An mmWave Dual-Band Integrated Substrate Gap Waveguide Single Cavity Filter with Frequency Selectivity

A novel dual-band ISGW cavity filter with enhanced frequency selectivity is proposed in this paper by utilizing a multi-mode coupling topology.Its cavity is designed to control the number of modes,and then the ports are determined by analyzing the coupling relationship between these selected modes.By synthesizing the coupling matrix of the filter,a nonresonating node(NRN)structure is introduced to flexibly tune the frequency of modes,which gets a dualband and quad-band filtering response from a tri-band filter no the NRN.Furthermore,a frequency selective surface(FSS)has been newly designed as the upper surface of the cavity,which significantly improves the bad out-of-band suppression and frequency selectivity that often exists in most traditional cavity filter designs and measurements.The results show that its two center frequencies are f01=27.50 GHz and f02=32.92GHz,respectively.Compared with the dual-band filter that there is no the FSS metasurface,the out-of-band suppression level is improved from measured 5 dB to18 dB,and its finite transmission zero(FTZ)numbers is increased from measured 1 to 4 between the two designed bands.Compared with the tri-band and quadband filter,its passband bandwidth is expanded from measured 1.17%,1.14%,and 1.13% or 1.31%,1.50%,0.56%,and 0.57% to 1.71% and 1.87%.In addition,the filter has compact,small,and lightweight characteristics.

Single Mode DR Filters for Wireless Base Stations

This paper presents state-of-the-art high Q single-mode dielectric resonator （DR） cavity filters for PCS wireless base stations. DR cavity filters shrink the cavity size significantly more than waveguide cavity filters and offer about twice higher Q than coaxial resonators. Thus, they have important applications in wireless base stations operating below 2.5 GHz. Dual-mode and triple-mode DR cavity filters have existed for a while; however, single-mode DR cavity filters are predominant because they are cheaper to manufacture. This paper summarizes the main characteristics of TE01 mode DR cavities, including mode chart and field distribution, and compares cavity Q with waveguide and combline （coaxial） cavities. Dielectric combline and TM010 mode DR cavities are analyzed and compared to TE01 mode DR cavities. General filter design techniques are discussed, and several design examples are given to show how filter technology has developed.

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures （CCSs） in two-dimensional （2D） photonic crystals （PCs） are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain （FDTD） method, and the results show that within a very short coupling distance of about 3λ, where ）, is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.

Theoretical analysis of transmission characteristics for all fiber,multi-cavity Fabry-Perot filters based on fiber Bragg gratings

The characteristics of transmission spectra for the all fiber, multi-cavity Fabry- Perot （FP） configuration based on fiber Bragg gratings （FBG） are theoretically analyzed and modeled. The general transmission matrix function for the structure with any number of cavities is derived, and explicit expression of the power trans- mission coefficient for symmetrical two-cavity FP is presented. The general condi- tions for flat-top single resonant peak at the central wavelength in FBG stop band are derived and verified in the numerical simulation section. The transmission peaks of single-cavity and two-cavity FP structures are compared and discussed, and results show that compared to the single-cavity FP, flatness of the top and steepness at the edge of transmission peak can be improved by introducing one more cavity. The resonant transmission peak properties of two-cavity structure are investigated in detail for various values of cavity length and FBGs with different reflection characteristics, and the design guidelines for transmission-type filters are presented. The results show that the steepness of peak slope can be improved by increase of FBG reflectivities, and these kinds of filters can be used as nar- row-band single-channel selectors and multi-channel wavelength de-multiplexing by properly choosing the length of cavities and reflectivities of FBGs.

High-performance colorful semitransparent perovskite solar cells with phase-compensated microcavities

We demonstrate highly efficient multi-colored semitransparent perovskite solar cells that can create high angular tolerant controllable transmissive colors up to 60~, based on phase-compensated microcavities. The efficiency of the semitransparent colors was improved by impedance matching, which was enabled by placing a dielectric functional layer on top of traditional optical microcavities, with negligible influence on color pureness. The vast majority of the visible part of solar radiation is efficiently utilized for solar energy harvesting, achieving 10.47%, 10.66%, and 11.18% of efficiency for red, green, and blue （RGB） colored solar cells, respective136 while a very small proportion of the visible solar spectrum is used for structural coloration that can be readily tuned by altering the cavity medium thickness. The approach described herein can be suitable for a variety of applications such as display systems with ultra-low power consumption, highly efficient colorful solar panels, low-power wearable electronics, and energy-efficient optoelectronics.