Frequency-Offset LO Cancellation for Reciprocal Mixing Isolation
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Solution Overview
Problem
Existing signal processing systems face challenges in isolating desired signals from received signals due to interference and noise, particularly reciprocal mixing, which degrades signal quality and requires complex and resource-intensive RF design solutions.
Innovation Solution
A frequency offset (FO) local oscillator (LO) signal is generated from the primary LO signal to downconvert received signals, allowing for effective cancellation of interference without the need for additional PLLs, thereby isolating signal components at different frequencies and reducing spurious artifacts and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate PLLs are used to generate separate LO signals for downconverting received signals to isolate signal components at different frequencies, then signal isolation capability is improved, but device complexity increases and power consumption increases
Solution Approach 1:
A single PLL is designed to perform multiple functions: generating the primary LO signal for normal downconversion and generating frequency offset LO signals for isolating signal components at different frequencies. This multi-functional approach eliminates the need for separate PLLs while maintaining signal isolation capability.
Solution Approach 2:
The system dynamically switches between different LO signal generation modes based on operational requirements. The single PLL can operate in normal mode for standard downconversion or in frequency offset mode for isolating specific signal components, providing adaptability without requiring multiple fixed-frequency PLLs.
2Adaptability or versatility
If separate PLLs are used to generate separate LO signals for downconverting received signals to isolate signal components at different frequencies, then signal isolation capability is improved, but power consumption increases
Solution Approach 1:
A single PLL is designed to perform multiple functions: generating the primary LO signal for normal downconversion and generating frequency offset LO signals for isolating signal components at different frequencies. This multi-functional approach eliminates the need for separate PLLs while maintaining signal isolation capability.
3Measurement precision
If multiple PLLs operate simultaneously to generate different LO signals, then signal component isolation is improved, but spurious artifacts and unwanted pulling effects increase
Solution Approach 1:
Multiple LO signal generation functions are merged into a single PLL architecture. The PLL generates both the primary LO signal and frequency offset LO signals through coordinated operation, eliminating the harmful interactions that occur when multiple independent PLLs operate simultaneously.
Solution Approach 2:
The single PLL acts as an intermediary that coordinates the generation of multiple LO signals. By centralizing the frequency synthesis function, the PLL ensures proper phase and frequency relationships between different LO signals, preventing spurious artifacts and pulling effects that would arise from independent PLL operations.
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 enables efficient cancellation of reciprocal mixing and out-of-band signals, improving signal quality and reducing design complexity and resource requirements, while maintaining performance in both normal operation and loopback-aided calibration modes.
Implementation Method 1
downconverter circuitry configured to downconvert the received signal using the LO signal to generate a downconverted received signal
Implementation Method 2
FOLO downconverter circuitry configured to use the FOLO signal to downconvert the received signal to generate a downconverted FO signal
Implementation Method 3
cancellation circuitry configured to cancel the downconverted received signal from the received signal to generate a desired signal
Data Source
AI summary
Systems, methods, and circuitries are disclosed for generating a desired signal from a received signal. In one example a signal cancellation system includes local oscillator (LO) downconverter circuitry, frequency offset (FO) signal estimation circuitry, and cancellation circuitry. The LO downconverter is configured to downconvert the received signal using an LO signal having an LO frequency to generate a downconverted received signal. The FO signal estimation circuitry includes FOLO generation circuitry configured to modify the LO signal to generate a FOLO signal having an offset frequency that is different from the LO frequency and FOLO downconverter circuitry configured to use the FOLO signal to downconvert a signal derived from the received signal to generate a downconverted FO signal. The cancellation circuitry is configured to cancel either the downconverted received signal or the downconverted FO signal from the received signal to generate the desired signal.