Signal Processing Circuit for Dynamic DC Offset Cancellation
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Solution Overview
Problem
Conventional signal processing units in direct conversion receivers face challenges in effectively addressing dynamic DC offset variations without losing the desired signal component, leading to issues with signal transmission and bit error rate degradation.
Innovation Solution
A signal processing unit with a high-pass filter (HPF) and a DC offset canceling loop that includes a determination element and switches to connect the output node to a power supply circuit when the signal voltage falls out of a predetermined threshold range, allowing for dynamic cancellation of DC offset while preserving the desired signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a high-pass filter is used to remove DC offset, then DC offset is reduced, but the desired signal component may be lost
Solution Approach 1:
The patent applies dynamics by making the high-pass filter's time constant variable rather than fixed. The control unit adjusts the time constant based on the detected DC offset amount, allowing the filter to adapt its characteristics dynamically. This resolves the contradiction by enabling the filter to be aggressive when DC offset is high while being gentle when the desired signal is present, thus removing DC offset effectively without losing the desired signal component.
2Power
If the gain of LNA is increased to amplify the desired signal, then signal intensity is improved, but dynamic DC offset increases
Solution Approach 1:
The patent implements feedback by having the control unit continuously detect the DC offset amount in the output signal and use this information to adjust the high-pass filter's time constant. This closed-loop feedback mechanism allows the system to compensate for the increased DC offset that results from higher LNA gain, thus maintaining signal intensity while controlling DC offset through real-time parameter adjustment.
3Object-generated harmful factors
If the cutoff frequency of HPF is increased to remove dynamic DC offset, then DC offset cancellation is improved, but the desired signal component is attenuated
Solution Approach 1:
The patent applies parameter changes by varying the time constant of the high-pass filter based on the detected DC offset conditions. Instead of using a fixed cutoff frequency that always attenuates the desired signal, the system changes the filter parameter (time constant) dynamically to match the actual DC offset level, thus removing DC offset effectively while preserving signal fidelity when the desired signal is present.
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 configuration enables effective countermeasures against dynamic DC offset while ensuring no loss of the desired signal component, improving signal transmission and reducing bit error rates by directly monitoring and responding to DC offset variations.
Implementation Method 1
a first element for cutting off the DC component of the input signal
Implementation Method 2
a determination element for determining whether or not the voltage of the output signal falls out of a predetermined detection threshold range
Implementation Method 3
a switch for connecting the output node of the first element to a power supply circuit when the voltage of the output signal was determined to fall out of the detection threshold range
Data Source
AI summary
A signal processing unit of the present invention includes: input terminal (21) to which an input signal is input; high-pass filter (23) for cutting off the DC component of the input signal; output terminal (22) for outputting a signal output from high-pass filter (23) as an output signal; determination element (26) for determining whether or not the voltage of the output signal falls out of a predetermined detection threshold range; and, switches (27,28) for connecting the output node of high-pass filter (23) to a power supply circuit when the voltage of the output signal is determined to fall out of the detection threshold range at determination element (26).