Low-IF Receiver Circuit Adaptation for Urban Interference
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Solution Overview
Problem
Current low-IF receiver architectures in cellular communications face challenges in effectively rejecting interferer signals, particularly in urban areas with strong radio interference, due to limited I/Q gain and phase imbalance calibration accuracy, which can lead to distorted signal bursts and increased manufacturing costs when extended calibration times are used.
Innovation Solution
A mobile wireless communications device with a low-IF receiver circuit that dynamically adjusts the local oscillator frequency settings based on signal-to-noise values during demodulation, using different low-IF local oscillator settings for RF channels and returning to a poorer performing setting after a predetermined number of data bursts to adapt to changes in the radio environment, thereby maintaining interferer signals at the same frequency as the wanted signal and filtering them at baseband frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If I/Q imbalance calibration is extended to improve interferer signal rejection, then measurement precision is improved, but manufacturing time and cost increase significantly
Solution Approach 1:
The patent performs I/Q imbalance calibration during the manufacturing process to establish baseline correction values before the device is deployed. This preliminary calibration captures the inherent imbalances in the receiver circuitry, allowing the system to compensate for them during operation without requiring extended calibration time in the field.
Solution Approach 2:
The system continuously monitors signal quality metrics and dynamically adjusts receiver parameters based on feedback from the radio environment. This closed-loop approach allows the receiver to adapt to changing interference conditions and maintain optimal performance without requiring manual recalibration or extended calibration periods.
2Measurement precision
If dynamic local oscillator frequency adjustment is implemented, then interferer signal rejection is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic local oscillator frequency adjustment that allows the receiver to switch between different frequency offsets based on the detected radio environment. This dynamic adaptation enables the system to optimize interferer rejection for different signal conditions without requiring completely redundant receiver paths, thereby managing complexity while improving performance.
Solution Approach 2:
The system changes the local oscillator frequency parameter dynamically based on detected interference conditions. By adjusting this single parameter rather than redesigning the entire receiver architecture, the patent achieves improved interferer rejection with minimal increase in overall device complexity.
3Measurement precision
If low-IF receiver architecture is used to eliminate DC offset and 1/F-noise, then signal quality is improved, but image signal issues are reintroduced
Solution Approach 1:
The patent acknowledges that the low-IF architecture inherently produces image signals, but converts this potential harm into a benefit by using the known image signal characteristics to inform the dynamic frequency adjustment strategy. The system deliberately positions the local oscillator to place interferers in predictable image locations that can then be filtered or rejected through digital signal processing.
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 enhances interferer signal rejection by dynamically optimizing local oscillator settings, improving signal quality and reducing manufacturing costs by avoiding the need for extended calibration times, thus providing better performance in urban areas with strong interference.
Implementation Method 1
the RF signal can be mixed down to a non-zero low or moderate intermediate frequency, typically a few megahertz in some examples
Implementation Method 2
the RF signal is band selected and downconverted to the frequency close to baseband
Implementation Method 3
A mobile wireless communications device with a low-IF receiver circuit that dynamically adjusts the local oscillator frequency settings based on signal-to-noise values during demodulation
Implementation Method 4
filtering the image signal at substantially baseband frequency
Data Source
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AI summary
A mobile wireless communications device, system and associated method includes a housing and circuit board that includes radio frequency (RF) circuitry and processor operative with each other. The RF circuitry includes a low-IF receiver circuit that is operative for maintaining an interferer signal at a same frequency side as a wanted signal relative to a local oscillator frequency setting, creating an interferer image signal, and filtering the image signal as substantially baseband frequency.