Low-Temperature Metallization and Laser Trimming Process for Microwave Dielectric Ceramic Filters

This paper describes a low-temperature metallization and laser trimming process for microwave dielectric ceramic filters. The ceramic was metalized by electroless copper plating at a temperature lower than those of conventional low-temperature co-fired ceramic (LTCC) and direct bond copper (DBC) methods. Compared with filters made via traditional silver paste sintering, the metal in the holes of the microwave dielectric filters is uniform, smooth, and does not cause clogging nor become detached. Further, the batches of fabricated filters do not require individual inspection, reducing energy, labor, cost, and time requirements. A microwave dielectric filter was then manufactured from the prepared ceramic using a laser trimming machine with a line width and position error within ±50 μm; this demonstrates a more accurately controlled line width than that offered by screen printing. After using HFSS software simulations for preliminary experiments, the microwave dielectric filter was tuned to a target Wi-Fi band of 5.15–5.33 GHz; the return loss was <−10 dB, and the insertion loss was >−3 dB. To implement the real-world process, the laser parameters were optimized. Laser trimming has a higher success rate than traditional manual trimming, and the microwave dielectric filter manufactured here verified the feasibility of this process.

MUTUAL COUPLING COEFFICIENTS OF ROTATING RECTANGULAR DIELECTRIC RESONATORS IN CUT-OFF RECTANGULAR WAVEGUIDE

Background. A further increase in the speed of information transfer is determined by more stringent requirements for the elements of communication devices. One of the most important components of such devices is various filters, which are often made on the basis of dielectric resonators. Calculation of the parameters of multi-section filters is impossible without further development of the theory of their design. The development of filter theory is based on electrodynamic modelling, which involves calculating the coupling coefficients of dielectric resonators in various transmission lines. Objective. The aim of the research is to calculate and study the coupling coefficients of rectangular dielectric resonators with a rectangular metal waveguide when their axes rotate. Investigation of new effects to improve the performance of filters and other devices based on them. Methods. Methods of technical electrodynamics are used to calculate and analyse the coupling coefficients. The end result is to obtain new analytical formulas for new structures with rectangular dielectric resonators, which make it possible to analyse and calculate their coupling coefficients. Results. New analytical expressions are found for the coupling coefficients of dielectric resonators with the rotation of their axes in a rectangular waveguide. Conclusions. The theory of designing filters based on new structures of dielectric resonators with rotation of their axes in metal waveguides has been expanded. New analytical relationships and new patterns of change in the coupling coefficients are found. Keywords: dielectric filter; rectangular dielectric resonator; rotation; coupling coefficients.

Design of Linear Variable Optical Filter for Hyperspectral Imaging

In this paper, the design and simulation of a Linear Variable Optical Filter (LVOF) for the visible and near-infrared (VNIR) 450-900nm region is reported. The design and simulation of LVOF are made based on all-dielectric [1–4] and metal-dielectric based induced transmission filter. In the given paper, we have compared the design approach based on all-dielectric and metal-dielectric filters. The LVOF filter based on the metal-dielectric method reduces the design and fabrication complexities and is also cost-effective as it doesn’t require any band rejection filters. The minimum spectral transmission of the metal-dielectric filter reported in the paper is 70% with a FWHM of 2–3% of central maxima.

Research on sintering behavior and microwave dielectric property of (Mg0.95Ca0.05)TiO3 ceramics for cross coupling filter

The microwave dielectric properties of [Formula: see text]–[Formula: see text] (abbreviated as 95MCT hereafter) ceramics have been studied for application in dielectric cross coupling filters. [Formula: see text] and [Formula: see text] were selected as liquid sintering aids to lower the sintering temperature and enhance the Qf value of 95MCT and simultaneously we varied the mole ratio of [Formula: see text] to tune the microwave dielectric properties of 95MCT. When the [Formula: see text] mole ratio was 1.5 and the co-doping content was 0.25 wt.%, the optimal sintering temperature of 95MCT ceramic could be lowered from [Formula: see text] to [Formula: see text] and the Qf value could be improved by about 7.7%. The optimal microwave dielectric properties obtained under this condition were Qf = 72730 GHz (6.8 GHz), [Formula: see text] and [Formula: see text], which demonstrated great potential usage in ceramic industry. High values of Qf ceramic were used to design the dielectric cross coupling filter. The dielectric filter measured at 2.35 GHz exhibited a 6.7% bandwidth (insert loss [Formula: see text] dB) of center frequency.