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The Belostotski LNA : Combining noise-cancelling and noise matching

Hoek, W.A. (2018) The Belostotski LNA : Combining noise-cancelling and noise matching.

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Abstract:In this report an analysis is performed on the gain and noise behavior of the active negative C LNA proposed by L. Belostotski. This LNA utilizes an active matching element to achieve negative ca-pacitance (negative susceptance proportional to frequency), thereby achieving a noise figure closer to NFmin (noise match). The goal of the research was to get a better understanding of the technique used in this LNA and to investigate whether it could also be used in other LNA topologies. Analysis shows that there are two sources of negative capacitance; 1) feedback of the output to the input through a common-gate transistor and 2) an active inductor formed by the same common-gate transistor which has negative capacitor behavior at frequencies up to a few GHz. Simulation of the negative C LNA in 22nm FDSOI using 1.5u/40n SLVT (super low Vt) transistors shows that the negative capacitance positively affects the noise figure but this improvement is shown to be mainly due to improved bandwidth. Comparison between the LNA proposed by Belostotski, a BALUN LNA and an active shunt-feedback LNA shows that the Belostotski LNA has better NF when compared to a BALUN LNA with equal power consumption. The regular active shunt-feedback LNA was shown to be on par with regard to noise figure but better linearity is shown in simulation for both the BALUN and shunt-feedback LNA. The conclusion of this research is that the Belostotski LNA (i.e. active negative C LNA) performs quite well compared to other noise-cancelling topologies, but a trade-off exists between linearity and NF. The presence of positive feedback via the cross-coupled transistors helps lower NF, but introduces the risk of high-frequency instability. This cross-coupling is not present in a regular active shunt-feedback LNA. The final design is aimed at application in the ISM-band at 5.8 GHz. Two desgin where made, one optimized for NF and a second one optimized for linearity: The fist design achieves 1.1 dB NF, 16 dB voltage gain and -16.5 dBm IIP3. The second design was made with more emphasis on linearity, achieving a NF of 2.2 dB, 10 dB voltage gain and -4 dBm of IIP3.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
Link to this item:https://purl.utwente.nl/essays/75544
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