T-junction Waveguide Research Articles

A novel H-plane based T-junction waveguide power divider for WR-10

A novel H-plane based T-junction waveguide power divider for WR-10

In-situ monitoring for liquid metal jetting using a millimeter-wave impedance diagnostic

This article presents a millimeter-wave diagnostic for the in-situ monitoring of liquid metal jetting additive manufacturing systems. The diagnostic leverages a T-junction waveguide device to monitor impedance changes due to jetted metal droplets in real time. An analytical formulation for the time-domain T-junction operation is presented and supported with a quasi-static full-wave electromagnetic simulation model. The approach is evaluated experimentally with metallic spheres of known diameters ranging from 0.79 to 3.18 mm. It is then demonstrated in a custom drop-on-demand liquid metal jetting system where effective droplet diameters ranging from 0.8 to 1.6 mm are detected. Experimental results demonstrate that this approach can provide information about droplet size, timing, and motion by monitoring a single parameter, the reflection coefficient amplitude at the input port. These results show the promise of the impedance diagnostic as a reliable in-situ characterization method for metal droplets in an advanced manufacturing system.

Uniform Field Re-entrant Cylindrical TE_{01text {U}} Cavity for Pulse Electron Paramagnetic Resonance Spectroscopy at Q-band

Uniform field (UF) resonators create a region-of-interest, where the sample volume receives a homogeneous microwave magnetic field (B_1) excitation. However, as the region-of-interest is increased, resonator efficiency is reduced. In this work, a new class of uniform field resonators is introduced: the uniform field re-entrant cylindrical TE_{text {01U}} cavity. Here, a UF cylindrical TE_{text {01U}} cavity is designed with re-entrant fins to increase the overall resonator efficiency to match the resonator efficiency maximum of a typical cylindrical TE_{011} cavity. The new UF re-entrant cylindrical TE_{text {01U}} cavity is designed for Q-band (34 GHz) and is calculated to have the same electron paramagnetic resonance (EPR) signal intensity as a TE_{011} cavity, a 60% increase in average resonator efficiency Lambda _mathrm{ave} over the sample, and has a B_1 profile that is 79.8% uniform over the entire sample volume (98% uniform over the region-of-interest). A new H-type T-junction waveguide coupler with inductive obstacles is introduced that increases the dynamic range of a movable short coupler while reducing the frequency shift by 43% during over-coupling. The resonator assembly is fabricated and tested both on the bench and with EPR experiments. This resonator provides a template to improve EPR spectroscopy for pulse experiments at high frequencies.

An Integratable Planar Waveguide Power Divider With Anti-Phases and Full Bandwidth

A novel integratable planar T-junction waveguide power divider, a so-called TEH(E-plane input and H-plane output) junction waveguide power divider, with anti-phase outputs and full bandwidth is proposed in this letter. It is basically a E-plane waveguide T-junction with its input port rotated around the axis of the two output ports by 90 degrees to form a planar structure. In order to expand its operation bandwidth, several stages of matching sections are added between the coupling cavity and each port. In order to verify the concept, a standard waveguide port TEH junction divider is designed and tested as an example. From the tested results, the reflection coefficient is lower than −20 dB and phase difference between the two output ports is within 177 +/−3 degrees in the full bandwidth from 26.3 to 40 GHz.

A COMPACT DIPLEXER BASED ON LOW PROFILE MULTILAYER FSS FILTERS FOR ULTRA-HIGH DATA RATE POINT TO POINT WIRELESS COMMUNICATION SYSTEM

In this paper, we propose the design of multilayer frequency selective surfaces (FSS) waveguide band-pass fllters (WBPF). The WBPFs are designed to operate at two difierent frequency channels, respectively 71{76GHz (Rx) and 81{86GHz (Tx). The cross section surface of the FSS is imposed by the WR12 waveguide rectangular section's dimensions. The WBPFs are inserted symmetrically in a T-junction waveguide to design a compact diplexer. This is a basic component developed for an e-cient integration in the future E-band millimeter-wave transceiver. The multilayer FSS structure uses only non-resonant sub-wavelength unit cell elements; metallic patch and slot. To reach high channel isolation (… 70dB) a seven order fllter was required. Hence, each fllter is composed of 13 capacitive and inductive metallic FSS spaced by 12 ultra-thin dielectric substrate layers. The dielectric material is Rogers Ultralam 3850 (Liquid Crystalline Polymer; LCP circuit material). The fllter's overall thickness is < ‚=4. The numerical studies have been performed using flnite element method simulator (HFSS) and CST Studio Suites Tools. The experimental validation has been also done in the X band frequency by developing a flfth order FSS WBPF. Good agreements between simulated and measured results are obtained.

Ultracompact 1×4 TM-polarized beam splitter based on photonic crystal surface mode

We provide an improved surface-mode photonic crystal (PhC) T-junction waveguide, combine it with an improved PhC bandgap T-junction waveguide, and then provide an ultracompact 1×4 TM-polarized beam splitter. The energy is split equally into the four output waveguides. The maximal transmission ratio of each output waveguide branch equals 24.7%, and the corresponding total transmission ratio of the ultracompact 1×4 beam splitter equals 98.8%. The normalized frequency of maximal transmission ratio is 0.397(2πc/a), and the bandwidth of the ultracompact 1×4 TM-polarized beam splitter is 0.0106(2πc/a). To the best of our knowledge, this is the first time such a high-efficiency 1×4 beam splitter exploiting the nonradiative surface mode as a guided mode has been proposed. Although we only employed a 1×4 beam splitter, our design can easily be extended to other 1×n beam splitters.

Design of surface mode photonic crystal T-junction waveguide using coupled-mode theory

We design a photonic crystal T-junction waveguide on the basis of the nonradiative surface mode and further optimize the transmission ratio of our surface mode photonic crystal T-junction waveguide with the guide of coupled-mode theory. Compared with a traditional bandgap photonic crystal T-junction waveguide, our surface mode T-junction waveguide can obtain almost zero reflectance and good transmission. Better still, its size is just half of the size of bandgap photonic crystal waveguide branches. To the best of our knowledge, it is the first time that such a high-efficiency T-junction waveguide that uses the surface mode as the guided mode is proposed.

Simplified T-junction Composite Waveguides

Various versions of T-junction composite waveguides with reduced-number cylinders are investigated by the finite-difference time-domain (FDTD) method in this work. The original structure comprises a T-junction ridge waveguide and three layers of square-lattice dielectric cylinders around the intersection region. And the simplified designs are obtained by deleting some less useful cylinders in the both sides of the input guide. And FDTD simulation results describe the output efficiencies of some simplified T-junction composite waveguides may be as good as that of the original one.

New configuration for optical waveguide power splitters

Different configurations of a T-junction power splitter are investigated using complex-envelope alternating-direction-implicit finite-difference time-domain method. The use of reflectors on both sides of the waveguide significantly improved the performance of the T-junction waveguide after optimising the gradient of the reflectors. Cavity resonators have been added to the structure, and the transmission power on both sides of the T-junction structure is maximised. Furthermore, a photonic crystal (PhC)-based T-junction has been investigated. The results show that the use of the PhC has a major impact on the performance of T-junction.

FDTD Analysis of a Novel 8mm E-Plane T-Junction Waveguide Circulator

A novel 8 mm E-plane T-junction waveguide circulator with off-center ferrite discs is developed. Detailed analysis of it using the three-dimensional finite-difference time-domain (FDTD) method is presented. The results of experiment show that the method to widen frequency band is useful. Frequency dependent insertions loss, isolation and reflection loss of the circulator are calculated over a wide band of frequencies with a single FDTD run, good agreement is found between theoretical analysis and results of experiment.

Topology optimization of photonic crystal structures: a high-bandwidth low-loss T-junction waveguide

A T junction in a photonic crystal waveguide is designed with the topology-optimization method. The gradient-based optimization tool is used to modify the material distribution in the junction area so that the power transmission in the output ports is maximized. To obtain high transmission in a large frequency range, we use an active-set strategy by using a number of target frequencies that are updated repeatedly in the optimization procedure. We apply a continuation method based on artificial damping to avoid undesired local maxima and also introduce artificial damping in a penalization scheme to avoid nondiscrete properties in the design domain.

Strain-tunable optical valves at T-junction waveguides in photonic crystals

We propose to use tunable splitting of a degenerate photon state inside the band gap of a photonic crystal for the design of active tunable photonic crystal circuits. The effect we exploit is analogous to the static Jahn-Teller effect in solids. We demonstrate that effect is tunable by the symmetry and magnitude of the lattice distortion. Using this effect, we design an optical valve that controls the resonant coupling of the photon modes at the corner of a T-junction waveguide structure.

T-junction waveguide experiment to characterize left-handed properties of metamaterials

The left-handed property of a metamaterial is demonstrated by measuring the power at the output of a T-junction waveguide loaded with a metamaterial having one edge cut at 45° with respect to the waveguide axis. Both experimental scattering data and numerical results are presented. The metamaterial sample is realized by using a periodic arrangement of wires and split-ring resonators, and the operating frequency is chosen to correspond to a refraction index of about −1. The results show that when the T junction is empty, most of the power is received at the output port directly facing the input port, whereas when it is loaded with the sample of metamaterial, most of the power is received at the output port perpendicular to the input axis. This indicates that the energy is bent by the oblique edge of the sample by an angle of −45° with respect to the normal, which suggests a negative index of refraction.

Full-wave verification of the fundamental properties of left-handed materials in waveguide configurations

The fundamental electromagnetic properties of left-handed materials (LHMs) are reviewed and verified by finite-element method full-wave analysis using rectangular waveguide structures loaded by a LHM and adopting an effective medium approach. The negative phase velocity, positive intrinsic impedance, and modified boundary conditions at an interface with a right-handed medium are verified by loading a waveguide section with a LHM that has edges perpendicular to the waveguide axis. In addition, the negative angle of refraction is demonstrated by loading the junction of a T-junction waveguide with a LHM having one edge 45° with respect to the waveguide axis. These properties are shown by the evolution of wave fronts in the LHM and by analysis of the S-parameters of the waveguide structures.

8 mm T-junction waveguide circulator with a ferrite sphere

A novel 8 mm T-junction waveguide circulator with a ferrite sphere is developed. The permeability tensor of a magnetised ferrite sphere is derived. A simple method is developed to determine the operation modes and the centre frequency of the circulator. The circulator performs as expected. Good agreement between the analytical results and measurements is observed.

High power circulator for the 433.3 MHz proton linac

A 433.3 MHz T-junction waveguide circulator with a dummy-load was constructed to isolate the klystron and a linac cavity at the high rf power level of 1 MW. The isolation is −34.9 dB at a low duty factor and it decreases to −23.8 dB at a high duty factor (1%), which shows enough performance for our linac operation.