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A photonic approach to realizing anti-chromatic dispersion transmission for a frequency and bandwidth-doubling dual-chirp microwave waveform is proposed and experimentally demonstrated. The system has no requirement on polarization devices or optical filters for only the integrated dual-drive dual-parallel Mach–Zehnder modulator employed. To overcome chromatic dispersion, the carrier frequency suppression approach is proposed. The anti-chromatic dispersion process is accomplished in a central station and independent to carrier frequency, fiber length, and dispersion coefficients. An experiment is conducted to verify the analysis. Dual-chirp waveforms at 13 GHz with a bandwidth of 0.8 GHz and time duration of 1 μs are obtained. After 25 km fiber transmission, the proposed approach shows a relatively flat curve in a frequency-power diagram, while the normally carrier-suppressed double-sideband modulation method experiences a significant power fading for fiber dispersion.

An effective approach to design miniaturized-element frequency selective surface (FSS) is presented. The FSS is based on an original Jerusalem cross-shaped slot one, whereas there is a metallic patch array with the same period laid over it. An equivalent circuit model analysis is presented to provide an insightful design procedure for the miniaturization. Numerical simulations indicate that one prototype of the designed FSS has been much compacter in size, the unit size is miniaturized to only 0.0371λ × 0.0371λ, where λ represents the resonant wavelength in free space; moreover, the miniaturization performance is stable with respect to different polarizations and incident angles. In addition, after the amelioration of the unit cell structure, the unit size is consumedly miniaturized to 0.0094λ × 0.0094λ. Finally, the prototype FSS is fabricated and measured, a good agreement between the measured and simulated results is observed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2572–2576, 2015

A triple-band low frequency ultra-compact metamaterial absorber (MA) is proposed, which is composed of a periodic array of 3D structures constructed in lossy FR4-epoxy dielectric slab, and another ultra-thin grounded dielectric substrate is attached to its bottom. The unit cell can be counted as a combiner of three 3D magnetic resonators, which have similar resonant mechanisms and can all be ultra-compact in size. By adjusting structural parameters of the unit cell, the proposed MA can perform well in absorptions at each low resonant frequency. For example, one MA with unit cell width 10.92 mm exhibits three absorption peaks at 2.151 GHz, 2.283 GHz, and 2.378 GHz with the corresponding absorptivities of 96.5%, 96.8%, and 99.6%, respectively; for the three low frequencies, the width of the unit cell is only 7.8%, 8.3%, or 8.6% of the free space wavelength, respectively. Furthermore, the three absorption peaks can be lowered to 1.220 GHz, 1.281 GHz, and 1.343 GHz when the relative permittivity of the ultra-thin grounded substrate is increased to 9.8. Finally, one waveguide experiment was conducted to verify the proposed MA effectively.

We present a design of a low frequency ultra-thin compact and polarization-insensitive metamaterial absorber (MA). The designed MA is a two-layer structure, a periodic array of novel split-ring resonators (SRRs), which are constructed in an FR4 dielectric layer, and another ultra-thin grounded sheet is attached to the bottom. Numerical simulated results show that the proposed MA can realize effective absorption at the frequency 281.9 MHz, and its overall thickness is just only 0.29% of the resonant wavelength, the unit space is only 2.57%, and the absorbance is kept well for a wide range of incident angles for different polarizations. In addition, the proposed MA is changed into a more compact one when the inter-digital structures are introduced in the SRRs. One convenient experiment is carried out in a rectangular waveguide simulator.

In this paper, we design a varactor-tunable metamaterial absorber (MA). The tunable MA is based on a mushroom-type high impedance surface (HIS), in which varactors are loaded between adjacent metal patches to adjust the capacitance and tune the resonance frequency, the primary ground plane is etched as the bias network to bias all of the varactors in parallel, and another ultra-thin grounded film is attached to the bottom. Its absorption characteristics are realized for electrically dielectric loss. The simulated values of a sample indicate that a tunable frequency range from 2.85 GHz to 2.22 GHz is achieved by adjusting the varactor capacitance from 0.1 pF to 2.0 pF, and better than 0.97 absorbance is realized; in addition, the tunable frequency range is expanded from 4.12 GHz to 1.70 GHz after optimization.

An effective approach to designing a tunable electromagnetic absorber is presented and experimentally verified; it is based on an idea that an existing frequency selective surface (FSS) absorber is regarded as a loaded receiving antenna array. The existing absorber is effectively simplified by withdrawing half of the loaded resistors; a more compact one is obtained when lumped capacitors are introduced. Building on this, a varactor-tunable absorber with a proper bias network is proposed. Numerical simulations of one tunable absorber with 1.6 mm in thickness show that a wide tuning range from 3.05 GHz to 1.96 GHz is achieved by changing the capacitance of the loaded varactor from 0.5 pF to 5.0 pF. An experiment is carried out using a rectangular waveguide measurement setup and excellent agreement between the simulated and measured results is demonstrated.