Large Bandwidth Ratio Research Articles

Independent dual-band absorptions with large frequency ratio and large bandwidth ratio from composite metamaterials of water pyramids over Helmholtz resonators

We demonstrate the perfect trapping of electromagnetic fields at dual frequencies through composite metamaterials of a water pyramid cascaded meta-surface loaded with a Helmholtz resonator array. More specifically, the water pyramid cascaded meta-surface functions as an ultra-wideband absorber at the frequency range of 6.6–100 GHz with more than a 175 % relative bandwidth, while operating as a transparent screen at lower frequencies for the Helmholtz resonators. On the other hand, the Helmholtz resonator array will absorb electromagnetic fields at 100 MHz with the Q factor of 63 and the total thickness of 1/160 wavelengths, while performing as the ground for the water pyramids. The proposed design, integrating the water pyramid cascaded meta-surface with a Helmholtz resonator array for the independent dual-band absorptions with a large frequency ratio and large bandwidth ratio, should pave the way for building up more advanced energy-harvesting meta-devices.

Millimeter-Wave Dual-Band Bandpass Filter With Large Bandwidth Ratio Using GaAs-Based Integrated Passive Device Technology

In this letter, a millimeter-wave (mm-wave) dual-band bandpass filter is proposed with large bandwidth ratio by using gallium arsenide (GaAs)-based integrated passive device (IPD) technology. To realize small chip size, one dual-mode on-chip resonator is designed by using quasi-lumped capacitors and microstrip lines. In addition, multiple transmission zeroes are generated by further introducing both the electric and magnetic couplings between adjacent resonators. To realize large bandwidth ratio of two passbands, the external quality factors are investigated at both passband, and can be independently controlled. For demonstration, a 28-/50-GHz dual-band bandpass filter is designed, fabricated, and measured. The fractional bandwidth ratio is 7.8, which is much larger than the reported on-chip filters. Meanwhile, very low insertion loss of 0.58-dB is realized for the lower passband at 28 GHz, indicating the proposed dual-band bandpass filter a promising application in mm-wave wireless systems.

A dual‐band superconducting filter with a large bandwidth ratio

In this study, we propose a stepped-impedance-stub loaded interdigital capacitor resonator for design of a dual-band band-pass filter with a large bandwidth ratio. The presented resonator has strong and weak couplings in the upper passbands (UPs) and lower passbands (LPs), respectively, so as to form a large upper/lower bandwidth ratio. Adopting a dual-branch phase-matched feedline structure can meet the external quality factors required for the UP/LP. Therefore, these two passbands, defined by their respective center frequencies and bandwidths, can be manipulated independently. A four-pole dual-band example filter with a lower bandwidth of 20 MHz at 1576 MHz and an upper bandwidth of 200 MHz at 2450 MHz is successfully designed on an YBCO/MgO superconducting wafer. The filter exhibits excellent frequency responses. The upper/LPs show insertion losses below 0.07/0.22 dB and return losses above 15.3/15.3 dB. The stopband rejection is better than 57 dB until the first spurious passband up to 6150 MHz (3.9fL).

All-metal frequency-selective absorber/emitter for laser stealth and infrared stealth.

In this paper, an all-metal nanostructure is designed with a large frequency ratio (∼6) and a large bandwidth ratio (∼32), and consists of period slit-box cavities and nanodisk clusters. It is a nearly perfect absorber at 1.064μm to achieve laser stealth, a frequency-selective emitter with low emissivity in wavelength ranges 3-5 and 8-14μm to achieve infrared stealth, and also an emitter with near unity emissivity at 2.709μm and 6.107μm to compensate for the decrease of radiation heat transfer owing to the low emissivity. The absorption/emission peaks are all the Lorentzian shape, and the bandwidths, defined as full width at half-maximum, are 35, 408, and 1124nm at 1.064, 2.709, and 6.107μm, respectively. The electric and magnetic field distribution shows that the slit behaves like a capacitor, the box behaves like an inductance, and the nanodisk clusters can excite electric dipole resonance. Considering the solar irradiation, the nanostructure maintains middle-wavelength infrared signal reduction rates greater than 80% from 450 to 1000K, and long-wavelength infrared signal reduction rates greater than 90% from room temperature to 1000K. The laser and infrared stealth performances of our nanostructure at 473K are also studied with different incident angles and polarization angles.

Dual-band dual-ring bandpass filter with large bandwidth ratio

A novel dual-band bandpass filter with large bandwidth ratio is proposed by using two dual-mode square ring resonators. By stretching the length of the loaded open stub of the inner ring, one of its first-order degenerate modes moves down and forms the first passband together with a pair of first-order degenerate modes of the outer ring resonator. Meanwhile, the second passband is constructed by another first-order degenerate mode of the inner ring resonator and its second-order degenerate mode. In this way, the realisable fractional bandwidth of the first passband can be largely enhanced with the new combination of multiple resonant modes. Finally, a prototype with a high fractional bandwidth ratio of two passbands has been realised and verified experimentally.