DC Offset Correction Timing in Frequency Hopping Radio Systems
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Solution Overview
Problem
In radio communication systems using direct conversion architecture, DC offset generated during frequency hopping causes noise and distortion, leading to reduced signal-to-noise ratio and increased demodulation errors, which shorten communication distance.
Innovation Solution
A radio communication apparatus with an offset adjustment unit providing correction signals corresponding to local oscillation frequencies and a timing adjustment unit synchronizing these signals with frequency switching, removing noise from the adder unit output and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC offset correction is applied in frequency hopping systems, then signal quality improves, but timing misalignment between correction signals and local oscillation frequency changes introduces noise
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the timing of DC offset correction signals to anticipate and align with local oscillation frequency changes. The timing adjustment unit proactively synchronizes correction signals before they are applied, ensuring they match the frequency hopping schedule and preventing timing misalignment noise.
Solution Approach 2:
The patent implements feedback by using the timing adjustment unit to monitor and synchronize the timing of DC offset correction signals with local oscillation frequency changes. This closed-loop timing synchronization ensures correction signals are applied at the correct moments, eliminating noise caused by timing mismatches while maintaining signal quality.
2Area of stationary object
If direct conversion architecture is used, then circuit area and cost are reduced, but DC offset generation increases
Solution Approach 1:
The patent converts the harmful DC offset effect into a beneficial correction process. By generating DC offset correction signals that mirror the local oscillation frequency changes and applying them through the adder unit, the system transforms the harmful self-mixing DC offset into a correctable parameter, effectively eliminating its negative impact while maintaining the compact direct conversion architecture.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the DC offset correction signal parameters (amplitude and timing) to match the local oscillation frequency changes. The offset adjustment unit modifies correction signal characteristics in real-time according to frequency hopping, ensuring optimal cancellation of DC offset effects across different frequency bands.
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 effectively reduces demodulation errors and extends communication distance by ensuring precise timing alignment of DC offset correction signals with local oscillation frequency changes, enhancing signal quality and reducing noise in the output.
Implementation Method 1
a mixer mixing a received signal and a local oscillation signal from a local oscillator
Implementation Method 2
an offset adjustment unit supplying a DC offset correction signal to an output of the mixer
Data Source
AI summary
An apparatus includes: an offset adjustment unit supplying an offset correction signal corresponding to a frequency switching to an adder unit receiving output from a mixer; a timing adjustment unit adjusting the timing of a frequency switching signal supplied to a local oscillator and the timing of an offset correction amount switching signal supplied to the offset adjustment unit for changing an offset amount in correspondence with the frequency switching in the local oscillator; a noise amount measurement and calculation unit receiving a signal obtained by amplifying and filtering the signal from the adder unit, to measure a noise amount of the signal and generates a timing determination signal based on the noise amount; and a control unit controlling frequency switching signal timing and the offset correction amount switching signal supplied to the timing adjustment unit, based on the timing determination signal from the noise amount measurement and calculation unit.