GaN C-Band HPA for Phased-Array Applications
In the UMS GH25-10 GaN MMIC technology a C-band high power amplifier (HPA) has been realized. The current design is primarily intended for use in a space-based SAR system with a center frequency of 5.4 GHz and a sweep bandwidth of 100 MHz. To enable reuse of the amplifier in other radar systems such as weather radar, a large bandwidth is required. A design bandwidth from 5 to 6 GHz has been used. Simulation and measurement data from on-wafer and mounted samples will be shown. Showing more than 50 W output power with 45% efficiency the HPA shows sufficient performance to be used in a module for state-of-the-art active electronically scanned arrays. The measured output power and efficiency are a record for MMIC amplifiers.
50 Watt S-band Power Amplifier in 0.25 µm GaN technology
A 50 W S-band High Power Amplifier in the UMS GH25-10 technology is presented. In order to increase the output power per area the size of the transistors is increased beyond the maximum size modelled by the foundry. For this reason the design procedure included the measurements of a transistor and the creation of a scalable Angelov-GaN model with the use of EM simulations. An output matching design approach is adopted which intrinsically optimizes the transistor harmonic load impedance. The results show that the amplifier delivers an output power of over 50 W within the frequency range from 3.05 to 3.5 GHz at a PAE of more than 62 %. The maximum measured output power is 63 W with a PAE of 65 %.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.