Abstract: The radar is designed to identify and then eliminate rain clutter signals. For this, the radar works in circular polarization with alternately identical and opposite polarization directions at transmission and reception, from one recurrence to the next one. The signals are identified by a comparator which compares the sigma video signals relating to the same distance quanta for two successive recurrences, the identifying criterion being a major difference in the level of the signals compared, for rain clutter signals, and little difference for useful echo signals. A switch controlled by the comparator eliminates the parasite signals.

Abstract: A self-synchronizing scrambler for high bit rates comprises a plurality of scrambler stages operating in parallel and which respectively represent the series connection of a first modulo-2 adder and a second modulo-2 adder and a shift register stage, whereby the output of the shift register stage is fed back to the input of the first modulo-2 adder of its own scrambler stage and the other input of the first modulo-2 adder is connected to a further scrambler stage.

Abstract: A multi-channel communication security system where the information in an original information message is split among a number of channels in accordance with a message splitting routine such that the interception and analysis of any single channel does not compromise the privacy of the communication. The system provides secure communication terminal adapters in cojunction with user terminals for splitting and recombining of private communications together with control facilities in an integrated services digital network (ISDN) for selecting amoung a multiplicity of possible of message splitting routines and generating security code signals for transmission in separate D-channels to the user equipment.

Abstract: A system for enciphering or deciphering wherein bit patterns in a binary number notation of a plurality of elements, which an irreducible polynomial in the Galois field GF (2.sup.i) has, are stored in registers arranged in a certain correspondence with the bit positions of input data or messages, as random numbers for an encryption key or decryption key. The bit patterns retained in the registers corresponding to the digit of bit "1" in the input data are subjected to a mod 2 addition operation independently for each digit of the random numbers, to thereby obtain encipher or decipher data corresponding to the input data. The elements to be used for the encipher and decipher keys have a specific relationship therebetween in conformity with the periodical characteristic of the elements the irreducible polynomial has.

Abstract: A multifunction active array system is disclosed, wherein the array aperture may be partitioned into a plurality of arbitrary subapertures. The array system includes N radiative elements, each coupled to a corresponding active module. Each module is in turn connected to an aperture partition selector, which includes an M-way power divider/combiner device, having a module port and M device ports. Each device port is coupled through an RF switch to a partition port of the device. M N-way manifolds are provided, having N manifold ports coupled to a respective one of said partition ports of each selector. The manifolds are coupled to a receiver and an excitation source. Each partition may be formed by the desired connection of a particular module to a manifold by the respective positions of the RF switches. The array system provides the capabilities of partitioning the array into M or less subapertures to simultaneously generate sum patterns, difference patterns, guard patterns, and adaptive nullings.

Abstract: An apparatus for detecting bodies in motion on the ground of a protected area, particularly for military use and the like, wherein, by means of an antenna buried and shielded from the air, an electromagnetic signal in the range of radio frequency is radiated into the ground. Receiver means comprising means for detecting variations of the signal intensity are placed at a known distance from the receiving antenna. The intensity variation is dependent on the presence of bodies in motion within the range of action of the apparatus.

Abstract: A scrambler system comprises in a transmitter part thereof as oscillator circuit for generating a local oscillation signal, a frequency dividing circuit for obtaining a frequency divided signal by frequency-dividing the local oscillation signal by 1/N, a triangular wave signal generating circuit for converting the frequency divided signal into a triangular wave signal and for controlling the oscillation frequency of the oscillator circuit by the triangular wave signal, a multiplying circuit for obtaining a frequency converted audio signal by multiplying the local oscillation signal with an input audio signal which is to be scrambled, a pilot signal generating circuit for generating from the frequency divided signal a pilot signal having a single frequency, and an adding circuit for obtaining a scrambled signal for transmission by adding the pilot signal and the frequency converted audio signal. A key is used for de-scrambling the scrambled signal in a receiver part of the scrambler system.

Abstract: When determining the detailed radar reflection cross-section of a radar target by ISAR techniques it is a known problem that one of the target motion components is to be compensated. This was done in the past by complicated numerical calculations of the path of the target. According to the described method, the motion compensation is determined by means of an auxiliary signal which is transmitted form the target. The described method enables the achievement of a radar reflection cross-section by real time data processing of the signals received. Also an apparatus for performing the method is described.

Abstract: A signal processing system in a transmitter/receiver system for reducing undesired amplitude, frequency and/or phase distortions arising due to variations from transmitter pulse to transmitter pulse. A plurality of sequential samples of transmitted pulses are averaged and a plurality of filter coefficients are determined therefrom. The coefficients are used in a plurality of filters which respond to a plurality of sequential samples of received pulses, the filters providing output signals in which such distortions are reduced.

Abstract: In order to protect secret information in the electronic storage medium, the storage medium is provided in a housing protected against access. This housing contains one or more detector elements, via which erasure of the memory contents is initiated when unauthorized access is detected. The detector elements are connected with a clock unit which sets these elements into operation for short periods of time at certain time intervals. This clocked operation allows for the energy consumption of the overall arrangement to be reduced many times over without any essential restriction of security.

Abstract: A technique is disclosed for encoding SAR image data to achieve data compression. In the image encoding stage, the SAR image is transformed into a list of high reflectivity radar discretes and a small array of frequency filters. In the target list, the location data and intensity levels above the local average background clutter are tabulated for a predetermined number of the highest intensity radar discretes. The array of frequency filters is divided into three zones; the inner, middle, and higher frequency zones relative to the d.c. filter. Only the inner and middle zones of filters are retained and the outer filters are discarded, thus acheiving the desired data reduction. The inner zone filters are quantized to a higher level of precision than the middle zone of filters. The saturation levels of the filters are determined adaptively. In the decoding stage, the original SAR image is reconstructed from the radar discrete list and the small array of frequency filters.

Abstract: The areal height and areal reflectivity of source data for defining a landmass are modified in real time in response to the areal reflectivity of the source data, so that the modified values may be processed for generating radar images to be displayed. The images may include stationary three-dimensional features, useful for a high resolution radar, without need to preprocess data or increase bulk storage medium size of landmass data. In addition, the features, which may include industrial, forestial, commercial and/or residential areas, and/or specific detail such as a predetermined airport, may be predeterminedly disposed within a landmass area more realistically to present an image that is to be expected from an actual operating environment.

Abstract: A device for mechanically resetting, by means of a simple manipulation, an optional number of status indicators of the type consisting of an electromagnet with an iron core, a magnetizing winding and some form of permanently magnetized indicating disk capable of rotating through 180.degree.. The device comprises a rail made of a non-magnetic material and being formed so as to enable a desired number of indicators to be mounted side-by-side. The rail has such a profile as to enable a shuttle with a corresponding profile to be in engagement with and be guided by and slide on the rail in its longitudinal direction. The shuttle is provided with a permanent magnet as well as with a pole piece mounted so as to form, together with the core in the electromagnet of each indicator, a magnetic circuit when the shuttle is pushed over the respective indicator whereby the rotatable indicating disk is influenced and is reset to indicate the reset position.

Abstract: An apparatus receives Loran-C pulses and tracks the phase of each received Loran-C pulse received from master and secondary stations. The apparatus comprises: (a) a phase comparator (12) for comparing the phase of the Loran-C pulse received from each transmitting station with that of a comparison signal; (b) a phase locked loop circuitry (16) for generating the comparison signal at a given integral multiple of the repetition rate of the Loran-C signal; (c) an S/N ratio detection circuit (14) for measuring the signal-to-noise ratio of the received signal; (d) a loop filter (13) for correcting the timing at which the comparison signal is generated toward coincidence with the phase of the received Loran-C pulse when a given number of phase comparisons by the phase comparator (12) produce results of the same polarity; and (e) a sample number control circuit (15) for adjusting at least one of the given integral multiple and the given number according to the measured signal-to-noise ratio.

Abstract: Voltage regulator which can compensate for the output voltage variation of a line modulator for use in transmitters for radar applications. The voltage variation in question is due to the modulation induced by the radar repetition frequency. This regulator is essentially made up of a network (1,2,3,4,5,6,7) which varies the value of the input signal to a comparator 8 in relation to a signal which is proportional to the variation of repetition frequency.

Abstract: In a multi-window system for setting a plurality of windows on the screen for independent display in each window, a novel display control method is disclosed in which a visible region of a given window is determined from the positions and overlapped relations between the windows on the display screen, and display data is selectively applied to the visible region. The visible region is checked for crossing between an object window and another window making up a reference window on the screen, and if they cross each other, the object window is divided into subregions, while the subregion not overlapped with the reference window is regarded as a new object region, which is collated with another reference window and subdivided. This process of collation and division is repeated. A display output is thus applied sequentially to the subregions which are found to be a visible region.

Abstract: A Radar Digital Data Processor has been developed which produces I (phase) and Q (quadrature) data obtained by sampling the receiver IF of a radar with a single A/D converter. A sampling technique was developed for this application to allow operation with radars employing a noncoherent transmitter such as a magnetron. Representative field results are presented employing spectral analysis proving the viability of the sampling technique for Doppler processing.

Abstract: Pulse position coding is used to transmit several channels of data from a ground radar transmitter to a receiver in an airborne, remotely-piloted vehicle. The system is designed to ignore interfering pulses, especially those which are synchronized with the transmitter's PRF, by combining a number of noise reduction devices. These include the redundant transmission of address and channel information, the transmission of true and complemented data, the tracking of channels transmitted in a predetermined order, developing an interference count to recognize synchronous pulses, comparing data received for a given channel with data subsequently received for that channel, the use of windows around the expected positions of pulses, and the use of parity. There is also a novel programming arrangement which enables several programs to be stored in a reduced amount of memory space.

Abstract: The power output and thus the range of sonar apparatus is limited by caviion of the water surrounding a sonar transducer at high output power levels. The invention "strengthens" the water surrounding a sonar transducer by increasing the hydrogen content to permit a many fold increase in the transducer output power before cavitation occurs.

Abstract: A method of reconstructing original images from synthetic aperture radar image data, wherein in order to speed up the reconstruction of an original image from image data provided by synthetic aperture radar (SAR), the process for generating a point image pattern in correspondence to each point on the original image and the fast Fourier transformation (FFT) process for the generated point image pattern and 1-line image data are carried out once for every certain number of lines. Positional and phase displacement created on a reconstructed image are corrected by multiplying a phase rotation factor to the product of the FFT-processed point image pattern and 1-line image data.