This antenna will be used for PMWIS （passive millimeter wave imaging system） which has 35 GHz operating frequency described as Ka Band. The antenna should work in that specific frequency because of having low attenu...This antenna will be used for PMWIS （passive millimeter wave imaging system） which has 35 GHz operating frequency described as Ka Band. The antenna should work in that specific frequency because of having low attenuation in that region according to frequency behavior in misty conditions. Antenna also should have approximately 50 ohm input impedance value so that perfect matching to the active circuits will occur. The input reflection coefficient, S11, has to be under -20 dB and the gain of the antenna, has to be over 10 dB value for better efficiency. Microstrip Vivaldi Fed Antenna provides all of the conditions for imaging system, was designed by using Antenna Magus Computer Program and later it was designed in detail with Computer Simulation Technology Studio Suite Computer Program. The last format of the VFA has -23.1 dB input reflection coefficient, 48.55 ohm input impedance and 12.3 dB gain for 35 GHz OF. It is ready to connect to the LNA and detector, which are active circuits of the PMWIS. At the end, the detector will be connected to the VA and computer. The receiver of PMWIS is composed to the VFA connected to the other equipment that is defined above will scan elevation and azimuth angles, as a result; the VA will transfer the signals to the computer. Computer will show the user the scanning area image. In this system, antenna is the most important section and particular attention was given to the antenna in this study.展开更多
Passive millimeter wave （PMMW） images inherently have the problem of poor resolution owing to limited aperture dimension. Thus, efficient post-processing is necessary to achieve resolution improvement. An adaptive p...Passive millimeter wave （PMMW） images inherently have the problem of poor resolution owing to limited aperture dimension. Thus, efficient post-processing is necessary to achieve resolution improvement. An adaptive projected Landweber （APL） super-resolution algorithm using a spectral correction procedure, which attempts to combine the strong points of all of the projected Landweber （PL） iteration and the adaptive relaxation parameter adjustment and the spectral correction method, is proposed. In the algorithm, the PL iterations are implemented as the main image restoration scheme and a spectral correction method is included in which the calculated spectrum within the passband is replaced by the known low frequency component. Then, the algorithm updates the relaxation parameter adaptively at each iteration. A qualitative evaluation of this algorithm is performed with simulated data as well as actual radiometer image captured by 91.5 GHz mechanically scanned radiometer. From experiments, it is found that the super-resolution algorithm obtains better results and enhances the resolution and has lower mean square error （MSE）. These constraints and adaptive character and spectral correction procedures speed up the convergence of the Landweber algorithm and reduce the ringing effects that are caused by regularizing the image restoration problem.展开更多
This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave （PMMW） imaging. The poor spatial resolution, which is limited by antenna size, should be improved ...This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave （PMMW） imaging. The poor spatial resolution, which is limited by antenna size, should be improved by post data processing. A conjugate-gradient （CG） algorithm is adopted to circumvent this drawback. Simulation and real data collected in laboratory environment are given, and the results show that the CG algorithm improves the spatial resolution and convergent rate. Further, it can reduce the ringing effects which are caused by regularizing the image restoration. Thus, the CG algorithm is easily implemented for PMMW imaging.展开更多
文摘This antenna will be used for PMWIS （passive millimeter wave imaging system） which has 35 GHz operating frequency described as Ka Band. The antenna should work in that specific frequency because of having low attenuation in that region according to frequency behavior in misty conditions. Antenna also should have approximately 50 ohm input impedance value so that perfect matching to the active circuits will occur. The input reflection coefficient, S11, has to be under -20 dB and the gain of the antenna, has to be over 10 dB value for better efficiency. Microstrip Vivaldi Fed Antenna provides all of the conditions for imaging system, was designed by using Antenna Magus Computer Program and later it was designed in detail with Computer Simulation Technology Studio Suite Computer Program. The last format of the VFA has -23.1 dB input reflection coefficient, 48.55 ohm input impedance and 12.3 dB gain for 35 GHz OF. It is ready to connect to the LNA and detector, which are active circuits of the PMWIS. At the end, the detector will be connected to the VA and computer. The receiver of PMWIS is composed to the VFA connected to the other equipment that is defined above will scan elevation and azimuth angles, as a result; the VA will transfer the signals to the computer. Computer will show the user the scanning area image. In this system, antenna is the most important section and particular attention was given to the antenna in this study.
基金the National Natural Science Foundation of China (60632020).
文摘Passive millimeter wave （PMMW） images inherently have the problem of poor resolution owing to limited aperture dimension. Thus, efficient post-processing is necessary to achieve resolution improvement. An adaptive projected Landweber （APL） super-resolution algorithm using a spectral correction procedure, which attempts to combine the strong points of all of the projected Landweber （PL） iteration and the adaptive relaxation parameter adjustment and the spectral correction method, is proposed. In the algorithm, the PL iterations are implemented as the main image restoration scheme and a spectral correction method is included in which the calculated spectrum within the passband is replaced by the known low frequency component. Then, the algorithm updates the relaxation parameter adaptively at each iteration. A qualitative evaluation of this algorithm is performed with simulated data as well as actual radiometer image captured by 91.5 GHz mechanically scanned radiometer. From experiments, it is found that the super-resolution algorithm obtains better results and enhances the resolution and has lower mean square error （MSE）. These constraints and adaptive character and spectral correction procedures speed up the convergence of the Landweber algorithm and reduce the ringing effects that are caused by regularizing the image restoration problem.
基金supported partly by the State Key Program of National Natural Science Foundation of China(60632020)the Youth Science Foundation of University of Electronic Science and Technology of China(JX0823).
文摘This paper designs a 3 mm radiometer and validate with experiments based on the principle of passive millimeter wave （PMMW） imaging. The poor spatial resolution, which is limited by antenna size, should be improved by post data processing. A conjugate-gradient （CG） algorithm is adopted to circumvent this drawback. Simulation and real data collected in laboratory environment are given, and the results show that the CG algorithm improves the spatial resolution and convergent rate. Further, it can reduce the ringing effects which are caused by regularizing the image restoration. Thus, the CG algorithm is easily implemented for PMMW imaging.
