Spur Mitigation in Heterodyne Upconversion Systems
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Solution Overview
Problem
Heterodyne upconversion systems face challenges in mmWave communications due to inadequate filtering of spurious signals and LO leakage, especially when the IF frequency is smaller than the RF bandwidth, leading to potential interference with adjacent frequency bands and difficulty in meeting stringent emission limits.
Innovation Solution
A dual-mode upconversion circuit dynamically switchable between low-side and high-side LO injection modes, controlled by a controller to select the appropriate mode based on the desired output frequency, ensuring effective mitigation of spurious signals and LO leakage by optimizing LO frequency and injection mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low-side LO injection is used for upconversion, then the desired RF signal is generated, but spurious signals and LO leakage cannot be adequately filtered when operating near frequency band edges
Solution Approach 1:
The system dynamically switches between low-side and high-side LO injection modes based on the desired output frequency. A controller monitors the operating frequency and automatically selects the appropriate injection mode to maintain adequate filtering margins across the entire frequency range, resolving the contradiction between operational flexibility and spurious emission control.
Solution Approach 2:
The invention changes the LO injection mode parameter (low-side vs. high-side) as a function of the operating frequency. By adjusting this parameter based on the desired output frequency, the system maintains optimal filtering performance across different frequency bands, preventing spurious signals from falling within the desired RF band.
2Ease of operation
If high-side LO injection is used for upconversion, then the desired RF signal is generated, but spurious signals and LO leakage cannot be adequately filtered when operating near frequency band edges
Solution Approach 1:
The system dynamically switches between low-side and high-side LO injection modes based on the desired output frequency. A controller monitors the operating frequency and automatically selects the appropriate injection mode to maintain adequate filtering margins across the entire frequency range, resolving the contradiction between operational flexibility and spurious emission control.
Solution Approach 2:
The invention changes the LO injection mode parameter (low-side vs. high-side) as a function of the operating frequency. By adjusting this parameter based on the desired output frequency, the system maintains optimal filtering performance across different frequency bands, preventing spurious signals from falling within the desired RF band.
3Adaptability or versatility
If the IF frequency is smaller than the RF bandwidth, then the system can operate in mmWave bands, but spurious signals fall within the desired RF band and cannot be filtered
Solution Approach 1:
The system dynamically adapts the LO injection mode based on the relationship between IF frequency and RF bandwidth. When operating in mmWave bands where IF < RF bandwidth, the controller selects the appropriate injection mode (low-side or high-side) to ensure spurious signals fall outside the desired RF band, maintaining compliance across all supported frequency ranges.
Solution Approach 2:
The invention changes the LO injection configuration parameter based on the operating frequency and bandwidth conditions. This parameter adaptation allows the system to maintain adequate separation between spurious signals and the desired RF band across different frequency ranges, including mmWave operations with constrained IF frequencies.
4Object-affected harmful factors
If conventional filtering techniques are used, then spurious signals can be reduced, but frequency separation must be maximized which limits operational flexibility
Solution Approach 1:
The system dynamically switches between low-side and high-side LO injection modes based on the desired output frequency. A controller monitors the operating frequency and automatically selects the appropriate injection mode to maintain adequate filtering margins across the entire frequency range, resolving the contradiction between operational flexibility and spurious emission control.
Solution Approach 2:
The invention changes the LO injection mode parameter (low-side vs. high-side) as a function of the operating frequency. By adjusting this parameter based on the desired output frequency, the system maintains optimal filtering performance across different frequency bands, preventing spurious signals from falling within the desired RF band.
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 reduces spurious emissions and LO leakage, ensuring compliance with restrictive emission limits and maintaining system performance across various frequency bands, particularly in the n258 band, by dynamically adjusting the LO frequency and mixer mode to minimize interference.
Implementation Method 1
The process of upconversion (also known as mixing) naturally involves the use of nonlinear circuit functions to generate replica information signals at the carrier frequency, specifically by combining (e.g., multiplying) the input (e.g., IF) signal and a LO (Local Oscillator) signal via a nonlinear function.
Implementation Method 2
One common technique is to include a signal filter at the RF output port that can remove or reduce the magnitude of the LO signal terms from being conducted to the transmitting antenna.
Data Source
AI summary
Exemplary embodiments dynamically select the LO frequency and mixer mode (i.e., low-side LO injection or high-side LO injection) for upconversion based on the desired RF output frequency in order to mitigate the effects of spurious and LO leakage signals that could violate radiation emission limits, e.g., in the case where the IF signal frequency is smaller than the RF operating band. By dynamically switching the LO frequency and mixer mode as a function of the requested operating RF channel, low-level emissions and spurious signal compliance with restricted bands can be achieved.