Programa del congreso

Gallium arsenide (GaAs) metamorphic high electron mobility transistors (mHEMT) and a grounded coplanar waveguide environment offer remarkable electronic properties, placing them into a key position for millimeter wave (mmW) and sub-mmW power amplifiers (PAs). At these high frequencies it is a great challenge to obtain accurate models that predict the real performance of the active components (i.e. transistors). This paper presents an experimental validation of a cascode configuration based on a multiport transistor model. The inhouse model shows very high accuracy for measurements in a broad range of frequencies (0.1 - 330 GHz). The good correlation of the simulation of the model and the posterior measurements was verified by the fabrication of a G-band (140 - 220 GHz) PA module. The packaged PA showed a small-signal gain of more than 13.4 dB for a broad bandwidth of 56 % and a maximum output power of 4.61 dBm at 210 GHz.

In this work, we develop a novel Monte Carlo method for solving the electromagnetic scattering problem. The method is based on a formal solution of the scattering problem as a modified Born series whose coefficients are found by a conformal transformation. The terms of the Born series are approximated by sampling random elements of its matrix representation, computed by the Method of Moments. Unlike other computational techniques, this Monte Carlo method does not require communications between processors, which makes it suitable for large parallel executions.

A gradient index flat lens with a directive beam-steering radiation pattern and configurable dual circular polarization is discussed in this contribution. The dielectric lens, designed to operate at W band (70-100 GHz), is perforated to achieve a radial decreasing dielectric permittivity characteristic, so high-directivity beam with planar wave front can be obtained. A precisely designed stereolithography 3D structure is adhered to the surface of the lens to turn the vertical or horizontal electric field polarization into RHCP or LHCP, respectively. An open-ended square waveguide is used as feeding structure in order to generate the vertical and horizontal polarization by the excitation of the degenerate modes TE10 and TE01. The system can achieve a wide beam-steering range of ±30° in both azimuth and elevation planes, attained by applying precise displacements to the feeding square waveguide position. In order to experimentally validate the antenna performance, the design is fabricated and measured.

New telecommunication and radar systems at high frequencies require high directive antennas with low scan losses to compensate the path loss and propagation attenuation. Geodesic lens antennas are a good candidate to these new applications since they can provide high directivity, high efficiency and low scan losses. Here, we explain how to produce rotationally symmetric geodesic lenses based on transformation optics. In particular, we calculate the equivalent geodesic shape of a Luneburg lens, which is able to transform cylindrical waves into planar waves. In order to demonstrate the potential of this technique, we designed a 11-port geodesic lens antenna, which is able to scan 120º. The beams have a maximum gain of 20 dB at 30 GHz with 0.5 dB scan losses. We describe possible manufacturing techniques, including their advantages and drawbacks in terms of assembly misaligments, surface roughness and tolerances.