A Threshold Voltage Tracking Circuit providing upto 20dB improvement in IIP2 of Single-ended Passive Mixers

Karun, Kasyap V and Chowdary, Gajendranath (2022) A Threshold Voltage Tracking Circuit providing upto 20dB improvement in IIP2 of Single-ended Passive Mixers. In: 2022 IEEE International Symposium on Circuits and Systems, ISCAS 2022, 27 May-1 June 2022, Austin.

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Abstract

The importance of area optimizations leads to the removal of balun between LNA and mixer in RF receivers and this, in turn, lead to the use of single-ended passive mixers in the place of its differential counterparts. But the single-ended topology resulted in the variation of IIP2 performance of mixers across temperature and process corners as well as across different frequencies of operation compared to its differential counterpart. The IIP2 of RF receivers showed peak performance at different mixer bias voltages at different corners and bands. In this paper, we propose a threshold voltage tracking circuit in 14-nm FinFET technology to bias the passive direct-conversion single-ended mixers such that it enhances the IIP2 performance of mixers up to 20dB across temperature and process corners. This design includes a temperature-dependent bias voltage generation circuit with different slopes over temperature which can be varied with a step size of nearly 8mV and an additional DC voltage calibration circuit to generate differential bias voltages independently in I and Q channels. The temperature slope of the bias voltage being generated is dependent on the NMOS width and the current flowing through the NMOS. This enables us to generate the mixer bias voltages with different slopes over temperature and allows us to employ the same circuit to bias the mixer at different frequencies of operation, temperature and process corners. © 2022 IEEE.

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