Active Balun with Center-Tapped Inductor and Double-Balanced Gilbert Mixer for GNSS Applications

Daniel Pietron,Tomasz Borejko,Witold Adam Pleskacz

doi:10.3390/electronics10111351

Abstract

A new 1.575 GHz active balun with a classic double-balanced Gilbert mixer for global navigation satellite systems is proposed herein. A simple, low-noise amplifier architecture is used with a center-tapped inductor to generate a differential signal equal in amplitude and shifted in phase by 180°. The main advantage of the proposed circuit is that the phase shift between the outputs is always equal to 180°, with an accuracy of ±5°, and the gain difference between the balun outputs does not change by more than 1.5 dB. This phase shift and gain difference between the outputs are also preserved for all process corners, as well as temperature and voltage supply variations. In the balun design, a band calibration system based on a switchable capacitor bank is proposed. The balun and mixer were designed with a 110 nm CMOS process, consuming only a 2.24 mA current from a 1.5 V supply. The measured noise figure and conversion gain of the balun and mixer were, respectively, NF = 7.7 dB and GC = 25.8 dB in the band of interest.

Highlights

The balun is a circuit widely used in radio frequency (RF) systems of single gigahertz up to hundreds of gigahertz
The balun is used to convert an unbalanced signal to a symmetrical one
Due to the use of a double-balanced circuit that requires an RF differential signal at the input, a balun circuit was present in the receiving path before the mixer

Summary

Introduction

The balun is a circuit widely used in radio frequency (RF) systems of single gigahertz up to hundreds of gigahertz. The use of a balun is required due to the necessity of providing a differential radio frequency signal to the input of a double-balanced mixer.

Results

Conclusion