Double corrugated waveguide for Ka-Band traveling wave tube

The double corrugated waveguide (DCW), incorpo- rating a row of metallic pillars on each side of the electron beam, is demonstrated as a promising slow-wave structure for millimeter wave, Ka-band, traveling wave tubes (TWTs). Different configurations, including novel bent couplers with tapered pillars, have been designed, realized, and validated by S-parameter measurements. The design and simulation of a DCW TWT demonstrated very good performance in the frequency band 32–37 GHz. The ease of fabrication and assembly make the DCW a suitable basis for a new generation of millimeter wave TWTs

Design and fabrication of double corrugated waveguide for a Ka-band traveling wave tube

The double corrugated waveguide is demonstrated to be a slow wave structure which is straightforward to manufacture and assemble. The design and fabrication of a Ka-band prototype is presented. The ability of the double corrugated waveguide to be bent through 90o has permitted the build of a compact slow wave structure with very good electrical behavior which is suitable for millimeter wave travelling wave tubes

Receptores homodinos a 300 GHz basados en tecnología CMOS

Using CMOS transistors for terahertz detection is currently a disruptive technology that offers the direct integration of a terahertz detector with video preamplifiers. The detectors are based on the resistive mixer concept and its performance mainly depends on the following parameters: type of antenna, electrical parameters (gate to drain capacitor and channel length of the CMOS device) and foundry. Two different 300 GHz detectors are discussed: a single transistor detector with a broadband antenna and a differential pair driven by a resonant patch antenna

Fivefold helically corrugated waveguide for high-power w-band gyro-devices and pulse compression

The design, simulation, manufacture and measurement of a W-band five-fold (5F) helically corrugated waveguide (HCW) is reported. The 5F HCW is based on the coupling of the traveling TE31 and near cut-off TE22 modes to create an operating eigenwave. The fabricated test structure has circular waveguide ports and features elliptical polariser sections and broadband TE11 to TE31 mode converters on either side of the 5F HCW. The optimised mode converter design, based on a four-fold (4F) HCW, has a predicted power conversion efficiency greater than 90% from 89 to 102.5 GHz, and 96% peak efficiency at 94 GHz. The optimization of the 5F HCW geometry produced an eigenwave suitable for gyro-devices, but the optimization could equally well have been directed to applications such as pulse compression and microwave undulators. Analysis of simulated electric field profiles showed that the propagating power in the 5F HCW was increased by a factor of 6 over that in the 3F HCW at equivalent peak electric field strength. This is due to the larger diameter of the waveguide. Test structures were manufactured through a combination of precision machining of a sacrificial mandrel, copper growth by electroforming followed by removal of the aluminium mandrel by chemically etching. Measurements of the 5F HCW structure’s dispersion showed excellent agreement with the prediction over the design range of 90 to 98 GHz

A high-power Schottky diode frequency multiplier chain at 360 GHz for Gyro-TWA applications

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 Schottky diode circuits optimized to handle high input powers, and neither exhibit saturation at the highest applied power

Towards Terawatt-Scale Spectrally Tunable Terahertz Pulses via Relativistic Laser-Foil Interactions

An ever-increasing number of strong-field applications, such as ultrafast coherent control over matter and light, require driver light pulses that are both high power and spectrally tunable. The realization of such a source in the terahertz (THz) band has long been a formidable challenge. Here, we demonstrate, via experiment and theory, efficient production of terawatt (TW)-level THz pulses from high-intensity picosecond laser irradiation on a metal foil. It is shown that the THz spectrum can be manipulated effectively by tuning the laser pulse duration or target size. A general analytical framework for THz generation is developed, involving both the high-current electron emission and a time-varying electron sheath at the target rear, and the spectral tunability is found to stem from the change of the dominant THz generation mechanism. In addition to being an ultrabright source (brightness temperature of about 1021 K) for extreme THz science, the THz radiation presented here also enables a unique in situ laser-plasma diagnostic. Employing the THz radiation to quantify the escaping electrons and the transient sheath shows good agreement with experimental measurements