Abstract: A radio direction-finding system comprises at least two adjacent, coplanar rectilinear antenna arrays (ARR.sub.1, ARR.sub.2) which face in different directions; phase measurements are performed on pairs of antennae of different spacings (ANT.sub.C /ANT.sub.1 -ANT.sub.N) in each array in order to derive the direction of incidence in the plane of the arrays and/or the direction of incidence with respect to said plane, e.g. bearing (.theta.) and elevation (.beta.) respectively. To reduce the number of channels required for resolving ambiguity in the phase measurement on the widest-spaced antenna pair (ANT.sub.C /ANT.sub.N) in each array, ambiguity is resolved as far as possible with more closely spaced pairs in each array and finally resolved on the two arrays jointly by amplitude comparison of signals received by the two arrays, even though the accuracy of the amplitude comparison may be insufficient to resolve ambiguity in the arrays separately.

Abstract: The invention relates to a microwave barrier which uses at least two aerial beams of which one forms a protected zone extending down to the ground while the other is inclined upwards relative to the horizontal. In this way by the use of a simple construction intruders can be prevented both from crawling under the barrier and jumping over it.

Abstract: Method and apparatus of obviating cycle-locking slippage errors in reception of Loran-C and similar radio-frequency signals covered by receiver location acceleration effects and other distortion effects simulating the same, that comprises, receiving the radio-frequency signals and producing data by sampling and tracking the cycles of the signal with a time-constant filter sufficiently fast to accommodate for the largest acceleration to be experienced by the receiver location to avoid cycle slippage in locating a predetermined cycle zero crossing, and independently post-filtering sufficiently slowly to smooth the data and without interaction with said sampling.

Abstract: A photo sensor circuit including an LED (12) and a phototransistor (14) coupled together by resistors (R.sub.1, R.sub.2) and connected to a drive and sense network (16) including resistors (R.sub.B, R.sub.3, R.sub.4), a source of positive voltage (+Vcc) and a PNP transistor (20) by a single conductor wire (W.sub.1). When the light path between the LED (12) and the phototransistor (14) is blocked, the circuit standby current is low and the transistor (20) is OFF, but when the light blockage is removed, the increase in current through the LED (12), triggered by an increase in current through the phototransistor (14) quickly drives the transistor (20) into saturation. The phototransistor (14) will keep full current flowing through the LED (12) as long as the light blockage is removed.

Abstract: A reflecting target device usable in space or on earth in the testing and simulation of weapons and other energy radiating space hardware. The disclosed embodiment includes an icosahedral reentrant cavity structure providing both infrared and radio-radar frequency retroreflective capability through the use of corner reflectors, conductive grid wires and coating layers. Launch-related apparatus are also described.

Abstract: The present invention relates to a method and a receiver for radionavigation, said receiver comprising a single filter mounted downstream of a mixer and adapted to allow the passage of the composite signal formed by the superposition of the signals of lower frequency at the output of the mixer, a sampler intended to sample the composite signal filtered at a predtermined frequency (f.sub.e), a unit intended to produce by a frequency analysis operation a series of signals including the same frequency components as the composite signal and means adapted to establish the phases and, if appropriate, the amplitude of the signals produced in the receiver by correlating these signals with the samples obtained from the sampler.

Abstract: An automatic gain control system is disclosed which utilizes a voltage coolled vario-losser means to vary the AGC System output. The control voltage is derived from the lowest detected level from any of a plurality of narrow band pass filters, such as the monolithic crystal type now available, each of which has a different peak transmittance frequency which is close to but different from a frequency of interest.

Abstract: A system and method of compensating a digital doppler processor for unbalance in in-phase I and quadrature Q signal inputs thereof is disclosed. The method includes the steps of measuring the unbalance in the I and Q signal inputs to the digital doppler processor, determining a desired set of weighting coefficients based on the measured unbalance, and performing doppler filter calculations in the digital doppler processor with the desired set of weighting coefficients. The system comprises a sensor for measuring the unbalance in the I and Q signal inputs to the digital doppler processor, and apparatus for determining a desired set of weighting coefficients for the doppler filter calculations of the doppler processor based on the measured unbalance of the sensor.