Quadrature LC VCO with passive coupling and phase combining network

A circuit and method for generating a signal is disclosed. The circuit includes a set of wide tuning LC tanks, a set of core transistors cross coupled to the set of wide tuning LC tanks, and a combining network coupled to the set of wide tuning LC tanks and the set of core transistors. The combining network further includes a set of inputs connected to the set of wide tuning LC tanks and the set of core transistors, a set of coupling transistors connected to the set of inputs, a set of source inductors connected to the set of coupling transistors, a coupling capacitor connected to the set of source inductors, a load resistor connected to the coupling capacitor. The combining network combines the set of inputs and the signal is delivered to the load resistor as a fourth order harmonic.Board of Regents, University of Texas Syste

Terahertz responsivity of field-effect transistors under arbitrary biasing conditions

Current biased photoresponse model of long channel field-effect transistor (FET) detectors is introduced to describe the low frequency behavior in complex circuit environment. The model is applicable in all FET working regions, including subthreshold, linear, saturated modes, includes bulk potential variations, and handles the simultaneous gate-source and drain-source detection or source-driven topologies. The model is based on the phenomenological representation that links the photoresponse to the gate transconductance over drain current ratio (gm/ID) and circuit theory. A derived method is provided to analyze the detector behavior, to characterize existing antenna coupled detectors, and to predict the photoresponse in a complex circuit. The model is validated by measurements of 180 nm gate length silicon and GaAs high electron mobility FETs

Ultra-wideband CMOS signal generator using tunable linear superposition

Department of Electrical EngineeringWireless communication frequency bandwidth and center frequency are have been widening for high speed transmission of data. But the frequency bandwidth a transceiver can cover is severely limited. The circuit designed in the paper, called "signal generator", can offer a variety of wireless bandwidths. In this paper, a ultra wideband signal generator, based in 65nm CMOS technology, is designed after proposing and verifying two different types of signal generator design. The first version design of the signal generator is proposed, which is composed of a four-stage LC-ring voltagecontrolled oscillator (VCO) and a frequency synthesis circuit. A new concept of tunable linear superposition is proposed for wideband frequency synthesis and implemented to provide VCO core (1X)/ twofold (2X)/ quadruple (4X) programmable frequency multiplication function. In order to expand frequency coverage further, the LCring VCO adopted the tunable inductors which are composed of switchable bondwire pairs. A ultra-wideband operation from 4.3GHz to 27.4GHz was experimentally verified. The second version design of the signal generator using a reconfigurable phase selection process is proposed, which is proposed and consists of a multi-phase signal generation and a programmable frequency multiplication. This chip is proposed for wideband frequency synthesis and implemented to provide VCO core (1X)/ twofold (2X)/ quadruple (4X) and octuplet (8X) programmable frequency multiplication function. An LC-ring oscillator and a selective rectifying combiner are reconstructed adaptively for various frequency synthesis modes, minimizing their power consumption. A fully-integrated prototype verified to have very wide frequency characteristic from 6.3GHz to 59.4GHz.ope

Materials Analysis Using a THz Imaging System Based on Atomic Vapour

This thesis studies the response of the interaction between Rydberg atomic vapour and a THz frequency field. When Caesium atoms at room temperature are excited to a Rydberg state using three infrared lasers and a 0.55 THz field resonant with the 14P3/2 → 13D5/2 transition is applied, the atoms respond by emitting a green optical fluorescence corresponding to the 13D5/2 → 6P3/2 decay. This response is exploited to investigate the absorption coefficient for different polymer materials that transmit well in the THz frequency range using the Beer–Lambert law. We calibrate the system to obtain a measure of THz intensity. As the THz imaging system is highly sensitive to environmental changes, and to show that our results are consistent, we provide a comparison of results between our atomic detection method and a commercial thermal power meter. Additionally, we measure the absorption coefficient of the same materials at a frequency of 1.1 THz, and the results are compared with those measured at 0.55 THz. The THz imaging system is also used to perform some experiments in order to demonstrate its effectiveness in real-world applications. The system provides an interesting image contrast in the case of a sample containing two different polymer materials measured at two THz frequencies. The result is a proof-of-concept that multispectral THz imaging can provide additional information and is motivation to improve our THz imaging system by introducing a dual-species THz imager. We also investigate the polarisation spectroscopy of an excited-state transition of rubidium vapour at room temperature as a step towards a rubidium THz imaging system. The narrow dispersive signal produced by this spectroscopy technique is ideal for laser frequency stabilisation of excited-state transitions

NASA Tech Briefs, November 2008

Topics covered include: Digital Phase Meter for a Laser Heterodyne Interferometer; Vision System Measures Motions of Robot and External Objects; Advanced Precipitation Radar Antenna to Measure Rainfall From Space; Wide-Band Radar for Measuring Thickness of Sea Ice; Vertical Isolation for Photodiodes in CMOS Imagers; Wide-Band Microwave Receivers Using Photonic Processing; L-Band Transmit/Receive Module for Phase-Stable Array Antennas; Microwave Power Combiner/Switch Utilizing a Faraday Rotator; Compact Low-Loss Planar Magic-T; Using Pipelined XNOR Logic to Reduce SEU Risks in State Machines; Quasi-Optical Transmission Line for 94-GHz Radar; Next Generation Flight Controller Trainer System; Converting from DDOR SASF to APF; Converting from CVF to AAF; Documenting AUTOGEN and APGEN Model Files; Sequence History Update Tool; Extraction and Analysis of Display Data; MRO DKF Post-Processing Tool; Rig Diagnostic Tools; MRO Sequence Checking Tool; Science Activity Planner for the MER Mission; UAVSAR Flight-Planning System; Templates for Deposition of Microscopic Pointed Structures; Adjustable Membrane Mirrors Incorporating G-Elastomers; Hall-Effect Thruster Utilizing Bismuth as Propellant; High-Temperature Crystal-Growth Cartridge Tubes Made by VPS; Quench Crucibles Reinforced with Metal; Deep-Sea Hydrothermal-Vent Sampler; Mars Rocket Propulsion System; Two-Stage Passive Vibration Isolator; Improved Thermal Design of a Compression Mold; Enhanced Pseudo-Waypoint Guidance for Spacecraft Maneuvers; Altimetry Using GPS-Reflection/Occultation Interferometry; Thermally Driven Josephson Effect; Perturbation Effects on a Supercritical C7H16/N2 Mixing Layer; Gold Nanoparticle Labels Amplify Ellipsometric Signals; Phase Matching of Diverse Modes in a WGM Resonator; WGM Resonators for Terahertz-to-Optical Frequency Conversion; Determining Concentration of Nanoparticles from Ellipsometry; Microwave-to-Optical Conversion in WGM Resonators; Four-Pass Coupler for Laser-Diode-Pumped Solid-State Laser; Low-Resolution Raman-Spectroscopy Combustion Thermometry; Temperature Sensors Based on WGM Optical Resonators; Varying the Divergence of Multiple Parallel Laser Beams; Efficient Algorithm for Rectangular Spiral Search; Algorithm-Based Fault Tolerance Integrated with Replication; Targeting and Localization for Mars Rover Operations; Terrain-Adaptive Navigation Architecture; Self-Adjusting Hash Tables for Embedded Flight Applications; Schema for Spacecraft-Command Dictionary; Combined GMSK Communications and PN Ranging; System-Level Integration of Mass Memory; Network-Attached Solid-State Recorder Architecture; Method of Cross-Linking Aerogels Using a One-Pot Reaction Scheme; An Efficient Reachability Analysis Algorithm

Mid infrared digital holography and terahertz imaging

Mid IR and Far IR (THz) regions have been attracting a continuously growing interest, especially for imaging applications. Mid IR imaging systems are widespread in the military, security and medical fields and are, consequently, in continuous development. Even greater expectation is placed on THz imaging techniques, because of the well-known capacity of THz radiation to penetrate many common materials and to provide important spectroscopic information about various strategic stuffs. In this scenario Digital Holography, a quite recent interferometric imaging technique, is proving to be mature enough to play a key role among the other imaging techniques, both in the Mid IR and in the Far IR

Dispersive Fourier Transformation for Versatile Microwave Photonics Applications

Abstract: Dispersive Fourier transformation (DFT) maps the broadband spectrum of an ultrashort optical pulse into a time stretched waveform with its intensity profile mirroring the spectrum using chromatic dispersion. Owing to its capability of continuous pulse-by-pulse spectroscopic measurement and manipulation, DFT has become an emerging technique for ultrafast signal generation and processing, and high-throughput real-time measurements, where the speed of traditional optical instruments falls short. In this paper, the principle and implementation methods of DFT are first introduced and the recent development in employing DFT technique for widespread microwave photonics applications are presented, with emphasis on real-time spectroscopy, microwave arbitrary waveform generation, and microwave spectrum sensing. Finally, possible future research directions for DFT-based microwave photonics techniques are discussed as well

Photodetectors

In this book some recent advances in development of photodetectors and photodetection systems for specific applications are included. In the first section of the book nine different types of photodetectors and their characteristics are presented. Next, some theoretical aspects and simulations are discussed. The last eight chapters are devoted to the development of photodetection systems for imaging, particle size analysis, transfers of time, measurement of vibrations, magnetic field, polarization of light, and particle energy. The book is addressed to students, engineers, and researchers working in the field of photonics and advanced technologies