Phased Array RF Transceiver Calibration Using Multi-Frequency Tone Injection
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Solution Overview
Problem
In wideband phased array transmitter and receiver systems, the phase errors due to long signal processing paths cause inaccuracies in beam direction and direction of arrival determination, as conventional calibration methods are inadequate for phase shifts exceeding 2π radians.
Innovation Solution
A method involving the injection of multiple frequency tones at the start point, measuring phase differences at the end point, and determining total delay and phase shift using these measurements, with the aid of linear programming optimization to unwrap phase shifts exceeding 2π radians.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods using reference signals are used, then phase error correction is achieved for small phase shifts, but the method fails when phase shift exceeds 2π radians due to phase wrapover
Solution Approach 1:
The patent segments the phase measurement problem by using multiple frequency tones instead of a single reference signal. Each tone provides a separate phase measurement, allowing the system to resolve phase shifts exceeding 2π by analyzing the phase differences across multiple frequencies. This segmentation of the measurement approach enables accurate calibration despite phase wrapover in individual measurements.
Solution Approach 2:
The patent transitions from a single-frequency calibration approach to a multi-frequency approach, adding the frequency dimension to the measurement process. By injecting multiple frequency tones and measuring phase differences across different frequencies, the system gains additional information that allows resolution of phase shifts beyond the 2π ambiguity, effectively moving the problem to a higher dimension of measurement space.
2Measurement precision
If multiple frequency tones are injected and phase differences are measured, then total delay and phase shift are accurately determined, but the system complexity increases
Solution Approach 1:
The patent makes the calibration system universal by using the same multi-frequency tone injection and phase measurement approach for both transmitter and receiver calibration. The method can be applied to any path length and phase shift condition, providing a universal solution that works across different system configurations without requiring separate calibration procedures for different scenarios.
Solution Approach 2:
The patent implements feedback by measuring the phase differences between injected reference tones and received signals, then using these measurements to calculate and apply compensation values. The system continuously monitors the phase shift and uses this feedback information to determine the total delay and adjust the calibration, creating a closed-loop calibration process that improves accuracy.
Data Source
AI summary
A method of determining a total delay to a radio frequency (RF) signal caused by a path between a start point and an end point comprising, injecting a plurality of frequency tones at the start point, wherein the frequency tones are of different frequency, receiving the plurality of frequency tones at the end point, measuring a plurality phase differences corresponding to difference of phase between the plurality of frequency tones injected at the start point and the corresponding plurality of the frequency tones received at the end point, and determining a total delay to the RF signal caused by the path from at least more than one of the plurality of phase differences measured. The method further comprises determining a total phase shift to the RF signal from the total delay and a frequency of the RF signal.