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RC Measurement Uncertainty Estimation Method for Directive Antennas and Turntable Stirring

Alejandro Antón Ruiz, John Kvarnstrand, Klas Arvidsson, Andrés Alayón Glazunov

TL;DR

The paper tackles measurement uncertainty in mmWave Reverberation Chambers operating in the lower FR2 band by dissecting spatial non-uniformity, finite sampling, and polarization imbalance. It adopts standardized 3GPP/CTIA methods for uncertainty assessment, applies correlation checks and ANOVA, and introduces a novel K-factor estimation method tailored for RC with turntables. Through 24 measurement configurations with a horn antenna, the study finds antenna orientation to be the dominant uncertainty driver and demonstrates a K-factor around $-10$ dB, validating the proposed estimation approach via Monte Carlo simulations. The work delivers practical guidance for uncertainty budgeting in RC-based mmWave OTA testing and advances K-factor estimation under stirring, with implications for faster, more reliable characterization of directive mmWave devices.

Abstract

This paper investigates measurement uncertainty in a Reverberation Chamber (RC) within the lower FR2 bands (24.25-29.5 GHz). The study focuses on the impact of several factors contributing to RC measurement uncertainty, including finite sample size, polarization imbalance, and spatial non-uniformity. A series of 24 measurements were conducted using a horn antenna, known for its directivity in mmWave frequencies, varying antenna parameters such as height, orientation, position on the turntable, and polarization within a predefined chamber volume. The measurement uncertainty was evaluated by a method based on the standardized 3GPP and CTIA approaches, incorporating uncorrelated measurements and analyzing Pearson correlation coefficients between measurement pairs. An analysis of variance (ANOVA) was performed on the frequency-averaged power transfer function to identify the significance and impact of each variable on measurement variability. Additionally, the K-factor was estimated for each measurement set as part of the RC characterization, using an alternative approach to account for the turntable stirring effect. The findings highlight which variables most significantly influence measurement uncertainty, where the antenna orientation emerges as the most significant factor for the mmWave directive antenna setup.

RC Measurement Uncertainty Estimation Method for Directive Antennas and Turntable Stirring

TL;DR

The paper tackles measurement uncertainty in mmWave Reverberation Chambers operating in the lower FR2 band by dissecting spatial non-uniformity, finite sampling, and polarization imbalance. It adopts standardized 3GPP/CTIA methods for uncertainty assessment, applies correlation checks and ANOVA, and introduces a novel K-factor estimation method tailored for RC with turntables. Through 24 measurement configurations with a horn antenna, the study finds antenna orientation to be the dominant uncertainty driver and demonstrates a K-factor around dB, validating the proposed estimation approach via Monte Carlo simulations. The work delivers practical guidance for uncertainty budgeting in RC-based mmWave OTA testing and advances K-factor estimation under stirring, with implications for faster, more reliable characterization of directive mmWave devices.

Abstract

This paper investigates measurement uncertainty in a Reverberation Chamber (RC) within the lower FR2 bands (24.25-29.5 GHz). The study focuses on the impact of several factors contributing to RC measurement uncertainty, including finite sample size, polarization imbalance, and spatial non-uniformity. A series of 24 measurements were conducted using a horn antenna, known for its directivity in mmWave frequencies, varying antenna parameters such as height, orientation, position on the turntable, and polarization within a predefined chamber volume. The measurement uncertainty was evaluated by a method based on the standardized 3GPP and CTIA approaches, incorporating uncorrelated measurements and analyzing Pearson correlation coefficients between measurement pairs. An analysis of variance (ANOVA) was performed on the frequency-averaged power transfer function to identify the significance and impact of each variable on measurement variability. Additionally, the K-factor was estimated for each measurement set as part of the RC characterization, using an alternative approach to account for the turntable stirring effect. The findings highlight which variables most significantly influence measurement uncertainty, where the antenna orientation emerges as the most significant factor for the mmWave directive antenna setup.

Paper Structure

This paper contains 17 sections, 7 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Considered uncertainty components
  3. Lack of spatial uniformity
  4. Finite number of samples
  5. Polarization imbalance
  6. Uncertainty characterization
  7. Chamber precharacterization measurements
  8. Uncertainty relation with K-factor
  9. K-factor estimation
  10. Proposed method
  11. Measurement setup
  12. Power transfer function measurement
  13. Considered cases for precharacterization measurements
  14. Results
  15. K-factor estimation simulations
  16. ...and 2 more sections

Figures (3)

  • Figure 1: Measurement setup. (a) $\mathrm{Z=ZL}$, $\mathrm{R=RM}$,$\mathrm{O=OH}$, and $\mathrm{P=P1}$. (b) $\mathrm{Z=ZH}$, $\mathrm{R=Rm}$,$\mathrm{O=OD}$, and $\mathrm{P=P2}$. The horn antenna can be observed in the turntable attached to a low-loss plastic holder. The structure for holding mmWave DUT is at the bottom left, on the chamber's floor.
  • Figure 2: Simulation results of the considered $K$-factor estimators.
  • Figure 3: Measurement results of the considered $K$-factor estimators. $t$ is the measurement index, ranging from $1$ to $T_{pre}=24$.