Self-Calibrated Phased Array Signal Injection via Reflectometer
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Solution Overview
Problem
Phased array radar calibration techniques face challenges due to reliance on long RF cables, which are prone to temperature fluctuations and mechanical stress, leading to inaccurate calibration results and the need for expensive, temperature-insensitive cables or strict temperature control.
Innovation Solution
The use of multiple switches and signal path configurations with an RF short at the cable end for real-time measurement of phase and amplitude variations, allowing for instantaneous calibration and correction of signal paths before system calibration, eliminating the need for long closed loop cables and strict temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If long RF cables are used for calibration test loops, then calibration coverage and test capability are improved, but temperature fluctuations and cable movement cause amplitude and phase measurement errors that degrade calibration accuracy
Solution Approach 1:
The patent extracts the measurement function from the traditional long cable loop configuration and implements it through a reflectometer-based setup. By using a reflectometer to measure cable characteristics and separately characterizing the cable effects, the system removes the harmful temperature and movement-induced errors from the calibration measurements while maintaining the ability to calibrate phased array systems.
Solution Approach 2:
The patent changes the measurement parameters by using reflectometer measurements to directly characterize cable amplitude and phase characteristics as functions of temperature and position. By measuring and storing these parameters at different temperatures, the system can later compensate for temperature effects during calibration, thereby maintaining accuracy despite environmental variations.
2Measurement precision
If temperature control is implemented to maintain cable stability, then calibration accuracy is improved, but system complexity and cost increase due to required temperature control equipment
Solution Approach 1:
The patent implements feedback by using the reflectometer to continuously or periodically measure cable characteristics and update the calibration data accordingly. The system measures the actual cable state at the time of calibration and uses this feedback information to correct for temperature and movement effects, eliminating the need for proactive temperature control while maintaining accuracy.
Solution Approach 2:
The calibration system performs self-characterization by using the reflectometer to automatically measure and store cable characteristics at different temperatures and positions. This self-service approach allows the system to build its own correction database without external temperature control, enabling it to compensate for environmental effects autonomously during calibration operations.
3Measurement precision
If expensive temperature-insensitive RF cables are used, then calibration accuracy is maintained under temperature variations, but hardware cost increases significantly
Solution Approach 1:
The patent creates a digital copy or model of the cable's temperature-dependent characteristics through reflectometer measurements. Instead of using expensive physical cables that are immune to temperature effects, the system measures and stores the cable's behavior at different temperatures and uses this digital model to correct measurements, achieving the same accuracy at lower cost.
Solution Approach 2:
The patent replaces expensive, specialized temperature-insensitive cables with ordinary, inexpensive cables whose temperature effects are measured and compensated through the reflectometer-based characterization method. The system accepts that the cables will exhibit temperature variations but uses the measured data to correct for these variations, thereby using cheap cables instead of expensive specialized ones.
4Ease of manufacture
If factory calibration with component cataloging is performed, then initial calibration state is achieved, but verification capability is lost and assembly errors cannot be detected
Solution Approach 1:
The patent implements verification capability through feedback measurements using the reflectometer. The system measures the actual calibrated state by injecting test signals and measuring the reflected signals, providing real-time verification that the calibration is correct. This feedback loop allows detection of assembly errors and verification of the calibrated state, which was missing in traditional factory calibration methods.
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
Enables accurate and efficient in-field calibration of phased array radar systems by real-time measurement and correction of cable phase and amplitude variations, ensuring calibration accuracy without the need for expensive cables or strict temperature control, and reducing hardware and maintenance costs.
Implementation Method 1
By providing a short to ground, a measurement system, which can be formed by an exciter and a receiver for example, can measure two-way cable amplitude and phase of the test setup
Data Source
AI summary
Methods and apparatus provide calibration of a system using a cable check configuration and a calibration test configuration. A short to ground reflects an injected signal to characterize a first signal path in the cable check configuration. Switch setting can then be adjusted to inject a signal that is coupled to an array element and received from a feed. The signal paths can be characterized to enable in-field calibration testing.