Measurement method for the TE mode cutoff frequency in EBG structures fabricated in LTCC for antenna applications

This paper presents characterization of low temperature co-fired ceramic (LTCC) based electromagnetic bandgap (EBG) structures. We show a new test method to measure the TE mode cutoff frequency of an EBG structure. This test method is implemented at millimeter wave frequencies. Exponentially-shaped TE mode surface wave launchers are fabricated in the same LTCC substrate as the EBG structure under test to realize a compact and repeatable test vehicle. A pair of two port coupling measurements experimentally yields the TE mode cutoff frequency, below which a bound TE mode surface wave is suppressed. The TE mode cutoff frequency is important where EBG structures are integrated into millimeterwave LTCC antennas because this cutoff frequency must be greater than the antenna´s operational frequency range. This proposed test method differs from previous experimental techniques because it employs a calibration test vehicle, and this test method provides a clear indication of the TE mode cutoff frequency.