Abstract: A device for detection of undesired objects on surfaces, for example airport runways co-ordinates sensed data from a plurality of sensor units. With radar sensors, synthetic aperture radar processing is found to be advantageous. A vehicle which is configured with a plurality of sensors may be either remotely controlled or autonomous. It may also be provided with communication equipment and debris retrieval apparatus and that includes both mobile sensing devices and fixed installations. A suitable mobile sensing device and a method for operating the debris detection system are also provided.

Abstract: A method of determining the position of a target comprising the steps of: providing a transmitter or a plurality of transmitters to transmit a signal to the target, providing a receiver or a plurality of receivers to receive signals reflected from said target. Determining the time of arrival information of said reflected signal at the or each receiver; using information pertaining to the position of the or each receiver and/or the or each transmitter and with the information obtained determining the target position. Preferably the signal includes a modulated or coded portion unique to the transmitter; and said signal portion is associated with the or each particular transmitter by virtue of said signal portion. The signal maybe a mobile phone transmission, DAB, digital TV, digital Radio or digital satellite transmissions.

Abstract: A method is presented for operating a phased array antenna comprising a number of sub-arrays. The method comprises the steps of introducing phase offsets into signals received from/transmitted to each element in the antenna, to provide directional transmit or receive sensitivity in a first direction; summing signals received from each element in each sub-array to provide respective sub-array signals; introducing respective phase offsets into the respective sub-array signals to adjust the direction of maximum sensitivity within a sensitivity envelope defined by the phase offsets applied to each element of the antenna as a whole.

Abstract: A method is presented for operating a phased array antenna comprising a number of sub-arrays. The method comprises the steps of introducing phase offsets into signals received from/transmitted to each element in the antenna, to provide directional transmit or receive sensitivity in a first direction; summing signals received from each element in each sub-array to provide respective sub-array signals; introducing respective phase offsets into the respective sub-array signals to adjust the direction of maximum sensitivity within a sensitivity envelope defined by the phase offsets applied to each element of the antenna as a whole.

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.