Abstract: A method of guiding an object by means of a radar information field, wherein a field is created comprising a beam which has a generally annular cross sectional region defining a central null in the field, controlling the beam so that the null is directed towards a destination or target, and positioning said object in or at a defined position relative to the null, said object including an antenna and receiver means responsive to the signal strength difference between the annular region of the information field and the null in order to guide the object to the destination or target.

Abstract: An MLS system comprising ground based equipment which includes a microwave signal transmitter arranged to feed microwave signals to radiator elements of an array antenna via phase shifter modules one of which is provided for each of the said elements, whereby the production of a scanned microwave signal beam is facilitated, signal monitor/detector means effective to provide a detected sample signal derived from the scanned beam, filter means responsive to the detected sample signals for providing a filtered signal derived in dependence upon effective sidelobe signals in the said beam, and comparator means responsive to the filtered signal for providing a transmitter shutdown signal when the filtered signal exceeds a predetermined threshold level for more than a predetermined time during a predetermined number of successive scans.

Abstract: The invention provides a method of and apparatus for determining if a newly reported target is correlatable with target tracks already stored in a data base. Correlation is effected in stages rejecting uncorrelatable stored target tracks and accepting closely correlated target tracks and includes decision applying means for accepting a stored target track as a correlated track only under stringent conditions.

Abstract: An interference suppressor comprises an amplitude limiter (2) to which a received signal is coupled. The limiter (2) is effective, when a dominant interfering signal (f1) is present together with a wanted signal (f1), to further increase the amplitude difference between interfering and wanted signals.A signal combiner (12) is fed with the received signal and also with a signal derived from the limiter (2) via a controlled attenuator (9) and which signal is arranged as to be in phase opposition to the received signal. A phase sensitive detector (8) is responsive to the output signal from the suppressor, which is provided by the signal combiner (12), and to the signal derived from the limiter (2) for providing a control signal for the attenuator (9). The control signal is effective to reduce the amplitude of the interfering signal present in the output signal.

Abstract: A pulse doppler radar system for helicopter recognition has a receiver (5) for receiving reflected pulse radar signals. A distinguishing circuit (22) is provided for distinguishing a group of received frequencies within a predetermined spectral range and for ignoring at least the largest amplitude frequency within that group. A threshold detector (24) is arranged to determine when the amplitude of the remaining frequencies in the group exceed a predetermined value to provide a recognition signal.

Abstract: A method of network management for a radio communications network comprising a plurality of stations each of which includes a transceiver and control means therefor, the transceiver and control means of the respective stations being substantially similar, and the stations being arranged to communication directly with any other station, the method comprising: assigning at least one control channel of predetermined frequency to the network for transmitting network control signals between the stations; assigning to each station which may assume control a ranking position in a priority list of stations which may assume control of the network; each station monitoring the control channel or channels to determine whether control has been established by another station, and if so accepting control signals from such other station, and if control has not been established, the station transmits at a time determined by the ranking position of the station control signals on said control channel or channels for assuming ne

Abstract: A circuit arrangement which includes a switched inductor comprises a spiral inductor and a MESFET coupled in parallel for switching the spiral inductor in and out of a circuit. The MESFET has at least two gates, at least one of which and at least one section of at least one turn of the spiral inductor, are all mounted adjacent to one another on an active mesa. The switched inductor thus enables parasitic capacitances to be reduced and saves space on the mesa.