Low-IF Receiver Circuit Adaptation for Interferer Rejection
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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 time is used.
Innovation Solution
The system dynamically adjusts the local oscillator frequency settings based on real-time signal-to-noise ratio feedback during demodulation, placing interferer signals in the baseband frequency for maximum attenuation, and switches between different LO settings to adapt to changing radio environments, ensuring the interferer remains on the same frequency side as the wanted signal, thereby improving signal quality and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If I/Q imbalance calibration is performed with extended calibration time, then interferer signal rejection is improved, but manufacturing costs increase significantly
Solution Approach 1:
The patent implements dynamic LO frequency adjustment that adapts to changing radio environments in real-time. The system monitors signal conditions and switches between different LO frequency settings to maintain optimal interferer rejection without requiring extended calibration procedures, thereby avoiding increased manufacturing costs while preserving measurement precision.
Solution Approach 2:
The system changes the LO frequency parameter dynamically based on detected signal conditions. By adjusting the LO frequency setting between different values (e.g., nominal frequency and offset frequencies), the system optimizes interferer rejection adaptively without needing prolonged calibration time, thus resolving the contradiction between measurement precision and manufacturing cost.
2Device complexity
If static LO frequency settings are used, then device complexity is reduced, but adaptability to changing radio environments deteriorates
Solution Approach 1:
The patent introduces dynamic LO frequency adjustment that allows the receiver to adapt to changing radio environments. The system monitors signal conditions and automatically switches between different LO frequency settings, providing environmental adaptability while maintaining relatively simple device architecture through software-controlled frequency switching rather than complex hardware reconfiguration.
Solution Approach 2:
The system uses a single LO circuit that can operate at multiple frequency settings (nominal frequency and various offset frequencies). This multi-functional LO circuit provides both static and dynamic operation modes, allowing the same hardware to serve multiple purposes: simple static operation for basic scenarios and dynamic adaptive operation for challenging environments, thus balancing device complexity with adaptability.
3Reliability
If interferer signals are placed away from baseband frequency, then signal quality is maintained, but interferer signal rejection deteriorates
Solution Approach 1:
The patent implements dynamic LO frequency adjustment that adaptively positions interferer signals relative to the baseband. The system monitors the radio environment and adjusts the LO frequency to place strong interferers away from the baseband frequency where they would cause maximum damage, while maintaining signal quality through careful frequency selection. This dynamic positioning resolves the contradiction by making the system adaptive rather than static.
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, maintains signal quality, and reduces manufacturing costs by dynamically adjusting local oscillator settings based on real-time feedback, effectively addressing the limitations of existing calibration methods in low-IF receivers.
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
This low-IF signal can be filtered with a low pass filter and amplifier before its conversion to the digital domain by an analog-to-digital converter (ADC)
Data Source
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.