This thesis reports on the design of a differential to single-ended anti-aliasing filter for Nuclear Physics experiments. The framework is the FARCOS (Femtoscope ARray for COrrelation and Spectroscopy) system whose purpose is to identify in charge, energy and mass the impinging charged particles in multifragmentation reactions. FARCOS is located inside an experimental vacuum chamber and the analog output signals are driven outside vacuum by differential line drivers to minimize the noise pick-up. The circuit presented in the thesis is responsible for converting the differential analog signals coming from FARCOS into single-ended signals. In addition it performs also an antialiasing filtering and provides the voltage shift required by the following backend electronics responsible of the digitization of the full output waveform shape. The research activity described in the thesis focused on the choice of the most suited topology for the differential to single-ended amplifier and on the design of the anti-aliasing filter, based on a Sallen-Key stage. The need of a 256-channel board leads to a very critical layout design and to the use of minimum size SMD components. A survey of different commercial operational amplifier lead to the choice of the OPA that meets all the required electrical performance and case size. A 4-channel prototype has been designed and qualified in order to verify the proper functionality.
Questa tesi descrive il progetto di un circuito di filtraggio anti-aliasing con conversione da segnale differenziale a segnale a singola uscita per esperimenti di Fisica Nucleare. L’ambito e’ il sistema FARCOS (Fremoscope ARray for COrrelation and Spectroscopy), il cui scopo e’ l’identificazione in massa, energia e stato di carica delle particelle cariche incidenti in esperimenti di multiframmentazione. FARCOS si trova all'interno di una camera a vuoto e i segnali di uscita analogici vengono trasmessi al di fuori della camera a vuoto in modo differenziale, per ridurre al minimo l’accoppiamento di disturbi. Il circuito presentato nella tesi è responsabile della conversione del segnale differenziale analogico proveniente da FARCOS in un segnale singolo, eseguendo anche un filtraggio antialiasing e provvedendo l’offset di tensione necessario per il funzionamento della successiva scheda per la digitalizzazione dell’intera forma del segnale di uscita. L'attività di tesi si è concentrata sulla scelta della topologia del ricevitore differenziale e del filtro anti-aliasing basato su uno stadio Sallen-Key. Le esigenze di una scheda a 256 canali portano ad un disegno del layout molto curato e all'utilizzo di componenti SMD di dimensioni minime. Una ricerca di diversi amplificatori operazionali commerciali ha portato alla scelta dell'OPA che soddisfa tutte le prestazioni elettriche richieste e la dimensione del package. Un prototipo a 4 canali è stato progettato e qualificato per verificare la corretta funzionalità.
256-channel differential to single ended antialiasing filter for pulse shape analysis in nuclear physics experiments
CHANG, PENGFEI
2016/2017
Abstract
This thesis reports on the design of a differential to single-ended anti-aliasing filter for Nuclear Physics experiments. The framework is the FARCOS (Femtoscope ARray for COrrelation and Spectroscopy) system whose purpose is to identify in charge, energy and mass the impinging charged particles in multifragmentation reactions. FARCOS is located inside an experimental vacuum chamber and the analog output signals are driven outside vacuum by differential line drivers to minimize the noise pick-up. The circuit presented in the thesis is responsible for converting the differential analog signals coming from FARCOS into single-ended signals. In addition it performs also an antialiasing filtering and provides the voltage shift required by the following backend electronics responsible of the digitization of the full output waveform shape. The research activity described in the thesis focused on the choice of the most suited topology for the differential to single-ended amplifier and on the design of the anti-aliasing filter, based on a Sallen-Key stage. The need of a 256-channel board leads to a very critical layout design and to the use of minimum size SMD components. A survey of different commercial operational amplifier lead to the choice of the OPA that meets all the required electrical performance and case size. A 4-channel prototype has been designed and qualified in order to verify the proper functionality.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/135113