Abstract
Wireless devices such as smart meters, trackers, and sensors need connections at multiple frequency bands with low power consumption, thus requiring multiband and efficient antenna systems. At the same time, antennas should be small to easily fit in the scarce space existing in wireless devices. Small, multiband, and efficient operation is addressed here with non-resonant antenna elements, featuring volumes less than 90 mm3 for operating at 698–960 MHz as well as some bands in a higher frequency range of 1710–2690 MHz. These antenna elements are called antenna boosters, since they excite currents on the ground plane of the wireless device and do not rely on shaping complex geometric shapes to obtain multiband behavior, but rather the design of a multiband matching network. This design approach results in a simpler, easier, and faster method than creating a new antenna for every device. Since multiband operation is achieved through a matching network, frequency bands can be configured and optimized with a reconfigurable matching network. Two kinds of reconfigurable multiband architectures with antenna boosters are presented. The first one includes a digitally tunable capacitor, and the second one includes radiofrequency switches. The results show that antenna boosters with reconfigurable architectures feature multiband behavior with very small sizes, compared with other prior-art techniques.
Highlights
Since the antenna booster is electrically small, its impedance is mainly reactive, and it is poorly matched at most of the bands of operation in the frequency range from 0.6 GHz up to 10.6 GHz, where many communication systems are allocated, such as cellular and short-range wireless communications. This mismatch issue is overcome with the addition of a multiband matching network, resulting in a multiband antenna system with a small antenna element and with competitive efficiency values [12,13,14,15,16,17]
A digitally tunable capacitor (DTC) is a microwave device where the capacitance can be digitally changed within a range from Cmin to Cmax
The DTC-based matching network for antenna boosters shown in the previous section is very attractive when only one component of the matching network can tune the frequency bands of operation
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Since the antenna booster is electrically small, its impedance is mainly reactive, and it is poorly matched at most of the bands of operation in the frequency range from 0.6 GHz up to 10.6 GHz, where many communication systems are allocated, such as cellular and short-range wireless communications This mismatch issue is overcome with the addition of a multiband matching network, resulting in a multiband antenna system with a small antenna element and with competitive efficiency values [12,13,14,15,16,17]. Multiband operation is addressed with antenna boosters combined with reconfigurable matching networks, comprising lumped passive components (capacitors and inductors) as well as active devices.
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