Metallic Rectangular Waveguide Research Articles

A novel millimeter‐wave gain equalizer using E‐plane microstrip‐line probe and waveguide resonator

AbstractIn this paper, a new millimeter‐wave gain equalizer based on metallic rectangular waveguide is presented, which is implemented by E‐plane microstrip‐line probe, metal rectangular waveguide resonator, waveguide coupling groove, and thin‐film resistor. The proposed gain equalizer has good tunability, high Q factor, and high power capacity. To demonstrate its performance, a modified gain equalizer, operating 90 to 97 GHz, is designed and fabricated. The final equalizer has achieved better performance and satisfied the need of actual application under a working range from 90 to 97 GHz.

Waveguide-Linear Antenna Array with a 180° Frequency Scanning Sector

Abstract—The paper proposes and investigates a linear waveguide-slot antenna array with a 180° frequency scanning sector, made in the form of a rectangular metal waveguide filled with a dielectric with periodically arranged pairwise transverse slots in a wide wall. In the frequency band corresponding to a single-mode waveguide, the waveguide-slot array in the low-frequency part of the range emits at a zero spatial harmonic, and in the high-frequency part, at the minus first harmonic. An approximate theory is used to determine the waveguide parameters that satisfy the frequency scanning requirement in a 180° sector. The results of the approximate theory are confirmed on the whole by the results of numerical simulation of the scanning characteristics using a finite element method.

Error estimates of asymptotic expansions in periodic waveguides

ABSTRACT The filtering problem of a periodically corrugated rectangular metallic waveguide of length l is used as an example to set an upper bound on the validity of the various orders of asymptotic approximation of the electromagnetic field in the waveguide. We limit the analysis to the first two orders of asymptotic expansion in powers of a small parameter δ characterising the amplitude of the periodic corrugations to minimise the detail, but the procedure is applicable to higher orders of approximation without loss of generality. The asymptotic expansions are obtained via the perturbation method of multiple scales. Following conventional practice in antenna work, a phase error of π/8 is used to set an upper bound on the phase error for each order of approximation. This bound is found by setting the difference between the results of simulation using the HFSS software package and the phase of either the first-order or the second-order approximation of the electromagnetic field equal to π/8. This bound sets an upper limit on δ for a given length I which gives the same results for a fixed (δ × I) product for the first-order expansion.

Fast Frequency Sweep Technique Based on Segmentation for the Acceleration of the Electromagnetic Analysis of Microwave Devices

The characterization of communication devices in a certain frequency band can be accelerated if a fast frequency sweep technique is used instead of a discrete frequency sweep. Existing fast frequency sweep techniques are either complex or specific for a certain electromagnetic solver. In this work, a new fast frequency sweep method is proposed that consists in segmenting the device under analysis into simple building blocks. Each building block is characterized with a generalized (multimode) circuital matrix whose elements present a simple and flat frequency response that is interpolated using natural cubic splines with very few points. In this way, the response of each block along the whole frequency band is obtained efficiently and accurately with as many frequency points as desired. Then, the circuital matrices of all the blocks are cascaded and the circuital matrix of the whole device in obtained. The new fast frequency sweep was successfully applied to the analysis of different types of devices (all metallic rectangular waveguide filter, dielectric loaded rectangular waveguide filter, and substrate integrated waveguide filter). The computational times were reduced to 15% or 19%, depending on the device, when compared with a discrete frequency sweep using the same electromagnetic solver.

Establishing a New Form of Primary Impedance Standard at Millimeter-Wave Frequencies

This paper investigates the possibility of using layers of graphene to form primary impedance standards for millimeter-wave rectangular metallic waveguide. It is shown that standards with values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Y_{0}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2Y_{0,}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3Y_{0}$ </tex-math></inline-formula> can be produced by a monolayer, bilayer, or trilayer of graphene, respectively, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Y_{0}$ </tex-math></inline-formula> is the characteristic admittance of the waveguide. These standards could then be used in the calibration of vector network analyzers.

Effect of Absorption on the Efficiency of Terahertz Radiation Generation in the Metal Waveguide Partially Filled with Nonlinear Crystal LiNbO3, Dast or ZnTe

The influence of terahertz (THz) radiation absorption on the efficiency of generation of coherent THz radiation in the system ‘nonlinear-optical crystal partially filling the cross section of a rectangular metal waveguide’ has been investigated. The efficiency of the nonlinear frequency conversion of optical laser radiation to the THz range depends on the loss in the system and the fulfillment of the phase-matching (FM) condition in a nonlinear crystal. The method of partially filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. The phase matching is achieved by numerical determination of the thickness of the nonlinear crystal, that is the degree of partial filling of the waveguide. The attenuation of THz radiation caused by losses both in the metal walls of the waveguide and in the crystal was studied, taking into account the dimension of the cross section of the waveguide, the degree of partial filling, and the dielectric constant of the crystal. It is shown that the partial filling of the waveguide with a nonlinear crystal results in an increase in the efficiency of generation of THz radiation by an order of magnitude, owing to the decrease in absorption.

A hybrid MoM/MM method for fast analysis of E-plane dielectric loaded waveguides

In this study, a hybrid method for fast frequency analysis of E-plane type dielectric loaded metallic rectangular waveguides is introduced. The computational efficiency of mode-matching (MM) method and the flexibility of method of moments (MoM) are integrated. MM based generalized scattering matrix (GSM) method is utilized for computation of scattering parameters and the required GSMs are constructed via MoM. The computational performance and accuracy of the proposed approach are evaluated by comparing with traditional MM and Finite Element Method (FEM) based software High Frequency Structure Simulator (HFSS) for various microwave devices built by dielectric loaded waveguides. The efficiency of the proposed method is also evaluated against arbitrarily shaped structures.

Microwave Liquid Crystal Technology

Tunable Liquid Crystal (LC)-based microwave components are of increasing interest in academia and industry. Based on these components, numerous applications can be targeted such as tunable microwave filters and beam-steering antenna systems. With the commercialization of first LC-steered antennas for Ku-band e.g., by Kymeta and Alcan Systems, LC-based microwave components left early research stages behind. With the introduction of terrestrial 5G communications systems, moving to millimeter-wave communication, these systems can benefit from the unique properties of LC in terms of material quality. In this paper, we show recent developments in millimeter wave phase shifters for antenna arrays. The limits of classical high-performance metallic rectangular waveguides are clearly identified. A new implementation with dielectric waveguides is presented and compared to classic approaches.

Millimeter wave (220 GHz–330 GHz) characterizations of carbon nanotube films

A carbon nanotube (CNT) film on a substrate is characterized at millimeter waves (220 GHz−330 GHz) by metal rectangular waveguide scattering parameters (S-parameters) measurements. The anisotropy of the CNT film is investigated for different orientations of the on-substrate CNT film. The standard Nicolson–Ross–Weir (NRW) approach has been adopted to extract the complex permittivity (εr=ε′-jε″) and permeability (μr=μ′-jμ″) of the on-substrate CNT film from the measured S-parameters. The effective medium theory is then applied to remove the impact of the substrate and characterize the intrinsic CNT film. The observed frequency independent and anisotropic behaviors of the CNT film are very promising indicators that this material could be invaluable for a range of millimeter-wave applications.

Concise relation among the effective index of the TE01 mode of the metal rectangular waveguide and those of the TE1 and TM0 modes of the metal parallel-plate waveguide for terahertz waves

For terahertz waves, we analytically present a concise relation of the effective indices among the TE01 mode of the metal rectangular waveguides, the TE1 mode, and the TM0 mode of the infinite metal parallel-plate waveguides. With the assumption that the modal field in the metal rectangular waveguide is linearly polarized and separable, the effective index of the TE01 mode can be obtained from the combination of the effective indices of the associated TE1 mode and TM0 mode. We further find that the real part of the effective index of the TE01 mode is mainly determined by that of the TE1 mode, while for the imaginary part, the TM0 mode dominates.

THz wavefront manipulation based on metal waveguides

In this paper, two waveguiding structures for arbitrary wavefront manipulation in the terahertz spectral region were proposed, designed and characterized. The first structure consists of parallel stack copper plates forming an array of parallel-plate waveguides (PPWGs). The second structure is three-dimensional metal rectangular waveguides array. The phase delay of the input wave after passing through the waveguide array is mainly determined by the effective index of the waveguides. Therefore, the waveguide array can be engineered using different core width distribution to generate any desired light beam. Examples, working at the frequency of 0.3 THz show that good focusing phenomenon with different focus lengths and spot sizes were observed, as well as arbitrarily tilted propagation of incident plane waves. The structure introduces a new method to perform wavefront manipulation, and can be utilized in many important applications in terahertz imaging and communication systems.

Cos-Gaussian modal field of a terahertz rectangular metal waveguide filled with multiple slices of dielectric

Based on the TE01 mode of a rectangular metal waveguide and the Gaussian mode of a fiber, we propose the cos-Gaussian mode of a terahertz rectangular metal waveguide filled with multiple slices of dielectric. First, we consider a rectangular metal waveguide filled with an ideal graded-index dielectric along one direction. Furthermore, we replace the graded-index dielectric with multiple slices of dielectric according to the effective medium theory. The modal field, the effective index, and the coupling efficiency of this waveguide are investigated. It is found that the approximately linearly polarized electric field is Gaussian along one dimensionality and cosine along the other one. In addition, the low loss and high coupling efficiency with a Gaussian beam can be acquired at 0.9 THz. By optimization, the coupling efficiency could reach 88.5%.

Ka-Band Characterization of Binder Jetting for 3-D Printing of Metallic Rectangular Waveguide Circuits and Antennas

The performance of additive manufactured (AM) RF circuits and antennas is continuously improving, and in some cases these AM components are comparable to state-of-the-art circuits made with traditional manufacturing techniques. Medium to high-power waveguides made with AM methods such as copper-plated plastics, selective laser melting (SLM), and copper additive manufacturing (3-D CAM) have shown good performance up to terahertz frequencies. In this paper, binder jetting (BJ) metal printing is characterized using electron beam microscopy [scanning electron microscopy (SEM)] and energy dispersive spectroscopy. The RF performance of the 3-D-printed circuits is benchmarked with Ka-band cavity resonators, waveguide sections, and a filter. An unloaded resonator $Q$ of 616 is achieved, and the average attenuation of the WR-28 waveguide section is 4.3 dB/m. The BJ technology is tested with a meshed parabolic reflector antenna, where the illuminating horn, waveguide feed, and a filter are printed in a single piece. The antenna shows a peak gain of 24.56 dBi at 35 GHz.

Mode filtering based on ponderomotive force nonlinearity in a plasma filled rectangular waveguide

Here a new scheme for mode filtering is proposed. Based on the ponderomotive force effect, propagation of the microwave dual-mode through a plasma-filled metallic rectangular waveguide is investigated. To excite the TE20 mode in a rectangular waveguide, the existence of fundamental modes is unavoidable. To filter the destructive mode (TE10), the waveguide is filled with a collisional plasma. Based on the coupling effect, the energy of this destructive TE10 mode is transferred to the TE20 mode. The proposed structure acts like a mode convertor. The TE10 mode become more attenuated and instead the TE20 mode is amplified. The plasma filled rectangular waveguide acts as a mode filtering tool.

Dissipation-assisted spin squeezing of nitrogen-vacancy centers coupled to a rectangular hollow metallic waveguide.

Spin squeezing has received much attention due to the interesting physics and important applications such as quantum metrology and quantum information processing. We here present a scheme to engineer stable spin squeezing in an array of nitrogen vacancy centers (NVCs) coupled to a rectangular hollow metallic waveguide. The remarkable feature of the waveguide as the common environment media is that one can switch on/off either the waveguide induced dipole-dipole interactions or correlated spontaneous emissions among the NVCs by designing their spatial separation. It permits us to achieve a dissipative Dicke model after the dipole-dipole interactions vanish due to destructive interference. With the external driving lasers on each NVC, a second-order phase transition is triggered, separating the steady state into two phases with and without collective spin squeezing. Supplying a physical realization of the dissipative Dicke model, our study gives a bridge between the generation of the stable spin squeezing and the phase transition physics.

RWG‐integrated SIW splitter for large scale SATCOM phased array applications

AbstractIn this article, the hybrid transition power splitter, which consists of metallic rectangular waveguide and substrate integrated waveguide, is presented for large‐scale millimeter‐wave antenna array broad band mobile satellite communication system. The power is coupled between the RWG and the SIW through two center‐slot transition, one etched on the SIW ground plane and the other cut through metallic RWG narrow side wall. The two‐way RWG‐SIW transition splitter was designed and simulated; then the four‐way splitter was designed, fabricated, and tested. The measured results show good agreements with the simulated ones and the measured return and insertion loss better than 10 and ∼1.50 dB were experimentally achieved over the band 28.70–30.20 GHz, respectively.

3D printed RWG with slot-transition for low cost millimeter-wave applications: Simulation and measurement

In this article, the potential of building an air-filled E-plane metallic rectangular waveguide (RWG) with slot transition fabricated by 3D printing technology is explored for millimeter-wave applications. It is low cost, light weight, and neither plating nor assembly is required compared to the traditional machined metallic RWG. A printed metallic RWG back-to-back transition is designed, fabricated, and tested over the frequency band 27–31 GHz. The measured results are compared to those of the machined metallic RWG. Good agreements between the measured results as well as the simulated results are observed.

Wideband transition between rectangular waveguide and microstrip using asymmetric fin line probe

A novel wideband waveguide-to-microstrip transition realised by inserting asymmetric fin line probe into metallic rectangular waveguide is presented. One back-to-back transition covering the Ka band is designed, fabricated and tested to show the advantages of such asymmetric fin line-probe inspired transition structure, and measured results consist well with simulations. An insertion loss less than 0.8 dB and a return loss better than 15 dB over 24–40 GHz are obtained for the back-to-back structure. This broadband fin line-probe transition between rectangular waveguide and microstrip can be used widely in microwave and millimetre-wave circuit and system.

Complex discontinuities cascading waveguides models studies and analysis

Abstract The paper proposes a method for S-matrix generalization to minimize discontinuities between one-axis rectangular guides in terms of reflection and transmission coefficients. We modelate successfully rectangular metal waveguide filters with geometrical and physical discontinuities, and a succession of heterogeneous media such periodic structure and containing Meta materials are presented. Method of S-matrix generalization based on modal development operating by breaking down electromagnetic fields on orthonormal basis for each formed discontinuity. Proposed hybrid method that reference to finite element method incorporation is discussed. We conclude that the Galerkin method application leads directly to the matrix of junction diffraction.

Modulation of TE propagation modes in rectangular metal waveguide with integrated graphene structure in the sub-terahertz frequency range

The propagation of TE modes in a rectangular metal waveguide with an integrated structure of finite length containing a graphene monolayer was studied by a modal decomposition method. The modal decomposition method generates a number of linear algebraic equations related to waveguide modes taken into account. The system of linear algebraic equations for the amplitudes of all modes was derived taking into account the propagation as well as a number of local evanescent modes. Truncation errors in the function of the number of modes taken were quantified by using the discontinuities of the boundary conditions for the transverse electric and magnetic field components at the interface of the discontinuities of the structure. The transmitted and reflected TE01 mode amplitudes were calculated versus the graphene layer length, its position inside the waveguide cavity and the graphene electrons chemical potential. It was shown that the symmetrical positioning of the graphene layer inside the waveguide cavity is the most suitable to achieve the largest amplitude modulation, whereas an asymmetrical positioning is suitable to achieve a large phase modulation of the transmitted mode. It was shown that the phase modulation increases with a transmission coefficient modulation increase and decreases with a transmission coefficient increase. It was found that the phase modulation firstly increases almost proportionally with the graphene layer length for relatively short structures; however, after passing through a maximum, the phase modulation becomes almost constant and hence only weakly dependent on the graphene layer length. Typical phase modulation values turn out to be about 15–20 degrees for minimal transmission coefficients of about 0.6–0.4; however, the phase modulation reaches a value of about 45 degrees if the transmission coefficient modulation equals 50%.