VLIF Receiver Control for Adjacent Channel Interference Detection
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Solution Overview
Problem
Very Low Intermediate Frequency (VLIF) receivers face interference and noise issues due to adjacent channel interferers, leading to inaccurate carrier detection and signal imbalance, which existing I/Q imbalance algorithms cannot adequately address.
Innovation Solution
A method and apparatus for controlling a VLIF receiver by estimating energy levels in on-channel and adjacent channel portions, detecting interference, and adjusting the local oscillator frequency to minimize interference, thereby improving carrier detection and sideband suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the local oscillator operates at a frequency close to the RF signal (VLIF), then the receiver achieves low cost and small size, but adjacent channel interferers cause interference on the side of the RF signal
Solution Approach 1:
The patent implements dynamic switching between two local oscillator frequencies (first and second frequencies) based on detected interference conditions. The receiver adapts its operating frequency in real-time to avoid adjacent channel interferers, transforming a static frequency-fixed system into a dynamic one that can respond to changing interference environments.
Solution Approach 2:
The patent changes the operating frequency parameter of the local oscillator between two predetermined values (first frequency and second frequency). By switching between these frequency parameters, the receiver can avoid adjacent channel interferers while maintaining VLIF operation benefits.
2Measurement precision
If I/Q imbalance compensation algorithms are used, then amplitude and phase imbalances are corrected under certain conditions, but noise and distortion still affect carrier detection accuracy
Solution Approach 1:
The patent introduces an intermediary frequency translation step that converts the VLIF signal to a higher intermediate frequency before further processing. This intermediary frequency domain separates the desired signal from adjacent channel interferers and noise, enabling more reliable carrier detection independent of I/Q imbalance conditions.
Solution Approach 2:
The patent implements a feedback mechanism where the receiver detects interference conditions and energy levels, then switches the local oscillator frequency in response. This closed-loop feedback system continuously adapts to maintain optimal reception despite noise and distortion variations.
3Measurement precision
If energy level estimation is performed on both on-channel and adjacent channel portions, then interference detection accuracy improves, but processing complexity increases
Solution Approach 1:
The patent segments the signal processing into distinct stages: first estimating energy in the on-channel portion, then estimating energy in the adjacent channel portion after frequency translation. This segmentation allows independent optimization of each estimation process and simplifies the overall complexity by breaking down the complex interference detection task into manageable parts.
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
The solution enhances adjacent channel selectivity, differentiates between on-channel signals and adjacent channel interferers, and stabilizes carrier detection, resulting in improved radio performance by reducing noise and distortion.
Implementation Method 1
A VLIF receiver combines a received radio frequency (RF) signal with a local oscillator prior to analogue to digital conversion. The local oscillator is set at a frequency close to that of the RF signal, but differing by an offset that is referred to as an intermediate frequency.
Implementation Method 2
estimating a second energy level in a second signal, wherein the second signal comprises an intermediate frequency translation of the first on-channel portion
Data Source
AI summary
A very low intermediate frequency (VLIF) receiver and a method of controlling a VLIF receiver. The method comprises estimating energy levels in first and second signals and detecting interference from a first adjacent channel interferer based upon a difference in energy in the first and second signals. The first signal comprising a first on-channel portion and an adjacent channel portion and the second signal comprises an intermediate frequency translation of the first on-channel portion. The energy levels are estimated for corresponding time instances and the adjacent channel interferer is of the adjacent channel portion. The VLIF receiver is then controlled based upon the detected interference.