Ridged Cavity Research Articles

Improving beam quality of tapered laser diodes by integrated metalens

High-power and high-beam-quality laser sources are required in numerous applications. Here, we theoretically investigate a tapered laser diode with integrated metalens, which can improve the lateral beam quality. By carefully designing the slot length and width at different lateral positions behind the front facet, the mode mismatch between the ridged cavity and the tapered cavity is overcome while ensuring high transmittance (>96%). The beam quality is greatly improved, and the lateral far-field divergence is reduced. The simulation results show that the lateral far-field divergence (second-moment level) decreases from 7.2° to 5.9°, and the M2 (second-moment level) decreases from 2.3 to 1.2. The proposed structure shows a good thermal stability in the simulation.

A W-Band Compact Substrate Integrated Waveguide Bandpass Filter With Defected Ground Structure in CMOS Technology

This brief proposes the first on-chip bandpass filter (BPF) based on substrate integrated waveguide (SIW) for W-band applications. Slot-loaded, folded ridge and quarter mode technology is used to reduce the cavity size. The coupling characteristic of two folded ridged quarter mode substrate integrated waveguide (QMSIW) cavities implemented in CMOS technology is investigated. A simplified equivalent lumped-element circuit model of the proposed wide-band BPF approach is provided and applied to study the coupling characteristic of slot-loaded folded ridged QMSIW cavity. Then, a novel coupling method using a defected ground structure is proposed to realize a proper coupling intensity for BPF design. Finally, the proposed BPF design is implemented in a commercial complementary metal-oxide-semiconductor (CMOS) technology, fabricated, and measured. The active size of the proposed cavity resonator is only 405 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times185\,\,\mu \text{m}$ </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">$0.22{\lambda }_{\mathrm{ g}} \times 0.1 \lambda _{\mathrm {g}}$ </tex-math></inline-formula> ), and the measured insertion loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert|\text{S}_{21}~\vert|$ </tex-math></inline-formula> ) is 3.15 dB with a central frequency of 85.5 GHz.

Miniaturized Folded Ridged Half-Mode and Quarter-Mode Substrate Integrated Waveguides for Filter Design

This paper characterizes the performance of a miniaturized folded ridged half-mode substrate integrated waveguide (SIW) and explores its use in quarter-mode bandpass filter (BPF) design. By folding the fundamental mode of a ridged half-mode SIW (RHMSIW) around the capacitive ridge structure, an additional 50% of miniaturization can be achieved over RHMSIW and up to 87.5% compared with the standard SIW. The monomode bandwidths of both folded ridged half-mode and ridged half-mode waveguide technologies are studied, yielding 1:4.28 or greater fundamental to the second-order mode ratios for all cases and approximately twice the monomode bandwidth compared with half-mode technology. Furthermore, the study of folded ridged half-mode and quarter-mode substrate integrated cavities is presented, yielding miniaturizations compared with standard substrate integrated cavities with respect to free-space lambda equal to 96.6% and 98.0%, respectively. The design of BPFs using folded ridged quarter-mode cavity is demonstrated, with two different prototypes measured to study the choice of substrate thickness with respect to filter performance. By increasing the substrate thickness while maintaining similar cavity miniaturization, an improvement of 26.1% in unloaded quality factor between the filters is realized experimentally.

Dual-Band Circularly Polarized Transmitarray Antenna for Satellite Communications at (20, 30) GHz

A novel dual-band polarization-independent transmitarray is introduced in this paper for communication systems in Ka -band. Thanks to its unit-cell topology, the transmitarray antenna demonstrates almost complete independent performance at two design frequency bands of 20 GHz and 30 GHz. As a proof-of-concept, a transmitarray antenna prototype having a plate size of $80 $ mm $\times 80$ mm has been fabricated using printed board technology. A dual-band circularly polarized ridged cavity antenna feeds this planar structure and the relative translational displacement between the feed and transmitarray allows beam steering. The antenna performance has been validated via experimental results, which demonstrate good agreement with the theoretical and simulation predictions carried out with commercial software packages.

Ultra‐wide band bowtie slot waveguide antenna array for SAR application

An ultra-wide bandwidth, high-efficiency, small-size and low-profile waveguide antenna is presented in this study. To extend the bandwidth without increasing the antenna size, the bowtie shape slot and the stepped square coaxial transition in a ridged waveguide cavity are utilised. The proposed antenna is well suited to use as an element for the phased array with the wide-angle scanning capability, and such array is a good candidate for the synthetic aperture radar (SAR) application. The development of an active solid phased array (ASPA) utilising bowtie slot waveguide antenna as the element is presented to illustrate the design procedure. The proposed ASPA is fabricated and the measured results are provided to demonstrate that the proposed array has good performance in field pattern and impedance matching over the full X-band (8-12 GHz). The ASPA's operating frequency band is cantered at 10 GHz with bandwidth 40%. This ASPA has been integrated into the latest SAR system with the maximum ground resolution of 0.05 m, and the SAR image is also provided at the end of this study.

Complex Permittivity Measurement Using a Ridged Waveguide Cavity and the Perturbation Method

A new cavity-based method to measure the complex permittivity of dielectric materials is presented here. The method uses a double-ridged waveguide for the cavity instead of the widely used rectangular waveguides, thus enhancing the operational frequency bandwidth by twofold. The bandwidth enhancement is advantageous when measuring the permittivities of frequency dispersive specimens. Building on the perturbation theory, this paper develops the measurement equations required for permittivity extraction. The measurement errors induced by the approximations in the perturbation theory are evaluated using numerical simulations, and the errors are quantified for different specimen sizes and dielectric constants. The experimental results are also presented. The complex permittivities of three common plastic specimens are measured at frequencies of around 3, 5, and 8 GHz using one double-ridged cavity. For comparison purposes, the same samples are also measured using two rectangular cavities operating in the S- and X- bands. Good agreement in the measured permittivity values is observed.

Efficient analysis of ridged cavity by modal FDTD method

SUMMARY A modal finite-difference time-domain (FDTD) method is extended for the analysis of ridged cavities, which are uniform in the z-direction. Assuming that the end surfaces of cavity are the perfect conductor, thus, the fields along the z-axis can be described by kz. Therefore, three-dimensional (3-D) problems can be simulated by the use of a two-dimensional model. Besides, to achieve a faster computation, the field components are expressed by two pairs of equations—sine and cosine. To validate the utility and efficiency of proposed method, we analyzed two ridged cavities. Numerical results show that less than one-tenth memory and CPU requirements are needed by the modal FDTD as compared with conventional 3-D FDTD method. Copyright © 2012 John Wiley & Sons, Ltd.

Note: Studies on x-ray production in electron cyclotron resonance x-ray source based on ridged cylindrical cavity

A ridged cylindrical cavity has been designed using MICROWAVE STUDIO programme and it is used in the electron cyclotron resonance (ECR) x-ray source. The experimental parameters of the source are optimized for maximizing the x-ray output, and an x-ray dose rate of ∼1000 μSv∕h was observed at 20 cm from the port, for 500 W of microwave power without using any target. With the molybdenum target located at optimum position of the ridged cavity, the dose rate is found to be increased only by 10%. In order to understand the experimental observation, the electric field pattern of the cavity with the target placed at various radial distances is studied. In this note, the experimental and theoretical studies on ECR x-ray source using the ridged cylindrical cavity are presented.

Beam acceleration test of the Ridgetron electron accelerator

A cw electron accelerator system with a ridged cavity resonator, the Ridgetron, has been developed for industrial irradiation. It is intended to accelerate an electron beam up to 10 MeV and extract a beam power of 25 kW. As the first step of investigation, a 2.5 MeV prototype system was constructed. It consists of a cylindrical ridged cavity, four bending magnets and an electron gun. The acceleration test was performed after preliminary commissioning and the electron beam of 5.3 kW was extracted in continuous operation mode.

The electron accelerator Ridgetron for industrial irradiation

A compact electron accelerator, the Ridgetron, with a ridged cavity resonator has been developed for industrial irradiation. It is of a recirculating acceleration type and is intended to have an energy range of 0.5–10 MeV and a beam power of 1–25 kW. The operating frequency is in a VHF band. In this band, a RF amplifier by use of a transmitting tube can be operated in cw mode. A prototype system with an energy of 2.5 MeV and a beam power of 6.5 kW was constructed to confirm the feasibility. The beam acceleration test with a low current beam was performed in the pulse mode operation.

Development of the new electron accelerator Ridgetron

A new cw electron accelerator, the Ridgetron, with a ridged RF cavity resonator is proposed. In the ridged cavity, the electric field excited in the TE110 mode is concentrated in the gap between two ridges and the magnetic field is zero in their gap and inside the hollow ridges. By using this symmetrical plane through the gap and the ridges, therefore, it is possible to accelerate charged particle beams without parasitic deflection by the magnetic field. The Ridgetron accelerates the beams in the radial direction through the plane and performs successive acceleration and focusing with bending magnets. This machine is suitable for accelerating the continuous electron beams at modest output power ratings between 1 and 25 kW in the 0.5–10 MeV range. It is more compact than other electron accelerators operated in the VHF band and can be installed in a compact space desired for an industrial electron irradiation facility. Its prototype is under development. The results of beam simulations showed that the beams can be accelerated stably up to the final energy.

Ridged cavity backed slot antenna with dielectric loading

A reduced size cavity backed slot antenna, consisting of a transverse slot in the flat broadwall of a deep single ridge waveguide cavity is described. Partial dielectric loading achieves significant further reduction in electrical size. Moderate dielectric loss increases bandwidth (and significantly reduces antenna gain).

Modified peniotron using a TE11rectangular waveguide cavity

This paper proposes a modified peniotron which is expected to increase both handling power and conversion efficiency compared with the original peniotron, and reports the analytical results or its operational characteristics using some computer simulations. Analytical results assuming the fundamental operation of ω0 ≃ ωc at l0GHz show that an extremely high transverse efficiency of nearly 100% may be attainable over a considerably wide range of output power. The tube uses a TE11 rectangular waveguide cavity instead of the double-pair ridged waveguide cavity used for the original peniotron.

Original improvements of TLM method

The use of the three-dimensional-TLM method is limited, first, by an excessive computation time and, secondly, by the variability of the results when the position of the point of observation varies. An original approach is described which improves the first point and avoids the second one. The resonant frequencies of the studied cavity are computed by applying Prony&apos;s method to time variations of the electric energy located inside the cavity. Numerical results are given in the case of the ridged waveguide cavity.

A shallow ridged-cavity crossed-slot antenna for the 240- to 400-MHz frequency range

An experimental study has been made of a shallow ridged-cavity crossed-slot antenna to determine its feasibility for operation in the 240- to 400-MHz band. The various trends are summarized for the VSWR response characteristics as the cavity and slot parameters are varied. The wideband antenna characteristics using a ridged cavity configuration are demonstrated. Based on the limited amount of data obtained from the experimental model, the VSWR is < 2.7:1 from 240 to 270 MHz and < 2.1:1 from 290 to 400 MHz for a cavity with a maximum dimension of 33 by 33 by 4 in. Measured radiation patterns with the cavity mounted on a finite-size fiat ground plane are shown.