replicas.
Implementation Method 1
RF mixers, which are used for frequency translation. For instance, in addition to up-converting a frequency of an input baseband signal to a desired carrier frequency
Implementation Method 2
the RF mixer may generate one or more spurious signal replicas across undesired carrier frequencies or tones
Implementation Method 3
A baseband compensation signal is generated based on the RF spurious signal, and a modified baseband signal is generated by subtracting the baseband compensation signal from a first baseband signal
Data Source
AI summary
Spurious signals are cancelled in a radio frequency (RF) transmitter. According to one method, a first baseband signal is fed into a first input port of an RF mixer of the RF transmitter, a carrier signal is fed into a second input port of the RF mixer, and an RF spurious signal is measured at an output port of the RF mixer. A baseband compensation signal is generated based on the first baseband signal and the RF spurious signal, and a modified baseband signal is generated by subtracting the baseband compensation signal from the first baseband signal. The modified baseband signal, instead of the first baseband signal, is fed into the first input port of the RF mixer.