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Design of Analog Integrated Circuits Robust to RF Interference

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1 – Introduction Furthermore, due to the widespread diffusion of wireless integrated systems, which is fostered by the availability of low cost RF systems on silicon, the level of environmental electromagnetic pollution is always increasing. As a consequence, an always increasing level of Electromagnetic Interference (EMI) is collected by wiring structures (cables, PCB traces, bondwires, etc...) in electronic systems from the outside environment and it is translated into RF voltages and currents superimposed onto SoC nominal signals. For instance, an RF incident field with a frequency of 900MHz and a peak amplitude of 10V/m, which is a common value in the proximity of a cell phone antenna, can induce on a PCB trace of 10cm, which acts as an electrical dipole, an RF voltage as high as 1Vpk. Finally, the threats related to the susceptibility to RFI become more and more severe in low voltage design. In fact, the reduction of IC power supply voltages which is imposed by geometrical scaling and by low power constraints makes the amplitude of RF interference very often comparable with the amplitude of ICs nominal signals or even larger, thus strongly reducing the Signal-to-Noise Ratio (SNR) within a chip. In conclusion, in order to be suitable to present day SoC challenges, an IC must be designed to operate properly even in the presence of RF interference with a magnitude comparable with nominal signals. In this work, the fulfilment of this requirement with reference to analog ICs, which should provide accurate continuous time, continuous amplitude waveforms, is addressed. 1.1 RFI in Analog Integrated Circuits Analog integrated circuits, in which the information is carried by continuous time, continuous amplitude voltage or current waveforms, have proven to be very suscep- tible to RFI. In fact, the RF disturbances which are superimposed onto nominal voltages and currents of an analog circuit are demodulated by the nonlinear char- acteristics of the active devices (MOS and BJT transistors) which are included in it, the demodulated RFI is added to the nominal output waveforms and their origi- nal information content is corrupted [6, 7, 8]. Demodulation of RFI is particularly hazardous because it converts out-of-band high frequency interference into in-band low frequency interference, which cannot be separated from nominal signals through linear filtering. In particular, in the presence of continuous wave (CW) RFI, the output voltage of analog circuits is affected by a DC offset. In standard analog circuits, the amount of in-band error which is due to the demodulation of out-of-band RFI is very often much higher than the nominal level of accuracy of these circuits. With reference to the widely employed CMOS Miller Opamp circuit connected in the voltage follower configuration shown in Fig.1.2, which operates from a 5V power supply, the amount of the measured RFI-induced DC offset voltage shift is plotted in Fig.1.3 versus the peak amplitude of CW RFI 2

Anteprima della Tesi di Paolo Stefano Crovetti

Anteprima della tesi: Design of Analog Integrated Circuits Robust to RF Interference, Pagina 2

Tesi di Dottorato

Dipartimento: Elettronica

Autore: Paolo Stefano Crovetti Contatta »

Composta da 158 pagine.

 

Questa tesi ha raggiunto 1216 click dal 10/01/2005.

 

Consultata integralmente 7 volte.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.