Standard Rectangular Waveguide Research Articles

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.

E-Plane dual band bandstop waveguide filter for possible X-band applications

ABSTRACT This paper presents, a novel second order E-plane planar insert based dual band bandstop waveguide filter. The circular shape with two T-shape resonators are printed on Roger RO4350 dielectric substrate to form planar insert. The insert are placed in such a way that positioned in E-plane of the standard WR-90 rectangular waveguide. The independent resonant frequency and bandwidth of the stopband can be adjusted by tuning the resonators. To achieve second order dual band bandstop filter response four asymmetrical circular shape with two T-shape resonators are designed on dielectric substrate to form different stopbands and separated by some specific distance to eliminate the unwanted coupling between them. The numerical analysis of the proposed filter is carried out using CST microwave studio. To validate the numerical analysis of the proposed filter, resonator, WR-90 rectangular waveguide is fabricated and measured. The measured results shows stopband characteristics having centre frequencies f 01g = 8.56 GHz and f 02 = 11.21 GHz and exhibits the bandwidth of 0.4146 GHz and 0.3824 GHz. The simulated and measured result are in good agreement.

A New Technique for Broadband Matching of Open-Ended Rectangular Waveguide Radiator.

The maximum reflection at an open end of a standard rectangular waveguide is about -10 dB in its operating frequency range. It is often used without matching. For critical applications, it is desirable to further reduce the reflection coefficient. In this paper, a new technique is presented for the broadband impedance matching of an open-ended rectangular waveguide. The proposed technique employs three thin capacitive matching elements placed at proper intervals via a low-loss dielectric material. The capacitance of, and distance between, the matching elements are optimized for broadband impedance matching using a simulation tool. Based on the proposed technique, two design examples are presented for the matching of a WR75 waveguide radiator. A reflection coefficient of less than -16 dB and -20 dB has been achieved over a ratio bandwidth of 2.13:1 and 1.62:1, respectively.

Simple and Easily Connectable Transition from Empty Substrate-Integrated Waveguide to a 3D Printed Rectangular Waveguide

3D printing is one of the most promising manufacturing methods in the most developed technological fields, including microwave hardware fabrication. On the other hand, the well-known manufacturing methods of planar substrate integrated circuits allow high-quality prototypes to be made at low cost and with mass production capabilities. The combination of both manufacturing methods, 2D or 2.5D (substrate integrated circuits) and 3D (3D printed structures), will allow us to take advantage of the main strengths of each technology and minimise disadvantages. In this article, for the first time, a transition structure between the Empty Substrate-Integrated Waveguide (ESIW) technology—a planar waveguide integrated on a printed circuit board—and a standard rectangular waveguide manufactured by 3D printing is proposed. This transition will make it possible to combine planar circuits with 3D structures, thus taking advantage of the benefits of both types of technologies. The fabricated prototype presents low losses (0.6 dB for the transmission coefficient and 15 dB for reflection coefficient), good electrical response (very flat), and simultaneously good mechanical stability and robustness to manufacturing and assembly errors. The proposed design for this transition piece is easily realisable for a wide range of affordable 3D printers. Repeatability is guaranteed and the proposed transition allows us to combine different SIC structures to 3D printed circuits. Hence, this transition will enable advancements in the fabrication of microwave devices, particularly with regard to satellite communications.

Dual-Mode Conical Horn Antenna with 2-D Azimuthal Monopulse Pattern for Millimeter-Wave Applications.

In this paper, a novel concept of a three-dimensional full metal system including a Dual-Mode Converter (DMC) network integrated with a high-gain Conical Horn Antenna (CHA) is presented. This system is designed for 5G millimeter wave applications requiring monopulse operation at K-band (37.5-39 GHz). The DMC integrates two mode converters. They excite either the TE11cir or the TE01cir modes of the circular waveguide of the CHA. The input of the mode converters is the TE10rec mode of two independent WR-28 standard rectangular waveguide ports. By integrating the DMC with the CHA, the whole system, called a Dual-Mode Conical Horn Antenna (DM-CHA), is formed, radiating the sum (Σ) and difference (Δ) patterns associated to the monopulse operation. To adequately prevent the propagation of higher order modes and mode mutual coupling, this integration procedure is carefully designed and fabricated. To prove the performance of the design, the DMC network was fabricated using subtractive manufacturing by Computer Numerical Control (CNC) technology. The CHA was fabricated using additive manufacturing by Direct Metal Laser Sintering (DLMS) technology. Finally, the simulation and measurement results were exhaustively compared, including return loss, isolation, radiation pattern, and gain of the full DM-CHA structure. It is noteworthy that this system provided up to ±11° per beam in the angular of arrival detection to support the high data rate operation for 5G satellite communications in the millimeter-wave band.

Computer-aided design of quadra-ridged waveguide transformers for full-band matching of half-height rectangular waveguides

A quadra-ridged waveguide transformer (QRWT) is proposed for full-band matching between a standard waveguide and a half-height waveguide, which meets the need for compact waveguide components and the need for multiple sections of irregular transmission lines for better matching in wider operation bands. Unlike conventional matching circuits with monotonically changing impedances, QRWTs form abrupt cross-section changes between transmission line steps. The initial configuration of QRWT is built by CST MICROWAVE STUDIO, a system-level electromagnetic compatibility and general high frequency passive device simulation software, according to the basic electromagnetic (EM) concept and then is optimized by optimization functions from an advanced EM simulator, during the optimization, releasing restrictions as many as possible. To explain the concept, a sample QRWT is designed to match a standard rectangular waveguide WR34 to a half-height waveguide. The reflection coefficient is less than −24 dB in the full operation bandwidth, from 21.7 to 33 GHz. The optimized QRWT has a length of 3.088 mm, 0.218 times the waveguide wavelength at its center operation frequency of 27.35 GHz. For comparison, a two-stage quarter-wave transformer matching circuit is optimized. For similar reflection coefficients in the same bandwidth, the QRWT has a length 57% shorter than the conventional one, and it has an easier manufacturing method using wire-electrode cutting. To verify the design, a back-to-back matching circuit was fabricated using brass material without extra dielectric material. Its measured reflections are less than −16.6 dB, and the insertion loss is less than 0.2 dB.

Ultra-Wideband Multi-Octave Planar Interconnect for Multi-Band THz Communications

An ultra-wideband (UWB) interconnect technology using indium phosphide (InP)-based transitions for coupling the output signals from terahertz (THz) photodiodes featuring coplanar waveguide (CPW) outputs to low-loss dielectric rod waveguides (DRWs) is presented. The motivation is to exploit the full bandwidth offered by THz photodiodes without limitations due to standard rectangular waveguide interfaces, e.g., for future high data rate THz communications. Full electromagnetic wave simulations are carried out to optimize the electrical performance of the proposed InP transitions in terms of operational bandwidth and coupling efficiency. The transitions are fabricated on 100-µm-thin InP and integrated with silicon (Si) DRWs. Experimental frequency domain characterizations demonstrate efficient THz signal coupling with a maximum coupling efficiency better than − 2 dB. The measured 3-dB and 6-dB operational bandwidths of 185 GHz and 280 GHz, respectively, prove the multi-octave ultra-wideband features of the developed interconnect technology. The 6-dB operational bandwidth covers all waveguide bands between WR-12 to WR-3, i.e., a frequency range between 60 and 340 GHz. In addition, the multi-octave performances of the fabricated interconnects were successfully exploited in proof-of-concept THz communication experiments. Using intermediate frequency orthogonal frequency division multiplexing (OFDM), THz communications are demonstrated for several frequency bands using the same interconnect. Considering soft-decision forward error correction, error-free transmission with data rates of 24 Gbps at 80 GHz and 8 Gbps at 310 GHz is achieved.

A Novel Low-Loss Overmoded Waveguide System for mm-Wave Cosmology

Millimeter-wave signals need to be carried over distances of 1 meter or more with low loss forapplications in precision cosmology such as beam pattern measurements of antennas. We present a novel,particularly simple approach to convert from standard rectangular waveguide to an overmoded circularwaveguide and back again. We give a design for a transition from rectangular W-band (75-110 GHz)waveguide to overmoded circular waveguide and for long circular waveguides made of copper tubes. Themeasured loss of the transitions is below 0.25 dB and the loss in the circular waveguide is 0.7 dB over a 3m length, including circular waveguide joints at each end. This result is consistent with calculations

Design and manufacturing of iris waveguide filters for satellite communication

We propose in this paper, two bandpass filters in waveguide technology having rectangular symmetrical discontinuities with a half-radius r , designed and operating respectively in the X-Band (9 - 11.5) GHz and C-Band (3.5 - 5.5) GHz. These filters consists of eight irises placed symmetrically respectively on standard rectangular waveguides WR90 and WR229 in which resonant irises are inserted. These irises are used to couple the sections very strongly in this filter, which allows the bandwidth to be increased and the matching to be controlled. The comparison between the numerical and electromagnetic results, which we obtained for the filters, constitutes a means of validation of computer simulation technology (CST) environment and Mician for the design of the other circuit elements in the various frequency bands. We observed excellent consistency between the simulation curves and those of the measurements. The results obtained are promising and pave the way for the use of these structures in the fields of telecommunications.

Millimeter-Wave Near-Field Evaluations of Polylactic Acid (PLA) Filament Used in Polymer-Based Additive Manufacturing (AM)

ABSTRACT Additive manufacturing (AM) remains to be a rapidly growing industry with applications that are extended beyond metals and to other materials, such as polymers, ceramics, and concrete, to name a few. However, advancement in the development of inspection techniques, particularly in-line nondestructive testing (NDT) methods, lags significantly. Most of the research in developing such methods has focused on metal-based AM. This paper investigates the efficacy of three high-resolution near-field millimeter-wave probes for detecting small voids in the feedstock polymeric filaments used for AM. The electromagnetic (EM) design and optimization of these probes are discussed in this paper. The design of the probes is based on concentrating the interrogating electric field of an open-ended waveguide in a small region corresponding to the area of a thin dielectric slab insert. This results in achieving a higher spatial resolution than when using only the open-ended waveguide. Extending the dielectric slab to an optimum value out of the waveguide makes the electric field more concentrated and potentially further improves the spatial resolution. These modifications also reduce the detection sensitivity as a function of increasing standoff distance. However, the spatial resolution of these probes varies more rapidly as the standoff distance increases. Subsequently, the efficacy of these three probes was studied and compared using a comprehensive set of numerical EM simulations at V-band (50–75 GHz). Afterward, three such probes were fabricated, at V-band (50–75 GHz), and were used to measure the reflection responses of the stock Polylactic Acid (PLA) filaments with a very small hemispherical surface void. Root-Mean-Squared-Error (RMSE), between reference and defective filaments and over the simulated and measured frequency range, was calculated as a criterion to compare the detection capability of the three probes in the entire frequency band. The results showed that at V-band (50–75 GHz) the spatial resolution of the standard open-ended rectangular waveguide is deemed sufficient detecting small surface voids of the stock PLA filaments.

Development of a microwave resonant waveguide slot antenna with in-phase slot excitation

The object of research in the work is the process of radiation of electromagnetic waves of a resonant waveguide-slot antenna with in-phase excitation of slots. The subject of research is the wave parameters and directional properties of a resonant slotted waveguide antenna with in-phase slot excitation. The existing problem is that it is necessary to ensure highly directional properties of the antenna with electrical control of its wave parameters at high transmitter power. This problem is due to the fact that to solve the problem of developing equipment for radio control, and radar of aircraft, highly directional antennas of small sizes are required. To solve this problem, the paper proposes the design of a simple and cheap version of a microwave resonant waveguide-slot antenna with in-phase slot excitation.
 As a basis for developing a resonant slotted waveguide antenna, the authors chose a standard R48 rectangular waveguide, which is a classic in the theory of directional systems in the microwave range. This is due to the fact that in order to calculate and study a microwave resonant waveguide-slot antenna with in-phase excitation of slots, the authors used well-known elements of the theory of aperture antennas. The design of a resonant slotted waveguide antenna consists of a rectangular waveguide, an exciter, and a feeder. The radiation surface of the antenna is a wide wall of a standard R48 rectangular waveguide along the central axis, of which slots are symmetrically cut in a checkerboard pattern. The exciter is made in the form of a metal pin inside a rectangular waveguide near the short-circuited wall. This pin acts as an asymmetric vertical vibrator that excites electromagnetic waves in a rectangular waveguide. The antenna is tuned to the maximum radiation power mechanically by moving the short-circuited wall of the rectangular waveguide. The pin feeds a feeder based on a coaxial cable with a characteristic impedance of 75 ohms.
 The developed resonant waveguide-slot antenna with in-phase excitation of slots operates in the frequency range of 4.0–6.0 GHz. In the frequency range of 4.0–5.45 GHz, the value of Voltage Standing Wave Ratio (VSWR) varies from 1.08 to 2.1. In the frequency range of 5.45–6.0 GHz, the Voltage Standing Wave Ratio (VSWR) value varies from 2.1 to 6.55. The directivity of the antenna in the operating frequency range is not less than 90. The width of the main lobe of the antenna pattern in the horizontal plane is not more than 3.1°. The antenna gain in the operating frequency band is at least 100. The efficiency is at least 90 % with a maximum generator signal power of 10 kW.

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.

Design of a Quasi-TEM Waveguide for the High-Intensity-Field Measurement of the Field-Induced Metasurfaces

Field-induced metasurface is an applicable technique to prevent the high-intensity-radiated-field (HIRF). To improve the measurement accuracy, this article presents the design of a waveguide that forms high-intensity TEM waves within its closed transverse boundaries. The proposed quasi-TEM waveguide adopts two artificial magnetic conductors (AMCs) on the sidewalls of a standard rectangular waveguide. And the construction of the AMC is based on the theory of high impedance surface (HIS), which performs perfect magnetic conductor (PMC) properties at its resonant frequency. Then, a prototype is designed and fabricated to measure the electric field distributions and demonstrate the theoretical analysis and simulation. The measurement results indicate that the proposed waveguide could realize a 1 dB rippled electric-field distribution in more than 90% region, compared to that of 30% in the standard waveguide. Finally, high-intensity-field measurements of a field-induced sample, energy selective surface (ESS), are compared in the proposed waveguide and a standard waveguide. The comparison result has proved that the proposed waveguide could better evaluate the HIRF performance of the field-induced metasurface.

Millimeter-Wave E-Plane Waveguide Bandpass Filters Based on Spoof Surface Plasmon Polaritons

A class of millimeter-wave E-plane waveguide bandpass filters (BPFs) based on spoof surface plasmon polaritons (SSPPs) have been presented in this article. Three kinds of SSPPs, with different patterns coated on the dielectric substrate, are inserted into the E-plane of WR-10 standard rectangular waveguide for the design of BPFs. To clarify the filtering characteristics of the proposed BPFs, the dispersive properties of different SSPP unit cells are investigated and discussed. The electromagnetic simulation results demonstrate that the bandwidths and center frequencies of the proposed E-plane waveguide BPFs can be flexibly adjusted by controlling the asymptotic frequencies of SSPP unit cells. For verifying the design feasibility, these three E-plane waveguide BPFs are fabricated and measured. Good agreement between measurements and simulations indicates that the proposed idea will be a good candidate for the BPF design with low insertion loss and flexible adjustment of center frequency and bandwidth.

Evaluation of the possibilities of 3D-printing for the making of waveguide photonic crystals

The paper considers the possibilities of 3D printing technology for the manufacture of X-band waveguide photonic crystals. The photonic crystals for an EIA WR-90 standard rectangular waveguide with a cross section of 22,86 10,16 mm2 in the X-band were designed and manufactured. Numerical modeling of the reflection characteristics of photonic crystals of several designs in the OpenEMS software package was carried out. Based on the simulation results, the best types of the structures were selected, which were manufactured using the physical modeling technique by the fusion method of PETG plastic. Experimental study of the manufactured layouts and comparison of the experimental data with the numerical simulation data were performed. The best types of manufactured models of waveguide photonic crystals showed transmittance and reflection drop in the corresponding frequency bands of the order of 1520 dB, which is acceptable for technical applications. The numerical modeling results are in good agreement with experiments, thus indicating the high efficiency and good control of the topology and dimensions of the manufactured photonic crystals structural elements in the used type of 3D printing technology.

Wideband RWG-SIW Interconnection With Improved Integration for Millimeter-Wave/Terahertz Application

In this letter, wideband interconnections are proposed to connect metal rectangular waveguide (RWG) and substrate integrated waveguide (SIW) based on printed circuit board (PCB) technology. For the purpose of easy fabrications and micro-assembly processes in millimeter-wave/terahertz (MMW/THz) applications, a standard RWG is used to feed the transition without any manufactures in the metal waveguide. The wideband interconnection structure with improved impedance matching is only designed in a single-layer PCB. Particularly, the novel interconnections are realized by stepped dielectric transformers using PCB technology. These integrations have the advantages of simple structure, low fabrication cost, and easy processes. To demonstrate the scheme, two 220-GHz band interconnections are designed as examples. Back-to-back interconnections are fabricated and measured. The measured results agree well with the simulated results. It can be concluded that the measured insertion and return losses of both single interconnections are better than 0.9 and 10 dB, respectively, in the frequency range from 180 to 240 GHz (28.6%).

High-Efficiency Excitation of Spoof Surface Plasmon Polaritons Through Rectangular Waveguide Using Dipole Antenna

In this communication, a high-efficiency rectangular waveguide-to-spoof surface plasmon polaritons transmission line (SSPPs TL) transition operating within terahertz frequencies is demonstrated. Terahertz signal fed by the rectangular waveguide is first coupled to the planar circuit through the dipole antenna. And then a taper and double-sided SSPPs TL are used to transform the resonant mode in the dipole antenna to the SSPPs mode and achieve impedance and momentum matching. The high transmission performance of the SSPPs TL is obtained by etching a series of periodically corrugated grooves on the metal strip in the top layer and a ground pad connected to the convexity of the rectangular waveguide is employed in the bottom layer. A back-to-back transition prototype was fabricated on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu \text{m}$ </tex-math></inline-formula> -thickness quartz substrate and designed for a terahertz device with WR-4.3 standard rectangular waveguide. The measured results show that the insertion loss is lower than 2 dB from 195 to 250 GHz, and the in-band return loss is better than 10 dB. To the best of our knowledge, this work presents the rectangular waveguide-to-SSPPs TL transition using a dipole antenna for the first time, which has potential applications for plasmonic-integrated circuits and systems in the terahertz range.

Direct Metal Laser Sintering Conformal Waveguide Array Antenna for Millimeter-Wave 5G Communications

An omnidirectional conformal array antenna has been implemented in air-filled waveguide technology for the 37–40 GHz band. The input port of the antenna is a standard WR28 rectangular waveguide. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode excited in the rectangular waveguide is used to generate the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode inside a circular waveguide by means of a TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> –TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode converter. The circular waveguide section is progressively widened, forming a radial waveguide structure, where the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode propagates radially through several radiating apertures. Due to the rotational symmetry of the structure, an omnidirectional radiating performance with low ripple can be achieved. This structure has been three-dimentional (3-D) manufactured using the direct metal laser sintering technology. A good agreement between simulations and measurements has been found. A reflection coefficient of below −15 dB, a low-ripple omnidirectional performance in a conical cut plane, a low cross-polar radiation, and a total efficiency higher than 83% are obtained. This conformal antenna design is proposed for fifth generation (5G) New Radio indoor applications.

A flexible low insertion‐loss wideband millimeter‐wave crossover based on ridge gap waveguide technology

This paper presents a flexible low insertion-loss wideband millimeter-wave crossover based on the ridge gap waveguide (RGW) technology. Based on the design of periodic metal pins of gap waveguide (GW), the transmission modes in the ridge have been analyzed in detail. The influence of different widths of the ridge on the cutoff frequency of the quasi-TEM mode and the first high-order mode in GW are mainly discussed. According to the results of the mode analysis, a flexible wideband low insertion-loss central-crossover covering 42–51 GHz is designed, which can be easily used to form the Butler Matrix (BM). Furthermore, a transition from standard rectangular waveguide to RGW has been designed. Finally, to validate the proposed design method, a complete crossover prototype based on RGW technology operating from 42 to 45.5 GHz in U-band is designed and fabricated. The measured results have a good agreement with simulated results.