IP2 Calibration for GNSS I/O Mixers Using DC Bias
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Solution Overview
Problem
GNSS receivers face challenges in maintaining signal processing performance due to strong interference from cellular uplink transmissions and other clock sources, leading to non-linearity issues that degrade the reception of weak satellite signals.
Innovation Solution
The method involves using a processor to downconvert modulated radio frequency waves and reduce mixer imbalance between I/O mixers through DC bias voltages from digital to analog converters (DACs), optimizing the linearity characteristics of the GNSS receiver components to minimize the impact of blocking signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the GNSS receiver processes weak satellite signals in the presence of strong cellular uplink transmissions and clock sources, then the signal processing performance degrades due to non-linearity issues, but increasing the signal processing capability to handle strong interference worsens the non-linearity and second-order products
Solution Approach 1:
The patent applies preliminary action by performing IP2 calibration before normal GNSS signal processing. The calibration process pre-adjusts the DC bias voltages of the I/O mixers to minimize second-order non-linearity, so that when strong cellular uplink transmissions are present, the receiver is already optimized to reduce second-order products. This preliminary optimization of mixer balance points prevents the degradation of signal processing performance that would otherwise occur in the presence of strong blockers.
2Object-affected harmful factors
If the mixer imbalance is reduced through DC bias voltage adjustment, then the second-order non-linearity is minimized, but additional calibration complexity is introduced
Solution Approach 1:
The patent implements self-service through automated IP2 calibration. The system automatically determines optimal DC bias voltages for the I/O mixers by measuring second-order non-linearity and adjusting the bias voltages without requiring manual intervention. This self-calibrating approach reduces mixer imbalance and minimizes second-order products while avoiding the complexity of manual calibration procedures, as the system performs the optimization autonomously.
3Manufacturing precision
If the DC bias voltages are optimized to minimize mixer imbalance, then the linearity characteristics are improved, but the device requires additional control and measurement mechanisms
Solution Approach 1:
The patent applies universality by integrating the IP2 calibration functionality into the existing GNSS receiver architecture. The same I/O mixers and DACs used for normal signal processing are also utilized for calibration purposes. The processor that handles GNSS signal processing is also used to control the calibration process and measure the second-order non-linearity. This multi-functional approach improves linearity characteristics through DC bias optimization without requiring separate dedicated calibration hardware, thereby avoiding additional device complexity.
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 second-order non-linearity, enhancing the GNSS receiver's ability to handle strong interference and maintain signal quality by optimizing mixer balance and reducing second-order products, thereby improving the overall performance in the presence of blockers.
Implementation Method 1
downconvert, by an input/output (I/O) mixer including a first mixer and a second mixer, a modulated radio frequency wave to an intermediate frequency
Implementation Method 2
reduce a mixer imbalance between the first mixer and the second mixer using direct current (DC) bias voltages from the first DAC and the second DAC
Implementation Method 3
filter the downconverted modulated radio frequency wave
Data Source
AI summary
An electronic device, a method, and a chipset for receiving global navigation satellite system (GNSS) signals are provided. An input/output (I/O) mixer including a first multiplier and a second multiplier downconverts a modulated radio frequency wave to an intermediate frequency. The modulated radio frequency wave is input to first inputs of the first multiplier and the second multiplier, and where an in-phase signal, from a first digital to analog converter (DAC), and a quadrature phase signal, from a second DAC, are input to second inputs of the first multiplier and the second multiplier, respectively. A mixer imbalance between the first mixer and the second mixer is reduced using direct current (DC) bias voltages from the first DAC and the second DAC. The DC bias voltages are determined based on a first and second DAC codes of the first and second DACs. The downconverted modulated radio frequency wave is filtered.