A Fast Method to Measure the Volume of a Large Cavity

Qian Xu Qian Xu,Zhouxiang Fei Zhouxiang Fei,Yi Huang Yi Huang,Zhihao Tian Zhihao Tian,Liuji Zheng Liuji Zheng,Lei Xing Lei Xing

doi:10.1109/access.2015.2476661

Qian Xu Qian Xu, Zhouxiang Fei Zhouxiang Fei + Show 4 more

Open Access

https://doi.org/10.1109/access.2015.2476661

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Abstract

How to quickly and accurately measure the volume of a large cavity is challenging. This paper presents an efficient method to measure the volume of a large conducting cavity. The proposed method is based on statistical wave theory. By measuring the Q factor in the time and frequency domains, the volume of the cavity can be extracted. In the time domain, the Q factor can be extracted directly from the time domain response, while in the frequency domain, the Q factor depends on the volume of the cavity and the transferred power; the transferred power can be measured directly. By correcting the frequency domain Q with the radiation efficiency of antennas, the Q factors obtained from both the time and frequency domains are equal in a well-stirred chamber; this provides an opportunity to measure the volume of the cavity. Measurements are conducted to verify the proposed method. Although the measurement is conducted using electromagnetic waves, acoustic waves can also be used; in this case, the approach can be applied to any cavity, not limited to a conducting cavity. The advantages and the limitations of the proposed method are also discussed.

Highlights

In the shipbuilding industry, to measure the volume/capacity of a ship hold is important and useful
To obtain the τ value, we can measure it in the time domain directly [8] or measure the S-parameters in the frequency domain and apply the inverse fast Fourier transform (IFFT) to the S-parameters
A fast measurement method to measure the volume of a large cavity has been proposed in this paper

Summary

INTRODUCTION

To measure the volume/capacity of a ship hold is important and useful. Q factor in both the time and frequency domains, the volume of the cavity can be obtained. We need to know the total efficiency of the transmitting (Tx) and receiving (Rx) antennas, which can be measured in a cavity with a known volume (as a calibration process). It can be seen that, if we know the total efficiency of the Tx and Rx antennas, we only need to measure the averaged τ value and S21 to obtain the volume value. MEASUREMENT IN AN RC we calibrate the total efficiency of antennas using an RC with known volume, and we change the environment: load the RC using radio absorbing materials (RAMs), open the door of the RC. After the environment is changed we repeat the measurement to validate the proposed method

CALIBRATION PROCESS

DISCUSSION AND CONCLUSIONS