IQ Modulator Calibration via Iterative Constellation Feedback
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Solution Overview
Problem
Existing calibration methods for IQ modulators in communications devices, such as radar systems, are inadequate due to non-ideal behavior, requiring improved techniques to achieve precise calibration without relying on external measurement equipment or knowledge of amplitude and phase behavior over the entire IQ range.
Innovation Solution
A method and system for calibrating IQ modulators by setting control values to generate an IQ modulating signal, transmitting it, receiving reflections, and iteratively adjusting the control values until the deviation from desired constellation points falls below a threshold, using a transceiver's built-in transmitter and receiver without external equipment, and storing optimized control values for future use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If model based calibration approaches are used for IQ modulator calibration, then calibration can be performed, but the calibration precision is insufficient due to non-ideal behavior of the IQ modulator
Solution Approach 1:
The patent implements an iterative feedback-based calibration process where the actual constellation points are measured and compared with desired constellation points. The control values are adjusted based on the deviation between actual and desired points, repeating the process until the deviation falls below a threshold. This closed-loop feedback mechanism significantly improves calibration precision under non-ideal conditions compared to open-loop model-based approaches.
Solution Approach 2:
The calibration method uses the IQ modulator's own transmitter and receiver components to perform self-calibration. The system transmits test signals through its own IQ modulator and measures the received signals using its own receiver, eliminating the need for external measurement equipment. This self-service approach ensures calibration accuracy while reducing system complexity.
2Measurement precision
If external measurement equipment is used for calibration, then measurement capabilities are enhanced, but device complexity and cost increase
Solution Approach 1:
The calibration system utilizes the IQ modulator's built-in transmitter and receiver components to perform calibration without requiring external measurement equipment. The transmitter generates test signals that pass through the IQ modulator, and the receiver measures the resulting signals to determine actual constellation points. This self-service approach maintains measurement capability while significantly reducing device complexity and cost.
Solution Approach 2:
The transmitter and receiver components of the IQ modulator are designed to serve dual purposes: normal signal transmission/reception and calibration measurement. By making these components multi-functional, the system eliminates the need for dedicated external measurement equipment, reducing overall system complexity while maintaining calibration capability.
3Measurement precision
If calibration is performed over the entire IQ range, then comprehensive calibration is achieved, but measurement time and complexity increase
Solution Approach 1:
The patent replaces exhaustive mechanical scanning of the entire IQ range with a smart sampling approach. Instead of measuring every possible control value combination, the system identifies and measures only the critical constellation points that define the modulation scheme. This substitution of comprehensive mechanical measurement with targeted intelligent measurement significantly reduces calibration time while maintaining comprehensive calibration effectiveness.
Solution Approach 2:
Rather than performing exhaustive calibration over the entire IQ range, the method applies partial action by focusing measurements only on the specific constellation points required for the modulation scheme. This targeted approach achieves comprehensive calibration coverage for the actual operating points without the time penalty of measuring the entire IQ range, including non-operational regions.
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 calibrates IQ modulators within radar systems, reducing errors caused by non-linearities and eliminating the need for external measurement devices, ensuring accurate signal transmission and reception while maintaining the power level of interest.
Implementation Method 1
The IQ modulating signal is then mixed with a carrier signal to generate an IQ modulated transmit signal
Implementation Method 2
The received reflection of the IQ modulated transmit signal is mixed with the carrier signal to generate a down-converted receive signal
Data Source
AI summary
The present disclosure relates to a concept for calibrating an IQ modulator. A calibration method comprises setting one or more control values of the IQ modulator corresponding to a desired constellation point of a constellation diagram to generate an IQ modulating signal; mixing the IQ modulating signal with a carrier signal to generate an IQ modulated transmit signal; transmitting the IQ modulated transmit signal towards a predefined object at a predefined location; receiving a reflection of the IQ modulated transmit signal from the predefined object; mixing the received reflection of the IQ modulated transmit signal with the carrier signal to generate a down-converted receive signal; comparing amplitude and/or phase of the down-converted receive signal with the desired constellation point of the constellation diagram; and adjusting the one or more control values of the IQ modulator until a deviation between the amplitude and/or phase of the received down-converted signal and the desired constellation point falls below a predefined threshold.