Phased-Array Antenna Self-Calibration Without OTA Testing
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Solution Overview
Problem
Phased-array antenna systems face challenges in precision calibration due to variations in wafer process, supply voltage, and temperature, which require expensive and complex over-the-air (OTA) testing setups, leading to high production costs and complexity.
Innovation Solution
A self-calibration method that adjusts the bias current of active devices and the gain of individual signal paths within the phased-array antenna system, using a calibration circuit that measures and adjusts current draw without requiring OTA testing, allowing for calibration in the field or factory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If over-the-air (OTA) calibration setup is used for phased-array antenna, then measurement precision can be achieved, but device complexity and production cost increase significantly
Solution Approach 1:
The patent implements self-calibration capability within the phased-array antenna system by integrating a calibration circuit that automatically measures and adjusts bias currents and gain settings of RF amplifiers without requiring external OTA testing equipment. The system calibrates itself by exercising different beamforming states and measuring output powers internally, eliminating the need for expensive anechoic chambers and far-field testing setups.
Solution Approach 2:
The patent extracts the calibration function from the external OTA testing environment and relocates it into the antenna system itself. By removing the dependency on external measurement equipment and creating an internal calibration subsystem, the solution eliminates the need for complex production testing infrastructure while maintaining calibration accuracy.
2Productivity
If over-the-air (OTA) calibration is performed in far-field chamber, then calibration speed improves, but the required chamber size becomes very large for big arrays
Solution Approach 1:
The patent transitions the calibration approach from spatial domain (far-field physical distance) to temporal/domain transformation domain by using beamforming weight transformations. Instead of physically moving antennas far apart to achieve far-field conditions, the system uses digital beamforming techniques to synthesize far-field measurement conditions through mathematical transformations of near-field measurements, effectively eliminating the need for large physical spaces.
3Manufacturing precision
If precision measurement of each signal path is performed via OTA setup, then manufacturing precision is improved, but loss of time increases due to large number of calibration states
Solution Approach 1:
The patent performs preliminary calibration actions by pre-characterizing the antenna array responses and storing calibration data in lookup tables before production. During actual manufacturing, the system quickly queries these pre-computed tables based on measured conditions rather than performing exhaustive multi-state measurements, dramatically reducing calibration time while maintaining precision.
4Manufacturing precision
If RF amplifiers are designed with high accuracy requirement (0.375 dB), then manufacturing precision improves, but device complexity increases due to compensation requirements
Solution Approach 1:
The patent achieves high amplifier accuracy not by increasing physical component precision during manufacturing, but by dynamically adjusting operational parameters (bias currents, gain settings) through software-controlled calibration. The system measures actual amplifier characteristics and compensates for variations by changing control parameters, thereby achieving 0.375 dB accuracy without requiring ultra-precise physical components.
Data Source
AI summary
Radio Frequency (RF) circuit (amplifiers, mixer, etc.) design with RFIC, e.g., implemented in CMOS, CaAs, SiGe, or other silicon processes, suffers performance variations (gain phase, frequency, bandwidth, nonlinearity) due to wafer process variations, temperature changes, and supply voltage changes, and random variations. In this invention, methods are proposed to precisely calibrate the bias current of all active devices in the system, and to precisely calibrate the gain of individual path leading to each amplifiers such that the same Pout is achieved for all antenna elements in the system.