Multifunction GaAs MMIC transmitter/receiver for onboard satellite equipment
This paper describes the development of a new GaAs MMIC to be used in transmit/receive modules for S band transponders. The IC, which includes five different functions, reduces the sue of the system whilst maintaining and even improving system performance. Amplification, phase shifting, and mixing are some of the functions integrated in the same chip. The goal of the work is to reduce the number, size, and consequently, the cost of the circuitry currently in use through an European commercial Enhancement/Depletion (E/D) pHEMT process, compatible with low noise reception. A maximum conversion gain more than 54 dB has been achieved with a gain control more than 27 dB. A 0 dBm output power at 1dB compression point (P1dB) has been measured when a CW stimulus was used as input signal, while more than 35 dB of Adjacent Channel Power Ratio (ACPR) was tested for a BPSK input signal.
Evolution and recent development in MMIC's for space application
A very aggressive policy has been set up in the early 1990s to introduce MMIC in space equipment in ALCATEL Space Industries. The first step was to choose preferred suppliers able to produce high reliability low level or power MMIC's up to Ku band even if the required quantities were not so important. MMIC processes have been formally space qualified following the methodology proposed by French Administration. The second step was to develop MMIC's as "building blocks," families of generic simple circuits were designed (gain block, LNA, MPA, HPA, phase shifter, flatness correctors, multipliers, mixers, oscillators, etc...) mainly in C band and Ku band. This represented more than 100 different MMIC's.
Resonant Auger decay study of C1s -> pi* core-excited OCS
The present work aims at characterizing short-lived C1s((-1)) pi*((1)) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s -> pi* resonance in the binding energy region 15-19eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the (A) over tilde, (B) over tilde and (C) over tilde final states. This is explained by (1) the variation in the C-O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s((-1)) pi*((1)) intermediate states can be predicted in analogy with e.g. the N-2, CO2 and N2O molecules. (C) 2009 Elsevier B.V. All rights reserved. (Less)