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Title: Efficient measurement techniques in reverberation chamber
Author: Tian, Zhihao
ISNI:       0000 0004 6495 994X
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2017
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The rapid expansion of electronic industry calls for effective and efficient electromagnetic (EM) measurements, including the characterization of devices under test (DUT), such as antennas or wireless devices, and the electromagnetic compatibility (EMC) testing. In the real world, EM measurements can be influenced by a number of uncontrollable factors which will afflict the measurements. These factors make the measurements very difficult especially when the measurements require high precision and/or low power relative to the background noise. To conduct EM measurements accurately, many different facilities/environments have been developed, including anechoic chambers (ACs), transverse electromagnetic (TEM) Cells, and reverberation chambers (RCs). These three environments have different characteristics. Over the past several decades, RCs have been enjoying growing popularity as a promising facility for the characterization of wireless devices and for the EMC testing. The RC measurement method exhibits much competitive superiority over the AC method and TEM Cell method, such as low cost, enhanced test repeatability, a more realistic test environment, and easily achieved high-field environment. The application of the RC for performing EMC testing was first proposed by H. A. Mendes in 1968. In the recent IEC 61000-4-21 standard, the importance of EMC testing using RCs as an alternative measurement technique has been recognized. To make the RC well stirred, a large number of independent samples (stirrer positions) are required. Consequently, the measurement time is usually long (typically several hours), which has greatly restricted the engineering applications of the RC measurement techniques. The purpose of this thesis is to present our studies on improving the measurement efficiency of RCs in recent years, including the efficient measurement of the averaged absorption cross section (ACS) with only one antenna, the rapid volume measurement method using the averaged ACS, the simplified shielding effectiveness (SE) measurement using the nested RC with two antennas, and the improved antenna array efficiency measurement in an RC. For ACS measurement, the proposed one-antenna methods in both the frequency domain and the time domain are presented. The measurement setup is greatly simplified and the measurement time is significantly shortened. The efficient measurement of the ACS can be used to obtain the volume of a chamber, which leads to the rapid volume measurement method. For the SE measurement of electrically large enclosures using a nested RC, four improved measurement methods are proposed. Both the frequency-domain and time-domain methods are studied. The proposed methods require only two antennas and provide efficient measurement of SE without losing the accuracy. Finally, the accurate array efficiency measurement method in an RC using a power divider is presented. A power divider is used to excite the feeding ports of the array elements simultaneously. Thus, the efficiency measurement of the entire array can be effectively treated in a manner similar to a single port antenna, which would simplify the measurement procedure and reduce the overall measurement time. By introducing proper attenuators between the array elements and the power divider to alleviate the effect of the reflected power from the array to the insertion loss of the power divider, the array efficiency can be measured accurately even when the elements of the array are not well-matched with the power divider. The proposed method is advantageous especially for wideband antenna arrays where good impedance matching of array elements is difficult to maintain. In this thesis, it is shown that our proposed methods have greatly improved the RC measurement efficiency and simplified the measurement setup at the same time. These contributions could promote the industrial application of RCs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available