DOI:10.1049/ecej:19900031

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Active control of sound results from destructive interference between the sound field of an original acoustic source and that from a controllable array of ‘secondary’ acoustic sources. For this destructive interference to occur over an appreciable region of space the sound field of the secondary sources must match that from the primary source in both time and space. The spatial matching requirement leads to an upper frequency of applicability of active control. Active control complements conventional passive methods of sound control, which do not work well at low frequencies. Practical feedforward controllers, using a multichannel generalisation of the well known LMS adaptive algorithm, have been developed, using as many as 16 loudspeakers and 32 microphones, and applied with considerable success in the control of low-frequency propeller noise inside aircraft and low-frequency engine noise inside cars.

DOI:10.1049/ecej:19900032

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Telecommunications networks based on synchronous 64 kbit/s channels are too restrictive for the future realisation of integrated broadband networks. New switching and transmission techniques, particularly those based on asynchronous transfer modes (ATM), are required. Roke Manor Research Ltd. and Plessey Research Caswell Ltd. are actively developing these new techniques at a system and technology level under the auspices of the European Commission's RACE programme. The paper introduces the issues pertinent to ATM, highlighting the system and technology aspects of the work being carried out within a RACE project entitled 'Broadband Local Network Technology' (BLNT) and also describes previous ATM work relevant to the current research activities.

DOI:10.1049/ecej:19900033

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Digital radio frequency memory (DRFM) is a technique in which high-speed sampling and digital memory is used to store radio frequency and microwave signals. It is becoming a popular technique for the implementation of false-target ECM systems. The paper discusses the principles of DRFM and the advantages of alternative system architectures.

DOI:10.1049/ecej:19900035

出版商:IEE    

年代:1990

数据来源: IET

摘要:

A technique has recently been developed at Roke Manor Research Ltd. for recovering three-dimensional (3D) information from conventional video data. This is based on matching features in a scene observed from different viewpoints, either as a result of intrinsic camera or object motion or through the use of multiple cameras. The technique has been examined as a means of supplying guidance information to a robot manipulator and an autonomous vehicle. Results indicate that the method is capable of recognising basic surface structure in a variety of indoor and outdoor situations. The essential elements of the technique are described and a real-time system implementation is outlined. A surveillance application is also discussed whereby the derived 3D representation can be exploited in a data compression device to communicate concise 3D information to a remote operator or observer.

DOI:10.1049/ecej:19900037

出版商:IEE    

年代:1990

数据来源: IET