• Title, Summary, Keyword: Microwave Attenuation

Search Result 54, Processing Time 0.033 seconds

Rain Attenuation over Terrestrial Microwave Links at 18 GHz as Compared with Prediction by ITU-R Model

  • Shrestha, Sujan;Lee, Jung-Jae;Kim, Sun-Woong;Choi, Dong-You
    • Journal of information and communication convergence engineering
    • /
    • v.15 no.3
    • /
    • pp.143-150
    • /
    • 2017
  • Absorption of microwave radio frequency signal by atmospheric rain is prevalent at frequencies above 10 GHz. This paper presents the studies on rain attenuation at 18 GHz for 3.2 km experimental link between Khumdang (Korea Telecom, KT station) and Icheon (National Radio Research Agency, RRA station). The received signal data for rain attenuation and rain rate were collected at 10 second intervals over a three year periods from 2013 to 2015. Out of several models, the paper present discussion and comparison of ITU-R P.530-16 model, Moupfouma model, Da Silva Mello model along with suitable rain attenuation prediction method. The limitation of research lies on the experimental system that is set up in only one location, however, the preliminary results indicate the application of suitable 1-minute rain attenuation model for specific site. The method provides useful information for microwave engineers and researchers in making decision over the choice of most suitable rain attenuation prediction in terrestrial links.

Developing a Scanner for Assessing Foliage Moisture

  • Nakajima, Isao;Ohyama, Futoshi;Juzoji, Hiroshi;Ta, Masuhisa
    • Journal of Multimedia Information System
    • /
    • v.6 no.3
    • /
    • pp.155-164
    • /
    • 2019
  • We intended to confirm that microwave attenuation by tree leaves is strongly linked to water content in leaves. We sampled natural broadleaves, including Japanese cinnamon, and investigated their effects on the microwave (3 to 20 GHz) frequency characteristics using a network analyzer. Experiments determined that microwave attenuation by foliage increases as a linear function of frequency per unit weight (gram). As the frequency increases, the spatial resolution increases, but the phase difference (imaginary component) increases. So we solved the dispersion of phase difference by sweeping the frequency and taking the intermediate value. Based on these experimental results, we developed a microwave scanner on 10Ghz to describe foliage moisture as a image and to enable assessments of leaf condition. Photosynthesis is the process whereby plants synthesize oxygen and sugars from carbon dioxide and water, thereby converting light energy into chemical energy. Since water is a major parameter of photosynthesis, the quantity of water accumulated inside a leaf reflects leaf health. The equipment described here and related microwave technologies will help assess the capacity of leaves to absorb atmospheric carbon dioxide.

The Material Constants and Microwave Absorbing Characteristics of ferroxplana Composite Microwave Absorber (복합 ferroxplana 전파흡수체의 재료정수와 전파흡수 특성)

  • 신재영;오재희
    • Journal of the Korean Magnetics Society
    • /
    • v.1 no.2
    • /
    • pp.49-54
    • /
    • 1991
  • In this study the correlation between material constants and microwave absorbing characteristics of ferroxplana composite microwave absorber used in X-band was investigated. The real part of permeability(${\mu}_{r}'$) was decreased and the imaginary part of permeability(${\mu}_{r}"$) of ferroxplana composite was increased with increaing ferroxplana loading ratio(F/R). The frequency showing maximum attenuation was shifted to lower frequency with increasing absorber thickness. The absorber 2.6 mm thick showed good band width property and 3.2 mm thick showed good attenuation property. From the apphcation of ferroxplana composite's material constants to the region of material constants which satisfy broad band width, it is found that the absorbing characteristics were estimated quantitatively. Estabhshment of material constants' region which satisfies broad band width can make practical application to design of high performance ferrite microwave absorber.

  • PDF

Experimental Study on Microwave Attenuation in Josephson Junction Stripline (조셉슨접합 스트립라인의 마이크로파 감쇠에 대한 실험적인 조사)

  • 홍현권;박세일;김규태
    • Progress in Superconductivity
    • /
    • v.4 no.1
    • /
    • pp.64-67
    • /
    • 2002
  • The attenuation of millimeter waves (70-100 ㎓) propagating along Josephson Junction stripline had been measured by pattern recognition near gap voltage and proximity current bump. Test series arrays of 2000, 3000, and 4000 Josephson junctions with the area of $12\mu\textrm{m}$$\times$ $38\mu\textrm{m}$ had two sub-arrays with 50 Junctions at both ends. The arrays were fabricated with and without applying a plasma nitridation process to Nb ground plane. The effects of a nitridationprocess measured by the pattern recognition near gap voltage and proximity current bump were about 1.3-1.7 ㏈ and 1.6-1.8 ㏈, respectively. This means that the last sub-arrays with a nitridation process receive 26-34% more power than those without a nitridation process.

  • PDF

The Experimented MF Propagation Modeling for Mountain geography (산악지형에 적합한 경험적 중파 전파 모델링)

  • Kim, Bum-Chang;Kwon, Se-Woong;Yoon, Young-Joong
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • /
    • pp.18-22
    • /
    • 2003
  • In this thesis, Middle frequency wave propagation modeling is studied for the varies mountain geography the experimented middle frequency propagation model is researched in a shot time to analyze the broad area that consists of mountains. Due to the Sommerfeld - Norton model which is used broadly the middle frequency propagation model to analyze the broad area in a short time is proposed introducing the newly attenuation parameter of the experimental results on the basis of actual experiments at the mountain configuration regardless of the area of mountain, plane, sea etc.

  • PDF

Characteristics of Carbon-Ferrite Microwave Absorbers (카아본-페라이트 전파흡수체의 특성)

  • ;;;Yoshiyuki Naito
    • Journal of the Korean Institute of Telematics and Electronics
    • /
    • v.26 no.11
    • /
    • pp.1721-1727
    • /
    • 1989
  • Carbon-ferrite microwave absorbers were designed experimentally and fabricated trialy, as a result of which the relative frequency bandwith of 7.3 to 8.2% were obtained under the tolerance limits of the reflection coefficients lower than -20 dB, and the matching thickness becomes 1.4 to 1.6mm, which is significantly thinner than that of the conventional ones. Furthermore, attenuation has been founded by measuring the material constants of the microwave absorbers for microwave oven and the results are compared and discussed.

  • PDF

A Study on the Rainfall Attenuation Adaptive Power Control System for Implementing B-WLL (B-WLL 구현을 위한 강우감쇠 적응형 출력제어장치에 대한 고찰)

  • 목진담;정희창
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • /
    • pp.462-466
    • /
    • 1999
  • As the spectrum migrates to the higher frequency band around several milimeters wavelength for implementing wideband highspeed communications, it is more important to consider the channel attenuation characteristics of microwave signals. Microwave channels in 27GHz used in B-WLL system must be considered by compensating the power attenuation due to rainfall. So, in the design of one cell, the radiation power enhancement considering rainfall attenuation has an effort on the receiver in other cell as interference. In this paper we consider the main characteristics for B-WLL systems, optimum cell radius, and serviceable limit of heavy rainfall the design of the radiation power control system in case of enhancing the power that prevents from reducing the system capacity by interference.

  • PDF

Measurement of Permittivity and Moisture Content of Powdered Food at Microwave Frequencies (분말식품의 마이크로파 유전율 및 수분함량 측정)

  • Kim, K.B.;Kim, J.H.;Lee, J.M.
    • Journal of Biosystems Engineering
    • /
    • v.32 no.4
    • /
    • pp.237-246
    • /
    • 2007
  • In this study, the microwave free-space transmission technique was used to measure the dielectric property of powdered food at microwave frequencies. The sample holder was designed and fabricated to transmit the microwave signals ranging from 1 to 15GHz. From the microwave propagation theory the equation expressing the dielectric property of powdered food was derived and validated by standard dielectrics. The dielectric property of powdered food such as wheat flour, coffee powder and milk powder was measured and analyzed. In the uniform range of bulk density of material, the real parts of permittivity of the food samples increased with the increase of moisture content, bulk density and temperature of the samples. The propagation properties such as attenuation and phase shift increased linearly as the moisture density of the food samples increased. As a measuring frequency of the moisture content, the X-band was recommended.

Determination of Microwave Dielectric Properties of Grain by Free Space Transmission Method (자유공간 전송방법을 이용한 마이크로파 유전특성연구)

  • 김종헌;김기복;노상하
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.233-235
    • /
    • 1997
  • A free sparse transmission method using X-band standard gain horn antenna is applied to measure the attenuation and phase shift of microwave signal through the wetted grain such as rough rice, brown rice and barley. The moisture content of grain varied from 11 to 25% based on its wetted condition. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The measured values of dielectric constants as a function of moisture density are compared with values of those obtained using the predicted model for estimating dielectric constants of grain.

  • PDF