Effect of internal reflections on the radiation properties and input impedance of integrated lens antennas-comparison between theory and measurements

Abstract

This paper presents the effect of internal reflections on the beam pattern and input impedance of integrated lens antennas. A silicon lens was designed and manufactured, and measurements were conducted at a frequency of 100 (impedance) and 500 GHz (beam pattern). A frequency-dependence characterization of the beam pattern clearly showed the existence and impact of internal reflections. The measurements confirmed that most of the frequency variations of the beam pattern could be attributed to internal reflections, as predicted by the model. An on-wafer measurement strategy for determining the antenna impedance at millimeter-wave frequencies is presented. The validity of the model was also proven by an excellent match of the input impedance measurements and predictions. Not only the level, but also the oscillation on the impedance curve was predicted accurately. Initial space qualification was performed in the form of thermal cycling. Index Terms-Integrated lens antennas, internal reflections and input impedance.

Broadband Integrated Lens for Illuminating Reflector Antenna With Constant Aperture Efficiency

“…However, in the canonical lenses the high material permittivity originates important internal reflections at the dielectric/air interface, degrading the beam pattern and the admittance of the antenna [20]. The quarter wavelength matching layer approach is commonly used to minimize these reflections [7], [18].…”

Noise temperature and beam pattern of an NbN hot electron bolometer mixer at 5.25 THz

“…34 The physical reasons for this are the internal reflection and surface roughness. 35,36 The nearly collimated ͑main͒ beam at 5.25 THz is confirmed by a separated measurement. Taking the beam width ͑radius͒ at the mixer to be the radius of the Si lens ͑5 mm͒, 37 we should expect a beam with a diameter of 16 mm at the position of the cold load, which is 290 mm away from the HEB and is the longest distance in the optical path in our vacuum setup.…”

Performance of reduced size substrate lens antennas for Millimeter-wave communications

“…Therefore multiple internal reflections must be taken into account to predict accurately the input impedance of the lens antenna. These effects-previously demonstrated using the PO approach combined with the induced EMF (electromotive force) method [29]-will be discussed in details as a function of the material and geometry of the lens in Section II-C.…”

“…The major conclusions are the following: 1) taking into account first-order reflections is sufficient to compute the radiation patterns with a reasonable accuracy when the relative dielectric constant of the lens is lower than 4 [30]; 2) the power contained in high order reflections is spread out in all directions, without changing significantly the shape of the main lobe; 3) the input impedance [29] and the mutual coupling between radiating elements like slots [31] are also known to be affected by multiple reflections inside lenses.…”