Double-ridged Waveguide Research Articles

High-efficiency phase-locking of compact multi-beam relativistic extended interaction oscillator array for coherent power combinations

This study describes a phase-locking mechanism for a relativistic extended interaction oscillator (REIO) that employs a precisely engineered double-ridge waveguide. The mechanism effectively synchronizes four REIOs operating in 3π mode within an angular array through an equivalent coupling loop design. By optimizing the coupling loop structure, the cutoff frequency is reduced, and the coupling strength is properly maintained, ensuring efficient phase-locking with phase jitter confined within ±1.5°. The collective output power of the four REIOs is nearly four times that of a single free-running REIO, producing 550 MW of 5.68 GHz microwaves with an electronic efficiency of 43.5%.

Compact broadband high‐gain dielectric rod antenna with air–dielectric hybrid design for millimetre‐wave applications

AbstractThis paper presents a compact, broadband, high‐gain dielectric rod antenna. By utilising an air–dielectric hybrid method for designing the radiating and matching sections, gradual variations in the average equivalent permittivity along the rod are achieved, and the mechanism of the method is analysed. This approach facilitates a smooth impedance transition from the feed to the air, resulting in good impedance matching characteristics. Additionally, the antenna is fed through a tapered double‐ridged waveguide (DRW) with a coaxial line to tapered DRW transition. The proposed antenna achieves an impressive impedance bandwidth of 90.2%, covering the entire K and Ka bands. The unique structure of the proposed dielectric rod significantly enhances the antenna's gain, reaching a maximum value of 17.86 dBi. With its small aperture and compact longitudinal dimensions, this antenna is suitable for applications in settings like the Space Environment Simulation Research Infrastructure (SESRI).

Design of Double-Ridge Waveguide Balanced Filter and Filtering Power Divider

Design of Double-Ridge Waveguide Balanced Filter and Filtering Power Divider

Dual-Band Antenna Array Fed by Ridge Gap Waveguide with Dual-Periodic Interdigital-Pin Bed of Nails.

A dual-band (K-/Ka-band) antenna array is presented. An ultra-wideband antenna element in the shape of a double-ridged waveguide is used as a radiation slot, and a novel dual-periodic ridge gap waveguide (RGW) with an interdigital-pin bed of nails (serving as a filter) is used to realize dual-band operation. By periodically arranging the pins of two different heights in two dimensions, the proposed RGW with interdigital-pin bed of nails is able to realize and flexibly adjust two passbands. The widely used GW-based back cavity boosts the realized gain and simplifies the feed network design. A 4 × 4 prototype array was designed, fabricated, and measured. The results show that the array has two operating bands at 24.5-26.4 GHz and 30.3-31.5 GHz, and the realized gain can reach 19.2 dBi and 20.4 dBi, respectively. Meanwhile, there is a very significant gain attenuation at stopband.

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.

Fundamental spatial mode high power 808 nm double trench wide ridge waveguide laser

—Lasers operating at a wavelength of 808 nm, with watt-level output power and high beam quality in the fundamental spatial mode, have garnered significant attention due to their potential applications across various fields. Transverse optical confinement in double trench ridge waveguide lasers is determined by the width of the ridge and the refractive index difference between the ridge and trench. In this study, we have designed and fabricated a wide ridge laser operating at 808 nm with high power output and stable fundamental spatial mode based on this principle. The fundamental spatial mode operation was successfully achieved with an 8 μm ridge waveguide laser, producing an impressive output power of 1.3 W. The device exhibits a stable far-field as the current was increased from 0.3 A to 1.8 A. The laser's output power exhibits a 14% reduction with an increase in temperature of 80 °C, demonstrating a decrease rate of only 1.25 mW/°C and a wavelength variation rate of 0.22 nm/°C, indicating low sensitivity to temperature changes.

Widely tunable single-mode interband cascade lasers based on V-coupled cavities and dependence on design parameters

We report an investigation of V-coupled cavity interband cascade (IC) lasers (ICLs) emitting in the 3-μm wavelength range, employing various waveguide structures and coupler sizes. Type-II ICL devices with double-ridge waveguides exhibited wide tuning ranges exceeding 153 nm. Type-I ICL devices with deep-etched waveguides achieved single-mode emission with wavelength tunable over 100 nm at relatively high temperatures up to 250 K. All devices exhibited a side-mode suppression ratio higher than 30 dB. By comparing the performance of all devices with different sizes and configurations, a good tolerance against the structural parameter variations of the V-coupled cavity laser (VCCL) design is demonstrated, validating the advantages of the VCCL to achieve single-mode emission with wide tunability.

Efficient and robust second-harmonic generation in thin-film lithium niobate using modal phase matching

A double-ridge waveguide is designed for efficient and robust second-harmonic generation (SHG) using the thin-film lithium-niobate-on-insulator (LNOI) platform. Perfect phase matching (PhM) is achieved between the fundamental waveguide mode at 1,550 nm and a higher-order mode at the second harmonic. The fabrication tolerances of the PhM condition are simulated using a finite-difference method mode solver, and conversion efficiencies as high as 3.92 W−1 are obtained for a 1-cm long waveguide. This design allows access to the largest element of the second-order nonlinear susceptibility tensor, and represents a scalable alternative to waveguides based on periodically-poled lithium niobate (PPLN). The design has the potential for generating pairs of entangled photons in the infrared C-band by spontaneous parametric down-conversion (SPDC).

Wideband dispersion-free THz waveguide platform

We present a versatile THz waveguide platform for frequencies between 0.1 THz and 1.5 THz, designed to exhibit vacuum-like dispersion and electric as well as magnetic field enhancement. While linear THz spectroscopy benefits from the extended interaction length in combination with moderate losses, nonlinear THz spectroscopy profits from the field enhancement and zero dispersion, with the associated reshaping-free propagation of broadband single- to few-cycle THz pulses. Moreover, the vacuum-like dispersion allows for velocity matching in mixed THz and visible to infrared pump-probe experiments. The platform is based on the motif of a metallic double ridged waveguide. We experimentally characterize essential waveguide properties, for instance, propagation and bending losses, but also demonstrate a junction and an interferometer, essentially because those elements are prerequisites for THz waveform synthesis, and hence, for coherently controlled linear and nonlinear THz interactions.

Ultrawideband Dual Circularly Polarized Waveguide Array Antenna for K- and Ka-Bands Satellite Communications

In the letter, a wideband dual circularly polarized (CP) waveguide antenna array is designed for K and Ka dual-band satellite communications. A multi-stage square waveguide structure is exploited into the radiating part to facilitate the excitation of a dual polarization response. A ridge waveguide polarizer is integrated to form the left-hand circular polarization (LHCP) and the right-hand circular polarization (RHCP). For a better arrangement of the feeding network, a transition structure with E-plane waveguides to double-ridge waveguides reduces the cross-sectional area of the feeding network. An 8 x 8 array antenna prototype was designed, fabricated and measured for demonstration purposes. The axial ratio (AR) and impedance bandwidth of the array antenna are more than 45%, according to simulation and measurement results. Input reflection coefficient and isolation lower than -15 dB for the dual CP from 19 to 30 GHz, the total antenna efficiency for the entire operating band exceeded 72%. For both polarizations, the peak gain ranges between 24.6 and 28.8 dBi from 19 to 30 GHz.

Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

A Wideband, 1-bit, Electronically Reconfigurable Phase Shifter for High-Power Microwave Phased-Array Applications

We present the design and high-power experimental characterization of a wideband, high-power-capable, electronically reconfigurable phase shifter for high-power phased-array applications. The device studied in this work offers an electronically switchable, 1-bit phase shift using the concept of polarization rotation (PR). The PR-based phase shifter is designed to work in a custom-designed, double-ridge (DR) waveguide environment. Two p-i-n diodes are used to control the transmission phase of the signal by rotating the polarization of the incident wave by either <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+90^\circ$</tex-math> </inline-formula> or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-90^\circ$</tex-math> </inline-formula> with respect to that of the incident wave, thereby creating a wideband, 1-bit phase shift between the two states. Simulation results demonstrated that this element can work over one octave bandwidth ranging from 6 to 12 GHz. A prototype of the device was fabricated and experimentally characterized at low and high power levels. The measurement results confirmed the simulations and demonstrated the wideband, high-power-density capability of the device. High-power continuous-wave (CW) experiments were conducted across the entire 6–12 GHz band and demonstrated that the unit-cell-averaged, CW power handling capability of the device exceeds 23.6 W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> . High-power pulsed power experiments conducted at 9.382 GHz demonstrated that the unit-cell-averaged, peak power handling capability of the device exceeds 347 W/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> for short-duration pulses.

High-Efficiency Air-Filled Wideband ±45° Dual-Polarized Slot Array Antenna

This communication presents a wideband ±45° dual-polarized slot array antenna based on full metal structure. Two sets of ±45°-tilted radiating slots are in staggered arrangement, which shifts the polarization plane to the low sidelobe plane. This achieves low sidelobe levels (SLLs) in E- and H-planes for both polarizations. The radiating slots in a row for each polarization are further combined, forming a long slot to obtain stable radiation performance over a wide frequency range. Two compact full-corporate feeding networks based on the double-ridge waveguide (DRW) and the square coaxial line (SCL) are employed to excite the radiating slots of respective polarizations. A prototype of ±45° dual-polarized 8×8 slot array operating at Ku-band is implemented for demonstration. Experimental results show that the antenna is free from grating lobes and exhibits stable, consistent radiation patterns for the two polarizations over the frequency range of 11-15 GHz. Moreover, the SLLs are less than -25.2 dB and the antenna efficiency is over 79.4% across the same frequency band.

Efficient Microwave Processing of Thin Films Based on Double-Ridged Waveguide

Microwave heating has a wide range of applications in the fields of industrial heating and drying. However, when microwave heating is applied to the thin film, it will be challenging due to its low loss and large heat dissipation area. In this paper, a double-ridged waveguide for thin-film heating is proposed. The double ridge structure is employed to enhance the electric field, thereby increasing the power-loss density in the thin film. Firstly, a double-ridged waveguide, in which the electric field strength can be about 2.5 times that of the conventional waveguide, was designed based on the transverse resonance method and the electromagnetic field simulation. Then, a multiphysics model was built to analyze the heating performance of the ridged waveguide, in which the electromagnetic field and heat transfer are coupled. The simulation results show that the heating performance of the proposed waveguide will be 35.0 times that of the conventional waveguide. An experiment was carried out to verify the proposed model, showing that the experimental results are in accordance with the simulation results. Finally, the influences of the thickness of the film, the permittivity, the distance between two ridges, and the working state on heating performance and heating uniformity were also discussed.

Dual-Band Shared-Aperture Variable Inclination Continuous Transverse Stub Antenna

This article presents a dual-band shared-aperture variable inclination continuous transverse stub (VICTS) antenna with large beam coverage for both frequency bands. A novel hybrid radiating structure is introduced to enable approximately consistent initial beam direction at the boresight for both bands and therefore large beam coverage, by exciting different sets of the radiation elements at each of the two bands. The hybrid structure is formed of interlaced conventional CTS elements and those backed by double-ridge waveguide slots. The latter suppresses the lower band while allowing the high band to radiate. This configuration allows maximum aperture reuse. A parallel-plate waveguide (PPW) diplexer combines the generated plane waves from the two bands to enable one-side excitation. Combined with the nonuniform slow wave structure (SWS), optimized amplitude distribution is achieved across the two frequency bands, thereby improving the antenna efficiency. A prototype is designed, fabricated, and measured for 12.25–12.75 GHz (Ku-band) and 19.6–21.2 GHz (K-band). The measured reflection coefficients are kept less than −11.5 dB during the beam steering. At the center frequencies of 12.5 and 20.4 GHz, the measured beam coverage of over ±49° and ±59° in elevation plane is demonstrated from a relative rotation angle of 40°. During the beam steering, the measured peak gain varies in the range of 26.1–21.1 dBi/30.4–25.2 dBi at these two frequencies.

Double-ridged waveguide for efficiently heating ultrafine filament fibers

Microwave heating has attracted wide attention in fiber dyeing, refining, drying and modification due to its energy saving and environmental protection. However, effectively heating ultrafine filament fibers is difficult to achieve using conventional microwave heating devices because of their low power density and rapid heat dissipation at their surfaces. Thus, we designed a double-ridged waveguide operating at 2.45 GHz, facilitating rapid heating of ultrafine structure by increasing the electric field strength, subsequently causing higher power absorption by the ultrafine materials. First, the proposed waveguide was compared with other types of cavities by building a multiphysics model, incorporating electromagnetics and heat conduction of the heated filament fiber with a relative permittivity of 5.7–0.2j and a diameter of 0.008 times of the wavelength of vacuum. The electric field strength and power absorbed of the filament fiber located in the proposed ridged waveguide were approximately 13.3 and 180 times higher than that in WR430, a commonly used rectangular waveguide in system designs. Additionally, we built an experimental system to demonstrate that the design can efficiently heat a single filament fiber at low input power of 70 W. Furthermore, the effects of the filament fiber size, material permittivity, and cavity temperature on heating were investigated based on the constructed model.

Wideband Dual-Polarized Hollow-Waveguide Slot Array Antenna

A wideband dual-polarized slot array antenna based on hollow waveguide (HW) is presented in this article. Its wide bandwidth and high performance are enabled by two separate feeding networks, from the side and the bottom, using square coaxial line and ridge waveguide structures, respectively. The full-corporate-feed networks excite the radiation slots in a one-to-one fashion without using backed cavities. Tight element spacing is made possible, suppressing the grating lobe and maintaining high cross-polarization discrimination (XPD) across the wideband. This resolves a usual tradeoff between bandwidth and grating lobe. A double-ridge rectangular waveguide cavity is devised as an orthogonal mode splitter for isolation enhancement. Several design features are used to minimize the signal path length and facilitate routing. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> element prototype in K-band is designed, fabricated, and measured. Experimental results show that the antenna has a wide bandwidth of 23.4% (from 17 to 21.5 GHz) free from grating lobes. More than 25.5 dBi peak gain higher than 51.2 dB isolation and over 43.6 dB XPD are also obtained for the dual polarizations.

High-Isolation Power Divider Based on Ridge Gap Waveguide for Broadband Millimeter-Wave Applications

In this article, a high-isolation power divider with ultrawideband characteristics for simultaneous operation in two adjacent bands is proposed. The power divider is developed based on a four-port coplanar Magic-T. The difference port of the Magic-T consists of a double-ridge gap waveguide (RGW) that supports quasi-TEM mode transmission, which provides the benefit of its broadband characteristics and allows for facilitated assembly. In addition, an inline microstrip line (MSL) containing a probe is inserted into the opposite side of the difference port to form the sum port. This basic configuration has actually achieved high isolation between the output arms and low return loss at each port, and however, its isolation bandwidth is limited by the narrowband matching of the sum port. To overcome this difficulty, a three-port microstrip T-junction is connected in series to the sum port of the Magic-T, resulting in a five-port 3-dB power divider with a wide isolation bandwidth. The process of considering this solution is analyzed and explained in detail in this article and the corresponding simulations and experimental verifications are performed. According to the obtained results, the proposed power divider has excellent overall performance, in particular low loss, ultrawideband, high isolation, and good amplitude/phase consistency.

Computer‐aided development and experimental investigation of a double‐ridged orthomode transducer for modern satellite and space communication systems

This article presents results of development, optimization, and experimental measurements of electromagnetic characteristics of a wideband orthomode transducer for satellite and space communications. Analyzed design of the transducer is based on a double-ridged waveguide junction, which allows to obtain high level of discrimination of fundamental electromagnetic modes with perpendicular linear polarizations. Numerical modeling of the designed microwave waveguide orthomode transducer was performed by an effective finite elements method in the frequency domain. Optimization of the structure elements allowed to obtain high quality of matching and to improve the isolation between orthogonal polarizations simultaneously. To optimize the electromagnetic performance of the developed orthomode transducer a trust region method, which previously demonstrated its effectiveness for the improvement of electromagnetic characteristics of waveguide polarization converters, was applied. Experimental measurements of all scattering parameters of an antenna feed system, which included a designed orthomode transducer and a corrugated horn, were performed for the verification of simulated results. Results of computer-aided modeling and of measurements are in agreement. Measured good matching and high level of isolation between orthogonal polarizations confirm effective electromagnetic performance of the developed orthomode transducer. Designed wideband waveguide device can be applied in modern microwave antenna systems operating simultaneously at two linear or circular polarizations of electromagnetic waves.

A Wideband Endfire Double Dipole Antenna Fed From Double-Ridge Gap Waveguides for Multibeam Array Application

In this letter, an endfire double dipole antenna fed from double-ridge gap waveguides (DRGWG) is proposed and designed for multibeam array application. Two dipoles with different lengths are connected to the extension of the ridges of DRGWG in series. Different resonances can be generated by these two dipoles, which contributes to a wide impedance bandwidth, high gain, and stable radiation patterns across the working band. The double dipole antenna is vertically polarized and has a wide H-plane beamwidth suitable for beam scanning application. To verify the performance of the double dipole antenna, a Butler matrix is designed based on ridge gap waveguides to feed a 1 &#x00D7; 4 double dipole array arranging in H-plane. The maximum gains achieved for Ports 1 and 2 are 13.94 and 12.68 dBi, respectively. Besides, the simulated radiation efficiencies for Ports 1 and 2 are both above 83&#x0025;.