Tunable Filter/Antenna Integration With Bandwidth Control

In this article, tunable integrated filter/antennas are demonstrated with two coupling configurations that provide design control of the bandwidth performance over the tuning range. The first is a single-layer third-order tunable filter/antenna with an increasing fractional bandwidth (FBW). The measured device has a frequency tuning range from 1.62 to 2.08 GHz, an FBW increasing from 3.0% to 4.8%, and a gain increasing from -7.3 to 3.6 dBi. The second is a double-layer vertically integrated third-order tunable filter/antenna that provides a constant absolute bandwidth over the tuning range. This design accounts for the frequency-dependent behavior of the antenna radiation Q. The constant absolute bandwidth device is tunable from 1.65 to 1.90 GHz, has a maximum bandwidth variation of 45.3 ±7.4 MHz over the tuning range, and exhibits a gain from -6.1 to 4.3 dBi.