In this paper, we design and fabricate dual-tunable waveguides in a two-dimensional periodic plate with threaded holes. Dual tunability is realized by using rods held with nuts as well as assembly prestress of the nuts. A straight waveguide, a bent waveguide, and a wave splitter are designed by changing the distribution of rods and nuts in different circuits. The experimental and numerical results show that the frequencies of guided waves can be tuned by the assembly prestress. By increasing the amount of prestress, the frequency range of the passing band can be shifted upward. Confinements, guiding, and splitting of Lamb waves are clearly observed in both experimental measurements and numerical simulations. This work is essential for the practical design of reconfigurable phononic devices.

A waveguide power divider based on ridge waveguide to microstrip line transition is presented in this paper. To improve the isolation performance, a probe insulator is inserted into the contact face from the center of the waveguide side wall, also two chip resistors are mounted on a planar substrate and connected with the probe to absorb the coupled energy. The impedance transformation is accomplished by ridge waveguide to microstrip line transition, which is hidden in the waveguide. This proposed power divider shows merits of waveguide power dividers and substrate-integrated waveguide power dividers simultaneously, i.e. planar output ports, compact size, and high isolation. For verification, a power divider operating at the Ka-band is simulated, fabricated, and measured. The obtained results show the return loss and isolation are better than 10 and 20 dB, respectively. The measured insertion loss is <1.5 dB, including the insertion loss of waveguide to microstrip line transitions at the output port in the range of 34.6–39 GHz.

Substrate-integrated waveguide (SIW) technology has recently drawn attention to its benefits in the microwave field, such as integration in planar microwave circuits, low manufacturing cost, and high-quality factor compared to other technologies. In this paper, a broadband and high gain SIW cavity-backed L-shaped slot antenna structure has been designed and made for X-band applications. Three pairs of L-shaped half-wave resonators are placed on the lower wall of the cavity (backed-slots) to further expand bandwidth and improve gain. The final antenna designed operates on a band ranging from 9.4 to 10.5 GHz with a bandwidth of 11%. Moreover, the gain reaches a value of 9.5 dBi. The final antenna is realized on a Rogers RT/Duroid 5870 substrate. The gain, the reflection coefficient, and the radiation patterns are measured and compared to the EM simulation results and a very good agreement is obtained. The proposed cavity-backed L-shaped slot antenna gives a good compromise between a high gain and a large bandwidth.

A mode converter design using the concept of periodic substrates loading in a circular waveguide, to convert TM01 mode to TE11 mode is presented in this paper. The detailed design principle, simulation, and measurement results are included in this study. Simulation results show that the purity of output fundamental TE11 mode of the converter approaches 99.2% for an operating frequency of 3.2 GHz. The mode conversion efficiency is more than 90% over 3.07–3.25 GHz band and the relative bandwidth is 5.6% (180 MHz). The proposed TM01–TE11 mode converter has advantages, such as the compact, lightweight structure, high conversion efficiency, and proper bandwidth. The fabrication cost is relatively low and the structure is easy to fabricate. The power-handling capability is limited to 10 MW due to dielectric-based design. The compactness and portability of the system (e.g. Space applications, Accelerators, High Power Microwave) can be improved significantly using the proposed mode converter.

The microwave waveguide and resonator methods are compared as applied to the experimental determination of the dielectric properties of high loss liquids. A differential microwave waveguide cavity for measuring high loss liquids complex permittivity in a small volume has been designed and studied. This cavity consists of two circular waveguide cells with central rods made of quartz and surrounded by high loss liquid tested. The cells have different lengths to eliminate complex propagation coefficient measurement errors due to the diffraction effect on the ends of the layered waveguide cells. We have measured the wave amplitude and phase coefficients for the waveguide cavity to estimate physical properties of a high loss liquid under test. The resonant frequencies and the Q-factor of a semi-disk dielectric resonator with high loss liquid filling a capillary have been measured. We have selected water-ethanol solutions as a high loss liquid under test for both techniques. We have determined the measurement sensitivity for these two techniques. The measuring results are discussed. Both the waveguide and resonator methods provide comparable sensitivity and can be successfully used for the complex permittivity characterization of high loss liquids in small volumes.

The effects of the phase variation, the evolution of the electron beam, the evolution of the radiation intensity, and the higher-order modes due to waveguides on a free-electron laser (FEL) oscillator have been analyzed by using two electron beams of different energies based on the proposed FEL facility which is to be operated in the far-infrared and infrared regions. The three-dimensional (3D) effects on a FEL oscillator due to waveguides and higher-order modes were studied using an extended 3D FEL code with two electron beams that we have developed. The effects of the variation on the amplitude of radiation on the electron beam's emittance and energy spreads were also calculated in the case of waveguide for multi-particle and multi-pass numbers by using a new 3D code. The phase variation, the variation in the beam envelope, the evolution of the amplitude, and power were calculated for the fundamental mode. The results were compared with those of the higher-order modes of the wiggler for various TE and TM modes for determining the FEL's performance which is required for high-quality electron beams.

This paper presents application of split ring resonators (SRR) in conventional waveguide slot array antenna to achieve performance improvement and multiband characteristics. Three SRRs have been placed on the transverse plane of a conventional slotted waveguide and has been simulated and measured. The measured results show that the antenna has dual band response with respective 10 dB return loss bandwidth 8.23–9.23 GHz (11.45%) and 9.68–11.01 GHz (12.87%). The measured gain and radiation pattern reveal that the proposed antenna has higher gain and front to back radiation ratio as compared with a conventional slotted waveguide antenna. Equivalent circuit of the proposed antenna also has been presented.

A specimen containing nanograms of sulfur, calcium, and 3d transition metal elements was measured by incident X-ray beams of various sizes restricted by a waveguide placed in a portable TXRF spectrometer. The signal to background ratios of spectra decreased with an increase in incident X-ray beam size. The portable spectrometer was also applied to rainwater and a specimen containing antimony and rare earth elements. Nanograms of elements in these specimens were detected by K-line or L-line excitation.

The possibility to characterize infinite and periodic frequency-selective surfaces (FSS) filters that have two orthogonal axes of symmetry inside a waveguide is reported. Thus, preliminary measurements can rapidly be obtained at low cost with few elementary cells instead of using a large FSS panel in free space. This is possible because of the equivalence that exists between the electromagnetic fields of two symmetric and oblique plane waves incident on and reflected from an infinite periodic surface and the incident/reflected fields that exist inside a single-mode rectangular waveguide containing a finite number of elementary cells. Comparisons of the measurements with some full-wave simulations for FSS belonging to the first three groups as they were defined by Munk confirm the good agreement between them. This is an interesting and simple assessment tool concerning the fabrication quality of FSS. The extension of this technique to non-symmetric FSS patterns is also discussed and supported by experimental and simulation results. The limitations of the technique are finally discussed.

A differential equation governing the wakefield potential (φ) in a plasma filled rectangular waveguide is derived analytically. This equation is solved numerically for the wakefield (Ew) generated with the help of three kinds of microwave pulses, namely sine pulse (SP), rectangular Gaussian pulse (RGP), and rectangular triangular pulse (RTP). The effect of microwave frequency (f), pulse duration (τ), waveguide width (b), equilibrium plasma density (n0), and microwave intensity (I) on the amplitude of the wakefield is studied. This amplitude is increased for the longer pulse duration and higher microwave intensity, but is decreased with growing waveguide width for all types of pulses. With regard to the variation of wakefield amplitude with plasma density, the RTP and SP behave in a similar fashion and the RGP behaves oppositely. The amplitude for the case of RGP gets increased with the plasma density. The amplitude is enhanced at larger microwave frequency for the cases of RGP and SP, but is decreased for the case of RTP. The comparative study of three types of pulses shows that the wakefield with larger amplitude is achieved with the help of rectangular triangular pulse, which is found to be sensitive with waveguide width, pulse duration and microwave intensity.

The wakefield acceleration driven by a single laser pulse in a narrow plasma-filled solid waveguide is considered. Parameters of the waveguide which provide the maximum energy gain of accelerated particles at a given length and peak power of the driver are found in the approximation of a relativistically weak driver. The obtained formulas are illustrated by calculating the electron energy gain achievable with the terawatt laser of Utsunomiya University.