Rectangular Waveguide Transition Research Articles

A D-Band Self-Packaged Low Loss Grounded Coplanar Waveguide to Rectangular Waveguide Transition With Silicon-Based Air Cavity-Backed Structure

A D-Band Self-Packaged Low Loss Grounded Coplanar Waveguide to Rectangular Waveguide Transition With Silicon-Based Air Cavity-Backed Structure

Broadband ridge waveguide to rectangular waveguide transition design in D‐band

AbstractThis article presents a D‐band (110–170 GHz) double ridge waveguide (WG) to standard rectangular WG transition with an E‐bend near the WG end. The transition incorporates metal ridge steps as impedance transformers, resulting in a compact total size of 3.53 mm × 1.95 mm × 1 mm. Fabricated using micro metal additive manufacturing with copper in a monolithic back‐to‐back configuration, the transition demonstrates a bandwidth of 50% (105–175 GHz) with an average insertion loss of 0.72 dB and return loss better than 15 dB, respectively. Measurement results align closely with simulation expectations, with deviations attributed to fabrication and assembly errors.

A high‐power coaxial to rectangular waveguide transition

AbstractThe high‐power characteristic of the coaxial to waveguide transition plays an important role in modern communication and radar systems. In this letter, a novel design of a high‐power transition from a 50 Ω coaxial line with an N‐type connector to a WR‐90 rectangular waveguide. The power handling capability (PHC) of the proposed structure is significantly enhanced by a cone‐shaped excitation probe with a bold end, a transitional cavity, and a mode conversion cavity with a curved shorted back wall. The simulated results reveal that the transition possesses high PHC of 257 kW at 8.5 GHz, which is the upper limit of the power tolerance for the N‐type connector. The measured results show that the return loss and insertion loss are better than 15 and 0.15 dB, respectively, in the range of 7.96–9.16 GHz. In addition, experimental validation confirms the normal operation of the structure under a 250 kW power level test, demonstrating the applicability of the proposed transition in high‐power microwave systems.

Antenna Array Design Based on Low-Temperature Co-Fired Ceramics.

With the continuous development of wireless communication technology, the frequency band of 6G communication systems is moving towards higher frequencies such as millimeter waves and terahertz. In such high-frequency situations, wireless transmission requires antenna modules to be provided with characteristics of miniaturization, high integration, and high gain, which presents new challenges to the development of antenna technology. In this article, a 4 × 4 antenna array using multilayered low-temperature co-fired ceramic is proposed, operating in W-band, with a feeding network based on substrate-integrated waveguide, and an antenna element formed through the combination of a substrate-integrated cavity and surface parasitic patches, which guaranteed the array to possess the advantages of high integration and high gain. Combined with the substrate-integrated waveguide to a rectangular waveguide transition structure designed in the early stage, a physical array with a standard metal rectangular waveguide interface was fabricated and tested. The test results show that the gain of the antenna array is higher than 18 dBi from 88 to 98 GHz, with a maximum of 20.4 dBi.

A 53–125 GHz chip to double‐ridge rectangular waveguide transition

AbstractA novel chip to double‐ridge rectangular waveguide transition, with an ultra‐broadband operation bandwidth exceeding three standard rectangular waveguide (WR) bands of WR15, WR12, and WR10 is demonstrated for the first time in this letter, to the best of authors' knowledge. This bandwidth is achieved by coupling the microstrip mode directly to the fundamental TE mode of the waveguide. A unique feature of this transition is that the transition design can be implemented on substrates with a high dielectric constant, which makes it suitable for integration with monolithic microwave integrated circuits (MMICs). A back‐to‐back transition is realized using a split‐block assembly and 254 thickness alumina substrate ( at 80 GHz). The latter acts as an MMIC substrate substitute, including a tapered microstrip and a 50 coplanar waveguide pad for probe‐based measurement. Two novel mechanical assembly concepts, involving die‐attach‐foil and indium solder, are used to build two split‐block prototypes. The simulated and measured S‐parameters of the transition are demonstrated from 35 to 125 GHz.

Analytical solutions for the guided modes of rectangular silicon optical waveguides: a plane-wave approach

Marcatili’s analytical solution for the guided modes of rectangular optical waveguides (ROWGs) depends on (1) using the separation of variables (SOV) and (2) applying the paraxial approximation. It results in two classes of modes: the TE-like and the TM-like modes which are supported by these waveguides. These modes are uncoupled under low-index-contrast conditions. In the case of silicon-on-insulator (SOI) waveguides, the coupling between them can no longer be neglected. This paper extends using the SOV to find analytical modal solutions of SOI-ROWGs. It expands these solutions in quadruples of plane waves and develops a novel non-paraxial scattering model to account for the polarization coupling between these waves under high-index-contrast conditions. This model yields approximate analytical expressions of the field components of the guided modes which are the sum of major and minor Marcatili’s TE-like and TM-like modal fields. Numerical examples show excellent agreement with the field components of full-vectorial mode solvers.

Design of single-ended CPW to rectangular waveguide transition on InP at 300 GHz for 5G applications

Abstract In this paper, we present the development of coplanar waveguide to rectangular waveguide (CPW-WG) transition for broadband millimetre wave applications. The traditional approach for interfacing of components in pure electronics is not possible to implement in micorwave photonics at high frequency range due to some limitations like rigidity and increased loss. In order to overcome this problem, transition structures are usually designed within the waveguide model through split block mechanism. The models developed so far are complex with minimum space of interconnects and less stable due to vertical placement of waveguide. The waveguide structure proposed in this paper is placed along horizontal direction due to which stability of structure is increased and has more space for interconnects. The transition model is designed using indium phosphide (InP) to increase the efficiency and reduce the propagation loss at high frequency range. The simulated design can operate over a bandwidth of 14 GHz with a return loss of 10 dB.

Pseudoelliptic Waveguide Filters Using U-Shaped Ridge Resonators

A new structure for the realization of inline waveguide pseudoelliptic filters using U-shaped ridge resonators has been presented. The basic structure is a U-shaped ridge placed inside a rectangular waveguide and can be utilized to realize both a pole and a transmission zero by either adjusting its offset from the waveguide center axis or by making the lengths of its two arms different from each other. The dominant mode of the feeding waveguide acting as the nonresonating mode, bypasses the U-shaped ridge and thus creates an alternate energy path, realizing a transmission zero. The dominant mode of rectangular waveguide also excites the resonating mode in U-shaped ridge because of the asymmetries introduced by either offset or different length arms. A transmission zero below the passband is achieved by offsetting the U-shaped ridge relative to the waveguide center axis. A transmission zero above the passband is realized by using a centered U-shaped ridge with different length arms. Both adjustments can also be made simultaneously to achieve further flexibility in realizing the desired filter response. A fourth-order filter with two transmission zeros, one in the lower stopband while the other in the upper stopband is designed, fabricated and measured. Measurements show good agreement with the simulations thus demonstrating the practicability of the proposed structure.

Compact Microstrip Line to Rectangular Waveguide Transition Using Corrugated Substrate Integrated Waveguide

To meet the packaging requirements of terahertz (THz) communication systems, a microstrip line (MSL) to rectangular waveguide (RWG) transition is proposed in this paper. In the transition, the MSL is connected to the corrugated substrate integrated waveguide (CSIW) by a tapered MSL for quasi-TEM to TE10-like mode conversion on substrate, which requires no via holes or shaped dielectric, and is easy to process in THz bands. Then, the CSIW is straightly connected to the RWG transformer and converted to standard RWG, resulting in a compact structure. The working principle of the proposed transition is analyzed, and the influence of several important parameters on the S-parameters of the transition is discussed. A single transition is designed for the 325–500 GHz operation, the S11 better than −14.5 dB and S21 better than −1.03 dB have been achieved in the entire frequency band.

Analytical approach for calculation of aperture efficiency enhancement of horn antennas using a thin metal cylinder

AbstractThis study aims to increase horn antenna gain and aperture efficiency in a way that are compatible with aperture electric field distribution similar to TE10 rectangular waveguide mode using analytical calculation method. The proposed analytical approach can be useful to calculate the performance of a horn antenna design with thin (r«λ) perfect electric conductor (PEC) cylinder placed on the antenna aperture dividing H‐plane. In the analytical solution, the aperture field distribution is obtained by solving the electromagnetic scattering from an infinitely long cylinder placed in front of the aperture. This structure not only improves the aperture electric field amplitude distribution but also corrects phase errors in the horn antenna. An X‐band pyramid horn antenna is manufactured by using three‐dimensional (3‐D) printer and coated with aluminum tape. The measurement results of the 3‐D printed antenna are also compared with the simulation results. The antenna gain is measured with and without the PEC cylinder on the aperture. It is found that, the antenna gain is increased by 1 dB. The results of the proposed analytical calculation method are compared with the simulation and measurement results and justified.

An Inline V-Band WR-15 Transition Using Antipodal Dipole Antenna as RF Energy Launcher @ 60 GHz for Satellite Applications

This article demonstrates the design and development of WR-15 transition using an antipodal microstrip dipole antenna at a frequency of 60 GHz for space applications. An inline microstrip line to rectangular waveguide (MS-to-RWG) transition is proposed for the V-band (50–75 GHz) functioning. The RF energy is coupled and launched through an antipodal dipole microstrip antenna. Impedance matching and mode matching between the MS line and dipole are achieved by a quarter wave impedance transformer. This results in the better performance of transitions in terms of insertion loss (IL > −0.50 dB) and return loss (RL < −10 dB) for a 40.76% relative bandwidth from 55.57 GHz to 65.76 GHz. The lowest values of IL and RL at 60 GHz are −0.09 dB and −32.05 dB, respectively. A 50 μm thick double-sided etched InP substrate material is used for microstrip antipodal dipole antenna design. A back-to-back designed transition has IL > −0.70 dB and RL < −10 dB from 54.29 GHz to 64.07 GHz. The inline transition design is simple in structure, easy to fabricate, robust, compact, and economic; occupies less space because the transition size is exactly equal to the WR-15 length; and is prepared using an InP substrate with high permittivity of 12.4 and thickness of 50 μm. Thus, the devices have the lowest insertion loss value and lowest return loss (RL) value, of <−31 dB, as compared to earlier designs in the literature. Therefore, the proposed design has the lowest radiation loss (because of thickness) and highest transmission (about 97% power). Easy impedance matching using only a single-step quarter-wave transformer between the antipodal dipole antenna and 50 Ω microstrip line (avoiding the multi-sections’ demand and microstrip line’s tedious complexity) is needed. Since, when the InP dielectric substrate is inserted in WR-15, the waveguide becomes a dielectric-filled waveguide (DFWG), and its characteristics impedance reduces to 143 Ω from 505 Ω at an operating frequency of 60 GHz. In the proposed transition, no ridge waveguide or waveguide back-short is utilized in WR-15. The microstrip line did not contain any via, fence, window, screw, galvanic structure, post, etc. Hence, the transition is suitable for high-data-rate 5G communications, satellite remote sensing, missile navigation, MIC/MMIC circuits’ characterization, and mm-wave applications. The electrical equivalent model of the proposed design has been generated and validated using an RF circuit simulator and was found to have excellent matching.

A Wideband SICL-to-Waveguide Transition for Multilayer Planar Circuit Applications at V-Band

A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> -band substrate integrated coaxial line (SICL) to rectangular waveguide (RWG) transition is proposed in this letter. In this design, a folded dipole is used to achieve a more compact structure and better impedance matching in the operating band. Compared with other transitions based on single-layer substrates, this design is more suitable for mixed multilayer circuits. For verification, a back-to-back transition prototype is fabricated by standard multilayer printed circuit boards processing and measured. The measured results show that the proposed transition has a wide −10-dB impedance bandwidth of 40% (from 50 to 75 GHz), and an insertion loss of lower than 4 dB over the operating bandwidth. Owing to compact size and wide operating bandwidth, the proposed transition is valuable to advanced millimeter-wave (mmW) circuit systems.

Rectangular Waveguide-Fed Surface-Wave Frequency-Scanning Antenna Utilizing Wavevector Mismatch

In this letter, we propose a design of rectangular waveguide-fed surface-wave frequency-scanning antenna utilizing the principle of wavevector mismatch. First, the transition from a side-fed rectangular waveguide mode to spoof surface plasmon polariton (SSPP) is achieved. Then the SSPP propagating on the metal-dielectric interface is modulated through wavevector mismatching that induces the SSPP to spatial radiating wave conversion. Theoretical deduction proves the frequency scanning nature of the generated radiating beam. Phase gradient metasurface (PGM) is used to realize the wavevector engineering that causes artificial wavevector mismatch. Simulated and experimental results, agreeing well with each other, showed that the antenna can realize beam scanning from −8° to 11.6° across 6.8 to 7 GHz, with realized gain varying from 5 to 5.98 dBi.

High-Efficiency Conversion From Rectangular Waveguide Mode to Spoof SPP Using Metasurface

In this letter, we propose a method to realize rectangular waveguide mode to spoof surface plasmon polaritons (SSPP) mode conversion using phase gradient metasurface (PGM). By applying a PGM with designed wavevector to the narrow wall of the rectangular waveguide, propagation mode and direction of the guided waves can be conversed and controlled due to wavevector matching. Such system can provide an excellent transition by matching the momentum of the rectangular waveguide mode and the SSPP mode. A smooth bridge between the rectangular waveguide system and the SSPP waveguiding system can be realized with potential advantages in conformal design, super-resolution imaging or signal manipulation. Simulated and experimental results, agreeing well with each other, validated the effectiveness of rectangular waveguide mode to SSPP mode conversion using PGM from 6.96-7.55 GHz. Furthermore, a dual channel rectangular waveguide to SSPP splitter is proposed and validated with applications for dual-channel power dividing and signal transmission, achieving an efficiency of 72.4%.

A Novel End-Wall Waveguide Excitation With Wide Bandwidth and Simple Structure for Millimeter-Wave/Terahertz Application

In millimeter-wave (MMW)/terahertz (THz) band, the insertion loss of interconnection between waveguide and planar transmission lines is usually high, and the microassembly process is complex. In this letter, a novel broadband end-wall waveguide electromagnetic wave mode excitation is proposed for MMW/THz application. A simple circular open-circuit stub is utilized to transform the quasi-TEM mode of grounded coplanar waveguide (GCPW) to the dominant TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode of rectangular waveguide (RWG). The operating frequency band can be adjusted and improved by controlling the positions of the matching via hole adjacent to RWG port. To further increase the excitation bandwidth, a U-shaped iris (U-iris) on the other side of the substrate is introduced and embedded in the end wall of the RWG to generate dual resonant excitation modes. A 0.2-THz transition from GCPW to RWG is designed as an example. Three back-to-back prototypes with different lengths are fabricated and measured. The measured return loss of single transition is better than 13 dB with an insertion loss of 0.8 ± 0.15 dB in the frequency range of 185–229 GHz (21.2% bandwidth). The proposed end-wall transition has the advantages of high efficiency, easy fabrication, and wideband performance.

A Substrate Integrated Waveguide-Based W-Band Antenna for Microwave Power Transmission.

A W-band slot array antenna based on a substrate integrated waveguide (SIW) for microwave power transmission (MPT) is proposed in this paper. By size optimization, the transition from the rectifier element to the antenna is limited to a small size. It realizes a compact arrangement of the radiating slots, which not only improves the aperture efficiency of the antenna but also makes it easy to integrate into a large-scale array. For antenna testing, a coplanar waveguide–SIW–rectangular waveguide transition structure is added at the end of the antenna, and an antenna with this transition structure is processed by PCB printing technology and measured. The measured reflection coefficient is less than −10 dB at 90–96 GHz, the aperture efficiency is greater than 60% at 93.5–94.5 GHz, the maximum gain is 13.2 dB at 93.5 GHz, and the aperture efficiency is 79%. The test results of the antenna show that the antenna has a good performance and can be applied to the MPT system as a rectenna.

Design and Experiment of 1 THz Slow Wave Structure Fabricated by Nano-CNC Technology

This article reports a slow-wave structure (SWS) working at 1 THz which can be fabricated through nano-computer numerical control (nano-CNC) technology for the first time. First, a 1 THz deformed quasi sine waveguide (D-QSWG) SWS has been designed and simulated in this article. To reduce the metal loss of input and output waveguide, a coupler which transit the waveguide to over mode rectangular waveguide has been designed. The simulation result shows that input and output waveguides with this coupler have lower metal loss than that of WR1 rectangular waveguide. To fabricate the designed D-QSWG SWS, tungsten steel endmills have been used. The fabricated SWS has the surface roughness around 58&#x2013;74 nm, the corresponding effective conductivity is around <inline-formula> <tex-math notation="LaTeX">$2\times 10^{{7}}$ </tex-math></inline-formula>&#x2013;1.85 <inline-formula> <tex-math notation="LaTeX">$\times 10^{{7}}$ </tex-math></inline-formula> S/m. And the cold test results show that the insertion loss of the fabricated model is less than 30 dB while the reflection loss is less than &#x2212;15 dB in the frequency range of 0.998&#x2013;1.016 THz, which has a good consistency with the simulated results. The beam-wave interaction simulation results based on the cold test results show that the designed D-QSWG traveling wave tube (TWT) has the output power of 300 mW, and the 3 dB bandwidth is around 3 GHz.

Terahertz out-of-plane coupler based on compact spot-size converter

Low-loss dielectric terahertz (THz) chips are efficient platforms for diverse THz applications. One of the key elements in the chip is the coupler. Most of the available THz couplers are in-plane and couple the THz wave from the metal waveguide to the dielectric waveguide. However, out-of-plane couplers are more suitable for wafer-scale testing and tolerant of alignment variation. In this work, we propose an out-of-plane THz coupler for coupling the antenna to the dielectric waveguide. The device is constructed using a grating and a compact spot-size converter. As the conventional optical spot-size converters that apply directly to THz chips are too large, we have designed a compact spot-size converter based on a tapered waveguide with a lens. The total device is 2.9 cm long and can couple a 7 mm diameter THz beam to a 500 µm wide waveguide. The device can scan the THz beam, radiate the input rectangular waveguide mode to free space, and drive the rotation angle of the fan beam through the scanning frequency. We fabricated the device using a single lithography step on a silicon wafer. The out-of-plane coupling efficiency was found to be ∼5 dB at 194 GHz. The fan-beam steering range was found to be around 40° in the frequency range of 170–220 GHz. The proposed out-of-plane coupling technique may provide an effective way for THz wafer-scale testing with a higher degree of freedom for on-chip integration. Also, the proposed technique being non-mechanical, beam steering using it, may therefore find applications in THz radar, communication, and sensing.

Design of a Wideband Coaxial-to-Rectangular Waveguide Transition Based on Supershapes

This paper proposes a wideband coaxial line to rectangular waveguide transition to use in high-power microwave systems. The proposed structure consists of a supershape excitation probe in a rectangular waveguide. The structure’s performance was measured and verified by fabricating a prototype. It was found that the measurement results are in good agreement with the simulation ones. The measured results indicate that the proposed structure’s reflection coefficient and insertion loss are lower than -15 dB and 0.25 dB, respectively. Also, bandwidth increased from 7.8 to 15 GHz which is more than 63%. Therefore, the proposed transition can be utilized in different high-power microwave components and antenna applications.

Millimeter wave-terahertz substrate integrated waveguide transition structure based on low temperature co-fired ceramic

In a microwave circuit system, the discontinuity caused by electromagnetic wave entering into another transmission medium from one transmission medium will greatly affect the transmission performance of the system, which has always been the focus of microwave circuit design. When the electromagnetic wave band enters into the millimeter wave and terahertz band, how to realize the efficient and low loss transmission of electromagnetic wave from the metal rectangular waveguide interface to the dielectric substrate is the key to the realization of millimeter wave terahertz communication system. Substrate integrated waveguide to rectangular waveguide transition structure is an important structure connecting waveguide interface and planar circuit in millimeter wave and terahertz communication system, and it is the basis of designing planar antenna array. In this paper, a W-band and D-band substrate integrated waveguide to rectangular waveguide transition structure is designed, which improves the transmission performance and expands the bandwidth through the stepped structure. On this basis, a one-in-two divider structure is designed, with an empty cavity structure used to reduce the loss and expand the bandwidth. These two structures have the characteristics of simple structure and easy processing, and their practicalities are verified by simulation optimization and actual low temperature co-fired ceramic substrate processing and assembly test. The actual test results show that the substrate integrated waveguide to rectangular waveguide transition structure can achieve a return loss of less than –10 dB in a frequency ranges of 126–149 GHz and 112–139 GHz, the one-in-two divider structure can achieve a return loss of less than –10 dB in the frequency band of 132–155 GHz.