Direct optical injection locking of 20 GHz superlattice oscillators

For the first time, a direct optically injection-locked oscillator based on the Esaki-Tsu effect in superlattices is reported. The microwave output power is -7 dBm at 20 GHz with an optical input power of -10 dBm at a wavelength of 1.3 μm     

Hybrid modeling techniques for multilayered printed circuit board in power electronics: association of electromagnetic methods

With the fast development of power electronics circuits at increasing switching frequency (over 10 MHz), the multilayered printed circuits boards (PCBs) are being used more and more in the field of power electronics. In this paper, two main computational methods are presented to simulate the dynamic behavior of power electronics interconnection systems. Our aim is to present a methodology to analyze the electromagnetic (EM) behavior of power PCB regarding parasitic effects ( EM couplings) or dynamic effects (impedance): a general procedure is given to calculate EM couplings between strip conductors in multilayered configurations based on the principle of hybrid methods. Finally, we propose a new method to limit computation time based on matrix sparsification.     

Millimeter Wave Subscriber Loops

Advantages and drawbacks of using millimeter waves in the telephone and data subscriber distribution network are listed. Fields in which it seems attractive to use millimeter wave loops are examined. For such applications, cost and reliability constraints led to the design of very simple systems. Two systems will soon be introduced into the French subscriber plant. The first one will be commissioned in 1983 to connect groups of remote subscribers, working at 31 GHz, using a homodyne millimetric front end. The second one, still under experiment, is designed for the connection of subscribers of the integrated service communication network; working at 23 GHz, it uses time-division multiplexing to assume duplex operation. The most drastic constraint when setting up such systems is the line-of-sight requirement. Investigations of that problem, using computer-aided coverage map plotting are discussed.     

Electrochemical studies of gold ore processing wastewater containing cyanide, copper, and sulfur compounds

The electrochemistry of real gold ore processing wastewater solutions from copper sulfide containing gold ore has been investigated. Analysis shows that the wastewater contains a range of sulfur compounds in various oxidation states from sulfide to sulfate. The electrochemical characteristics of the gold ore processing wastewater were evaluated using rotating disk, cyclic voltammetric, polarization and preparative electrolysis studies. The solutions show clear differences versus synthetic alkaline copper cyanide solutions. The copper cyanide/copper oxide catalysis normally seen in synthetic alkaline copper cyanide solutions is strongly inhibited. Two components of the wastewater solution identified as inhibiting the copper cyanide/copper oxide catalysis are copper sulfide complexes and thiocyanate. The inhibition of the copper cyanide/copper oxide catalysis appears to have an initiation time possibly related to the accumulation of copper-sulfur compounds at the electrode surface. The passivated surface is still able to oxidize cyanide, though at a maximum rate that corresponds to the limiting current for free cyanide assuming 1 electron per cyanide. The lack of the copper oxide coating that typically forms during oxidation of synthetic alkaline copper cyanide solutions, plus possibly the presence of various sulfur compounds, results in corrosion at higher anodic potentials when stainless steel is used as an electrode. However, stainless steel can be successfully used as an electrode material to treat the solutions if the potential is carefully controlled.     

Switching atomic fountain clock microwave interrogation signal and high-resolution phase measurements

This paper focuses on the development of tools aiming to solve several problems related to the microwave interrogation signal in atomic fountains. We first consider the problem related to cycle synchronous phase transients caused by the sequential operation of the atomic fountain. To search for such systematic phase variations deeply buried in the microwave synthesizer phase noise, we have developed a novel triggered-phase transient analyzer capable of processing the microwave signal to extract the phase in a synchronous manner even in the presence of frequency modulation. With this device we check in vivo the LNE-SYRTE fountain's interrogation signals with a resolution approaching 1 microradian. In addition, using this device, we investigate an innovative approach to solve a second problem, namely, the shift caused by microwave leakage in the fountain. Our approach consists of switching off the fountain microwave interrogation signal when atoms are outside the microwave cavity. To do that, we have developed a switch that is almost free of phase transients and is thus able to eliminate the frequency shift caused by microwave leakage without inducing significant phase transients on the interrogation signal.     

Optically frequency modulated GaAs MESFET oscillator

A GaAs MESFET X-band oscillator has been frequency modulated by an amplitude modulated optical signal injected on the active device. A modulation index of 0.5 corresponding to MSK modulation has been achieved at 2 Mbit/s without parasitic amplitude modulation. It is shown that the FM modulation index variation against frequency is directly related to the drain current response of the FET considered as a photodetector. This responsivity has been measured to decrease above 5 MHz, which limits the oscillator FM capability.