摘要:

The i.f. phase comparison hyperbolic position-fixing technique that became the Decca Navigator was invented in 1937 in the USA. Tests there in 1941, sponsored by the Decca Company, demonstrated an unprecedented position-line accuracy. In the UK the Air Ministry had reservations about the technique but the Admiralty saw it as the possible basis of a navigation system for use on the projected invasion of the French coast. After further development and seagoing trials under the codename QM, the system played a key part (overlooked by historians) in operation Overlord/Neptune of 1944. QM was later employed for hydrographic surveying in the Scheldt estuary. When the system was released for commercial use in 1945 as the Decca Navigator, the design of a lane-identification facility was presenting problems. An intermediate solution (‘Mk. V’) was developed, followed in the 1950s by the ‘Multipulse’ technique used today.

DOI:10.1049/jiere.1985.0069

出版商:IERE    

年代:1985

数据来源: IET

摘要:

To facilitate field test procedures several regulations recommend the use of parallel plate antennas or related configurations. The electrical field between the two plates is calculated from the applied voltage and the geometrical separation of the two plates. The field distortion caused by test objects is normally neglected for small objects or only roughly taken into account by special correction factors. In reality the test object induces an antenna mismatch and creates new field components because of reflections and surface currents. The surrounding field is not uniform but is a function of the test object's geometry. The paper presents an approach for the evaluation of these phenomena by calculating mismatch problems and static field distributions in two-dimensional situations. For this purpose the configuration of antenna and test object is transformed into a parallel plate configuration without boundary effects by the method of conformal mapping together with the Schwarz-Christoffel Transformation. The results—characteristic impedances, v.s.w.r.-ratios, static field distributions, minima and maxima of field strength—are presented.

DOI:10.1049/jiere.1985.0070

出版商:IERE    

年代:1985

数据来源: IET

摘要:

Metal evaporated video tape (hereinafter referred to as ME tape or ME thin film) has been developed for the next generation VTR recording media on the scale of mass production. The feature of this tape is that the magnetic thin film of 0.15 μm is directly formed on a polyester base by an entirely new process which is not a conventional binder coating but a continuous vacuum deposition coating. We have sharply improved many properties of the magnetic layer, such as coercivity, remanent magnetism, corrosion resistance, durability, coefficient of friction, and noise level by the selection of Co–Ni alloy as the magnetic material and the adoption of oblique incidence deposition and oxygen reactive deposition as the deposition method. Magnetic recording media which possess both higher performance for short wave length recording and excellent durability in practical use are realized by ME tape. This ME tape has the possibility of extending the application of magnetic recording and to advance the theory of magnetic recording mechanisms.

DOI:10.1049/jiere.1985.0071

出版商:IERE    

年代:1985

数据来源: IET

摘要:

After a brief historical survey of the subject, the paper describes, in general terms, the current state of expert system technology and then outlines the way in which a specific system operates. The limitations of these systems are touched upon and the future direction of research and applications in the field is suggested.

DOI:10.1049/jiere.1985.0072

出版商:IERE    

年代:1985

数据来源: IET

摘要:

The signal processing requirements are described for a single magnetic recording channel with a very high transfer rate (117 Mb/s). On the record side it is necessary to compensate for the relatively slow rise-time of the head fringing field. On the playback side the use of Class IV partial response improves the effective signal-to-noise ratio. A Viterbi detector operates on the redundancy inherent in the ternary partial response samples to provide further processing gain.

DOI:10.1049/jiere.1985.0075

出版商:IERE    

年代:1985

数据来源: IET