Loss Measuring of Large Aperture Quasi-Optics for W-Band Imaging Radiometer System

Abstract

Abstract-A loss of large aperture quasi-optics which consist of a lens and a feed antenna is firstly measured using a radiometer receiver via the modified reference control method for a W-band imaging radiometer system. The quasi-optical loss is mainly decided by the dielectric loss of the lens with good quasi-optical transformation efficiency between the lens and the feed antenna. The quasi-optics composed of an aspheric lens and a dielectric rod antenna are designed for high resolution, low aberration, and compact size. The fabricated quasi-optics with the aperture diameter of 500 mm have the quasioptical transformation efficiency of more than 95%. The radiometer receiver is designed applying a total power type and a direct conversion topology for simplicity, compact size and low temperature sensitivity. The manufactured receiver has the temperature sensitivity less than 1 K for both a hot source and a cold source. The calculated and measured results of the quasi-optics are very well matched by approximately 1.6 dB. The expected measurement errors by the reference control method are also analyzed as the functions of the characteristic parameters of the radiometer receiver.

Optimized Design of W-Band Quasi-Optical Lens by Using Optical Simulator and Numerical Analysis

“…The incident fieldĒ i 1 at P 1 is the radiation field of the feed which is obtained with the method mentioned above. Then the incident field at P 2 is given bȳ (8) whereĒ i 1v andĒ i 1p are the components ofĒ i 1 which are perpendicular and parallel to the incident plane respectively; T 1v and T 1p are the Fresnel transmission coefficients at P 1 ; R 12 is the distance between P 1 and P 2 ; L εr is the dielectric loss of the lens, which can be obtained as follow [14] L εr = 10 − 27. 3·R 12 20λ ·tan δ· n n−1 (9) in which n is the index of refraction, tan δ the loss tangent of the medium, and λ the wave length.…”

“…Δs i (13) where N is the number of the grid elements;r si is the unit vector in the direction from i-th element to field point; Δs i is the area of the i-th triangular element;J ei andJ mi are the equivalent current and magnetic current at i-th triangular element, which arē (14) in whichn i is the unit normal vector of i-th triangle, andĒ si andH si are the average fields of the three nodes of i-th triangular element. The electric field distribution on the optical axis and the beam pattern at the waist of the lens were calculated with the hybrid numerical method.…”

Development and Calibration of a K-Band Ground-Based Hyperspectral Microwave Radiometer for Water Vapor Measurements

“…However in this kind of design, the receiver array of 80 channels is required, which seriously increased the complexity of microwave radiometer system. The receiver of the BHU-K80 combined several advantages of traditional microwave radiometer [12][13][14][15] receiver. It is a single sideband superheterodyne receiver architecture, which divides the spectral channels continuously to reduce the complexity of the receiver.…”

Quasi-optical lens antenna made of electromagnetic-induction materials

“…The performance of the focusing lens used in AMMW system directly affects the image quality. So far, the focusing lenses for MMW focal plane imaging are mainly made of polymer materials, such as Rexolite, polyethylene and Teflon [6][7][8]. However, lenses made of polymer material have not been widely used in practical applications [3].…”