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Three types of radial power combiners/dividers in Ka or Ku-band are proposed using resistive septum to improve the isolation and port matching. The measured results illustrate that these radial power combiners have good performance at high isolation, low loss and compact size.
A high-power Schottky diode frequency multiplier chain at 360 GHz, with a 3 dB bandwidth above 20 GHz is presented. The cascaded frequency doublers show peak efficiencies of 35% and 23% at 180 and 354 GHz, respectively. While the 180 GHz doubler generates a maximum power of 69 mW at 300 mW input, the second stage doubler delivers 12 mW output at 360 GHz. Both doublers consist of low parasitic GaAs...
The potential of the Low THz spectrum for high resolution imaging applications such as automotive radar is described. Experiments require compact and portable equipment which may be achieved by extending the operation of current battery powered vector network analyzers. The development of a novel hybrid 670 GHz VNA based frequency extender is described including instrument performance data.
Broadband microwave windows for applications in both millimeter wave and terahertz wave vacuum electron devices were designed, simulated and a W-band multilayer window constructed and measured. These windows are based on the multilayer configuration and offer broadband transmission with a very low reflection. Operating over a wide frequency bandwidth of 10% and 5% in their respective frequency bands...
This paper presents the design, simulation and measurement of two mode converting corrugated horns for application as the output launcher for a gyro-amplifier. Operating over the 90 to 100 GHz frequency range the horns act to convert the TE11 mode to the Gaussian-like HE11 mode. The difference in the horns is one was made initially to meet a more moderate Gaussian content specification while the other...
A W-band quasi-optical horn with smoothly profiled circular inner surface was optimized and measured for a gyrotron traveling wave amplifier. It was designed to achieve low reflection, high fundamental Gaussian mode content and high directivity in the desired frequency range of 90 to 100 GHz. In the measurement, the reflection of the TE11 mode was lower than −37 dB and the directivity was ∼27 dB with...
A 300 GHz waveguide filter, designed to block the unwanted upper sideband from reaching a heterodyne mixer, is presented. This WR-3 filter is based on three cross-coupled TE101 resonators. It is designed to have a Chebyshev response, and cross-coupling between first and third resonators provides transmission zeros in the stopband. The filter is fabricated using a multilayered SU-8 micromachining process...
Terahertz(THz)-driven dielectric-lined waveguides have applications in electron manipulation, particularly acceleration, as the use of dielectric allows for phase velocities below the speed of light. However matching a single frequency to the correct velocity does not maximise electron-THz interaction; waveguide dispersion typically results in an unmatched group velocity and so the pulse envelope...
In this paper, a slotted waveguide antenna array at W band is proposed. The design procedure of the radiating element parameter extracting and the synthesis of planar array are introduced. A 9 × 9 slotted waveguide antenna array is designed and simulated. The results show that the Gain of the antenna is about 26.3dBi and the bandwidth is about 2.1GHz.
This paper presents our study on image reconstruction algorithms for THz near field scanning systems. Based on the principle of Physical Optics (PO) algorithm, we have proposed and investigated a novel transposed convolution image reconstruction algorithm (TC), in comparison with the back propagation algorithm (BP) in simulation and experiment.
Extended interaction oscillator based on a modulation electron beam is studied in order to develop a compact, miniaturization, and low voltage millimeter wave vacuum devices. A modulation electron beam can be obtained by a field emission carbon nanotube cold cathode electron gun based on a microstrip structure. A disc-loaded waveguide structure EIO operating in 2π mode is simulated. Simulation results...
Frequency selective surface (FSS) based on substrate integrated waveguide (SIW) technology is a passband spatial filter with periodic arrays of slots, which has wide applications, such as the sub-reflecting surface of the reflector antenna, and the antenna radome. Compared with the conventional FSS, the SIW FSS is a better candidate with high rectangular coefficient, good incident angle stability,...
We demonstrated the enhanced terahertz transmission through superconducting NbN subw ave length hole arrays. The transmission peak value and frequency exhibit thermal tuning behaviors, which can be attributed to the temperature-dependent complex permittivity of superconducting film. The microscopic hybrid wave model was adopted to analyze the role of surface waves in the enhanced transmission theoretically...
Terahertz in-line sensing was successfully demonstrated for measuring the film coating thickness of individual pharmaceutical tablets during the film coating process. This paper reports our recent progress to further validate the terahertz in-line measurement technique with discrete element modelling for a lab-scale tablet mixing process inside a tablet pan coater.
A 220 GHz traveling wave tube (TWT) is being developed in our lab. This TWT is based on a folded waveguide circuit with an electron beam focused by periodic permanent magnets (PPMs). To measure the transmission loss of the TWT directly, a prototype without a sever has been built. The maximum output power of this prototype is 1.1 W at 225 GHz. The gain, output power and transmission loss are close...
We report on the realization of a 3D terahertz imaging system for industrial radome inspection. The system has been designed to be operated within a machining center for radome manufacturing. In order to provide the required flexibility in respect to image resolution and penetration depth, we developed a system, which combines two frequency-modulated continuous-wave terahertz sensing units, operating...
In this work, a typical two-dimensional (2D) material WS2 on a dielectric substrate is measured by terahertz time-domain spectroscopy (THz-TDS) and analyzed using the Drude conductivity model. The transmittance and sheet conductivity of monolayer WS2 have been obtained. This technology can be used to measure the thin film 2D materials in THz frequency regions.
This paper presents a design of transmission line based RF switch with graphene. The on-off states of the switch can be adjusted electrically due to the unique properties of monolayer graphene. The transmission between two ports varies more than 30dB when voltage changes from 0 to 30 V. The RF switch provides enough insertion loss and good isolation in on and off states.
In this work, terahertz time-domain spectroscopy was employed to establish the fingerprints of Radix Angelicae Dahuricae (RAD). Principal component analysis (PCA) and k-subspace clustering were employed to study the similarities and dissimilarities among the 120 RAD samples. The methods can be successfully used to classify these samples according to their regions. The results show that the referred...
The terahertz absorption spectra of BSA (Bovine Serum Albumin) in aqueous solution were measured under different pH values from 2.2 to 8. The absorption spectra were analyzed using the two-dimensional correlation spectroscopy (2DCOS). By comparing the cross peaks corresponding to the different pH values, it can be obtained that the conformation is related to the pH condition.
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