Compact multi-element antennas of sinusoidal printed monopoles for sensors and portable devices

We present small printed sinusoidal monopoles as enhanced meander-line antennas shaped after smooth curves, capable of forming compact multi-element antennas. The antennas were designed at 2-3 GHz according to the size and bandwidth constraints of multimedia sensor networks. Their performance was characterized in terms of electrical size, bandwidth, and broadband radiation efficiency. Results show that the sinusoidal monopole achieves 68% more bandwidth compared to a meander-line antenna of similar size and efficiency. Moreover, when forming compact arrays with closely spaced elements, element detuning is not severe, whereas envelope correlation stays below 0.5 even for lambda₀/10 spacing.