Design of tunable single band and concurrent low noise amplifier
Loading...
Date
2015-11-01
Authors
Hamidreza Ameri Eshghabadi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Low noise amplifier (LNA) is one of the key building blocks in receiving chain as they aimed to amplify the signal while adding minimum possible noise to it. Thus, several noise optimization techniques were proposed by researchers to minimize the noise of LNAs. Among these techniques, the PCSNIM (power constrained simultaneous noise and input matching) is found to be a popular approach; however, it limits the gain of the LNA according to literature. Therefore, to tackle the mentioned issue and to support the requirement for multi-band, this thesis presents the design of four LNAs (LNA1 to LNA4) based on inductive source degenerated (ISD) to cover single-band (e.g. IEEE 802.11.b/g, Bluetooth) and concurrent (e.g. WIFI) applications. LNA1 is targeted to solve the reduced-gain issue of single-band LNA by utilizing a gain-enhancer at the output of LNA. To obtain the concurrent reception of two frequency bands (2.45/ 5.2 GHz in WIFI standard), LNA3 is designed based on the same topology of LNA1. This LNA is implemented in fully-integrated structure to eliminate the off-chip components. Meanwhile, the design of LNA2 and LNA4 are resulted from the problem of frequency shift that occurred after the fabrication of LNA1 and LNA3. Hence, to tackle the issue, a tunable structure using varactors is used at the input/output matching of LNA2 and a new system (GPAPU-general purpose analog programmable unit) is introduced and implemented to the concurrent structure to obtain the tunable-concurrent amplifier (LNA4). For this work, LNA1, LNA2, and LNA3 were fabricated in 0.13 μm CMOS technology while LNA4 was designed only up to pre-layout simulation level. The measured forward gain and noise figure (NF) values for LNA1 are 19.84 dB and 2.59 dB respectively, while achieving the input/output return losses of -9.39 dB and -39.23 dB. LNA1 consumes 4 mA of dc current from 1.2 V supply. Meanwhile, 260 MHz frequency-shift was observed at the output of LNA1 due to the process tolerances during fabrication. The measured forward gain and NF values of LNA2 are 14.62 dB and 3.73 dB respectively, while consuming 5 mW of dc power. Moreover, the tuning ranges of 140 MHz at the input and 50 MHz at output are accomplished by LNA2 for the input/output matching. Due to the varactor-based tuning structure at the input and output of LNA2, the gain (and respectively NF) was traded-off with input/output matching to achieve tunable function comparing to LNA1. LNA3 is measured with the forward gain values of 17.11 and 10.42 dB at 2.45 and 5.2 GHz frequencies respectively, while consuming 4.8 mW of dc power. Also, the obtained values for input and output return losses are -19.48 and -39.23 dB respectively at the lower band and -25.51 and -10.64 dB respectively at upper band. The measured NF of this LNA3 is 4.09 dB at the lower-band and 10.47 dB at the upper band. The achieved gain and NF are different from the expected simulation results due to the observed 1 GHz frequency-shift at upper-band due to process variation during fabrication. From the simulation results of LNA4, the forward gain values obtained for lower and upper bands are 21 and 18 dB respectively. Also, the achieved NF values are 2.53 and 2.96 dB respectively in the mentioned bands while consuming 5.5 mW of dc power. In addition, the output network of the LNA4 can be tuned in range of 300 MHz. In conclusion, the implemented method of gain-enhancer in LNA1 works perfectly and the reduced-gain issue of PCSNIM technique is solved. Also, the problem of frequency-shift in single-band amplifier was tackled using the tunable structure of LNA2. Furthermore, a fully-integrated concurrent PCSNIM amplifier (LNA3) is designed and implemented successfully to receive simultaneous frequency bands of WIFI standard. Finally, a new tunable structure (GPAPU) was introduced and theoretically proved to be functional based on the simulation results of LNA4.