Microstrip patch antenna on LTCC metamaterial substrates in millimeter wave bands

There has been much research to improve the properties and to reduce the size of microstrip antennas and high permittivity dielectric substrates have been considered to reduce the size of microstrip antennas [1–2]. High permeability materials are considered for the substrates of microstrip antennas instead of high permittivity materials [3–6]. But, Pendry was the first to suggest the use of Split Ring Resonators (SRRs) as a canonical metamaterial structure that gives rise to an effective magnetic response without the need for magnetic materials [7]. When we design a microstrip antenna on the metamaterial substrate, which has SRR structures in the substrate, we can reduce the size of a microstrip patch antenna [8]. Additionally, if we use the SRRs that have various scales in the substrate, we can design the multi-band antenna [9]. The SRR is a ring with a gap. When the axis of the ring is parallel with the magnetic field, the strong induced current in the SRR results in a magnetic resonance whose frequency depends on the scale of the geometry. We can change the resonance frequency from low frequency to optical bands by changing the scale of the SRR. Metamaterial substrates for millimeter wave bands can also be designed by scaling the SRR structures. Millimeter wave systems have many advantages for military and commercial applications. They have better resolution than microwave systems because of the narrow beamwidth. This is proper for radar systems [10]. In the commercial area, the demand on the EM frequency spectrum has suddenly increased with the rapid growth of wireless systems. However, the frequency spectrum is limited and microwave frequency bands are saturated, hence millimeter frequency bands can be a solution to provide more spectrum resources [11].