A Vector Network Analyzer(VNA)can be used to identify oscillation frequency of a signal source with moderate or low Radio Frequency(RF)power if certain care is taken according to experimental results.Unlike reported i...A Vector Network Analyzer(VNA)can be used to identify oscillation frequency of a signal source with moderate or low Radio Frequency(RF)power if certain care is taken according to experimental results.Unlike reported in the literature that a resonant peak of measured absolute value of reflection coefficient greater than 1 that corresponds to an oscillation frequency,we report that by observing the magnitude change of one-port reflection coefficient across the entire swept frequency range,a sudden peak or a dip corresponds to an oscillation frequency,this is more accurate than other reports.In addition,using modern VNA as a signal detection method can significantly reduce measurement time and increase measurement accuracy to VNA capability for developing emerging signal generating devices at early stage,especially for planar,large quantity and operating in a wide frequency range.展开更多
As a simple,fast,and non-destructive measuring technology,dielectric spectroscopy is usually used to analyze the dielectric properties of agricultural products and food,and then to predict the main components of mater...As a simple,fast,and non-destructive measuring technology,dielectric spectroscopy is usually used to analyze the dielectric properties of agricultural products and food,and then to predict the main components of materials.However,the large and expensive vector network analyzers(VNA)with expensive analysis software applied in measuring dielectric properties make research limited to the laboratory.To acquire dielectric spectra in situ,a model for solving relative complex permittivity was derived,and its performance was validated.Then,a low-cost portable dielectric spectrometer with a mini VNA,a Raspberry Pi,and a coaxial probe as core parts was developed over the frequency range of 100-3000 MHz.The stability and accuracy of the developed spectrometer were tested using milk and juice.The results indicated that the relative errors of the model were within±5%for dielectric constant(ε′)and loss factor(ε″).The coefficients of variation of measuredε′andε″by the developed spectrometer at 100-3000 MHz were less than 1%and 2%,respectively.Compared with the dielectric properties obtained by using a commercial dielectric measurement system,the relative errors of measuredε′andε″were within±3.4%and±6.0%,respectively.This study makes fast,non-destructive,and on-site food quality detection using dielectric spectra possible.展开更多
文摘A Vector Network Analyzer(VNA)can be used to identify oscillation frequency of a signal source with moderate or low Radio Frequency(RF)power if certain care is taken according to experimental results.Unlike reported in the literature that a resonant peak of measured absolute value of reflection coefficient greater than 1 that corresponds to an oscillation frequency,we report that by observing the magnitude change of one-port reflection coefficient across the entire swept frequency range,a sudden peak or a dip corresponds to an oscillation frequency,this is more accurate than other reports.In addition,using modern VNA as a signal detection method can significantly reduce measurement time and increase measurement accuracy to VNA capability for developing emerging signal generating devices at early stage,especially for planar,large quantity and operating in a wide frequency range.
基金financial support provided by the National Natural Science Foundation of China(Grant No.32172308)Startup Foundation for Doctors of Yan'an University(No.YDBK2022-79).
文摘As a simple,fast,and non-destructive measuring technology,dielectric spectroscopy is usually used to analyze the dielectric properties of agricultural products and food,and then to predict the main components of materials.However,the large and expensive vector network analyzers(VNA)with expensive analysis software applied in measuring dielectric properties make research limited to the laboratory.To acquire dielectric spectra in situ,a model for solving relative complex permittivity was derived,and its performance was validated.Then,a low-cost portable dielectric spectrometer with a mini VNA,a Raspberry Pi,and a coaxial probe as core parts was developed over the frequency range of 100-3000 MHz.The stability and accuracy of the developed spectrometer were tested using milk and juice.The results indicated that the relative errors of the model were within±5%for dielectric constant(ε′)and loss factor(ε″).The coefficients of variation of measuredε′andε″by the developed spectrometer at 100-3000 MHz were less than 1%and 2%,respectively.Compared with the dielectric properties obtained by using a commercial dielectric measurement system,the relative errors of measuredε′andε″were within±3.4%and±6.0%,respectively.This study makes fast,non-destructive,and on-site food quality detection using dielectric spectra possible.
