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Behaviour of Electromagnetic Waves in Different Media and Structures Part 5

Tham khảo tài liệu 'behaviour of electromagnetic waves in different media and structures part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 108 Behaviour of Electromagnetic Waves in Different Media and Structures To avoid the influence of air-gap to the testing result a rock sample holder is make as shown in fig. 3. The practical testing equipment including a VNA is shown in Fig. 4. In equation 17 and 18 because the Bessel function has oscillating property the main difficulty focuses on the Bessel function with integral variable. Obviously these nonlinear equations have no analytical solution. So we uses numerical solution here. A big number 12500 is used for the positive infinite of the upper limit during the numerical intergal. The value of the big number is determined by different testing of many conditions. 2.3 Calibration The calibration in this measurement includes two steps one is the transmission line calibration and the other is the probe calibration. 2.3.1 Transmission line calibration The VNA is a exact device and is connected to coaxial probe through a coaxial cable. According to the operation requirement of the network analyzer the coaxial line is calibrated using calibrating kits. The detailed operation process as follows. 1. VNA parameters setting. The frequency range is between IMHz-lGHz in this test according to our request. Power can be selected by our need for example OdBm. Large power is believed to sense large sample volume. We choose 1000 sampling points here. 2. Calibration process. We use single port calibration here because we only measure Sil. The calibration kits which including the device SHORT LOAD and OPEN are used to calibrate the VNA. After this process the reference plane for VNA is at the end of the coaxial cable. However because the reflection surface is on the flange surface not the end of the cable further calibration is still needed. 2.3.2 Probe calibration Probe calibration is an indirect method. We use short-circuit the air and the de-ionized water to calibrate the probe. If m is the reflection coefficient obtained through measuring and Ta is the practical .