Low-IF Receiver LO Side Selection for Blocker Rejection
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Solution Overview
Problem
Low IF receivers face challenges in separating wanted signals from blocker signals due to image rejection issues, leading to degradation in bit error rates, especially in scenarios with strong adjacent channel interference.
Innovation Solution
A low IF receiver architecture that dynamically adjusts the local oscillator (LO) frequency based on the power of blocker signals, switching between high and low band injection to optimize signal separation and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a low IF receiver uses a fixed LO frequency, then the receiver architecture is simple, but the adjacent channel rejection is poor when there is a strong blocker signal
Solution Approach 1:
The patent implements dynamic LO frequency selection by switching between high-side and low-side injection based on the relative power levels of the desired signal and blocker. The receiver determines which injection side places the blocker in the image frequency position, then dynamically adjusts the LO frequency accordingly to reject the blocker while maintaining proper downconversion of the desired signal.
2Object-affected harmful factors
If the receiver uses dynamic LO frequency adjustment to improve blocker rejection, then the adjacent channel rejection improves, but the device complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the receiver continuously monitors the power levels of both the desired signal and blocker, compares these levels, and uses this information to control the LO frequency selection. The system determines the relative power relationship and adjusts the injection side accordingly, creating a closed-loop control system that adapts to changing signal conditions.
Solution Approach 2:
The patent changes the LO frequency parameter dynamically based on signal conditions. By switching between high-side and low-side injection frequencies, the system alters the LO frequency to position the blocker in the image frequency position, thereby rejecting the blocker while maintaining proper reception of the desired signal.
3Ease of operation
If the receiver maintains fixed LO frequency for simplicity, then the device operation is simple, but the bit error rate degrades under strong adjacent channel conditions
Solution Approach 1:
The patent implements dynamic LO frequency selection by switching between high-side and low-side injection based on the relative power levels of the desired signal and blocker. The receiver determines which injection side places the blocker in the image frequency position, then dynamically adjusts the LO frequency accordingly to reject the blocker while maintaining proper downconversion of the desired signal.
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 effectively improves receiver sensitivity and mitigates spurious emissions by dynamically selecting the LO frequency, thereby enhancing bit error rate performance and reducing distortion from image signals.
Implementation Method 1
a first mixer component configured to down convert the wanted RF signal and the blocker RF signal to an intermediate frequency (IF) signal, based on the frequency of the LO signal
Data Source
AI summary
A low IF receiver for operation at an intermediate frequency (IF), comprises an antenna port configured to receive a receive signal comprising a wanted RF signal at an RF frequency and a blocker RF signal at a mirror image frequency of the wanted RF signal with respect to a frequency of an local oscillator (LO) signal, from an antenna. Further, the low IF receiver comprises a first mixer component configured to down convert the wanted RF signal and the blocker RF signal to an intermediate frequency (IF) signal, based on the frequency of the LO signal, wherein the IF signal comprises a wanted IF signal at a first intermediate frequency and a blocker IF signal at a second intermediate frequency and a second mixer component configured to receive the IF signal, separate the IF signal into the wanted IF signal and the blocker IF signal, and provide the wanted IF signal at a first output thereof and the blocker IF signal at a second output thereof, based on a tuning signal. In addition, the low IF receiver comprises a power estimation component configured to receive the blocker IF signal, measure a power of the blocker IF signal and select the frequency of the LO signal to be applied to the first mixer component from a plurality of LO frequencies, based on the measured power of the blocker IF signal.