摘要:

Digital magnetic recording on flexible media has grown from ½ in tape in 1959 to include mass storage systems, digital cassettes, data cartridges and flexible disks in 1980. The properties of greatest interest are the capacity of the removable unit, the access time to the data and the rate at which data can be communicated to another device. To the customer the price he must pay per bit of data stored is very important but he must also consider the price of the drive unit and not just the price of the removable unit. The characteristic by which different storage devices are most commonly compared is their storage capacity. To increase this continuously in response to the ever-increasing amount of information that must be stored in machine-accessible form requires a steady improvement in the amount of data that can be packed into each unit of area. The problems encountered in increasing this areal storage density are discussed in detail. Three kinds of limit to bit and track density are considered: the fundamental limit, the technological limit and the economic limit. No estimate is attempted for the economic limit which is strongly machine-dependent but the fundamental limit to bit and track density is given as 20 000 bits or tracks per mm (500 000/in). The technological limit for bit density is given as 4000–8000 b/mm (100 000–200 000 bpi) and for track density 600 t/mm (15 000 tpi).

DOI:10.1049/ree.1980.0041

出版商:IERE    

年代:1980

数据来源: IET

摘要:

In a simple phase lock loop type of frequency synthesizer the closed-loop dynamic performance dictates the settling time after a frequency step, the close-in noise spectrum, the achievable cancellation of microphony in the output oscillator, and the flatness of the frequency modulation characteristic. The dynamic performance is controlled mainly by the proportional and not the integral part of the loop gain. Several techniques are described for ensuring a constant loop gain and hence good overall performance for the synthesizer over a wide frequency range of operation.

DOI:10.1049/ree.1980.0042

出版商:IERE    

年代:1980

数据来源: IET

摘要:

Digital signals received from theMeteosatsatellite consist of a serial bit stream which contains the output of the satellite's spin scan radiometer after computer processing at Darmstadt, Germany. This paper describes a system which recognizes the particular format being transmitted, picks out a chosen channel from the data, and turns it into a form suitable for display on a facsimile recorder or similar instrument.

DOI:10.1049/ree.1980.0043

出版商:IERE    

年代:1980

数据来源: IET

摘要:

The application of pulse-slimming to digital magnetic recording is investigated, and analysed using super-position. Representative criteria are used to determine the maximum achievable packing density both before and after slimming. The results indicate that pulse-slimming is of little value for an already-optimized recording system, but could be used to trade-off timing margin against amplitude margin in a new design.

DOI:10.1049/ree.1980.0044

出版商:IERE    

年代:1980

数据来源: IET

摘要:

The paper describes an extension to the Tracer technique for monitoring and tracking the positions of remote and unattended objects, allowing the signals transmitted by Decca Navigator stations to be used. The problems of retransmitting the multi-frequency Decca Navigator signals have been overcome by receiving a single frequency and decoding the time-multiplexed ‘multipulse’ signals in time-division form.A number of applications of the system are described and results presented. The accuracy, fix repeatability and skywave sensitivity of the system are seen to compare favourably with those of conventional receivers.

DOI:10.1049/ree.1980.0045

出版商:IERE    

年代:1980

数据来源: IET