Microwave Measuring Carbon Instrument With Six-port Circuit System Development,

The technology development of microwave measurement is be closely linked with the development of microwave devices, furthermore microwave measurements with high precise and speediness always depend on the research and exploitation of precise devices. Six-port measurement technology based on powers is a kind of effective method which is able to precisely measure the reflection coefficients of microwave units. At the same time this technology can be widely applied in many domains, such as microwave measurement, security detection, industrial detection, and so on. Therefore, the six-port measurement technology has been focused on by many researchers in many countries since it was proposed, and has become one of the most important tools for microwave measurement.In order to realize the real-time, continuous, precise measurement of the carbon content of the fly ash in the flue of the power station, we transfer the measurement of the carbon content to the measurement of the microwave network parameters─phase deviation and attenuation coefficient by microwave sensors. In this paper, a kind of microstrip circuit was designed and realized on the base of the six-port network technique, which can simultaneously measure the phase deviation and attenuation coefficient. Six-port network possesses many advantage, such as simple circuit form, calibration through software and high measurement precision. We analyzed the general six-port network, and discussed the general formulae, design norm and calibration. The detailed analysis of the dismatching and Q-point distribution of a kind of special six-port network, composed of perfect directional coupler and matched reciprocal lossless five-port was provided, and optimum microstrip ring parameters were deduced. At last, we proved that this circuit has higher measurement precision through experiments.