Papers by Keyword: Vector Network Analyzer

Abstract: Effects of filler concentration and sonication time on the structure, morphology, reflection loss and absorption percentage of ZnO composite was investigated. The structure, morphology, reflection loss and absorption percentage of the composite was investigated using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Vector Network Analyzer (VNA). The ZnO composite was made by solution mixing method with the epoxy resin as a filler varied of 10 wt%, 20 wt%, and 30 wt%. The hardener was mixed to the ZnO composite by the composition of 2: 1. The sonication time was varied of 30, 45 and 60 minutes. The XRD showed that the crystal structure of ZnO composite was confirmed as a hexagonal structure and the structure was not change for all composite. The VNA results showed that the optimum reflection loss value was-9.37042 dB at the frequency of 12.3 GHz for the filler composition of 20 wt% and sonification time of 45 minutes. On the other hand, the minimum reflection loss value was-6.86845 dB at the frequency of 12.3 GHz for the filler composition of 10 wt% and sonification time of 45 minutes. In addition, the optimum absorption percentage was 18 % at a filler composition of 10 wt% with 60 minutes sonication time. This study demonstrates a promising method to improve a microwave absorption of ZnO composites.

Abstract: With the development of science and technology ,microwave measuring instrument become more important in the radar equipment maintenance support task.This paper expounds the principles of microwave measuring instrument work and test, describes the application of microwave measuring instrument in the maintenance detection of radar antenna feed system、radar antenna pattern test、power amplifier parameters measurement、the local oscillator test and receiving systems component test. Scientific applications of microwave measuring instrument is the important guarantee to ensure the radar equipment operate effectively.

Abstract: We measured the microwave and millimeter-wave behaviors of ceramics and metal powders as a basis for developing microwave and millimeter-wave heating technology. In this study, nitride powders were subjected to microwave absorption measurements at elevated temperature. These measurements were performed using a system comprising a vector network analyzer, a circular wave-guide fixture, and a vacuum furnace. The sample’s microwave absorbency was evaluated by the change in reflection power from the sample in the circular wave-guide fixture under vacuum heating. Measurements were performed at approximately 24 GHz and at temperature up to approximately 1100°C. Boron nitride (BN) exhibited almost no absorption of microwaves up to 1100°C, similar to the results of a low-loss oxide powder such as alumina. Dichromium mononitride (Cr2N) powder exhibited a rather high absorption of microwaves at room temperature. During vacuum heating, absorbency of Cr2N started to decrease at 300°C, and became almost zero at temperature greater than 600°C, similar to the behavior of iron powder. This result indicated that roughly packed Cr2N powder absorbs microwave radiation; however, during vacuum heating, the compact body was sintered and the whole sample body became a reflector of microwaves. This change was irreversible, and the sample maintained its reflection behavior upon the cooling. When a mixed powder of Cr2N (20 mass%) and Al2O3 was heated under vacuum, the compact sample exhibited microwave absorption that increased with increasing temperature. This change was reversible upon cooling. These results indicated that the mixed powder did not become reflector of microwaves; Cr2N particles were not electrically connected each other because the Al2O3 particles kept the Cr2N particles separate during the vacuum heating process.

Abstract: To solve complex measurement and difficult remote operation in the test for frequency response characteristic of SAW device, an automatic test system for frequency response characteristic of SAW device based on vector network analyzer is proposed. The system consists of the vector network analyzer, the crossover cable, the computer, the fixtures and the SAW device. The user interface of test system is developed with the VB language. By means of calling the VISA-COM library, the SCPI commands can send to the vector network analyzer. Many functions of the automatic test system for frequency response characteristic of SAW device include the settings of measurement parameters, the measurement calibration, the data storage, the data display, the data transmission, the marker analysis and the data output. By the actual measurement of a SAW device with the center frequency at 101.764MHz, the experimental results show that the transmission loss of SAW device is-27.532dB, and the reflection loss is-7.715 dB.

Abstract: Complex permittivity spectra of 1-Propanol (1-PrOH), Fluorobenzene (FB) and their binary mixtures are obtained in radio and microwave frequency range using Vector network analyzer (VNA) operating in the frequency range 0.3 MHz to 3.0 GHz and standard microwave benches operated at 9.1 GHz and 19.61 GHz. Static dielectric constant (ε₀) and high frequency limiting dielectric constant (ε_∞1) for binary mixtures of 1-PrOH and FB are obtained by extrapolating the complex permittivity data towards low frequency side and high frequency side on complex plane plots. Optical dielectric constant (ε_∞ = n²) for binary mixtures are measured using Abbe's refractometer. Excess static dielectric constant (ε₀)^E, Kirkwood correlation parameters (g, g^eff and g_f) and Bruggeman factor (f_B) are determined from the values of static dielectric constant (ε₀) and optical dielectric constant (ε_∞). These parameters have been discussed to explore the molecular interaction between the molecular species.

Abstract: The complex permittivity of a soil is a very much useful parameter in remote sensing applications. The measurement of complex permittivity of soil at various microwave frequencies can be related with the moisture content in the soil, which is useful in Agriculture, Hydrology and Meteorology. The complex dielectric spectra of dry and wet soil samples were measured in the frequency range from 20 Hz to 20 GHz. For this, various instruments and different methods were used. The complex permittivity of the soils, in the frequency range from 20 Hz to 2 MHz, was measured using a precision LCR meter, and a newly designed and developed coaxial capacitor probe. The complex permittivity of the soils, in the frequency range from 75 MHz to 1.5 GHz, was measured using a Vector Network Analyzer. The complex permittivity of the soils at 5.65 GHz, 9.5 GHz and 19.3 GHz was measured using microwave bench set up. The results are presented in the paper.

Abstract: By using a four port Vector Network Analyzer (VNA), a caesium clock, a time-interval counter and a signal source to measure the delay of CEI system segmentally. Design measuring methods respectively for three segments of the circuit. When measure the delay, it is found that, delay of antenna’s amplifier output port to the input port of down converter (DC) is stable; the fluctuation of DC’s delay is less than 2ns; the cable delay’s standard deviation is stable at 0.1ns; we get a nanosecond accuracy for whole system. The methods of time delay measurement and the design of CEI system will provide a foundation and primary data for future deep space missions.

Abstract: Stabilized zirconia shows rather high microwave absorbency at room temperature, and the absorbency become higher with increasing temperature. In this study, stabilized zirconia powder, partially stabilized zirconia powder and zirconia fiber were subjected for microwave absorption measurements at elevated temperature. Microwave absorption measurements were done by using a system consists of a microwave vector network analyzer, a circular wave-guide fixture and a vacuum furnace. Microwave absorbency was evaluated by the reflection power change from the sample in the circular wave-guide fixture under vacuum heating. Microwave absorbency of stabilized zirconia powder, partially stabilized zirconia powder and zirconia fiber gradually increased with the increase of temperature. We supposed that the increase of microwave absorbency is related to the ionic (oxygen) conduction behavior of stabilized zirconia. Stoichiometric composition ZrO2 powder was also subjected for a measurement to consider the relation between microwave absorbency and ion conduction of zirconia. As the result, stoichiometric composition ZrO2 powder was not absorbed microwave power even when the powder was heated up to 900oC because it isn’t an oxygen ion conductor.