摘要:

In the measurement of screening of cables and connectors it is found that a dedicated instrument working in the time domain has many advantages over a swept frequency set-up. Comparison is made using calibration circuits to simulate the screening properties of connectors as well as on genuine cable assemblies.Using the simplest possible relationship between time and frequency domains, quite good agreement can be reached whether the measurement is made on a calibrator or a real connector. The conversion can be used on the homogeneous screen of a semi-rigid cable if care is taken in its application.

DOI:10.1049/jiere.1985.0043

出版商:IERE    

年代:1985

数据来源: IET

摘要:

This paper describes the development of an optical shaft encoder which is direct reading and has a resolution of 16 bits. The principles of design of the encoder, which employs a novel multi-element l.e.d. array as light source, are given. The smallest feature size on the encoder disc pattern is 20 μm × 4 μm. The angular position of the encoder shaft is obtained in serial form by pulsing the array elements in turn to produce a pulse train in a single detector placed behind the encoder disc. The fabrication and assembly of the mechanical components of the encoder are described, together with details of the electronic control package. Finally an indication is given of possible further develop-ments of the instrument.

DOI:10.1049/jiere.1985.0044

出版商:IERE    

年代:1985

数据来源: IET

摘要:

This paper describes an error correction scheme which uses the inherent error detection capability of a channel code as one dimension of the correction process. This reduces the total overheads in terms of hardware and data rate required for correction, allowing the advantages of a channel code whilst minimizing the overheads.

DOI:10.1049/jiere.1985.0045

出版商:IERE    

年代:1985

数据来源: IET

摘要:

The development of a new computerized interferometer is described which allows non-contact measurement of surface topography with vertical resolution better than 0.5 mm over a 0.5 mm by 0.3 mm sample area. A detailed (40000 vertical measurement) three-dimensional image (phase map) is graphically displayed along with a video contrast micrograph of the same sample area. Post-processing of the data yields, average deviation, r.m.s. deviation, peak-to-valley, and asperity volumes are reported on all or user selected subsets of the data. During this post-processing, the region currently being measured in the phase map is highlighted in the video contrast micrograph allowing positive correlation of contrast micrograph features with measurements in the phase map. Applications to video tape, rigid disk, substrate, and read-write head measurements are discussed.

DOI:10.1049/jiere.1985.0046

出版商:IERE    

年代:1985

数据来源: IET

摘要:

This paper describes a microprocessor-based (Zilog Z80) position control system for anX-Ytable which is a precision specimen stage in an electron-beam lithographic machine used to define patterns on semiconductor wafers. The controller receives commands which specify the coordinates, on a user specified Cartesian grid, to which the workpiece is to be moved. After checking that the requested position is within the table's movement range the microprocessor rotates and translates these user coordinates into the representation used by the position sensor, a two-axis laser interferometer. This interferometer measures the positions of mirrors, which are mounted on the specimen table, to an accuracy of 79 nm. Coarse positioning of the table is achieved by means of stepper motors which drive a pair of crossed lead screws whilst fine adjustment of the specimen's effective position is provided by applying a small offset to the electron-beam deflection drivers via digital-to-analogue converters. Thus although the table is only near to the required position, the specimen is nevertheless effectively aligned with the working point of the electron-beam. When the table has been placed in the desired position and come to rest, a signal is given to indicate that processing may resume. An operator panel provides for push-button manual control of the drive motors and a liquid crystal display shows the table's position.

DOI:10.1049/jiere.1985.0047

出版商:IERE    

年代:1985

数据来源: IET