Article

A Better Balun? Done The Design of a 4:1 Wideband Balun Using a Parallel-Connected Transmission-Line Balun

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Abstract

This article presents a 4:1 wide-band balun that won the student design competition for wide-band baluns held during the 2016 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2016) in San Francisco, California. For this contest, sponsored by Technical Committee MTT-17, participants were required to implement and evaluate their own baluns, with the winning entry achieving the widest bandwidth while satisfying the conditions of the competition rules during measurements at IMS2016. Some of the conditions were revised for this year's competition compared with previous competitions as follows.

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... Balun finds usefulness in wide ranging applications such as antenna arrays, balanced mixers, amplifiers [1]. The key metrics for a balun are balanced phase and magnitude at the differential outputs and the impedance matching at all the ports. ...
... The emergence of wireless communication devices has also necessitated miniaturized baluns, with good isolation between the output ports, able to provide good performance at multiple frequencies [2][3][4][5]. Furthermore, an added feature of baluns is their impedance transformation ability as this could be extremely useful in applications such as power amplifiers and rectifying antennas in energy harvesting [1,6,7]. An added degree of flexibility can be obtained in the DGS structure in [6] whereas the additional burden on impedance transformer could be avoided in [7] with an inherent impedance transforming component in RF front end system. ...
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... Balun finds usefulness in wide ranging applications such as antenna arrays, balanced mixers, and amplifiers [1]. The key metrics for a balun are balanced phase and magnitude at the differential outputs and the impedance matching at all the ports. ...
... The emergence of wireless communication devices has also necessitated miniaturized baluns, with good isolation between the output ports, able to provide good performance at multiple frequencies [2][3][4][5]. Furthermore, an added feature of baluns is their impedance transformation ability as this could be extremely useful in applications such as power amplifiers and rectifying antennas in energy harvesting [1,6,7]. An added degree of flexibility can be obtained in the DGS structure in [6] whereas the additional burden on impedance transformer could be avoided in [7] with an inherent impedance transforming component in RF front end system. ...
Preprint
A dual-band balun with inherent impedance transformation is presented in this paper. The inherent impedance transformation ratio from a range of 0.4 to 4.0 makes the balun ideal for the on-chip fabrication. The proposed dual-band balun exhibits excellent input port matching, equal output signal with phase difference of 180 • , and extremely good isolation and matching at the output ports. A table is provided with the design parameters at the extreme impedance transformation ratios. The design concept of the proposed balun has been validated through a prototype fabricated on a Rogers RO5880 substrate. The measurement results are in good agreement with the EM simulation measurements.
... This year's competition rules were similar to those of the previous year, as follows [1]: ...
... In the figure, Z0 represents the characteristic impedance of the transmission line, which is determined by the impedance of the ports. The characteristic impedance of the transmission line must be carefully determined to obtain good performance [1]. The Z0 of the transmission line for the Guanella's balun is given in [8] by ...
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