In this paper, we first demonstrate a metasurface that offers spectral filter performances not yet reported for a single-layer metasurface because of the limited number of geometric parameters. The configuration of the metasurface is determined by a conformational space annealing algorithm, which is a key toward being able to design for a desired frequency, bandwidth, and response type for various wireless communication devices, including the fifth-generation (5G) millimeter-wave communication devices. As a proof-of-concept, we fabricate a very thin (50 μm) single-layer metasurface combined with a 5G antenna array to experimentally demonstrate high frequency-selectivity with stable frequency responses with oblique incidences and polarizations. The gain of the 4 × 4 patch antenna array with the metasurface bandpass filter was reduced by only 0.48 dB compared with that of the 4 × 4 patch antenna array itself at 27.5 GHz, whereas the gain of the 4 × 4 patch antenna array with the metasurface bandstop was reduced by 20 dB compared with that of the 4 × 4 patch antenna array itself at 28.5 GHz.

In this letter, we propose a multifunctional frequency selective surface (FSS) designed for wide incident angles, optimized for X-band reflection and K-/Ka-band transmission. To verify its applicability, we analyzed the performance variations of the FSS with respect to polarizations and incidence angles. The proposed FSS facilitates space communication in the K/Ka-band, while simultaneously minimizing electromagnetic interference for X-band defense applications. The pixelated structures of the FSS are optimized to realize fine frequency selectivity in the target frequency bands. The proposed FSS is implemented in a double-layer to provide higher-order characteristics. To validate its performance, measurements are conducted in a free-space measurement system with spot-focusing lens horn antennas. The proposed structure demonstrates a -1.5 dB bandwidth from 17.41 to 20.97 GHz in the pass band of the K-band and 30.09 to 33.24 GHz in the pass band of the Ka-band, with fractional bandwidths of 18.6% and 9.9%, respectively. Additionally, it satisfies -15 dB blocking performance across the entire X-band.

We propose dual-band filters made from a single-layer metasurface for operating on the 28 and 39 GHz bands in mm-wave fifth generation (5G) communication systems. We use the conformational space annealing method, a global optimization technique, and test the usefulness of dual-band metasurfaces through design, fabrication, and measurement with 2916 square-shaped pixels per unit cell defined on a single layer. Each square-shaped pixel has only two states: either filled with metal or free of metal. We were able to obtain transmissive metasurfaces capable of performing three different functions, bandpass/bandpass, bandpass/band-stop, and band-stop/bandpass, by setting three different objective functions applicable to 5G communications. The designed filters have insertion loss of less than 3 dB in the passband region and greater than 20 dB in the stop band region. As a proof-of-concept, we fabricate very thin (50 μm) single-layer metasurfaces etched on only one side of a single dielectric substrate combined with a 5G antenna array to demonstrate high-frequency-selectivity with dual-band operation experimentally.

An integrated electro-optic (EO) sensor and its dedicated control system for intense electromagnetic pulse measurements are designed and implemented. The sensor performance, specifically the sensitivity, dynamic range, linearity, and bandwidth, is evaluated. For optimal measurements of intense electromagnetic pulses representing an electronic threat, a technique to optimize the sensitivity of the integrated EO sensors is presented. The sensors measure pulses with rise time of 2–3 ns and duration of 23–26 ns, and electric field strength up to 50 kV/m, thus meeting the requirement of MIL-STD-461G RS105 radiated susceptibility test for transient electromagnetic field such as nuclear electromagnetic pulses.

We propose field-calibrated electro-optic probes that are designed for millimeter-wave 5G phased array antenna and Ka-band rectangular waveguide. A method to enhance the probes’ sensitivity and the practical limit for realization are presented. The fabricated probes are specifically minute enough to fit inside a standard millimeter-wave waveguide section for calibration in a minimally invasive way. The proposed calibration method is validated by analyzing the field invasiveness and through a simulation. Using a calibrated probe associated with a heterodyning probe control system, electric field distributions with absolute V/m scale from a millimeter-wave antenna are presented.