Abstract: A radar tracking system for an anti-aircraft, missile, including angle tracking, doppler tracking and range tracking feedback loops operating on sum and difference channels. Fast fourier transform digital filters are used to provide a frequency spectrum of the sum and difference I.F. channels and detection and confirmation algorithms are employed for selecting the F.F.T. target ‘bin’. Adjacent F.F.T. bins are used to simulate a bin centered on the target frequency, shifts of the latter with target/missile acceleration causing frequency errors which are detected by a discriminator and used to control the target I.F. Confirmation of target acquisition is achieved by successive summations of the target bin power the totals being accumulated and compared with upper and lower thresholds. Confirmation and rejection results from total levels outside the thresholds while further accumulation and comparison follow the intermediate condition.

Abstract: Described herein is a quasi-optic rotating joint (100) which allows circularly polarised radiation to be transmitted therethrough irrespective of the angle of rotation of the joint. The rotating joint (100) comprises a first quasi-optic lens (102) having a first axis (112), which is carried on an inner part (116, 118) of bearings (108, 110) and which shares first axis (112). An outer part (122) of bearing (110) carries a quasi-optic mirror (104) and a second quasi-optic lens (106). The second lens (106) has a second axis (114) which is orthogonal to the first axis (112) of the first lens (102) and which intersects at the mirror (104). A Gaussian beam waist is formed at the mirror (104) by the first lens (102) and the second lens (106) is matched to the reflection of the beam waist at the mirror (104). Circularly polarised Gaussian beams passing through the joint (100) suffer a phase shift of angle ? which increases at the same rate as the increase in angle of rotation of the joint (100).

Abstract: An HF radar system comprises a transmitting system, a receiving system, a signal processing system and a frequency management/ionospheric sounding system. The transmitting system comprises a transmitting antenna array configured to transmit a beam in a near vertical direction and a transmitting device arranged to drive the transmitting antenna array at frequencies suitable for downward refraction by the ionosphere. The receiving system comprises a receiving antenna array configured to receive returning signals from a target area returning to the receiving antenna array via refraction at the ionosphere. The signal processing system comprises a digital data processing system. The frequency management/sounding system comprises cooperating transmitting and receiving systems sending HF signals to the ionosphere and analysing the returning signals. Alternatively, the system may have a duplexed antenna array.

Abstract: The invention relates to a method of interference suppression in a radar system (10) and also to a system (10) operating according to the method. The system (10) incorporates a first antenna (40) and associated electronic circuits for emitting interrogating radar radiation towards a remote scene (S). Moreover, the system (10) also incorporates a second antenna (45) and associated electronic circuits for receiving interrogating radiation reflected from the scene (S) and generating correponding first and second processed signals. The first and second processed signals correspond to a broader main beam response of the antenna (45) and to a narrower main beam response thereof respectively. By mutually comparing the first and second processed signals, the system (10) is operable to identify those second processed signals affected by interference from the scene (S).

Abstract: In a capacitive fuse for a missile interference due to discharge of static electricity from transmitter or receiver electrodes or to movement of the missile's control surfaces in flight is reduced by using as a receiver input signal the difference between signals at a pair of like receiver electrodes. The receiver includes a phase detector, and a small proportion of the transmitted signal is passed to the receiver input to cancel any standing receiver current. The output from two or more sets of receiver electrodes may be combined to produce s desired response pattern.

Abstract: A HF radar uses the same antenna array (414, 424, 424′, 424′) for both transmission (TX) and reception (RX). Each radiating element of the array may be driven by its own local transmitter and may have its own local receiver, both being connected to a central processor via fiber optic cables conveying digital data to the local transmitter relating to element energization in the TX mode and data representing signals received by the radiating elements in the RX mode. Each antenna element may have its own TX/RX unit, or a single TX/RX unit may serve two or more radiating elements. Each radiating element may comprise a skeletal pyramidal dipole mounted at ground level.

Abstract: A right circular cylindrical body of an isotropic dielectric such as a cross-linked styrene copolymer, has respective pluralities of mutually parallel grooves formed in its axial end faces, spaced apart by an intermediate portion whose dimension c is a half wavelength. The axial lengths a, b of the grooves are such that when a wave passes through the body, a quarter wavelength phase difference is produced between a component of a wave having its E-vector parallel to the grooves and a component of the wave having its E-vector orthogonal to the grooves. Alternatively the plate may consist of two or more discrete bodies whose grooves are dimensioned to produce a total differential phase shift of one quarter wavelength.