Optimal reduction of the influence of RF feed cables in small antenna measurements

✍ Scribed by C. Icheln; M. Popov; P. Vainikainen; S. He

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 230 KB
• Volume: 25
• Category: Article
• ISSN: 0895-2477
• DOI: 10.1002/(sici)1098-2760(20000505)25:3<194::aid-mop11>3.0.co;2-#

✦ Synopsis

Figure 5 Measurement errors in the real and imaginary parts of the permittivity of the PVC with a sample length of L s 120 mm and ⌬ L s 0.1 mm

From these values, an excellent agreement is observed with those reported previously in the literature, also plotted w x in Figure 4 as reference values 7 . The measurement accuracy also has been calculated using the procedure described Ž . in Eq. 7 , and is plotted in Figure 5. From this figure, it can be seen that the error in the determination of the dielectric constant is lower than 0.5%, while for the loss factor, this value is increased to approximately 10%. Both values are in good concordance with the theoretical analyses presented in this paper, which may be reduced by considering longer samples, as previously outlined.

IV. CONCLUSION

A fast and simple method for determining the complex dielectric properties of materials without ambiguity has been developed based on one-port reflection measurements made by an ANA. The developed algorithm solves the inherent ambiguity of the problem under analysis, and eliminates the need for any initial estimation of the dielectric properties, as required by other reflection methods.

The error has been analyzed taking into account the typical uncertainty of the measurement equipment and the unascertained sample dimensions. Using these uncertainties, the sample length has been identified as a very important parameter to obtain high accuracy in the dielectric characterization. For low-loss materials, the accuracy of the method may be limited if very long samples are not considered. In this case, resonant cavity methods might be used to increment the accuracy.

Although the application of this method is useful for all materials, it is particularly recommended for liquids, powders, and granular materials.