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The development's results of the 7-beam Ka-band TWT with high electronic efficiency (∼20%), the gain coefficient (∼50dB) and a broad band operating frequency (∼2.5%) are presented.
L-3 Communications Electron Technologies Inc., (L-3 ETI), continues to push the envelope for spacedownlink qualified mm-wave helix TWTs. We report results of high-power, wide bandwidth, and extreme environmental margin testing on the mm-wave family of helix TWTs from 22 GHz to 75 GHz.
A W-band sheet-beam extended interaction klystron (EIK) has been fabricated and tested. The EIK integrates a 3-cavity circuit with our previously demonstrated 20-kV, 3.5-A beamstick. The EIK has produced a saturated peak output power of over 7.5 kW and a small-signal gain of almost 40 dB, in very good agreement with our simulations.
A 220 GHz power amplifier has been demonstrated as part of the DARPA HiFIVE program. This amplifier is based on a folded waveguide circuit, and operates at 19 kV and 250 mA. Short pulse tests resulted in 56 W at 214 GHz and a 5.0 GHz bandwidth.
Using a simple model we derive a universal condition for oscillation in a traveling wave tube for frequencies near a band edge, when the adjacent band gap is small. The condition is expressed graphically as a value for the maximum allowable (stable) small signal gain as a function of the size of the band gap. As an example of the application of the general condition, a simple upper bound on the E-plane...
The design and simulation of a predistortion type lineariser based on schottky diodes are proposed. With increase of input power, different combinations of the gain expansion and phase shift can be achieved over input power dynamic range. Because of this feature, it can compensate both AM-AM and AM-PM distortions for different travelling wave tube amplifiers (TWTAs) significantly. Also, it does not...
Comparisons between predictions of the NRL large signal codes CHRISTINE and TESLA-FW and measurements of small signal gain of NRL's G-Band serpentine waveguide TWT are presented. Results of a sensitivity study of the effects on gain of the circuit dispersion allow us to identify the most critical physical circuit dimensions for TWT design and to quantify required circuit fabrication tolerances.
A high-order-mode harmonic multiplying gyro-TWA could allow the amplifier to achieve high average powers. An improved mode-selective circuit is employed for suppressing non-TE0n competing modes while wall losses are employed for suppressing TE0n competing modes. A G-band second harmonic multiplying gyro-TWT is predicted to yield a peak output power of 56 kW at 200 GHz with an efficiency of 11%, a...
A square cross section ring-bar slow-wave structure with straight-edge connections has been simulated with a cylindrical electron beam for application in a traveling-wave tube amplifier. An electric field probe has been designed for coupling between the square ring-bar and a WR-10 rectangular waveguide. The saturated output peak power varies from 9.1 W to 28.6 W over the frequency range of 90–98 GHz...
The analysis of the lossy interaction structure for Ka-band Gyro-TWT has been carried out and discussed. In this paper, dispersion and interaction impedance characteristics of the interaction structure have been determined using 3-D simulator CST-MWS. The beam-wave interaction analysis has been carried out using particle-in-cell (PIC) code MAGIC. The simulated result shows that the interaction structure...
In this paper, the design and optimization of a V-band helix TWT is carried out and prototype tubes have been assembled. The test results show that the output power of the TWT is over 15W with the overall efficiency of over 14.5% and a gain of over 43dB. The beam transmission experiment shows that a transmission ratio is over 97%.
The experimental study of a Q-band gyrotron-travelling-wave tube (gyro-TWT) amplifier operating in the circular TE01 mode at fundamental cyclotron harmonic is presented. A periodic dielectric loaded structure is adopted in the interaction circuit of the gyro-TWT to suppress spurious modes TE11 and TE21. A saturated peak power of 175 kW is obtained corresponding to saturated gain of 53 dB and an efficiency...
A 0.850 THz vacuum electronic power amplifier capable of >50 mW output power is being tested at Northrop Grumman Electronic Systems. The compact power amplifier is based on a DRIE-fabricated folded waveguide slow-wave circuit, together with a high current density thermionic cathode, a high field permanent magnet solenoid, and a single-stage depressed collector for overall device efficiency. The...
A gyrotron amplifier that uses a novel photonic band gap (PBG) interaction circuit has achieved a peak small signal gain of 38 dB at 247.7 GHz, 32 kV and 0.35 A. The instantaneous −3 dB bandwidth of the amplifier at peak gain is 0.4 GHz. A peak output power of 45 W has been measured. The output power is not saturated but is limited by the 7.5 mW of available input power; the saturated output power...
We present the hot test results of a 220 GHz, serpentine waveguide vacuum electron amplifier showcasing a novel embedded monofilament microfabrication technique based on UV-LIGA. The instantaneous operating bandwidth exceeds 15 GHz and the small signal gain of the circuit is over 14 dB. By varying the voltage slightly, an operating bandwidth of almost 40 GHz is realizable with a minimum circuit gain...
This paper describes RF performance on a Ka/Q-band mini-TWT. An output power of greater than 80 W has been demonstrated in the Ka and Q communication bands.
The realization of millimeter wave klystrons is limited by cavity dimensions. High order mode cavities permit larger dimensions for a same frequency, but their low Q and R/Q are not adequate for klystron realization. A new topology of klystron is proposed to effectively support high order mode cavities at millimeter waves.
A new field emitter geometry that utilizes a dielectric shield between the emitter tip and gate has been optimized to eliminate flashover in the cathode emitter cavities and improve cathode reliability. A high average power testbed has been designed and fabricated to test these cathodes at currents and current densities required for TWT operation in the X/Ku-Band frequency regime. Experimental tests...
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