A novel in‐line half‐mode substrate integrated waveguide (HMSIW) bandpass filter with interdigital slots has been proposed in this letter. Here, the interdigital slot shows attenuation resonance ...characteristics and generates a finite frequency transmission zero (TZ). The proposed filter generates two TZs without additional coupling or extra space and exhibits wide stopband characteristics. To validate this method, the in‐line two‐pole quasi‐elliptic bandpass filter is synthesized and fabricated on RT/Duroid 5880 substrate using printed circuit board technology. The experimental results show that center frequency, 3‐dB fractional bandwidth, insertion loss, and return loss are 3.6 GHz, 6.0%, 1.9 and 18 dB, respectively, and are very much similar to the simulated S‐parameters.
This article presents the realistic initial design studies of a 300-GHz, 1-MW, conventional-cavity gyrotron for its probable application in the next-generation thermonuclear fusion reactors. Keeping ...the design goals, parameters, and constraints in view, the very high-order TE 49,18 mode is chosen as the operating mode after a careful mode-selection calculation considering realistic ohmic cavity losses. After mode selection and mode competition studies, the cold-cavity design and initial design of a triode-type magnetron injection gun (T-MIG) and a gyrotron magnet are carried out and an electron beam radius of 8.11 mm is obtained with 2.4% velocity spread. Furthermore, investigation on RF behavior of the cavity is performed with the T-MIG beam parameters. By varying the nominal beam parameters, single-mode self-consistent calculations are conducted and achieved the desired output power. Then, multimode time-dependent self-consistent calculations are carried out before and after space-charge neutralization (SCN) with realistic velocity spread (up to 6%) and different beam radii for the assessment of the start-up scenario. Before SCN without velocity spread, the beam voltage is depressed to 70.08 kV and 0.72-MW output power is obtained, whereas with velocity spread (6%), 0.69-MW output power is obtained with 8.11 mm of beam radius. After 60% of SCN in the start-up scenario with velocity spread (6%), the beam voltage increases to 74.83 kV, and thereby, an output power of 0.91 MW is obtained.
Insert misalignment studies are carried out for a coaxial-cavity gyrotron with triangular corrugations on the insert wall using the full-wave approach, space harmonics method (SHM). By applying ...electromagnetic boundary conditions, dispersion relation is derived for a coaxial-cavity with misaligned insert. Misalignment of the insert caused by axial displacement as well as tilting of the insert axis from the outer resonator axis are taken into consideration in the study. As the electromagnetic fields in the interaction space vary with the insert misalignment, due to this the mathematical formulations of the beam-coupling coefficient, wall losses, RF interaction efficiency, and output power are modified. For a 2-MW, 220-GHz gyrotron, the insert misalignment studies are carried out using the proposed full-wave model with the help of our in-house code Gyrotron Design Suite. For validation, the results obtained using the SHM approach are compared with that of the surface impedance model (SIM) approach. In addition, comparison studies between SIM and SHM approaches are performed for the practically developed 170-GHz, 2-MW coaxial-cavity gyrotron with both triangular and rectangular corrugations in the insert.
A planar printed multi-input–multiple-output (MIMO) antenna with pattern diversity is proposed. The two printed dipole-like radiators have omnidirectional radiation patterns in the orthogonal planes. ...The antennas are printed on the opposite sides of a dielectric substrate, which makes it a compact MIMO system with excellent isolation between the antenna elements. With an external loaded capacitor, the MIMO antenna shows a wide frequency tunable range.
This paper presents a novel approach to generating conical-shaped radiation patterns by utilizing the orbital angular momentum property of electromagnetic waves. Unlike the existing conical beam ...antennas, the proposed uniform circular array (UCA) uses circular polarization (CP) patches as array elements for generating a conical radiation pattern with high azimuthal symmetry. The UCA is designed at 5.9 GHz with eight-CP antenna elements rotated and positioned at
45
∘
in a clockwise direction with a uniform feed network. As proof of concept, the designed UCA structure is fabricated on an FR4 substrate of 140 mm
×
150 mm in size and tested experimentally. The measurements confirm that the designed UCA possesses conical radiation pattern with high azimuthal symmetry at 5.9 GHz. Due to high azimuthal symmetry in the generated conical-shaped radiation pattern, the proposed UCA antenna could be advantageous for numerous wireless and vehicular communication applications.
In this letter, a low-profile planar microstrip antenna is proposed to operate at lower WLAN (2.4 GHz) and WiMAX (3.5 GHz) frequency bands. The antenna has good omnidirectional radiation pattern for ...both the bands with compact form-factor. The obtained result shows that the proposed dual-band omnidirectional microstrip antenna has better impedance bandwidth and high radiation efficiency while maintaining the structural compactness. The electromagnetic model of the proposed antenna is developed in CST Microwave Studio for analysis and optimization. The fabricated antenna and measured results are presented.
In this paper, a spoof surface plasmon polaritons based reconfigurable bandstop filter is designed and simulated at a resonant frequency of 0.216 THz. The proposed filter design comprises corrugated ...L-shaped resonators that are excited using a spoof transmission line. The designed filter is simulated using Co-EM simulation and it is evident from the simulation results that the designed filter can be tuned from 0.216 to 0.219 THz by employing a variable capacitor. Microwave frequency design studies are conducted to validate the designed methodology experimentally, and the BSF is fabricated on a 1.52 mm thick Rogers R4003C substrate using an SMV 1430 varactor diode. The measured results indicate that raising the reverse bias voltages across the varactor diode from 0.5 to 10 V, shifts the resonance tuned over a frequency range of 0.03 GHz with 0.22 GHz absolute bandwidth. The designed THz filter holds the potential to be employed as a compact filter in polymer industries for spectroscopic imaging.
Widely separated dual‐band half‐mode SIW bandpass filter Pelluri, Sambaiah; Kartikeyan, M.V.
International journal of RF and microwave computer-aided engineering,
October 2020, 2020-10-00, 20201001, Volume:
30, Issue:
10
Journal Article
Peer reviewed
Open access
A novel half‐mode substrate integrated waveguide (HMSIW) based dual‐band bandpass filter (DBBPF) is proposed. Back to back connected two defected ground structure (DGS) resonators on the top layer of ...HMSIW cavity constitute the passband with two transmission zeros (TZs) at a lower frequency. The higher modes TE301 and TE302 of HMSIW cavity give the passband response at higher frequency using the mode shifting technique with slot perturbation. The source‐load coupling has been used to create finite frequency TZs to improve the selectivity of the second passband. Therefore, the proposed filter gives two widely separated passbands, center frequencies (CFs) at 5.83 and 18.1 GHz with an attenuation of greater than 10 dB between the passbands. The synthesized filter is fabricated using a low‐cost single layer PCB process, and the measured S‐parameters are almost mimic the EM‐simulation results.
In this paper, the design studies of a triple frequency (170/204/236GHz) coaxial cavity gyrotron are carried out which is suitable for plasma heating application in a commercial fusion demonstration ...(DEMO) tokamak class prototype reactor. To reduce the spatial and maintenance requirements in the heating system of the DEMO tokamak, the output power of the proposed gyrotron is targeted at<inline-formula> <tex-math notation="LaTeX">\approx 3 </tex-math></inline-formula> MW for all the three operating frequencies. The cavity modes are selected by considering various physical and technical constraints of the multifrequency gyrotron. The dimensions of the interaction cavity are optimized for the chosen modes at the desired frequencies through cold-cavity calculations. Mode competition studies are then performed to understand the effect of the parasitic modes on the desired modes around the operating frequencies. A triangular corrugated coaxial insert is considered for reducing the problem of localized heating. Initial optimization of beam parameters and magnetic field is carried out using single-mode calculations for the maximum output efficiency. A triode-type coaxial magnetron injection gun is designed for supporting this multifrequency operation. Startup calculations are carried out with beam space-charge neutralization at all the three operating frequencies. These studies predict that a 3-MW, continuous-wave operation is possible at the desired frequencies of the proposed DEMO class gyrotron.
