Abstract-An advanced aspheric and asymmetric large aperture dielectric lens antenna is proposed firstly here for high resolution at Wband frequency. Large aperture and aspheric lens provides minimum focusing error and high resolution in millimeter wave quasi-optics application. To the best of the authors' knowledge we design first time 500 mm large aperture lens for W-band quasi optics application. Near field radiation pattern, beam size and focal length of the lens are obtained theoretically and experimentally as well. Dielectric rod waveguide antenna is also designed and employed as a source antenna for the lens. The measured and simulated results of the DRW antenna also show very good performance at W-band frequency, and it has 15.3 dB gain with −22.5 dB sidelobe levels at 94 GHz.

Abstract-In passive millimeter-wave imaging systems used indoors, the radiometric temperature contrast is barely enough for coarse object detection, being usually insufficient for recognition due to the absence of cold sky. The image contrast results from a combination of emissivity and reflectivity which are dependent on the dielectric constant of objects, the angle of incidence, and the polarization direction. To improve the capability of target recognition, we proposed the linear polarization sum imaging method which is based on the combination of the different polarization images for increasing the intensity contrast between the target area and the background area. In order to capture the linear polarization sum images of a metal sphere, a metal and a ceramic cup, we designed W-band quasi-optical imaging system which can generate the polarization dependent images by manually changing the linear polarization direction of its radiometer receiver from 0 to π/2 by the step size of π/8. The theoretical and experimental results of the linear polarization sum imaging show that it is capable for achieving good image quality enough to recognize the target.

Quasi-optical imaging systems require low blurring effect and large depth of focus (DOF) to get an acceptable sharpness of the image. To reduce aberration-limited blurring, the aspheric convex plano lenses with an aperture diameter of 350 mm are designed in W-band. We analyzed theoretically and experimentally the millimeter-wave band lens characteristics, such as beam spot size, spatial resolution (SR), and DOF, via f-number. It is first used to verify the DOF through f-number in the system-level test with the developed W-band radiometer imaging system. We have confirmed that the larger f-number of quasi-optical lens leads to a larger DOF but a lower SR.

grating separation, and birefringence can be measured simultaneously. In application, the multiplexed sensors can be employed by using the changes in Bragg wavelength, birefringence, and dip separation between two gratings. The distributed sensors by using more gratings along the sensing fiber are also available. Furthermore, the use of simultaneous and multiplexed sensing measurements for the strain and birefringence related parameter is plausible, while the self calibration between them is available.ABSTRACT: Modification in tapered dielectric rod waveguide antenna is achieved by the implementation of step change in width in metallic waveguide transition. The proposed antenna has circular symmetric radiation pattern and gain about 15.3 dB with improved return loss and side lobes level at W-band. It has 10 dB beamwidth 53.2 and 48.6 in the E-and H-plane. Proposed antenna can be used for a millimeter wave quasi-optics feed array design in W-band imaging radiometer design.

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