Wideband microwave circuits for radioastronomy applications= Circuitos de microondas de banda ancha para aplicaciones de radioastronomía

Zusammenfassung

The analysis of the Cosmic Microwave Background radiation as main evidence of the Big Bang theory involves the development of very high sensitivity receivers and broadband working in millimetre-wave frequencies. In this thesis, the 26 to 36 GHz frequency band QUIJOTE (Q-U-I JOint TEnerife) instrument receiver is designed and integrated, which is based on phase switching using 180º and 90º phase switches. The phase switching circuits must ensure a flat phase difference, 180º or 90º respectively, in the whole frequency range covered by the receiver. Besides, microwave detectors based on Schottky diode are developed which convert the power of the microwave signal into output voltages. The behaviour and variations in performance of circuits and discrete devices are also analysed as a function of the working physical temperature. Finally, the modelling of microwave diodes, such as Schottky and PIN, is described, which are intended for their use on the design stage of the circuits at room and cryogenic (around 15 K) temperatures.