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Two linear arrays of split ring resonators (SRR) with broad side coupling and various relative positions are investigated for controllable wave transmission in a rectangular waveguide. Each array is designed to have a different unit size of SRRs. A rectangular waveguide with a cutoff frequency of 3.2 GHz shows an additional stopband between 3.4 GHz and 4.8 GHz when a five element SRR array with a unit SRR dimension of 18mm by 18 mm and a pitch of 25mm is loaded. The other five element array with a unit dimension of 10mm by 10mm and a pitch of 25mm is inserted adjacent to the first array with a broad side coupling resulting in another stopband between 5 GHz and 6.5 GHz, where the coupling gap between two arrays is approximately 3mm (120mil) and the dielectric constant is 2.55. The center frequency of the stopband is tunable depending on the degree of alignment between those two arrays. One of the SRR arrays has a piece of magnet attached to its edge, and in-situ tuning is achieved by moving it by a ferrite (or a permanent magent) from outside of the waveguide. The tuning results of numerical simulation show good agreement with those of measurement.

A self-packaged folded patch antenna in a rectangular waveguide shape is greatly reduced in size by loading a complimentary split ring resonator (CSRR) on the edge of its ground plane. The dimensions of the proposed antenna are 15mm×15mm×20mm, showing 72% volume reduction compared to one without CSRR loading at the same radiation frequency of 2.4GHz. Impedance matching between the patch and the feeding line is obtained by adjusting the gap between two edges of the folded patch not necessitating an additional impedance matching circuit. Also, the inside cavity surrounded and packaged by the folded patch is electromagnetically well shielded from the external circuit. This antenna offers a quasi-omni-directional radiation pattern. All those features make the proposed antenna very suitable for a compact sensor network application. To our knowledge, this is the first report a non-planar CSRR applied to antenna size reduction.

A self-packaged antenna obtained by folding a normal patch antenna into rectangular waveguide shape has been recently reported by the authors. In this work, by applying electric vias at the edge of the folded patch as well as inductive dents on the edge, the folded antenna dimension is greatly reduced. At the same radiation frequency of 2.4GHz, the vertical length of the newly proposed antenna is reduced from 40mm to 19mm which is 52.5% size reduction. The cross section area is 20mm × 20mm. Since this architecture allows PCB layout or other electronics inside the cavity of the folded antenna, it is considered a self-packaged structure. If designed carefully, this antenna may take zero footprint and offers electromagnetic interference shielding to the PCB enclosed in its cavity. Meanwhile, this antenna does not require additional impedance matching circuits, which makes it very useful for compact devices. A quasi-omni-directional radiation pattern is obtained. Theoretical analysis, numerical simulation, fabrication and measurement are performed. Good agreement is observed between simulation and measurement data.