Contributors:Siripon, N., Chongcheawchamnan, M., Robertson, I. D.
A novel sub-harmonic injection-locked balanced oscillator is proposed. The circuit provides two outputs with a 180° ° phase difference by employing a transmission line section for impedance transformation to meet the oscillation conditions. A coupling network is connected at the mid-point of the transmission line to inject the sub-harmonic frequency. This eliminates the need for a circulator or balun. The circuit is small and consumes low DC power. Under the locking state, the circuit provides double the injection frequency and also the phase noise of the two outputs is substantially improved.
In this paper, we present a 22-GHz ultra low
phase noise push-push dielectric resonator oscillator (DRO)
using MMICs fabricated by 2- m GaAs HBT process.
This circuit demonstrated a low phase noise of -114 dBc/Hz and -134 dBc/Hz at offset frequency of 100 kHz and 1 MHz,
respectively. The second harmonic output power is above 6
dBm with a fundamental suppression of over 30 dBc. This
DRO exhibits good phase noise performance based on the
figure-of-merit carrier frequency, offset frequency, and dc
power compared with the reported push-push DRO, which
is due to low 1/f noise HBT and reproducible MMIC chips.
In addition, this is the first reported push-push DRO
implemented using MMICs.
A new approach is presented for the transient simulation of lossy transmission lines in high-speed circuits. The approach is based on developing a model for the transmission line which is structured around natural modes of oscillation unlike other transmission-line models which are based on travelling waves. The principal advantage of the new approach is that conversion of frequency-domain prototype models for the transmission lines to the time domain for use in circuit simulators is particularly straightforward and obviates the need for numerical convolution. An illustrative caseis given to confirm the efficacy of the new approach.
Contributors:Camprini, M., Magrini, Iacopo, Collodi, G., Cidronali, A., Nair, Vijay, Manes, Gianfranco
The monolithic integration of Tunneling Diodes (TDs)with other semiconductor devices,creates novel quantum functional devices and circuits with unique properties:the Negative Differential Resistance (NDR)and the extremely low DC power consumption.In this paper we present the design,fabrication and characterization of a Self-Oscillating Mixer (SOM)based on InP-HEMT \TD technology.The circuit is based on a 2.526 GHZ VCO that draws a current of 1.3mA at 500mV and generates an output power of –21.5dBm on a 50 : load.The SOM is able to down-convert RF signals in the 2.25 –2.85 GHz band to an IF frequency in the 20-300 MHz band,with a conversion loss in the range 32-40 dB.
Contributors:Borgna, Irene <1982>
The energy released during a seismic crisis in volcanic areas is strictly related to the physical processes in the volcanic structure.
In particular Long Period seismicity, that seems to be related to the oscillation of a fluid-filled crack (Chouet , 1996, Chouet, 2003, McNutt, 2005), can precedes or accompanies an eruption.
The present doctoral thesis is focused on the study of the LP seismicity recorded in the Campi Flegrei volcano (Campania, Italy) during the October 2006 crisis.
Campi Flegrei Caldera is an active caldera; the combination of an active magmatic system and a dense populated area make the Campi Flegrei a critical volcano.
The source dynamic of LP seismicity is thought to be very different from the other kind of seismicity ( Tectonic or Volcano Tectonic): it’s characterized by a time sustained source and a low content in frequency. This features implies that the duration–magnitude, that is commonly used for VT events and sometimes for LPs as well, is unadapted for LP magnitude evaluation. The main goal of this doctoral work was to develop a method for the determination of the magnitude for the LP seismicity; it’s based on the comparison of the energy of VT event and LP event, linking the energy to the VT moment magnitude. So the magnitude of the LP event would be the moment magnitude of a VT event with the same energy of the LP.
We applied this method to the LP data-set recorded at Campi Flegrei caldera in 2006, to an LP data-set of Colima volcano recorded in 2005 – 2006 and for an event recorded at Etna volcano.
Experimenting this method to lots of waveforms recorded at different volcanoes we tested its easy applicability and consequently its usefulness in the routinely and in the quasi-real time work of a volcanological observatory.
Contributors:Peressini, Carlo <1973>
The dynamics of a passive back-to-back test rig have been characterised, leading to a multi-coordinate approach for the analysis of arbitrary test configurations. Universal joints have been introduced into a typical pre-loaded back-to-back system in order to produce an oscillating torsional moment in a test specimen. Two different arrangements have been investigated using a frequency-based sub-structuring approach: the receptance method. A numerical model has been developed in accordance with this theory, allowing interconnection of systems with two-coordinates and closed multi-loop schemes. The model calculates the receptance functions and modal and deflected shapes of a general system. Closed form expressions of the following individual elements have been developed: a servomotor, damped continuous shaft and a universal joint. Numerical results for specific cases have been compared with published data in literature and experimental measurements undertaken in the present work. Due to the complexity of the universal joint and its oscillating dynamic effects, a more detailed analysis of this component has been developed. Two models have been presented. The first represents the joint as two inertias connected by a massless cross-piece. The second, derived by the dynamic analysis of a spherical four-link mechanism, considers the contribution of the floating element and its gyroscopic effects. An investigation into non-linear behaviour has led to a time domain model that utilises the Runge-Kutta fourth order method for resolution of the dynamic equations. It has been demonstrated that the torsional receptances of a universal joint, derived using the simple model, result in representation of the joint as an equivalent variable inertia. In order to verify the model, a test rig has been built and experimental validation undertaken. The variable inertia of a universal joint has lead to a novel application of the component as a passive device for the balancing of inertia variations in slider-crank mechanisms.