Achim Walber

Submillimetre-wave receiver developments for ICI onboard MetOP-SG and ice cloud remote sensing instruments

The development of heterodyne receiver channels at frequencies ranging from 183 GHz up to 664 GHz, and compatible with the requirements of both the ICI instrument onboard MetOp-SG and the ISMAR instrument onboard the FAAM aircraft are presented. In order to optimize the performance VS cost factor, multi-channels architecture that enhances commonalities as well as maximum redundancies in the use of planar Schottky diode is adopted. The performance of each component is close if not at the state-of-the-art. For these receivers, broadband high power and high efficiency mutlipliers, and also high sensitivity subharmonic mixers are required. These developments are also possible thanks to the availability of novel test equipment systems such as VNA and Spectrum Analyser extenders up to 750 GHz in order to characterize fully each component. Performance of these submillimetre wave test equipment systems developed by RPG is also presented.

67–116 GHz single sideband Schottky-based receiver operating at room temperature

This paper describes the design and development of a single-sideband receiver using semiconductor Schottky and MMIC technology operating at room temperature from 67 GHz to 116 GHz to meet the extended frequency range of ALMA Band 2&3 simultaneously. Special care has been taken to design a fundamental balanced mixer that is sensitive from cut-off frequency up to second propagation mode of the WR-10 waveguide. Preliminary measured receiver noise temperature in the range of 3000-6000 K SSB is obtained at room temperature, in relatively good agreement with the predictions, assuming a sideband separation better than 10 dB.

THz Schottky diodes on epitaxial AlGaAs-membrane

Schottky structures based on quasi-vertical diode (QVD) design concept are essentially improved by optimization of the GaAs/AlGaAs wafer layout and fabrication process. Insertion of a 4 mum-thin epitaxial AlGaAs layer permits more accurate micromachining of the membrane-substrate without significant degradation of anode parameters. This greatly improved repeatability and increased the yield of the fabrication process. New technology tolerances allowed further optimization of structure geometry, which in turn led to achievement of state-of-the-art mixer performance at millimeter-waves.

Room temperature platinum nano-strip bolometer for mm & submm-wave applications

We demonstrate a W-band bolometer based on a platinum nano-strip which is integrated with a waveguide probe on a polymer substrate. We measure a high thermal response of 49000 K/W thanks to the small size of the Pt resistor and the thermal properties of the polymer. Furthermore, its small thermal capacity allows to decrease the time constant to 2.2 ms. A good matching in the entire W-band is achieved by a careful design of the probe. The linearity of the bolometer is demonstrated over 4 decades of RF power. As it is based on traditional microelectronic fabrication techniques, all dimensions of the circuit can be easily reduced to design full-band bolometers for smaller waveguides and higher frequency band up to the THz.