Metamaterial Zeroth Order Resonance Research Articles

Channel Selectivity of Satellite Transponders with the Antenna Combined with a Size-Reduced Metallic Waveguide Bandpass Filter Having Thin Metamaterial Resonators.

Global and intercontinental networking relies on satellite communication. Its wireless communication system always has antennas and their feed assembly comprising waveguides. This makes the satellite payload heavy and costly. In this paper, a novel method is proposed to effectively reduce the size of a waveguide bandpass filter (BPF). Because the metallic cavities make the conventional waveguide end up with a large geometry, especially for high-order BPFs, very compact waveguide-type resonators having metamaterial zeroth-order resonance (WG-ZOR) are designed on the cross-section of the waveguide and substituted for the cavities. While the cavities are half-wavelength resonators, the WG-ZOR is shorter than one eighth of a wavelength. A substantial reduction in size and weight of the waveguide filter is observed as the resonators are cascaded in series through coupling elements in the X-band much longer than K- or Ka-band. An X-band of 7.25~7.75 GHz is chosen to verify the method as the passband with attenuation of 40 dB at 7.00 GHz and 8.00 GHz as the roll-off in the stopband. The BPF is manufactured using the CNC milling technique. The design is carried out with geometrical parameters, not of the level of 10 μm, but the level of 100 μm, which is good for manufacturers but a big challenge for component designers. The measurement of the manufactured metal waveguide filter reveals that the passband has about ≤1 dB and ≤-15 dB as insertion loss and reflection coefficient and the stopband has ≤-40 dB as attenuation, which are in good agreement with the results of the circuit and simulation. The proposed filter has a length of 3.5 λg as the eighth-order BPF, but the conventional waveguide is 5 λg as the seventh-order BPF for the same area of the cross-section. This metamaterial BPF is combined with a horn antenna. The filter enables the wide-band antenna to distinguish the band of transmission from that of noise suppression. This channel selectivity is obviously observed by the filter integrated antenna test.

Effective Size Reduction of the Metallic Waveguide Bandpass Filter with Metamaterial Resonators and Its 3D-Printed Version.

In this paper, a novel method is proposed to effectively reduce the size of a waveguide bandpass filter (BPF). Because the metallic cavities make the conventional waveguide end up with a large geometry, especially for high-order BPFs, very compact waveguide-type resonators having metamaterial zeroth-order resonance (WG ZOR) are designed on the cross section of the waveguide and substituted for the cavities. While the cavities are half-wavelength resonators, the WG ZOR is shorter than one-eighth of a wavelength. A substantial reduction in the size and weight of the waveguide filter is observed as the resonators are cascaded in series through coupling elements in the X-band that is much longer than that in K- or Ka-bands. The proposed metamaterial filter is realized as a 3D-printed structure to be lighter and thus more suitable for low earth orbit (LEO) satellites. An X-band of 7.25-7.75 GHz is chosen to verify the method as the passband with an attenuation of 40 dB at 7.00 GHz and 8.00 GHz as the roll-off in the stopband. The BPF is manufactured in two ways, namely the CNC-milling technique and metal coating-added 3D printing. The design is carried out with a geometrical parameter of not 10-2 mm but rather 10-1 mm, which is good for manufacturers but challenging for component designers. The measurement of the manufactured metal waveguide filters reveals that the passband has about ≤1 dB and ≤-15 dB as the insertion loss and the reflection coefficient, respectively, and the stopband has an attenuation of ≤-40 dB, which are in good agreement with the results of the circuit and the simulation. The proposed filter has a length of 14 cm as the eighth-order BPF, but the conventional waveguide is 20 cm as the seventh-order BPF for the same area of the cross section.

Metamaterial Zeroth-Order Resonator RF Coil for Human Head: Preliminary Design for 10.5 T MRI

The objective is to develop a highly efficient RF head coil on a thin substrate for the ultra-high magnetic field MRI systems. The metamaterial zeroth-order resonator is investigated for this purpose. Simulation and experimental results are provided for an eight-channel M-ZOR-based RF coil in comparison with a standard high performance eight-channel dipole-based RF coil for the 10.5 T MRI system. Each element is 18 cm (approximately a quarter of a wavelength λ0) long, identical, evenly spaced along the circumference of the cylindrical phantom, loaded with dielectric material, and referred to as an inverted metamaterial zeroth-order resonator. The resonator elements are open circuited, matched, and tuned to 447.06 MHz with the phantom. An unloaded to loaded Q-factor ratio of 2.97 is obtained from the scattering matrix of the proposed design. The length independent nature of the proposed design and the flexibility of the lumped elements have provided an optimized element with a substrate thickness of roughly 3 mm (λ0/200). With the proposed design, there is a similar RF magnetic field strength (B1+) to SAR ratio with a reduced 10 g averaged SAR of 2.892 for the same input power compared to that of a dipole coil. This could make the coil acceptable for the clinical high-quality imaging.

Millimeter-wave beam-steering high gain array antenna by utilizing metamaterial zeroth-order resonance elements and Fabry-Perot technique

Millimeter-wave (mm-wave) beam-steering antennas are preferred for reducing the disruptive effects, such as those caused by high atmospheric debilitation in wireless communications systems. In this work, a compact broadband antenna array with a low loss feed network design is introduced. To overcome the short-range effects on mm-wave frequencies, a feed network – with a modified Butler matrix and a compact zeroth-order resonance antenna element – has been designed. Furthermore, the aperture feed technique has been utilized to provide a broadside stable pattern and improve the delivered gain. A Fabry-Perot layer without the height of the air layer is used. Taking advantage of this novel design, a broadband and compact beam-steering array antenna – capable of covering impedance bandwidths (from 33.84 to 36.59 GHz) and scanning a solid angle of about ~94°, with a peak gain of 17.6 dBi – is attained.

A wide band metamaterial ZOR antenna of a patch coupled to a ring mushroom

We present a new low-profile composite right- and left-handed metamaterial zeroth order resonance (ZOR) antenna of the simulated and measured fractional bandwidth 30 and 57%, respectively, for a center frequency 2.5 GHz and gain over 3 dBi, while other ZOR antennas have narrow bandwidths much less than 10% with low antenna gain below or around 0 dBi. The proposed antenna shows the monopolar radiation pattern over the entire band. The design approach is verified by the circuit and 3D EM simulations, and measurement.

Compact metamaterial zeroth-order resonator bandpass filter for a UHF band and its stopband improvement by transmission zeros

A microstrip bandpass filter for a UHF 900 MHz band is significantly miniaturised and its performance is enhanced using metamaterial (MTM) zeroth order resonator (ZOR) characteristics. Firstly, the authors propose that each of the resonators for a bandpass filter is implemented by a one-cell ZOR, and the coupling between neighbouring different ZORs is controlled to meet the primary goal on the bandpass filtering in the form of a sequential coupling mechanism. Secondly, this MTM ZOR filter is suggested to have transmission zeros (TZs) owing to source–load coupling to improve the isolation from other wireless communication bands. The first and second proposed filters are less than one-sixth of the conventional filters in terms of size, and they present lower insertion loss and return loss in the passband and higher isolation in the stopband owing to the TZs, as verified by simulation and measurement. In addition, the MTM properties are verified with a dispersion diagram and the no-phase variation electric field distribution over the ZOR by a 3D EM simulation.