Engineering topics
Javadi, Hamid
Publications and source records attributed to Javadi, Hamid.
Entanglement-Assisted Communication System for NASA's Deep-Space Missions
For this project we have studied various forms of quantum communication, and quantum-enhanced classical communication. In particular, we have performed the first realization of a novel quantum protocol, superdense teleportation. We have also showed that in some cases, the advantages of superdense coding (which enhances classical channel capacity by up to a factor of two) can be realized without the use of entanglement. Finally, we considered some more advanced protocols, with the goal to realize 'superactivation' - two entangled channels have capabilities beyond the sum of the individual channels-and conclude that more study is needed in this area.
In-Phase Power-Combined Frequency Tripler at 300 GHz
This design starts with commercial 85- to 115-GHz sources that are amplified to as much as 250 mW using power amplifiers developed for the Herschel Space Observatory. The frequency is then tripled using a novel waveguide GaAs Schottky diode frequency tripler. This planar diode produces 26 mW at 318 GHz. Peak conversion efficiency is over 15 percent, and the measured bandwidth of about 265 - 30 GHz is limited more by the driving source than by the tripler itself. This innovation is based on an integrated circuit designed originally for a single-chip 260- to 340-GHz balanced tripler. The power-combined version has two mirror-image tripler chips that are power-combined in-phase in a single waveguide block using a compact Y-junction divider at the input waveguide, and a Y-junction combiner at the output waveguide. The tripler uses a split-block waveguide design with two independent DC bias lines.
Local oscillator chain for 1.55 to 1.75 THz with 100-(mu)W peak power
We report on the design and performance of a fix-tuned x2x 3x 3 frequency multiplier chain that covers 1.55-1.75 THz. The chain is nominally pumped with 100 mW at W-band. At 120 K the measured output power is larger than 4 (mu)W across the band with a peak power of 100 (mu) W at 1.665 THz. A similar chain operated at room temperature produced a peak power of 21 (mu)W. These power levels now make it possible to deploy multipixel heterodyne imaging arrays in this frequency range.
Multi-Anode Frequency Triplers at Sub-Millimeter Wavelengths
We report on the design methodology of fix-tuned split-block waveguide balanced frequency triplers working at 300,600 and 900 GHz. They feature four to six GaAs Schottky planar diodes in a balanced configuration. A 6-anode 300 GHz tripler, a 6-anode 560 GHz tripler and a 4-anode 900 GHz tripler will be fabricated with JPL membrane technology in order to minimize dielectric loading and ensure accurate thickness of the substrate. A 4-anode 600 GHz tripler was fabricated with JPL substrateless technology that delivers 0.8-1.6mW in the 540-640 GHz band at room temperature. When cooled to l2OK this tripler delivers 2-4mW from 540 to 640 GHz.
Capability of THz sources based on Schottky diode frequency multiplier chains
We have developed and tesed a number of fixed-tuned GaAs Schottky diode frequency doubler and tripler designs covering over 50 percent of the 100 - 2000 GHz band, with best measured 120 K peak efficiencies ranging from 39 percent for 190 GHz doubler to 0.94 percent for a 1800 GHz tripler.
Tunable All-Solid-State Local Oscillators to 1900 GHz
We present a status report of an ongoing effort to develop robust tunable all-solid-state sources up to 1900 GHz for the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory. GaAs based multi-chip power amplifier modules at W-band are used to drive cascaded chains of multipliers. We have demonstrated performance from chains comprised of four doublers up to 1600 GHz as well as from a x2x3x3 chain to 1900 GHz. Measured peak output power of 23 (micro)W at 1782 GHz and 2.6 (micro)W at 1900 GHz has been achieved when the multipliers are cooled to 120K. The 1900 GHz tripler was pumped with a four anode tripler that produces a peak of 4 mW at 630 GHz when cooled to 120 K. We believe that these sources can now be used to pump hot electron bolometer (HEB) heterodyne mixers.ter (HEB) heterodyne mixers.
Tunable all-solid-state local oscillators to 1900 GHz
Explore the source record for details and available documents.
Composite Material Switches
A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.
Two Electrical Switching Phenomena In A Silver-Filled Epoxy
Two distinct electrical switching phenomena observed in experiments on commercial silver-filled epoxy: Depending on geometry of epoxy layer or strip and of metal electrical contacts, either transition from "off" (high-resistance) state at low applied electric field to "on" (low-resistance) state at high applied electric field; or transition from "on" (low resistance) at low applied electric field to "off" (high resistance) at high applied electric field. Improved understanding of phenomena leads to design of new and improved surge arrestors.
Composite Material Behavior Under High Electric Fields: II- Material Switches to 'High Current Carrying' State
Explore the source record for details and available documents.