A First Implementation of a Single-Layer 4×4 Butler Matrix on Flexible PET Using Printed Silver

This paper shows the fruition of a first ever 4×4 12.5 GHz Butler Matrix built on 127 µm (5 mil) polyethylene terephthalate (PET) substrate; using conductive printed silver [Ag] on the top layer and plain copper (tape) on the bottom (back) ground layer. The beam(s) of the matrix had peak realized gain of −32 dBi due to the heavy loss (S
21
= −30dB to −40dB at 12.5 GHz) of the matrix. While thin PET is lossy (tanδ≈ 0.02) and printed silver has poor conductivity (σ = 2.6 × 10
⁶
S/m), the thin PET's flexibility and silver ink's quick printing ability can be valuable to lots of practical applications in the mass production sector (and Ag can always be replaced by copper to improve loss). It is with hope that this work incites (and gives rise) to further progress and research in this field for the future development and improvement of such flexible and steerable antennas.