Abstract: In order of maintaining at the more constant level the CO.sub.2 content in the gaseous mixture discharge of a transversely excited atmospheric pressure laser, a polymer product is included in advance of the laser operation in the laser chamber or within the closed fluidtight circuit where the gaseous mixture is recycled. Such polymer is produced by irradiating tripropylamine with ultraviolet photons and/or with energy electrons in the form of a layer whereby at least a portion of a solid support is coated.

Abstract: Adaptive radar signal processor apt to detect the useful echo in the presence of an additive disturbance made up of clutter and noise, through which the disturbance can be cancelled and the useful signal can be enhanced by means of the synthesis of a filter, adapted to the useful signal, which rejects the disturbance spectrum frequency components by adapting itself in real time to its variations.

Abstract: A device for the detection of undesirable echoes which have significant correlation in azimuth which is applicable to surveillance or tracking radars. The device works through autocorrelation function estimation over a pair of pulses received by averaging, over N range cells, the complex product of the received signal Z.sub.k (t.sub.1), relevant to the K-th range bin and time instant t.sub.1, with the complex conjugate value Z.sub.k (t.sub.1 +T), still relevant to the K-th range bin, at instant t.sub.1 +T (where T is the pulse repetition period, PRT).

Abstract: The invention regards a perfectioning in reply type radar systems, in particular SSR (Secondary Surveillance Radar) or IFF (Identification Friend or Foe). The invention has as its aim that of eliminating or reducing undesired replies due to reflections from fixed obstacles or from structural peculiarities in the main radar system (i.e. radome) and other similar effects. The suppression of undesired replies is attained by varying azimuthally the emission power of the radio-frequency impulses according to a memorized law.

Abstract: A digital MTD processor interposed between a coherent video detector and a signal extractor of a surveillance radar comprises a plurality of Doppler filters connected in parallel to the video-detector output, including a zero filter, working into respective modulus extractors connected by way of respective threshold circuits to a common OR gate. Each threshold circuit includes a fixed-threshold comparator and an adaptive-threshold comparator with inputs connected in parallel to the output of the associated modulus extractor, either of these comparators being connectable to the OR gate via a switch controlled with the aid of a rain-clutter map so that the adaptive threshold is used only during exploration of regions with heavy rain.

Abstract: A receiving section of a surveillance radar equipped with a power oscillator in its transmitting section comprises several registers for the storage of values, perferably in complex digital form, representing the starting phase of a continuous wave at the instant of transmission of an outgoing pulse, these values being used thereafter to establish coherence with an incoming echo pulse at a time when the power oscillator is no longer able to do so on account of unavoidable frequency drifts or because of intervention of a new recurrence period. Thus, the stored values permit the correct detection of targets at the far end of the range and/or the cancellation of second-time-around clutter echoes. The continuous wave may be generated by a coherent oscillator, phase-locked during each recurrence period by the outgoing pulse, or a separate crystal-controlled oscillator of highly stable frequency.

Abstract: A sealed structure laser apparatus is disclosed which utilizes corona discharge as a pre-ionizing means wherein the laser discharge space is defined by a dielectric material channel with C cross section and one of the two discharge main electrodes is located along the inner wall of the C channel opposite the C aperture while the other electrode confronts said aperture from the outside of the channel the latter being enveloped by a conducting material grid, two opposite slits being defined between the two edges of said C channel gap and a dielectric material wall located in front of said gap.

Abstract: A method of making a field effect transistor with a modified metal semiconductor Schottky barrier depletion region wherein a GaAs semiconductive active layer on a semiinsulating substrate is supplied with a pair of ohmic contacts and with a gate or barrier electrode between the ohmic contacts and spaced therefrom so that below the surface of the active layer upon which the barrier electrode and ohmic contacts are supplied, an electron-depletion region is formed between each ohmic contact and the gate or barrier electrode. According to the invention, this surface region is treated by bombardment with nitrogen or by the application of a layer thereto to modify the depth of the depletion region so that this depth beneath the treated surface region will differ from that beneath the gate or barrier electrode.

Abstract: A radar receiver, associated with a transmitter sending out circularly or linearly polarized waves, has two parallel channels for the respective processing of incoming echo signals derived from incident waves with mutually orthogonal linear (e.g. horizontal and vertical) polarization. For the suppression of interfering signals from a jammer, each channel includes an adaptive compensator generating a cancellation signal from the incoming signal of the other channel and from a feedback signal originating at the output of its own channel; this cancellation signal is subtracted from the incoming signal received by the respective channel. The resulting purged signals are fed to a channel selector which compares their power and directs the momentarily predominating signal to a load.

Abstract: In order to determine the distance of a target, illuminated by a remote pulsed laser, from a nearby observation point, the time interval between the arrivals of a direct laser pulse and of a reflection of the same pulse from the target is measured along with the angle included between the two directions of incidence. From these data the target distance can be calculated with reasonable accuracy, e.g. for the purpose of emitting an alarm signal if the calculated distance lies within a predetermined range. The device implementing this procedure could also be used in a feedback loop of a system for the automatic pointing of a pulsed laser beam.

Abstract: A device for estimating the scanning frequency of an unfriendly tracking radar of the conically scanning type comprises input circuitry for eliminating the d-c component of a detected radar signal and a sampler deriving a train of amplitude pulses from that signal which, after digitization, are fed to a calculator performing a Fourier analysis thereon. The index of the term of the resulting Fourier series with the largest sum of the absolute values of its real and imaginary coefficients is selected and weighted with a corrective factor obtained from the numerical values of the coefficients of a limited number of preceding and succeeding terms in the series; the corrected index yields the estimated scanning frequency.

Abstract: A longitudinal-discharge-pulse laser has two coaxial sections in the form of glass tubes joined together by a grounded central electrode and terminated by two outer electrodes. Each glass tube carries on its outer surface a multiplicity of metal rings connected in parallel, via a step-up transformer, to the anode of a first thyratron for energization with a steep negative pulse to generate a corona effect for the preionization of a gas mixture in the tubes on command of a pulse-cadence generator. This generator also controls a second thyratron, with a predetermined delay, which applies negative trigger pulses to the two outer electrodes for initiating a pumping discharge of the laser.

Abstract: A radar of the MTI type has a transmitter connected to a source of outgoing pulses whose carrier frequency is variable under the control of a mode selector for selective operation with fixed frequency, frequency diversity or frequency agility, depending on detected environmental conditions. A multiweight Doppler filter serves for the detection of mobile targets in each of these three modes. With frequency-agility operation, samples of echoes of an outgoing pulse received during a given sweep are stored in a memory in accordance with the carrier frequency used for that pulse, this frequency changing in random fashion from one pulse to the next among a certain number of predetermined values.

Abstract: A double-acting hydraulic jack, comprising a hollow piston reciprocable in a surrounding cylinder, includes a tubular shaft extending axially inside and carrying a nut of the circulating-ball type which coacts with a screw coaxially disposed in that shaft. The screw is rigid with the piston whereby an axial displacement of the latter is translated into a rotation of the shaft; a toothed wheel on the shaft, engaged by a spring-loaded detent, acts as a one-way brake enabling such rotation only in one direction and blocking it in the opposite direction unless the detent is withdrawn by a hydraulic servomotor which is pressurized concurrently with the admission of fluid to the cylinder tending to displace the piston in the normally blocked direction.

Abstract: In order to focus the beam of a laser onto a receiving end of an optical fiber substantially coaxial therewith, the laser output is formed by a planoconvex lens with a semitransparent flat face confronting the laser cavity and an antireflecting curved face turned toward the fiber. Alignment of the laser beam with the fiber axis is accomplished by the adjustment of two oppositely pointing juxtaposed wedges interposed between the lens and the laser.

Abstract: A bipolar main transistor Q.sub.1 designed to amplify a high-frequency signal applied to its base, for driving a load connected to its collector lead, has its emitter connected through a low-ohmic feedback resistor R.sub.E to a point of stabilized potential constituted by the emitter of a biasing transistor Q.sub.2 of the same conductivity type (e.g. NPN) as the main transistor, the latter emitter being connected to a terminal of a d-c supply through a much larger resistor R.sub.3 ; the two series-connected resistors R.sub.E, R.sub.3 are capacitively shunted for high frequencies. The biasing transistor Q.sub.2 is driven at a much larger direct current than the main transistor by a control transistor Q.sub.3 traversed by a direct current substantially equaling that of the main transistor Q.sub.1, this control transistor being biased by a voltage divider including a fourth transistor Q.sub.4 connected as a diode and traversed by a current substantially equaling that of the biasing transistor Q.sub.2.

Abstract: A detector for infrared radiation, having a multicell photosensor disposed at the top of a cold finger in an evacuated container, comprises a stack of annular ceramic layers coaxially surrounding the cold finger and serving as supports for several arrays of radially extending metallic strips screen-printed on respective layers in angularly offset relationship. The metallic strips are conductively connected to respective cells of the sensor to serve as output leads thereof. The conductive connections include axially extending metal pins spacedly surrounding the cold finger while being linked with the sensor cells by short, thin wires spanning an intervening annular gap.

Abstract: A pair of excitation electrodes in a laser cavity, filled with a gas mixture at substantially atmospheric pressure, are connected across a pumping capacitor by way of part of the winding of an autotransformer in series with a pre-ionizing device within the cavity acting as a trigger switch. The pre-ionizing device comprises a dielectric tube carrying a plurality of axially spaced-apart metal rings constituting a condenser chain, the rings being provided with pointed extensions confronting one another to serve as corona electrodes. Contral pulses applied to a conductor inside the tube cause a spark discharge through the cascaded corona gaps of the trigger switch with resulting energization of the autotransformer and discharge of the pumping capacitor across the excitation electrodes. The metal rings may be interconnected by high-ohmic resistors establishing a uniform field distribution therebetween.

Abstract: In order to provide a semiconductive substrate such as gallium arsenide with an oxide layer, the substrate is positively biased in a plasma reactor in which an oxidizing gas is ionized by radiofrequency excitation while the substrate is heated to an elevated temperature increasing its conductivity. The substrate may be placed for this purpose on a graphite pedestal which is inductively heated from the same radiofrequency source.

Abstract: A portable instrument for testing the integrity and measuring the attenuation of a subscriber line of a telecommunication system comprises a metering unit joined to a plug by which an associated service telephone can be connected across a line to be tested. The metering unit includes a pilot-tone generator as well as a digital attenuation indicator and is provided with three pushbuttons, two of which disconnect the service telephone from the line on being respectively actuated for transmitting the locally generated pilot tone to the line or feeding an incoming pilot tone to the attenuation indicator. Operation of the third pushbutton connects the local generator to the indicator for calibration purposes. Any of these pushbuttons, when depressed, supplies operating current from a normally open-circuited local battery to all other components of the unit.