Stability analysis of the self-phase-locked divide-by-2 optical parametric oscillator

The properties of all-optical phase-coherent frequency division by 2, based on a self-phase-locked continuous-wave (cw) optical parametric oscillator (OPO), are investigated theoretically. The coupled field equations of an OPO with intracavity quarter-wave plate are solved analytically in steady-state, yielding a condition for self-phase-locked operation. In the self-phase-locked state, two different values for the pump power at threshold are obtained. By using a linear stability analysis, it is proven that only the lower threshold value is stable, whereas the higher threshold value is unstable. The analytical investigations of the steady-state field values further reveal a twofold symmetry in phase space. The theoretical consideration is completed by a numerical analysis based on the integration of the envelopes of the three OPO fields, which allows for studying the temporal evolution of different initial values. The numerical investigation of the OPO subharmonic phases shows that the two-phase eigenstates are equivalent with respect to experimental parameters and are assumed by the self-phase-locked OPO in dependence of the initial phases of the subharmonic fields, dividing phase space into two symmetric basins of attraction

A unique modulation system for two channel data transmission

A simple low cost system is reported for the telemetry of information from meteorological rocket payloads including parachute borne systems. It uses S- or L-band microwave links with low cost oscillator type transmitters. An extension of this system to transmit two channels of data simultaneously by standard time and frequency multiplexing techniques as a sampled pulse is described. One channel is represented by the pulse repetition rate while the other channel is represented by the instantaneous duty cycle of the pulse train

Initial results from the NASA-Lewis wave rotor experiment

Wave rotors may play a role as topping cycles for jet engines, since by their use, the combustion temperature can be raised without increasing the turbine inlet temperature. In order to design a wave rotor for this, or any other application, knowledge of the loss mechanisms is required, and also how the design parameters affect those losses. At NASA LeRC, a 3-port wave rotor experiment operating on the flow-divider cycle, has been started with the objective of determining the losses. The experimental scheme is a three factor Box-Behnken design, with passage opening time, friction factor, and leakage gap as the factors. Variation of these factors is provided by using two rotors, of different length, two different passage widths for each rotor, and adjustable leakage gap. In the experiment, pressure transducers are mounted on the rotor, and give pressure traces as a function of rotational angle at the entrance and exit of a rotor passage. In addition, pitot rakes monitor the stagnation pressures for each port, and orifice meters measure the mass flows. The results show that leakage losses are very significant in the present experiment, but can be reduced considerably by decreasing the rotor to wall clearance spacing

Test results for 20-GHz GaAs FET spacecraft power amplifier

Test were conducted to measure the performance of the 20-GHz solid state, proof-of-concept amplifier. The amplifier operates over the 17.7 to 20.2-GHz frequency range and uses high power gallium arsenide field effect transistors. The amplifier design and test methods are briefly described. NASA and contractor performance data are compared

Demodulator for carrier transducers

A carrier type transducer is supplied with a carrier wave via an audio amplifier, a filter, a frequency divider, and an oscillator. The carrier is modulated in accordance with the parameter being measured by the transducer and is fed to the input of a digital data system which may include a voltmeter. The output of the oscillator and the output of each stage of the divider are fed to an AND or a NAND gate and suitable variable and fixed delay circuits to the command input of the digital data system. With this arrangement, the digital data system is commanded to sample at the proper time so that the average voltage of the modulated carrier is measured. It may be utilized with ancillary circuitry for control of the paramete

An adjustable-ratio flow dividing hydraulic valve

This thesis proposes a new type of hydraulic valve: an adjustable-ratio flow divider. This valve attempts to split one input flow into two output flows in a predetermined ratio, independent of load pressure or total flow. The valve uses a two dimensional structure to form a two-stage valve with only one moving part; the pilot stage uses the spool s rotary position, and the main stage uses its linear position. This arrangement allows for a cheaper, simpler valve with smaller volumes (translating into faster response). The ratio of outlet flows can be set on the fly by the angular position of the spool, driven by a stepper motor or other low-power input. In order to evaluate the initial feasibility of the concept, steady state and dynamic models were developed and the effects of the physical parameters were studied. Two non-linear non-derivative multiobjective optimization strategies were used to determine the optimum parameters for a prototype. Finally, the prototype s performance was experimentally examined and appears to work as expected

Size Reduction and Harmonics Suppression in Microwave Power Dividers: A Comprehensive Review

In this paper, several types of microstrip power divider are studied and compared in terms of harmonics suppression and size reductions. The importance of this research lies in the fact that power dividers are critical components in various communication systems, and their performance directly affects the overall system efficiency. The conventional structure of the power divider has an acceptable performance at operating frequency in terms of excellent output ports isolation, low insertion loss, and high return loss, but occupies large size and passes unwanted signals at higher frequencies along with desired signal without any suppression. Harmonics are popular distortion and has different distortion impacts in many different facilities. Recently, several techniques are introduced to overcome these drawbacks. Applied open stubs, applied resonators, lumped reactive components such as capacitors and inductors, coupled lines, defected ground structure (DGS), and electronic band gaps are common methods, which are widely used to overcome these drawbacks. Finally, the study results show that the resonator-based power dividers and coupled-line-based power dividers have good performances in terms of size reduction and harmonic suppression but increase insertion loss parameter. Furthermore, the lumped reactive component-based power dividers and applied DGS and electromagnetic bandgap cells suppress unwanted harmonics, but they need extra process to fabrication, which is undesirable. Moreover, the open-stub-based power dividers have moderate performance with simple structure, but size reduction and harmonics suppression are not so superior in this method

Signal distortion in a regenerative frequency divider

A regenerative frequency divider can be constructed with one integrated circuit and a single-pole tuned circuit. The divider can be used as a means for reducing the modulation index of either deterministic or random signals. This reduction in modulation index can simplify many signal processing schemes. This technique can be used up to S-band frequencies. The mathematical model of the regenerative frequency divider corresponds very closely to that of a first order Phase Locked Loop (PLL). The loop gain is determined in part by the nonlinear element used in the feedback loop. The loop gain is also proportional to the ratio of the input envelope amplitude and the output envelope amplitude. Theoretical and measured performance of the regenerative frequency divider indicates that it is slightly superior to that of the first order PLL for processing nondeterministic signals such as a frequency modulated signal corrupted by wide-band Gaussian noise. Measured performance on a divide by two shows that the probability of cycle skipping for carrier plus wide-band Gaussian noise is an order of magnitude less than the corresponding PLL for a loop signal-to-noise ratio of 5dB. The similarity between higher order PLL models and the regenerative frequency divider with higher order loop filters is very close when the loop error is small --Abstract, page ii