Modeling the optical switching of MESFET's considering the externaland internal photovoltaic effects

One of the aspects of the merging of microwave and optical technologies is the use of optical signals to switch electronic circuits in general and microwave circuits in particular (including MMIC). During the last decade, the feasibility of optical switching of MMIC's has been demonstrated. This paper presents a novel model for the optical switching of the MESFET, which is the building block of MMIC's. The model predicts the optical switching performance as a function of the optical signal parameters, the bias level, and the device physics and geometry. The results and conclusions from the theory are verified by measurements. The new model can serve as a design tool for designing an optimal MESFET for optical switching purposes     

An improved analytical AC large-signal model for the GaAs MESFET

An improved analytical AC large-signal model for a MESFET is presented. The model is an upgrading of a previously presented model. The improvement is basically in the expressions for the conduction current. Simulation results are presented and compared to measured data. The calculated gain and power are slightly greater than the measured values. This is expected, since the matching networks have some loss, which is not included in the calculation. The loss in the input matching network can be appreciable due to the large transformation ratio     

In vitro fertilization treatment for severe male factor: a comparative study of intracytoplasmic sperm injection with testicular sperm extraction and with spermatozoa from ejaculate

PURPOSE: Our purpose was to evaluate whether the source of spermatozoa influences the results of intracytoplasmic sperm injection (ICSI) treatment in couples with severe male-factor infertility. METHODS: A retrospective analysis of 40 cases of ICSI with testicular-retrieved spermatozoa, matched with 40 cases of ICSI with ejaculated spermatozoa, was performed. We included only couples with normoovulatory females younger than 37 years who were matched according to the day of ovum pickup with the patients in the study group. RESULTS: Eighty cycles were analyzed: 40 cycles using testicular spermatozoa and 40 cycles using ejaculated spermatozoa. In 32 (80%) of the 40 ICSI transcutaneous needle aspiration cycles, we obtained enough spermatozoa to inject all the mature oocytes retrieved. In eight (20%) cases there were not enough spermatozoa to inject all the oocytes. Only 76 (54%) of 141 available oocytes were injected in these eight patients. The oocyte fertilization rates were 42% for the study group and 55.5% for the controls (P < 0.005). Thirty-six (90%) patients in the group with nonobstructive a zoospermia (NOA) and 37 (92.5%) patients in the oligoteratoasthenospermia (OTA) group had embryos for replacement. The mean cleavage rates per cycle (96% with testicular and 93% with ejaculated spermatozoa), the mean number of embryos per transfer (3.72 +/- 1.6 in the NOA group and 4.24 +/- 1.5 in the OTA group), the embryo quality (cumulative embryo scoring = 34.03 +/- 22.62 in the testicular sperm group and 36.08 +/- 19.28 in the ejaculated sperm group), and the clinical pregnancy rates (22.5% in the NOA patients and 20% in the ejaculate group) were not significantly different between groups. CONCLUSIONS: High fertilization, cleavage, and pregnancy rates can be achieved with intracytoplasmic testicular sperm injection from patients with NOA, reaching levels comparable with those of ICSI using ejaculated spermatozoa.     

RF Mixers Driven by Pseudorandom Signals

Mixers driven with RF, biphase-modulated, pseudorandom signals are analyzed. The main properties considered are insertion loss and matching conditions. Application to Doppler radar is discussed.     

A fully analytical AC large-signal model of the GaAs MESFET fornonlinear network analysis and design

A fully analytical version of an AC large-signal model for the GaAs MESFET is presented. The source model is based on basic principles and the actual physics and geometry of the device. The analytical version was developed by curve fitting the analytical expressions to the source model. The accuracy of the model for microwave circuits is demonstrated using simulation examples of a power amplifier and a mixer     

Impact of light illumination and passivation layer on siliconfinite-ground coplanar-waveguide transmission-line properties

The modeling of silicon finite-ground coplanar-waveguide (FGCPW) transmission lines is presented in this paper. It is shown that the effective substrate conductivity increases in the presence of illumination and in the presence of a passivation layer in the slot regions independently. As a result, the losses of trenched FGCPW are lower than conventional FGCPW transmission lines. The strong dependence of the substrate conductivity on illumination suggests that optically controlled attenuators can be implemented with FGCPW transmission lines exhibiting practically no phase change between the different attenuation states. A new contrast ratio for optically controlled transmission lines is derived     

Repression of beta-actin synthesis and persistence of ribosomal protein synthesis after infection of HeLa cells by herpes simplex virus type 1 infection are under translational control

Multibacillary (MB) leprosy patients treated with multidrug therapy (MDT) or MDT + immunotherapy (IMT) with BCG + heat-killed Mycobacterium leprae were tested annually for their ability to proliferate in vitro to the mycobacterial antigens BCG, M. leprae soluble extract, and intact M. leprae. IgM antibody responses to phenolic glycolipid I (PGL-I) were measured, as well as serum nitrite levels in patients' sera, before, during and after treatment. Patients who received only MDT did not present cellular reactivity to intact M. leprae antigens, in contrast to the results obtained with BCG, which elicited reactivity at time zero, that increased after treatment. Regarding PGL-I antibody variations in relation to the initial value, we observed a statistically significant marked decrease at the end of 2 years which continued to fall in successive evaluations. MB patients showed high initial serum nitrite concentrations which dropped drastically with treatment. This decay was apparently associated with the bacillary load present in these patients. The group submitted to IMT + MDT showed high and long-lasting T-cell responses to mycobacterial antigens in a significant number of initially unresponsive MB patients. There was a marked increase to M. leprae soluble extract and BCG, as well as a more variable response to whole bacilli. The antibody levels in this group of patients are sustained for a somewhat longer period and decreased more slowly during the 5-year follow up.     

Analytical model for optically generated currents in GaAs MESFETs

The MESFET as an optically sensitive microwave element in MMICs has attracted much attention. The theoretical modeling of the device, however, needs more consideration. The authors propose an analytical model for the illuminated MESFET, complete in that all major contributions to the optical response are considered. The dependence of the response on bias conditions, the wavelength and intensity of the optical input, and the particulars of device structure, are incorporated in the model. The importance of the internal photovoltaic effect, which has not been properly modeled previously, is emphasized. The novel theoretical model is verified by experimental results     

Performance prediction and optimization of a coherent phasemodulated low noise analog optical link operating at microwavefrequencies

Analog optical communication links operating at microwave frequencies are useful for applications like antenna remoting, transceivers, optical signal distribution (CATV), etc. In recent years great progress has been achieved on AM optical links, however, very little has been published on the use of coherent optical links for analog applications. In this paper, we present the analysis, calculated performance, and design guidelines for a coherent phase modulated analog optical link. The performance of this link is compared to that of AM links, and a substantially improved performance is predicted