Telefonaktiebolaget Lm Ericsson (publ)

Bengt Lennart Andersson

Sten H Ahlbom

Per-Olof Gerhard Gustavsson

Bo A Morwing

Ragner Arvidsson

Martin Henning Heed

The present invention relates to methods and to arrangements for monitoring an object which emits a rotating or oscillating beam whose angular velocity is unknown. The time points at which the beam passes a predetermined number of measuring positions are determined. An angular velocity start value is generated and a predetermined number of object position determinations (at least two independent determinations) are made on the basis of the determined time points, the measuring positions and the start value. It is determined whether or not the position determinations can be considered to be sufficiently in agreement with one another. When agreement is considered sufficient, the start value is accepted as an approximate value, this value approximating the angular velocity of the beam with an acceptable degree of accuracy. If the position determinations are not found to be sufficiently in agreement, the start value is modified and new position determinations are made. This procedure is repeated as often as is required for the position determinations to become sufficiently in agreement with one another, wherewith the start value is accepted as a approximate value of the angular velocity. Subsequent to having obtained the approximate value of the angular velocity, a final position determination of the object can be made.

Method and arrangement for monitoring objects

The duty cycle of a pulse train from a pulse radar antenna is increased by dividing the antenna aperture into sub-apertures ( ), generating separate pulse trains from said sub-apertures ( ), and time shifting the separate pulse trains between themselves to produce a resulting pulse train having shorter pulse spacing or wider pulses.

Method and arrangement for duty cycle enlargement

A method and a system for determining an altitude of an object of interest, for example, an airplane that transmits electromagnetic radiation in the form of radar signals. A number of sub-units that can detect the radar signals are spread out in an area, preferably in a large geographical area, where the radar signals of the airplane/object it is possible to detect. The sub-units communicate to the information center when they are able to detect the radar signals. The information center determines the altitude of the airplane based on the airplanes line of sight, i.e., its radar horizon, and thus which sub-units can detect the radar signals.

System and method for measurement

The velocity vector of a moving object is precisely determined by using radar measurements of the angle to and the radial speed of a moving object. This can be done in a radar system comprising one or more units. The technique also makes it possible to precisely determine the range to a moving object from a single moving radar unit.

Method for determining object movement data

Method for reducing false target echo indications in a pulse Doppler radar having at least two different pulse repetition frequencies during the period in which the main beam of the radar illuminates a target. A target which is detected gives rise to a number of primary detections in each PRF. The method includes use of at least one variable criterion and a final criterion, which are both of the M/N type. The factor M in the variable criterion is initially greater than the factor M in the final criterion. The method also includes the feature that primary detections which are all to be found in the same range gate in a number of PRF's, which number is equal to the factor M in the variable criterion, are approved as targets in this range gate. If the factor M in the variable criterion and the final criterion are not equal, the approved primary detections and all other primary detections corresponding thereto, are removed from further processing, and if the factor M in the variable and the other criterion are not equal, a predetermined number is subtracted from the factor M in the variable criterion.

Method for reducing false target echo indications

A system for surveillance of, and taking measures in respect of, phenomena that are observable. The system includes at least one information center with associated cells that can be divided into one or more groups. The system also includes means for communication between an information center and each cell. Each cell includes at least one sensor, with which chemical or physical measuring methods can be used to observe the phenomenon or detect the signals which the phenomenon generates. This system further includes at least three cells that are distributed geographically in the area of interest in a sufficiently dense net. In the cells the signals can be used for determining for example the time, place, intensity or the type of the phenomenon. Data can be transferred from the cells to their respective information center for processing. Activities can be initiated and carried out by equipment inside or outside the cells in accordance with rules in the cells, and these activities can be started as a response to the detected signals.

System for surveillance

System for determining the position of radar transmitters where the system includes at least one information center with associated cells and means of communication between the information center and the cells with a restricted transfer rate utilising existing infrastructure in the country, such as for example a national telephone network and also mobile telephone networks and their base stations. Each cell includes at least one sensor in order to be able to detect radar signals. Leading edges of pulses in the radar signals are detected and time-marked after which they are sorted according to PRI (Pulse Repetition Interval). The time of arrival for the first pulse in a pulse train is calculated and data reduced by modulo calculation to a value that as a maximum is the propagation time difference for pulses between two cells in a pair of cells/sensors that are used together for calculating the bearing. Bearings calculated from at least two pairs of cells are correlated in the information center which thereafter calculates the position of the radar transmitter.

System for direction determination

A procedure and a device transmit information in a pulse radar device simultaneously with the ordinary radar function of the pulse radar device. The radar device includes a control unit, a radar transmitter and an antenna. The control unit controls the radar transmitter to generate radar pulses in pulse groups that are transmitted via the antenna. The pulse groups for the ordinary radar function are information coded by position coding by the control unit of the information that is to be transmitted. The pulse groups are position coded by transmitting radar pulses with time displacements relative to their nominal radar pulse positions. Pulses are received and information decoded to thereby recreate, in the form of an information copy, information that has been positions coded and transmitted by a radar device.

Procedure and device for the control of a radar unit

A procedure and a system increase the performance of a group of radar units. The radar units are arbitrarily located in such a way that the respective antenna beam of a radar unit functioning as a normal radar at least partially coincides with the antenna beam of at least one other radar unit in the group. The radar units are synchronised to transmit alternately and in turn, preferably with an increased energy output. All the radar units in the system are synchronised to work continuously in their ordinary reception mode. In this way at each moment echo signals originating from the radar unit transmitting at that moment are received and processed.

Procedure and system for the control of a number of radar units

A procedure and a device for controlling, in a radar unit for the measurement of target data, the transmission of radar pulses and the reception of target echoes originating from the transmitted radar pulses, in such a way that the performance of the radar unit increases, in order thereby to gain a longer range during a period of time. The period of time is preferably repeated continually. The period of time is divided into a first and a second partial period of time where the first and the second partial periods of time are each at least twice as long as a pulse repetition interval which is used during the first partial period of time. During the first partial period of time the radar unit is controlled so that it transmits radar pulses for the measurement of target data with a higher energy content than what is possible in a steady state. The control is carried out in such a way that the amount of transmitted energy of the radar unit during the period of time is at the most the possible energy transmission of the radar unit in a steady state during a corresponding period of time. There is thereby obtained a more efficient signal integration by means of the signal integration of the target echoes that originate from the radar unit being concentrated during the first partial period of time. The radar unit is also controlled so that it does not transmit radar pulses for the measurement of target data during the second partial period of time.

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Kullavik, Sweden

Bengt Lennart Andersson