Investigation of advanced Butler matrices with integrated filter functions

Tornielli di Crestvolant, Vittorio (2015). Investigation of advanced Butler matrices with integrated filter functions. University of Birmingham. Ph.D.

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Abstract

This study presents a novel synthesis technique for Butler matrices that include filter transfer functions through a circuit based only on resonators. The Butler matrix is the fundamental building block to split and recombine the signals in Multi-port Power Amplifiers, where multiple inputs are delivered to a bank of amplifiers sharing them, and later recombined through an output network. However, to suppress spurious frequencies generated by the amplifiers or to provide near-band rejection in order not to interfere with other transmission/receiving bands, separate filtering is often required. Here, the traditional properties of the Butler matrix are included together with filtering selectivity into one single device based only on coupled resonators. An analytical synthesis procedure of the coupling matrix is presented here for the first time. The proposed solution has shown significant advantages in terms of size reduction compared to the traditional baseline consisting of a Butler matrix plus a bank of band-pass filters. Based on the technique proposed, three prototypes are designed and manufactured: a 180° hybrid coupler based on resonators and two versions of a 4x4 Butler matrix with filtering, built with additive manufacturing and with milling. Experimental measurements are in good agreement with simulations and theoretical expectations.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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