Multiband Impedance Matching Using Microstrip-Embedded MTM-EBGs

This work investigates a general method of multiband impedance matching using a double-stub tuner (DST) loaded with metamaterial-based electromagnetic bandgap structures (MTM-EBGs). MTM-EBGs are uniplanar and fully printable and can be embedded directly into microstrip (MS) stubs to imbue them with designable electrical lengths at two or more harmonically unrelated frequencies, without increasing the stub footprint. Combinations of these stubs, inspired by the DST, can produce multiband impedance matching to arbitrary, complex, and frequency-dependent loads. A dual-band matching network is first presented with this method, and a general design procedure is developed to match at two desired frequencies while maximizing bandwidth. Matching bandwidths of 44.4% and 22.1% around 2.4 and 5.8 GHz are observed. Next, a tri-band matching network is designed and fabricated for operation at 2.4/3.6/5.8 GHz, again following a general and well-established design procedure and presenting bandwidths of 16.8%/6.6%/18.3% around the three operating frequencies, respectively. The resulting circuits are uniplanar and compact, requiring a similar footprint to that of a single-band DST, and the matching networks are designed to ensure that dissipative losses in the matched bands are minimized. In all cases, measurement results of the uniplanar devices show excellent agreement with simulations.